r amateur book
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Radio amateur handbook.TRANSCRIPT
ProjectGutenberg'sTheRadioAmateur'sHandBook,byA.FrederickCollins
ThiseBookisfortheuseofanyoneanywhereatnocostandwith
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Title:TheRadioAmateur'sHandBook
Author:A.FrederickCollins
PostingDate:March21,2013[EBook#6934]
ReleaseDate:November,2004
FirstPosted:February13,2003
Language:English
***STARTOFTHISPROJECTGUTENBERGEBOOKTHERADIOAMATEUR'SHANDBOOK***
ProducedbyAlanMillarandtheOnlineDistributedProofreadingTeam.
THERADIOAMATEUR'SHANDBOOK
PhotographunavailableA.FrederickCollins,InventoroftheWirelessTelephone,1899.AwardedGoldMedalforsame,
AlaskaYukonPacificExposition,1909.
THERADIOAMATEUR'SHANDBOOKAComplete,AuthenticandInformativeWorkonWirelessTelegraphyandTelephony
BYFREDERICKCOLLINS
InventoroftheWirelessTelephone1899;HistorianofWireless1901-1910;Authorof"WirelessTelegraphy"1905
1922
TOWILLIAMMARCONI
INVENTOROFTHEWIRELESSTELEGRAPH
INTRODUCTION
Beforedelvingintothemysteriesofreceivingandsendingmessageswithoutwires,awordastothehistoryoftheartanditspresentdayapplicationsmaybeofservice.Whilepopularinterestinthesubjecthasgoneforwardbyleapsandboundswithinthelasttwoorthreeyears,ithasbeenamatterofscientificexperimentformorethanaquarterofacentury.
ThewirelesstelegraphwasinventedbyWilliamMarconi,atBologna,Italy,in1896,andinhisfirstexperimentshesentdotanddashsignalstoadistanceof200or300feet.ThewirelesstelephonewasinventedbytheauthorofthisbookatNarberth,Penn.,in1899,andinhisfirstexperimentsthehumanvoicewastransmittedtoadistanceofthreeblocks.
ThefirstvitalexperimentsthatleduptotheinventionofthewirelesstelegraphweremadebyHeinrichHertz,ofGermany,in1888whenheshowedthatthesparkofaninductioncoilsetupelectricoscillationsinanopencircuit,andthattheenergyofthesewaveswas,inturn,sentoutintheformofelectricwaves.Healsoshowedhowtheycouldbereceivedatadistancebymeansofaringdetector,whichhecalledaresonator.
In1890,EdwardBranly,ofFrance,showedthatmetalfilingsinatubecoheredwhenelectricwavesactedonthem,andthisdevicehetermedaradioconductor;thiswasimproveduponbySirOliverLodge,whocalleditacoherer.In1895,AlexanderPopoff,ofRussia,constructedareceivingsetforthestudyofatmosphericelectricity,andthisarrangementwastheearliestonrecordoftheuseofadetectorconnectedwithanaerialandtheearth.
Marconiwasthefirsttoconnectanaerialtoonesideofasparkgapandagroundtotheothersideofit.Heusedaninductioncoiltoenergizethesparkgap,andatelegraphkeyintheprimarycircuittobreakupthecurrentintosignals.AddingaMorseregister,whichprintedthedotanddashmessagesonatape,tothePopoffreceptorheproducedthefirstsystemforsendingandreceivingwirelesstelegraphmessages.
PhotographunavailableCollins'WirelessTelephoneExhibitedattheMadisonSquareGarden,October1908.
AfterMarconihadshowntheworldhowtotelegraphwithoutconnectingwiresitwouldseem,onfirstthought,tobeaneasymattertotelephonewithoutwires,butnotso,fortheelectricsparksetsupdampedandperiodicoscillationsandthesecannotbeusedfortransmittingspeech.Instead,theoscillationsmustbeofconstantamplitudeandcontinuous.ThatadirectcurrentarclighttransformsapartofitsenergyintoelectricoscillationswasshownbyFirthandRogers,ofEngland,in1893.
Theauthorwasthefirsttoconnectanarclampwithanaerialandaground,andtouseamicrophonetransmittertomodulatethesustainedoscillationssosetup.Thereceivingapparatusconsistedofavariablecontact,knownasapill-boxdetector,whichSirOliverLodgehaddevised,andtothiswasconnectedanEricssontelephonereceiver,thenthemostsensitivemade.Alaterimprovementforsettingupsustainedoscillationswastheauthor'srotatingoscillationarc.
Sincethosememorabledaysofmorethantwodecadesago,wonderfuladvanceshavebeenmadein
bothofthesemethodsoftransmittingintelligence,andtheendisasyetnowhereinsight.Twelveorfifteenyearsagotheboysbegantogetfunoutoflistening-intowhattheshipandshorestationsweresendingand,further,theybegantodoalittlesendingontheirownaccount.Theseyoungsters,whocausedtheprofessionaloperatorsmanyapang,werethefirstwirelessamateurs,andamongthemexpertsweredevelopedwhoareforemostinthepracticeofthearttoday.
Awaybackthere,thesparkcoilandthearclampweretheonlyknownmeansforsettinguposcillationsatthesendingend,whiletheelectrolyticandcrystaldetectorsweretheonlyavailablemeansfortheamateurtoreceivethem.Asitwasnexttoimpossibleforaboytogetacurrenthavingahighenoughvoltageforoperatinganoscillationarclamp,wirelesstelephonywasoutofthequestionforhim,sohehadtosticktothesparkcoiltransmitterwhichneededonlyabatterycurrenttoenergizeit,andthis,ofcourse,limitedhimtosendingMorsesignals.Astheelectrolyticdetectorwascumbersomeandrequiredaliquid,thecrystaldetectorwhichcameintobeingshortlyafterwasjustassensitiveandsoondisplacedtheformer,evenasthishaddisplacedthecoherer.
Afewyearsaheadoftheseamateurs,thatistosayin1905,J.A.Fleming,ofEngland,inventedthevacuumtubedetector,buttenmoreyearselapsedbeforeitwasperfectedtoapointwhereitcouldcompetewiththecrystaldetector.Thenitsusebecamegeneralandworkerseverywheresoughtto,anddidimproveit.Further,theyfoundthatthevacuumtubewouldnotonlyactasadetector,butthatifenergizedbyadirectcurrentofhighvoltageitwouldsetupsustainedoscillationslikethearclamp,andthevalueofsustainedoscillationsforwirelesstelegraphyaswellaswirelesstelephonyhadalreadybeendiscovered.
Thefactthatthevacuumtubeoscillatorrequiresnoadjustmentofitselements,thatitsinitialcostismuchlessthantheoscillationarc,besidesotherconsiderations,isthereasonthatitpopularizedwirelesstelephony;andbecausecontinuouswaveshavemanyadvantagesoverperiodicoscillationsisthereasonthevacuumtubeoscillatorisreplacingthesparkcoilasawirelesstelegraphtransmitter.Moreover,byusinganumberoflargetubesinparallel,powerfuloscillationscanbesetupand,hence,thewavessentoutareradiatedtoenormousdistances.
WhileoscillatortubeswerebeingexperimentedwithintheresearchlaboratoriesoftheGeneralElectric,theWestinghouse,theRadioCorporationofAmerica,andotherbigcompanies,alltheyouthfulamateursinthecountryhadlearnedthatbyusingavacuumtubeasadetectortheycouldeasilygetmessages500milesaway.Theuseofthesetubesasamplifiersalsomadeitpossibletoemployaloudspeaker,sothataroom,ahall,oranout-of-dooraudiencecouldhearclearlyanddistinctlyeverythingthatwasbeingsentout.
Theboyamateurhadonlytoletfatherormotherlisten-in,andtheyweredulyimpressedwhenhetoldthemtheyweregettingitfromKDKA(thePittsburghstationoftheWestinghouseCo.),forwasnotPittsburgh500milesaway!Andsothey,too,becameenthusiasticwirelessamateurs.Thisnewinterestofthegrown-upswasatoncemetnotonlybythemanufacturersofapparatuswithcompletereceivingandsendingsets,butalsobythebigcompanieswhichbeganbroadcastingregularprogramsconsistingofmusicandtalksonallsortsofinterestingsubjects.
Thisisthewireless,orradio,astheaverageamateurknowsittoday.Butitisbynomeansthelimitofitspossibilities.Onthecontrary,wearejustbeginningtorealizewhatitmaymeantothehumanrace.TheGovernmentisnowutilizingittosendoutweather,cropandmarketreports.Foreigntradeconditionsarebeingreported.TheNavalObservatoryatArlingtoniswirelessingtimesignals.
Departmentstoresarebeginningtoissueprogramsandadvertisebyradio!Citiesarealsotakingupsuchprograms,andtheywilldoubtlessbeincludedsoonamongtheregularprivilegesofthetax-payers.Politiciansaddresstheirconstituents.Preachersreachthestay-at-homes.Greatsingersthrillthousandsinsteadofhundreds.Soonitwillbepossibletohearthefinestmusicalprograms,entertainers,andorators,withoutbudgingfromone'seasychair.
IntheWorldWarwirelessprovedofinestimablevalue.Airplanes,insteadofflyingaimlessly,keptinconstanttouchwithheadquarters.Bodiesoftroopsmovedalertlyandintelligently.Shipsatseatalkedfreely,overhundredsofmiles.Scoutsreported.Everywhereitsinvisibleaidwasinvoked.
Intimeofpeace,however,ithasprovedandwillprovethegreatestservantofmankind.Wirelessmessagesnowgodailyfromcontinenttocontinent,andsoonwillgoaroundtheworldwiththesamefacility.Shipsindistressatseacansummonaid.Vesselseverywheregettheday'snews,eventobaseballscores.Dailynewtasksarebeingassignedthistireless,wirelessmessenger.
Messageshavebeensentandreceivedbymovingtrains,theLackawannaandtheRockIslandrailroadsbeingpioneersinthisfield.Messageshavealsobeenreceivedbyautomobiles,andoneinventorhassuccessfullydemonstratedamotorcarcontrolledentirelybywireless.Thismethodofcommunicationisbeingemployedmoreandmorebynewspapers.Itisalsoofgreatserviceinreportingforestfires.
Collegesarebeginningtotakeupthesubject,someofthefirstbeingTuftsCollege,HunterCollege,Princeton,Yale,Harvard,andColumbia,whichhaveregularlyorganizeddepartmentsforstudentsinwireless.
Insteadoftheunwieldyandformidablelookingapparatusofashorttimeago,experimentersarenowvyingwitheachotherinmakingsmallornovelequipment.Portablesetsofallsortsarebeingfashioned,fromonewhichwillgointoanordinarysuitcase,toonesosmallitwilleasilyslipintoaBrowniecamera.Onereceiverdepictedinanewspaperwasoneinchsquare!Anotherwasaringforthefinger,withasettingoneinchbyfive-eighthsofaninch,andanumbrellaasa"ground."Walkingsetswithreceiversfastenedtoone'sbeltarealsocommon.Dailynewnoveltiesandmarvelsareannounced.
Meanwhile,theradioamateurtowhomthisbookisaddressedmayhavehisshareinthejoysofwireless.Togetallofthesegoodthingsoutoftheetheronedoesnotneedarodoragun--onlyacopperwiremadefastateitherendandareceivingsetofsomekind.Ifyouareasheerbeginner,thenyoumustbeverycarefulinbuyingyourapparatus,forsincethegreatwaveofpopularityhaswashedwirelessintotheheartsofthepeople,numerouscompanieshavesprungupandsomeofthesearesellingtheveriestkindsofjunk.
Andhow,youmayask,areyougoingtobeabletoknowthegoodfromtheindifferentandbadsets?Bybuyingamakeofafirmwithanestablishedreputation.Ihavegivenafewoffhandattheendofthisbook.Obviouslytherearemanyothersofmerit--somany,indeed,thatitwouldbequiteimpossibletogetthemallinsuchalist,butthesewillserveasaguideuntilyoucanchooseintelligentlyforyourself.
F.C.
CONTENTS
CHAPTER
I.HOWTOBEGINWIRELESS
KindsofWirelessSystems--PartsofaWirelessSystem--TheEasiestWaytoStart--AboutAerialWireSystems--AbouttheReceivingApparatus--AboutTransmittingStations--KindsofTransmitters--TheSparkGapWirelessTelegraphTransmitter--TheVacuumTableTelegraphTransmitter--TheWirelessTelephoneTransmitter.
II.PUTTINGUPYOURAERIAL
KindsofAerialWireSystems--HowtoPutUpaCheapReceivingAerial--ATwo-wireAerial--ConnectingintheGround--HowtoPutupaGoodAerial--AnInexpensiveGoodAerial--TheBestAerialThatCanbeMade--AssemblingtheAerial--MakingaGoodGround.
III.SIMPLETELEGRAPHANDTELEPHONERECEIVINGSETS
AssembledWirelessReceivingSets--AssemblingYourOwnReceivingSet--TheCrystalDetector--TheTuningCoil--TheLooseCoupledTuningCoil--FixedandVariableCondensers--AboutTelephoneReceivers--ConnectingUptheParts--ReceivingSetNo.2--AdjustingtheNo.1Set--TheTuningCoil--AdjustingtheNo.2Set.
IV.SIMPLETELEGRAPHSENDINGSETS
ACheapTransmittingSet(No.1)--TheSparkCoil--TheBattery--TheTelegraphKey--TheSparkGap--TheTuningCoil--TheHigh-tensionCondenser--ABetterTransmittingSet(No.2)--TheAlternatingCurrentTransformer--TheWirelessKey--TheSparkGap--TheHigh-tensionCondenser--TheOscillationTransformer--ConnectingUptheApparatus--ForDirectCurrent--HowtoAdjustYourTransmitter.TurningWithaHotWireAmmeter--ToSendOuta200-meterWaveLength--TheUseoftheAerialSwitch--AerialSwitchforaCompleteSendingandReceivingSet--ConnectingintheLightningSwitch.
V.ELECTRICITYSIMPLYEXPLAINED
ElectricityatRestandinMotion--TheElectricCurrentanditsCircuit--CurrentandtheAmpere--ResistanceandtheOhm--WhatOhm'sLawIs--WhattheWattandKilowattAre--ElectromagneticInduction--MutualInduction--High-frequencyCurrents--ConstantsofanOscillationCircuit--WhatCapacitanceIs--WhatInductanceIs--WhatResistanceIs--TheEffectofCapacitance.
VI.HOWTHETRANSMITTINGANDRECEIVINGSETSWORK
HowTransmittingSetNo.1Works--TheBatteryandSparkCoilCircuit--ChangingthePrimary
SparkCoilCurrentIntoSecondaryCurrents--WhatRatioofTransformationMeans--TheSecondarySparkCoilCircuit--TheClosedOscillationCircuit--HowTransmittingSetNo.2Works-WithAlternatingCurrent--WithDirectCurrent--TheRotarySparkGap--TheQuenchedSparkGap--TheOscillationTransformer--HowReceivingSetNo.1Works--HowReceivingSetNo.2Works.
VII.MECHANICALANDELECTRICALTUNING
DampedandSustainedMechanicalVibrations--DampedandSustainedOscillations--AboutMechanicalTuning--AboutElectricTuning.
VIII.ASIMPLEVACUUMTUBEDETECTORRECEIVINGSET
AssembledVacuumTubeReceivingSet--ASimpleVacuumTubeReceivingSet--TheVacuumTubeDetector--ThreeElectrodeVacuumTubeDetector--TheDryCellandStorageBatteries--TheFilamentRheostat--AssemblingtheParts--ConnectingUptheParts--AdjustingtheVacuumTubeDetectorReceivingSet.
IX.VACUUMTUBEAMPLIFIERRECEIVINGSETS
AGridLeakAmplifierReceivingSet.WithCrystalDetector--TheFixedResistanceUnit,orGridLeak--AssemblingthePartsforaCrystalDetectorSet--ConnectingupthePartsforaCrystalDetector--AGridLeakAmplifyingReceivingSetWithVacuumTubeDetector--ARadioFrequencyTransformerAmplifyingReceivingSet--AnAudioFrequencyTransformerAmplifyingReceivingSet--ASixStepAmplifierReceivingSetwithaLoopAerial--HowtoPreventHowling.
X.REGENERATIVEAMPLIFICATIONRECEIVINGSETS
TheSimplestTypeofRegenerativeReceivingSet--WithLooseCoupledTuningCoil--ConnectingUptheParts--AnEfficientRegenerativeReceivingSet.WithThreeCoilLooseCoupler--TheABatteryPotentiometer--ThePartsandHowtoConnectThemUp--ARegenerativeAudioFrequencyAmplifier--ThePartsandHowtoConnectThemUp.
XI.SHORTWAVEREGENERATIVERECEIVINGSETS
AShortWaveRegenerativeReceiver,withOneVariometerandThreeVariableCondensers--TheVariocoupler--TheVariometer--ConnectingUptheParts--ShortWaveRegenerativeReceiverwithTwoVariometersandTwoVariableCondensers--ThePartsandHowtoConnectThemUp.
XII.INTERMEDIATEANDLONGWAVEREGENERATIVERECEIVINGSETS
IntermediateWaveReceivingSets--IntermediateWaveSetWithLoadingCoils--ThePartsandHowtoConnectThemUp--AnIntermediateWaveSetwithVariocouplerInductanceCoils--ThePartsandHowtoConnectThemUp--ALongWaveReceivingSet--ThePartsandHowtoConnectThemUp.
XIII.HETERODYNEORBEATLONGWAVETELEGRAPHRECEIVINGSET
WhattheHeterodyneorBeatMethodIs--TheAutodyneorSelf-heterodyneLongWaveReceivingSet--ThePartsandConnectionsofanAutodyneorSelf-heterodyne,ReceivingSet--TheSeparateHeterodyneLongWaveReceivingSet--ThePartsandConnectionsofaSeparateHeterodyneLongWaveReceivingSet.
XIV.HEADPHONESANDLOUDSPEAKERS
WirelessHeadphones--HowaBellTelephoneReceiverisMade--HowaWirelessHeadphoneisMade--AboutResistance,TurnsofWireandSensitivityofHeadphones--TheImpedanceofHeadphones--HowtheHeadphonesWork--AboutLoudSpeakers--TheSimplestTypeofLoudSpeaker--AnotherSimpleKindofLoudSpeaker--AThirdKindofSimpleLoudSpeaker--ASuperLoudSpeaker.
XV.OPERATIONOFVACUUMTUBERECEPTORS
WhatisMeantbyIonization--HowElectronsareSeparatedfromAtoms--ActionoftheTwoElectrodeVacuumTube--HowtheTwoElectrodeTubeActsasaDetector--HowtheThreeElectrodeTubeActsasaDetector--HowtheVacuumTubeActsasanAmplifier--TheOperationofaSimpleVacuumTubeReceivingSet--OperationofaRegenerativeVacuumTubeReceivingSet--OperationofAutodyneandHeterodyneReceivingSets--TheAutodyne,orSelf-HeterodyneReceivingSet--TheSeparateHeterodyneReceivingSet.
XVI.CONTINUOUSWAVETELEGRAPHTRANSMITTINGSETSWITHDIRECTCURRENT
SourcesofCurrentforTelegraphTransmittingSets--AnExperimentalContinuousWaveTelegraphTransmitter--TheApparatusYouNeed--TheTuningCoil--TheCondensers--TheAerialAmmeter--TheBuzzerandDryCell--TheTelegraphKey--TheVacuumTubeOscillator--TheStorageBattery--TheBatteryRheostat--TheOscillationChokeCoil--TransmitterConnectors--ThePanelCutout--ConnectingUptheTransmittingApparatus--A100-mileC.W.TelegraphTransmitter--TheApparatusYouNeed--TheTuningCoil--TheAerialCondenser--TheAerialAmmeter--TheGridandBlockingCondensers--TheKeyCircuitApparatus--The5WattOscillatorVacuumTube--TheStorageBatteryandRheostat--TheFilamentVoltmeter--TheOscillationChokeCoil--TheMotor-generatorSet--ThePanelCut-out--TheProtectiveCondenser--ConnectingUptheTransmittingApparatus--A200-mileC.W.TelegraphTransmitter--A500-mileC.W.TelegraphTransmitter--TheApparatusandConnections--The50-wattVacuumTubeOscillator--TheAerialAmmeter--TheGridLeakResistance--TheOscillationChokeCoil--TheFilamentRheostat--TheFilamentStorageBattery--TheProtectiveCondenser--TheMotor-generator--A1000-mileC.W.TelegraphTransmitter.
XVII.CONTINUOUSWAVETELEGRAPHTRANSMITTINGSETSWITHALTERNATINGCURRENT
A100-mileC.W.TelegraphTransmittingSet--TheApparatusRequired--TheChokeCoils--TheMilli-ammeter--TheA.C.PowerTransformer--ConnectingUptheApparatus--A200-to500-mileC.W.TelegraphTransmittingSet-A500-to1000-mileC.W.TelegraphTransmittingSet--TheApparatusRequired--TheAlternatingCurrentPowerTransformer-ConnectingUptheApparatus.
XVIII.WIRELESSTELEPHONETRANSMITTINGSETSWITHDIRECTANDALTERNATINGCURRENTS
AShortDistanceWirelessTelephoneTransmittingSet--With110-voltDirectLightingCurrent--TheApparatusYouNeed--TheMicrophoneTransmitter--ConnectingUptheApparatus--A25-to50-mileWirelessTelephoneTransmitter--WithDirectCurrentMotorGenerator--TheApparatusYouNeed--TheTelephoneInductionCoil--TheMicrophoneTransformer--TheMagneticModulator--HowtheApparatusisConnectedUp--A50-to100-mileWirelessTelephoneTransmitter--WithDirectCurrentMotorGenerator--TheOscillationChokeCoil--ThePlateandGridCircuitReactanceCoils--ConnectinguptheApparatus--A100-to200-mileWirelessTelephoneTransmitter--WithDirectCurrentMotorGenerator--A50-to100-mileWirelessTelephoneTransmittingSet--With100-voltAlternatingCurrent--TheApparatusYouNeed--TheVacuumTubeRectifier--TheFilterCondensers--TheFilterReactanceCoil--ConnectingUptheApparatus--A100-to200-mileWirelessTelephoneTransmittingSet--With110-voltAlternatingCurrent--ApparatusRequired.
XIX.THEOPERATIONOFVACUUMTUBETRANSMITTERS
TheOperationoftheVacuumTubeOscillator--TheOperationofC.W.TelegraphTransmitterswithDirectCurrent--ShortDistanceC.W.Transmitter--TheOperationoftheKeyCircuit--TheOperationofC.W.TelegraphTransmittingwithDirectCurrent--TheOperationofC.W.TelegraphTransmitterswithAlternatingCurrent--WithaSingleOscillatorTube--HeatingtheFilamentwithAlternatingCurrent--TheOperationofC.W.TelegraphTransmitterswithAlternatingCurrent--WithTwoOscillatorTubes--TheOperationofWirelessTelephoneTransmitterswithDirectCurrent--ShortDistanceTransmitter--TheMicrophoneTransmitter--TheOperationofWirelessTelephoneTransmitterswithDirectCurrent--LongDistanceTransmitters--TheOperationofMicrophoneModulators--TheInductionCoil--TheMicrophoneTransformer--TheMagneticModulator--OperationoftheVacuumTubeasaModulator--TheOperationofWirelessTelephoneTransmitterswithAlternatingCurrent--TheOperationofRectifierVacuumTubes--TheOperationofReactorsandCondensers.
XX.HOWTOMAKEARECEIVINGSETFOR$5.00ORLESS.
TheCrystalDetector--TheTuningCoil--TheHeadphone--HowtoMounttheParts--TheCondenser--HowtoConnectUptheReceptor.
APPENDIX
UsefulInformation--Glossary--WirelessDon'ts.
LISTOFFIGURES
Fig.1.--SimpleReceivingSetFig.2.--SimpleTransmittingSet(A)Fig.3.--FlatTop,orHorizontalAerial(B)Fig.3.--InclinedAerial(A)Fig.4.--InvertedLAerial(B)Fig.4.--TAerialFig.5.--MaterialforaSimpleAerialWireSystem(A)Fig.6.--SingleWireAerialforReceiving(B)Fig.6.--ReceivingAerialwithSparkGapLightningArrester(C)Fig.6.--AerialwithLightningSwitchFig.7.--Two-wireAerial(A)Fig.8.--PartofaGoodAerial(B)Fig.8.--TheSpreaders(A)Fig.9.--TheMiddleSpreader(B)Fig.9.--OneEndofAerialComplete(C)Fig.9.--TheLeadinginSpreader(A)Fig.10.--CrossSectionofCrystalDetector(B)Fig.10.--TheCrystalDetectorComplete(A)Fig.11.--SchematicDiagramofaDoubleSlideTuningCoil(B)Fig.11.--DoubleSlideTuningCoilComplete(A)Fig.12.--SchematicDiagramofaLooseCoupler(B)Fig.12.--LooseCouplerComplete(A)Fig.13.--HowaFixedReceivingCondenserisBuiltup(B)Fig.13.--TheFixedCondenserComplete(C)and(D)Fig.13.--VariableRotaryCondenserFig.14.--PairofWirelessHeadphones(A)Fig.15.--TopViewofApparatusLayoutforReceivingSetNo.1(B)Fig.15.--WiringDiagramforReceivingSetNo.1(A)Fig.16.--TopViewofApparatusLayoutforReceivingSetNo.2(B)Fig.16.--WiringDiagramforReceivingSetNo.2Fig.17.--AdjustingtheReceivingSet(A)and(B)Fig.18.--TypesofSparkCoilsforSetNo.1(C)Fig.18.--WiringDiagramofSparkCoilFig.19.--OtherPartsforTransmittingSetNo.1(A)Fig.20.--TopViewofApparatusLayoutforSendingSetNo.1(B)Fig.20.--WiringofDiagramforSendingSetNo.1Fig.21.--PartsforTransmittingSetNo.2(A)Fig.22.--TopViewofApparatusLayoutforSendingSetNo.2(B)Fig.22.--WiringDiagramforSendingSetNo.2Fig.23.--Usinga110-voltDirectCurrentwithanAlternatingcurrentTransformerFig.24.--PrincipleoftheHotWireAmmeterFig.25.--KindsofAerialSwitchesFig.26.--WiringDiagramforaCompleteSendingandReceivingSetNo.1
Fig.27.--WiringDiagramforCompleteSendingandReceivingSetNo.2Fig.28.--WaterAnalogueforElectricPressureFig.29.--WaterAnaloguesforDirectandAlternatingCurrentsFig.30.--HowtheAmmeterandVoltmeterareUsedFig.31.--WaterValveAnalogueofElectricResistance(A)and(B)Fig.32.--HowanElectricCurrentisChangedintoMagneticLinesofForceandTheseintoanElectricCurrent(C)and(D)Fig.32.--HowanElectricCurrentSetsupaMagneticFieldFig.33.--TheEffectofResistanceontheDischargeofanElectricCurrentFig.34.--DampedandSustainedMechanicalVibrationsFig.35.--DampedandSustainedElectricOscillationsFig.36.--SoundWaveandElectricWaveTunedSendersandReceptorsFig.37.--TwoElectrodeVacuumTubeDetectorsFig.38.--ThreeElectrodeVacuumTubeDetectorandBatteryConnectionsFig.39.--AandBBatteriesforVacuumTubeDetectorsFig.40.--RheostatfortheAorStorage-batteryCurrent(A)Fig.41.--TopViewofApparatusLayoutforVacuumTubeDetectorReceivingSet(B)Fig.41.--WiringDiagramofaSimpleVacuumTubeReceivingSetFig.42.--GridLeaksandHowtoConnectthemUpFig.43.--CrystalDetectorReceivingSetwithVacuumTubeAmplifier(ResistanceCoupled)(A)Fig.44.--VacuumTubeDetectorReceivingSetwithOneStepAmplifier(ResistanceCoupled)(B)Fig.44.--WiringDiagramforUsingOneAorStorageBatterywithanAmplifierandaDetectorTube(A)Fig.45.--WiringDiagramforRadioFrequencyTransformerAmplifyingReceivingSet(B)Fig.45.--RadioFrequencyTransformer(A)Fig.46.--AudioFrequencyTransformer(B)Fig.46.--WiringDiagramforAudioFrequencyTransformerAmplifyingReceivingSet.(WithVacuumTubeDetectorandTwoStepAmplifierTubes)(A)Fig.47.--SixStepAmplifierwithLoopAerial(B)Fig.47.--EfficientRegenerativeReceivingSet(WithThreeCoilLooseCouplerTuner)Fig.48.--SimpleRegenerativeReceivingSet(WithLooseCouplerTuner)(A)Fig.49.--DiagramofThreeCoilLooseCoupler(B)Fig.49.--ThreeCoilLooseCouplerTunerFig.50.--HoneycombInductanceCoilFig.51.--TheUseofthePotentiometerFig.52.--RegenerativeAudioFrequencyAmplifierReceivingSetFig.53.--HowtheVarioCouplerisMadeandWorksFig.54.--HowtheVariometerisMadeandWorksFig.55.--ShortWaveRegenerativeReceivingSet(OneVariometerandThreeVariableCondensers)Fig.56.--ShortWaveRegenerativeReceivingSet(TwoVariometerandTwoVariableCondensers)Fig.57.--WiringDiagramShowingFixedLoadingCoilsforIntermediateWaveSetFig.58.--WiringDigramofIntermediateWaveReceptorwithOneVarioCouplerand12SectionBank-woundInductanceCoilFig.59.--WiringDiagramShowingLongWaveReceptorwithVarioCouplersand8Bank-
woundInductanceCoilsFig.60.--WiringDiagramofLongWaveAutodyne,orSelf-heterodyneReceptor(ComparewithFig.77)Fig.61.--WiringDiagramofLongWaveSeparateHeterodyneReceivingSetFig.62.--CrossSectionofBellTelephoneReceiverFig.63.--CrossSectionofWirelessHeadphoneFig.64.--TheWirelessHeadphoneFig.65.--ArkayLoudSpeakerFig.66.--AmplitoneLoudSpeakerFig.67.--AmplitronLoudSpeakerFig.68.--MagnavoxLoudSpeakerFig.69.--SchematicDiagramofanAtomFig.70.--ActionofTwo-electrodeVacuumTube(A)and(B)Fig.71.--HowaTwo-electrodeTubeActsasRelayoraDetector(C)Fig.71.--OnlythePositivePartofOscillationsGoesthroughtheTube(A)and(B)Fig.72.--HowthePositiveandNegativeVoltagesoftheOscillationsActontheElectrons(C)Fig.72.--HowtheThree-electrodeTubeActsasDetectorandAmplifier(D)Fig.72.--HowtheOscillationsControltheFlowoftheBatteryCurrentthroughtheTubeFig.73.--HowtheHeterodyneReceptorWorksFig.74.--SeparateHeterodyneOscillator(A)Fig.75.--ApparatusforExperimentalC.W.TelegraphTransmitter.(B)Fig.75.--ApparatusforExperimentalC.W.TelegraphTransmitter.Fig.76.--ExperimentalC.W.TelegraphTransmitterFig.77.--Apparatusof100-mileC.W.TelegraphTransmitterFig.78.--5-to50-wattC.W.TelegraphTransmitter(withaSingleOscillationTube)Fig.79.--200-mileC.W.TelegraphTransmitter(withTwoTubesinParallel)Fig.80.--50-wattOscillatorVacuumTubeFig.81.--AlternatingCurrentPowerTransformer(forC.W.TelegraphyandWirelessTelephony)Fig.82.--WiringDiagramfor200-to500-mileC.W.TelegraphTransmittingSet.(WithAlternatingCurrent.)Fig.83.--WiringDiagramfor500-to1000-mileC.W.TelegraphTransmitterFig.84.--StandardMicrophoneTransmitterFig.85.--WiringDiagramofShortDistanceWirelessTelephoneSet.(MicrophoneinAerialWire.)Fig.86.--TelephoneInductionCoil(usedwithMicrophoneTransmitter).Fig.87.--MicrophoneTransformerUsedwithMicrophoneTransmitterFig.88.--MagneticModulatorUsedwithMicrophoneTransmitter(A)Fig.89.--WiringDiagramof25--to50-mileWirelessTelephone.(MicrophoneModulatorShuntedAroundGrid-leakCondenser)(B)Fig.89.--MicrophoneModulatorConnectedinAerialWireFig.90.--WiringDiagramof50-to100-mileWirelessTelephoneTransmittingSetFig.91.--PlateandGridCircuitReactorFig.92.--FilterReactorforSmoothingOutRectifiedCurrentsFig.93.--100-to200-mileWirelessTelephoneTransmitter(A)and(B)Fig.94.--OperationofVacuumTubeOscillators
(C)Fig.94.--HowaDirectCurrentSetsupOscillationsFig.95.--PositiveVoltageOnlySetsupOscillationsFig.96.--RascoBabyCrystalDetectorFig.97.--HowtheTuningCoilisMadeFig.98.--Mescoloop-ohmHeadSetFig.99.--SchematicLayoutofthe$5.00ReceivingSetFig.100.--WiringDiagramforthe$5.00ReceivingSet
LISTOFILLUSTRATIONS
FrederickCollins,InventoroftheWirelessTelephone,1899.AwardedGoldMedalforsame,AlaskaYukonPacificExposition,1909Collins'WirelessTelephoneExhibitedattheMadisonSquareGarden,October,1908GeneralPershing"Listening-in"TheWorld'sLargestRadioReceivingStation.OwnedbytheRadioCorporationofAmericaatRockyPointnearPortJefferson,L.I.FirstWirelessCollegeintheWorld,atTuftsCollege,MassAlexanderGrahamBell,InventoroftheTelephone,nowanardentRadioEnthusiastWorld'sLargestLoudSpeakerevermade.InstalledinLytlePark,Cincinnati,Ohio,topermitPresidentHarding'sAddressatPointPleasant,Ohio,duringtheGrantCentenaryCelebrationtobeheardwithinaradiusofonesquareUnitedStatesNavalHighPowerStation,Arlington,Va.GeneralviewofPowerRoom.AttheleftcanbeseentheControlSwitchboards,andoverhead,thegreat30K.W.ArcTransmitterwithAccessoriesTheTransformerandTuneroftheWorld'sLargestRadioStation.OwnedbytheRadioCorporationofAmericaatRockyPointnearPortJefferson,L.I.BroadcastingGovernmentReportsbyWirelessfromWashington.ThisshowsMr.GaleatworkwithhissetinthePostOfficeDepartmentWirelessReceptor,thesizeofaSafetyMatchBox.AYouthfulGeniusinthepersonofKennethR.Hinman,whoisonlytwelveyearsold,hasmadeaWirelessReceivingSetthatfitsneatlyintoaSafetyMatchBox.WiththisInstrumentandaPairofOrdinaryReceivers,heisabletocatchnotonlyCodeMessagesbuttheregularBroadcastingProgramsfromStationsTwentyandThirtyMilesDistantWirelessSetmadeintoaRing,designedbyAlfredG.Rinehart,ofElizabeth,NewJersey.ThislittleReceptorisaPracticalSet;itwillreceiveMessages,Concerts,etc.,measures1"by5/8"by7/8".AnordinaryUmbrellaisusedasanAerial
CHAPTERI
HOWTOBEGINWIRELESS
Inwritingthisbookitistakenforgrantedthatyouare:first,oneoftheseveralhundredthousandpersonsintheUnitedStateswhoareinterestedinwirelesstelegraphyandtelephony;second,thatyouwouldliketoinstallanapparatusinyourhome,andthird,thatitisallnewtoyou.
Nowifyouliveinacityortownlargeenoughtosupportanelectricalsupplystore,thereyouwillfindthenecessaryapparatusonsale,andsomeonewhocantellyouwhatyouwanttoknowaboutitandhowitworks.Ifyouliveawayfromthemartsandhivesofindustryyoucansendtovariousmakersofwirelessapparatus[Footnote:AlistofmakersofwirelessapparatuswillbefoundintheAppendix.]fortheircataloguesandprice-listsandthesewillgiveyoumuchusefulinformation.Butineithercaseitisthebetterplanforyoutoknowbeforeyoustartintobuyanoutfitexactlywhatapparatusyouneedtoproducetheresultyouhaveinmind,andthisyoucangainineasystepsbyreadingthisbook.
KindsofWirelessSystems.--Therearetwodistinctkindsofwirelesssystemsandtheseare:thewirelesstelegraphsystem,andthewirelesstelephonesystem.Thedifferencebetweenthewirelesstelegraphandthewirelesstelephoneisthattheformertransmitsmessagesbymeansofatelegraphkey,andthelattertransmitsconversationandmusicbymeansofamicrophonetransmitter.Inotherwords,thesamedifferenceexistsbetweentheminthisrespectasbetweentheMorsetelegraphandtheBelltelephone.
PartsofaWirelessSystem.--Everycompletewirelessstation,whethertelegraphortelephone,consistsofthreechiefseparateanddistinctpartsandtheseare:(a)theaerialwiresystem,orantennaasitisoftencalled,(b)thetransmitter,orsender,and(c)thereceiver,or,moreproperly,thereceptor.Theaerialwireispreciselythesameforeitherwirelesstelegraphyorwirelesstelephony.Thetransmitterofawirelesstelegraphsetgenerallyusesasparkgapforsettinguptheelectricoscillations,whileusuallyforwirelesstelephonyavacuumtubeisemployedforthispurpose.Thereceptorforwirelesstelegraphyandtelephonyisthesameandmayincludeeitheracrystaldetectororavacuumtubedetector,aswillbeexplainedpresently.
TheEasiestWaytoStart.--Firstofallyoumustobtainagovernmentlicensetooperateasendingset,butyoudonotneedalicensetoputupanduseareceivingset,thoughyouarerequiredbylawtokeepsecretanymessageswhichyoumayoverhear.Sincenolicenseisneededforareceivingsettheeasiestwaytobreakintothewirelessgameistoputupanaerialandhookupareceivingsettoit;youcanthenlisten-inandhearwhatisgoingonintheall-pervadingetheraroundyou,andyouwillsoonfindenoughtomakethingshighlyentertaining.
Nearlyallthebigwirelesscompanieshavegreatstationsfittedwithpowerfultelephonetransmittersandatgivenhoursofthedayandnighttheysendoutsongsbypopularsingers,dancemusicbyjazzorchestras,fashiontalksbyandfortheladies,agriculturalreports,governmentweatherforecastsandotherinterestingfeatures.Thenbysimplyshiftingtheslideonyourtuningcoilyoucanoftentune-insomeonewhoissendingMorse,thatis,messagesinthedotanddashcode,or,perhapsafriendwhohasawirelesstelephonetransmitterandistalking.Ofcourse,ifyouwanttotalkbackyoumusthave
awirelesstransmitter,eithertelegraphicortelephonic,andthisisamuchmoreexpensivepartoftheapparatusthanthereceptor,bothinitsinitialcostandinitsoperation.Awirelesstelegraphtransmitterislesscostlythanawirelesstelephonetransmitteranditisaverygoodschemeforyoutolearntosendandreceivetelegraphicmessages.
Atthepresenttime,however,therearefifteenamateurreceivingstationsintheUnitedStatestoeverysendingstation,soyoucanseethatthemajorityofwirelessfolkscaremoreforlisteningintothebroadcastingofnewsandmusicthantosendingoutmessagesontheirownaccount.Theeasiestwaytobeginwireless,then,istoputupanaerialandhookupareceivingsettoit.
AboutAerialWireSystems.--Tothebeginnerwhowantstoinstallawirelessstationtheaerialwiresystemusuallyloomsupasthebiggestobstacleofall,andespeciallyisthistrueifhishouseiswithoutaflagpole,orotherelevationfromwhichtheaerialwirecanbeconvenientlysuspended.
Ifyouliveinthecongestedpartofabigcitywheretherearenoyardsand,particularly,ifyouliveinaflatbuildingoranapartmenthouse,youwillhavetostringyouraerialwireontheroof,andtodothisyoushouldgettheowner's,oragent's,permission.Thisisusuallyaneasythingtodowhereyouonlyintendtoreceivemessages,foroneortwothinwiressupportedateitherendofthebuildingareallthatareneeded.Ifforanyreasonyoucannotputyouraerialontheroofthenrunawirealongthebuildingoutsideofyourapartment,and,finally,ifthisisnotfeasible,connectyourreceivertoawirestrungupinyourroom,oreventoanironorabrassbed,andyoucanstillgetthenear-bystations.
Animportantpartoftheaerialwiresystemistheground,thatis,yourreceivingsetmustnotonlybeconnectedwiththeaerialwire,butwithawirethatleadstoandmakesgoodcontactwiththemoistearthoftheground.Whereahouseorabuildingispipedforgas,waterorsteam,itiseasytomakeagroundconnection,forallyouhavetodoistofastenthewiretooneofthepipeswithaclamp.[Footnote:Pipesareofteninsulatedfromtheground,whichmakesthemuselessforthispurpose.]Wherethehouseisisolatedthenalotofwiresorasheetofcopperorofzincmustbeburiedinthegroundatasufficientdepthtoinsuretheirbeingkeptmoist.
AbouttheReceivingApparatus.--Youcaneitherbuythepartsofthereceivingapparatusseparateandhookthemupyourself,oryoucanbuytheapparatusalreadyassembledinasetwhichis,inthebeginning,perhaps,thebetterway.
Thesimplestreceivingsetconsistsof(1)adetector,(2)atuningcoil,and(3)atelephonereceiverandthesethreepiecesofapparatusare,ofcourse,connectedtogetherandarealsoconnectedtotheaerialandgroundasthediagraminFig.1clearlyshows.Therearetwochiefkindsofdetectorsusedatthepresenttimeandtheseare:(a)thecrystaldetector,and(b)thevacuumtubedetector.Thecrystaldetectoristhecheapestandsimplest,butitisnotassensitiveasthevacuumtubedetectoranditrequiresfrequentadjustment.Acrystaldetectorcanbeusedwithorwithoutabatterywhilethevacuumtubedetectorrequirestwosmallbatteries.
Atuningcoilofthesimplestkindconsistsofasinglelayerofcopperwirewoundonacylinderwithanadjustable,orsliding,contact,butforsharptuningyouneedaloosecoupledtuningcoil.Whereasinglecoiltunerisusedafixedcondensershouldbeconnectedaroundthetelephonereceivers.Wherealoosecoupledtunerisemployedyoushouldhaveavariablecondenserconnectedacrosstheclosedoscillationcircuitandafixedcondenseracrossthetelephonereceivers.
Whenlistening-intodistantstationstheenergyofthereceivedwirelesswavesisoftensoveryfeeblethatinordertoheardistinctlyanamplifiermustbeused.Toamplifytheincomingsoundsavacuumtubemadelikeadetectorisusedandsometimesasmanyashalf-a-dozenofthesetubesareconnectedinthereceivingcircuit,orincascade,asitiscalled,whenthesoundsareamplified,thatismagnified,manyhundredsoftimes.
Thetelephonereceiverofareceivingsetisequallyasimportantasthedetector.Asinglereceivercanbeusedbutapairofreceiversconnectedwithahead-bandgivesfarbetterresults.Thenagainthehighertheresistanceofthereceiversthemoresensitivetheyoftenareandthosewoundtoashigharesistanceas3,200ohmsaremadeforusewiththebestsets.Tomaketheincomingsignals,conversationormusic,audibletoaroomfullofpeopleinsteadoftojustyourselfyoumustusewhatiscalledaloudspeaker.Initssimplestformthisconsistsofametalconelikeamegaphonetowhichisfittedatelephonereceiver.
AboutTransmittingStations--GettingYourLicense.--Ifyouaregoingtoinstallawirelesssendingapparatus,eithertelegraphicortelephonic,youwillhavetosecureagovernmentlicenseforwhichnofeeorchargeofanykindismade.Therearethreeclassesoflicensesissuedtoamateurswhowanttooperatetransmittingstationsandtheseare:(1)therestrictedamateurlicense,(2)thegeneralamateurlicense,and(3)thespecialamateurlicense.
Ifyouaregoingtosetupatransmitterwithinfivenauticalmilesofanynavalwirelessstationthenyouwillhavetogetarestrictedamateurlicensewhichlimitsthecurrentyouusetohalfakilowatt[Footnote:AKilowattis1,000watts.Thereare746wattsinahorsepower.]andthewavelengthyousendoutto200meters.Shouldyouliveoutsideofthefive-milerangeofanavystationthenyoucangetageneralamateurlicenseandthispermitsyoutouseacurrentof1kilowatt,butyouarelikewiselimitedtoawavelengthof200meters.Butifyoucanshowthatyouaredoingsomespecialkindof
wirelessworkandnotusingyoursendingstationforthemerepleasureyouaregettingoutofityoumaybeabletogetaspecialamateurlicensewhichgivesyoutherighttosendoutwavelengthsupto375meters.
WhenyouarereadytoapplyforyourlicensewritetotheRadioInspectorofwhicheveroneofthefollowingdistrictsyoulivein:
FirstDistrict..............Boston,Mass.
Second"..............NewYorkCity
Third"..............Baltimore,Md.
Fourth"..............Norfolk,Va.
Fifth"..............NewOrleans,La.
Sixth".............SanFrancisco,Cal.
Seventh".............Seattle,Wash.
Eighth".............Detroit,Mich.
Ninth"..............Chicago,Ill.
KindsofTransmitters.--Therearetwogeneraltypesoftransmittersusedforsendingoutwirelessmessagesandtheseare:(1)wirelesstelegraphtransmitters,and(2)wirelesstelephonetransmitters.Telegraphtransmittersmayuseeither:(a)ajump-spark,(b)anelectricarc,or(c)avacuumtubeapparatusforsendingoutdotanddashmessages,whiletelephonetransmittersmayuseeither,(a)anelectricarc,or(b)avacuumtubeforsendingoutvocalandmusicalsounds.Amateursgenerallyuseajump-sparkforsendingwirelesstelegraphmessagesandthevacuumtubeforsendingwirelesstelephonemessages.
TheSparkGapWirelessTelegraphTransmitter.--Thesimplestkindofawirelesstelegraphtransmitterconsistsof:(1)asourceofdirectoralternatingcurrent,(2)atelegraphkey,(3)aspark-coiloratransformer,(4)asparkgap,(5)anadjustablecondenserand(6)anoscillationtransformer.Wheredrycellsorastoragebatterymustbeusedtosupplythecurrentforenergizingthetransmitteraspark-coilcanbeemployedandthesemaybehadinvarioussizesfromalittlefellowwhichgives1/4-inchsparkuptoalargeronewhichgivesa6-inchspark.Wheremoreenergyisneededitisbetterpracticetouseatransformerandthiscanbeworkedonanalternatingcurrentof110volts,orifonlya110voltdirectcurrentisavailablethenanelectrolyticinterruptermustbeusedtomakeandbreakthecurrent.AsimpletransmittingsetwithaninductioncoilisshowninFig.2.
Awirelesskeyismadelikeanordinarytelegraphkeyexceptthatwherelargecurrentsaretobeuseditissomewhatheavierandisprovidedwithlargesilvercontactpoints.Sparkgapsforamateurworkareusuallyof:(1)theplainorstationarytype,(2)therotatingtype,and(3)thequenchedgaptype.Theplainspark-gapismoresuitableforsmallspark-coilsets,anditisnotsoapttobreakdownthetransformerandcondenserofthelargersetsastherotarygap.Therotarygapontheotherhandtendstopreventarcingandsothebreakisquickerandthereislessdraggingofthespark.Thequenchedgapismoreefficientthaneithertheplainorrotarygapandmoreoveritisnoiseless.
CondensersforsparktelegraphtransmitterscanbeordinaryLeydenjarsorglassplatescoatedwithtinorcopperfoilandsetintoaframe,ortheycanbebuiltupofmicaandsheetmetalembeddedinaninsulatingcomposition.Theglassplatecondensersarethecheapestandwillserveyourpurposewell,especiallyiftheyareimmersedinoil.Tuningcoils,sometimescalledtransmittinginductancesandoscillationtransformers,areofvarioustypes.Thesimplestkindisatransmittinginductancewhichconsistsof25or30turnsofcopperwirewoundonaninsulatingtubeorframe.Anoscillationtransformerisaloosecoupledtuningcoilanditconsistsofaprimarycoilformedofanumberofturnsofcopperwirewoundonafixedinsulatingsupport,andasecondarycoilofabouttwicethenumberofturnsofcopperwirewhichislikewisefixedinaninsulatingsupport,butthecoilsarerelativelymovable.Anoscillationtransformer(insteadofatuningcoil),isrequiredbygovernmentregulationsunlessinductivelycoupled.
TheVacuumTubeTelegraphTransmitter.--Thisconsistsof:(1)asourceofdirectoralternatingcurrent,(2)atelegraphkey,(3)avacuumtubeoscillator,(4)atuningcoil,and(5)acondenser.Thiskindofatransmittersetsupsustainedoscillationsinsteadofperiodicoscillationswhichareproduced
byasparkgapset.TheadvantagesofthiskindofasystemwillbefoundexplainedinChapterXVI.
TheWirelessTelephoneTransmitter.--Becauseajump-sparksetsupperiodicoscillations,thatis,theoscillationsarediscontinuous,itcannotbeusedforwirelesstelephony.Anelectricarcoravacuumtubesetsupsustainedoscillations,thatis,oscillationswhicharecontinuous.Asitisfareasiertokeeptheoscillationsgoingwithavacuumtubethanitiswithanarctheformermeanshasallbutsupplantedthelatterforwirelesstelephonetransmitters.Theapparatusrequiredandtheconnectionsusedforwirelesstelephonesetswillbedescribedinlaterchapters.
UsefulInformation.--ItwouldbewiseforthereadertoturntotheAppendix,beginningwithpage301ofthisbook,andfamiliarizehimselfwiththeinformationtheresetdownintabularandgraphicform.Forexample,thefirsttablegivesabbreviationsofelectricaltermswhichareingeneraluseinallworksdealingwiththesubject.Youwillalsofindtherebriefdefinitionsofelectricandmagneticunits,whichitwouldbewelltocommittomemory;or,atleast,tomakesothoroughlyyourownthatwhenanyofthesetermsismentioned,youwillknowinstantlywhatisbeingtalkedabout.
CHAPTERII
PUTTINGUPYOURAERIAL
Asinferredinthefirstchapter,anaerialforreceivingdoesnothavetobenearlyaswellmadeorputupasoneforsending.Butthisdoesnotmeanthatyoucanslipshodtheconstructionandinstallationofit,forhoweversimpleitis,thejobmustbedonerightandinthiscaseitisaseasytodoitrightaswrong.
Tosendwirelesstelegraphandtelephonemessagestothegreatestdistancesandtoreceivethemasdistinctlyaspossiblefromthegreatestdistancesyoumustuseforyouraerial(1)copperoraluminumwire,(2)twoormorewires,(3)havethemtheproperlength,(4)havethemashighintheairasyoucan,(5)havethemwellapartfromeachother,and(6)havethemwellinsulatedfromtheirsupports.Ifyouliveinaflatbuildingoranapartmenthouseyoucanstringyouraerialwiresfromoneedgeoftherooftotheotherandsupportthembywoodenstaysashighaboveitasmaybeconvenient.
Shouldyouliveinadetachedhouseinthecityyoucanusuallygetyournext-doorneighbortoletyoufastenoneendoftheaerialtohishouseandthiswillgiveyouagoodstretchandafairlyhighaerial.Inthecountryyoucanstretchyourwiresbetweenthehouseandbarnorthewindmill.Fromthisyouwillseethatnomatterwhereyouliveyoucannearlyalwaysfindwaysandmeansofputtingupanaerialthatwillserveyourneedswithoutgoingtotheexpenseoferectingamast.
KindsofAerialWireSystems.--Anamateurwirelessaerialcanbeanywherefrom25feetto100feetlongandifyoucangetastretchofthelatterlengthandaheightoffrom30to75feetyouwillhaveonewithwhichyoucanreceiveathousandmilesormoreandsendoutasmuchenergyasthegovernmentwillallowyoutosend.
Thekindofanaerialthatgivesthebestresultsisonewhosewire,orwires,arehorizontal,thatis,parallelwiththeearthunderitasshownatAinFig.3.Ifonlyoneendcanbefixedtosomeelevatedsupportthenyoucansecuretheotherendtoapostintheground,buttheslopeoftheaerialshouldnotbemorethan30or35degreesfromthehorizontalatmostasshownatB.
Theleading-inwire,thatis,thewirethatleadsfromandjoinstheaerialwirewithyoursendingand
receivingset,canbeconnectedtotheaerialanywhereitismostconvenienttodoso,butthebestresultsarehadwhenitisconnectedtooneendasshownatAinFig.4,inwhichcaseitiscalledaninvertedLaerial,orwhenitisconnectedtoitatthemiddleasshownatB,whenitiscalledaTaerial.Theleading-inwiremustbecarefullyinsulatedfromtheoutsideofthebuildingandalsowhereitpassesthroughittotheinside.Thisisdonebymeansofaninsulatingtubeknownasaleading-ininsulator,orbulkheadinsulatorasitissometimescalled.
Asaprotectionagainstlightningburningoutyourinstrumentsyoucanuseeither:(1)anair-gaplightningarrester,(2)avacuumtubeprotector,or(3)alightningswitch,whichisbetter.Whicheverofthesedevicesisuseditisconnectedinbetweentheaerialandanoutsidegroundwiresothatadirectcircuittotheearthwillbeprovidedatalltimesexceptwhenyouaresendingorreceiving.Soyouraerialinsteadofbeingamenacereallyactsduringanelectricalstormlikealightningrodanditisthereforearealprotection.Theair-gapandvacuumtubelightningarrestersarelittledevicesthatcanbeusedonlywhereyouaregoingtoreceive,whilethelightningswitchmustbeusedwhereyouaregoingtosend;indeed,insomelocalitiestheFireUnderwritersrequirealargelightningswitchtobeusedforreceivingsetsaswellassendingsets.
HowtoPutUpaCheapReceivingAerial.--Thekindofanaerialwiresystemyouputupwilldepend,chiefly,ontwothings,andtheseare:(1)yourpocketbook,and(2)theplacewhereyoulive.
ASingleWireAerial.--Thisisthesimplestandcheapestkindofareceivingaerialthatcanbeputup.Thefirstthingtodoistofindoutthelengthofwireyouneedbymeasuringthespanbetweenthetwopointsofsupport;thenaddasufficientlengthfortheleading-inwireandenoughmoretoconnectyourreceivingsetwiththeradiatororwaterpipe.
YoucanuseanysizeofcopperoraluminumwirethatisnotsmallerthanNo.16BrownandSharpegauge.Whenyoubuythewiregetalsothefollowingmaterial:(1)twoporcelaininsulatorsasshownatAinFig.5;(2)threeorfourporcelainknobinsulators,seeB;(3)either(a)anairgaplightningarrester,seeC,or(b)alightningswitchseeD;(4)aleading-inporcelaintubeinsulator,seeE,and(5)agroundclamp,seeF.
Tomaketheaerialslipeachendofthewirethroughaholeineachinsulatorandtwistitfast;nextcutoffandsliptwomorepiecesofwirethroughtheotherholesintheinsulatorsandtwistthemfastandthensecurethesetothesupportsattheendsofthebuilding.Takethepieceyouaregoingtousefortheleading-inwire,twistitaroundtheaerialwireandsolderittherewhenitwilllooklikeAinFig.6.Nowifyouintendtousetheairgaplightningarresterfastenittothewallofthebuildingoutsideofyourwindow,andbringtheleading-inwirefromtheaerialtothetopbindingpostofyourarresterandkeepitclearofeverythingasshownatB.Ifyouraerialisontheroofandyouhavetobringtheleading-inwireoverthecorniceoraroundacornerfixaporcelainknobinsulatortotheoneortheotherandfastenthewiretoit.
Nextboreaholethroughtheframeofthewindowatapointnearestyourreceivingsetandpusha
porcelaintube5/8inchindiameterand5or6incheslong,throughit.Connectalengthofwiretothetoppostofthearresterorjustaboveittothewire,runthisthroughtheleading-ininsulatorandconnectittothesliderofyourtuningcoil.Screwtheendofapieceofheavycopperwiretothelowerpostofthearresterandrunittotheground,onporcelainknobsifnecessary,andsolderittoanironrodorpipewhichyouhavedrivenintotheearth.FinallyconnectthefixedterminalofyourtuningcoilwiththewaterpipeorradiatorinsideofthehousebymeansofthegroundclampasshowninthediagrammaticsketchatBinFig.6andyouarereadytotunein.
Ifyouwanttousealightningswitchinsteadoftheair-gaparresterthenfastenittotheoutsidewallinsteadofthelatterandscrewthefreeendoftheleading-inwirefromtheaerialtothemiddlepostofitasshownatCinFig.6.Runawirefromthetoppostthroughtheleading-ininsulatorandconnectitwiththesliderofyourtuningcoil.Nextscrewoneendofalengthofheavycopperwiretothelowerpostoftheaerialswitchandrunittoanironpipeinthegroundasdescribedaboveinconnectionwiththespark-gaplightningarrester;thenconnectthefixedterminalofyourtuningcoilwiththeradiatororwaterpipeandyouraerialwiresystemwillbecompleteasshownatCinFig.6.
ATwo-wireAerial.--Anaerialwithtwowireswillgivebetterresultsthanasinglewireandthreewiresarebetterthantwo,butyoumustkeepthemwellapart.Toputupatwo-wireaerialget(1)enoughNo.16,orpreferablyNo.14,solidorstrandedcopperoraluminumwire,(2)fourporcelaininsulators,seeBinFig.5,and(3)twosticksabout1inchthick,3incheswideand3or4feetlong,forthespreaders,andbore1/8-inchholethrougheachendofeachone.Nowtwisttheendsofthewirestotheinsulatorsandthencutofffourpiecesofwireabout6feetlongandrunthemthroughtheholesinthewoodspreaders.Finallytwisttheendsofeachpairofshortwirestothefreeendsoftheinsulatorsandthentwistthefreeendsofthewirestogether.
Fortheleading-inwirethatgoestothelightningswitchtaketwolengthsofwireandtwistoneendofeachonearoundtheaerialwiresandsolderthemthere.TwisttheshortwirearoundthelongwireandsolderthisjointalsowhentheaerialwilllooklikeFig.7.Bringthefreeendoftheleading-inwiredowntothemiddlepostofthelightningswitchandfastenitthereandconnectupthereceivertoitandthegroundasdescribedunderthecaptionofASingleWireAerial.
ConnectingintheGround.--Ifthereisagasorwatersystemorasteam-heatingplantinyourhouseyoucanmakeyourgroundconnectionbyclampingagroundclamptothenearestpipeashasbeenpreviouslydescribed.Connectalengthofbareorinsulatedcopperwirewithitandbringthisupto
thetableonwhichyouhaveyourreceivingset.Iftherearenogroundedpipesavailablethenyouwillhavetomakeagoodgroundwhichweshalldescribepresentlyandleadthegroundwirefromyourreceivingsetoutofthewindowanddowntoit.
HowtoPutUpaGoodAerial.--Whileyoucanusethecheapaerialalreadydescribedforasmallspark-coilsendingsetyoushouldhaveabetterinsulatedonefora1/2ora1kilowatttransformerset.Thecostforthematerialsforagoodaerialissmallandwhenproperlymadeandwellinsulateditwillgiveresultsthatarealloutofproportiontothecostofit.
AnInexpensiveGoodAerial.--Afarbetteraerial,becauseitismorehighlyinsulated,canbemadebyusingmidgetinsulatorsinsteadoftheporcelaininsulatorsdescribedunderthecaptionofASingleWireAerialandusingasmallelectroseleading-ininsulatorinsteadoftheporcelainbushing.Thismakesagoodsendingaerialforsmallsetsaswellasagoodreceivingaerial.
TheBestAerialthatCanBeMade.--Tomakethisaerialgetthefollowingmaterialtogether:(1)enoughstrandedorbraidedwireforthreeorfourlengthsofparallelwires,accordingtothenumberyouwanttouse(2)sixoreightelectroseballinsulators,seeB,Fig.8;(3)two5-inchor10-inchelectrosestraininsulators,seeC;(4)sixoreightS-hooks,seeD;onelargewithewithoneeyeformiddleofendspreader,seeE;(6)twosmallerwitheswithoneeyeeachforendspreader,seeE;(7)twostillsmallerwithes,withtwoeyeseachfortheendsoftheendspreaders,seeE(8)twothimbles,seeF,for1/4-inchwirecable;(9)sixoreighthardrubbertubesorbushingsasshownatG;and(10)twoendspreaders,seeH;onemiddlespreader,seeI;andoneleading-inspreader,seeJ.
Forthisaerialanyoneofanumberofkindsofwirecanbeusedandamongtheseare(a)strandedcopperwire;(b)braidedcopperwire;(c)strandedsiliconbronzewire,and(d)strandedphosphorbronzewire.Strandedandbraidedcopperwireisveryflexibleasitisformedofsevenstrandsoffinewiretwistedorbraidedtogetheranditisverygoodforshortandlightaerials.Siliconbronzewireisstrongerthancopperwireandshouldbeusedwhereaerialsaremorethan100feetlong,whilephosphorbronzewireisthestrongestaerialwiremadeandisusedforhighgradeaerialsbythecommercialcompaniesandtheGovernmentfortheirhigh-powerstations.
Thespreadersshouldbemadeofspruce,andshouldbe4feet10incheslongforathree-wireaerialand7feet1inchlongforafour-wireaerialasthedistancebetweenthewiresshouldbeabout27inches.Theendspreaderscanbeturnedcylindricallybutitmakesabetterlookingjobiftheytaperfromthemiddletotheends.Theyshouldbe2-1/4inchesindiameteratthemiddleand1-3/4inchesattheends.Themiddlespreadercanbecylindricaland2inchesindiameter.Itmusthaveholesboredthroughitatequidistantpointsforthehardrubbertubes;eachoftheseshouldbe5/8inchindiameterandhaveahole5/32inchindiameterthroughitfortheaerialwire.Theleading-inspreaderisalsomadeofspruceandis1-1/2inchessquareand26incheslong.Borethreeorfour5/8-inchholesatequidistantpointsthroughthisspreaderandinserthardrubbertubesinthemaswiththemiddlespreader.
AssemblingtheAerial.--Beginbymeasuringoffthelengthofeachwiretobeusedandseetoitthatallofthemareofexactlythesamelength.NowpushthehardrubberinsulatorsthroughtheholesinthemiddlespreaderandthreadthewiresthroughtheholesintheinsulatorsasshownatAinFig9.
Nexttwisttheendsofeachwiretotheringsoftheballinsulatorsandthenputthelargewithesonthemiddleofeachoftheendspreaders;fixtheotherwithesonthespreaderssothattheywillbe27inchesapartandfastentheballinsulatorstotheeyesinthewitheswiththeS-hooks.Nowslipathimblethroughtheeyeofoneofthelongstraininsulators,threadalengthofstrandedsteelwire1/4inchindiameterthroughitandfastentheendsofittotheeyesinthewithesontheendsofthespreaders.
Finallyfastena40-inchlengthofsteelstrandedwiretoeachoftheeyesofthewithesonthemiddleofeachofthespreaders,looptheotherendoverthethimbleandthenwraptheendaroundthewiresthatarefixedtotheendsofthespreaders.OneendoftheaerialisshowncompleteatBinFig.9,andfromthisyoucanseeexactlyhowitisassembled.Nowcutoffthreeorfourpiecesofwire15or20feetlongandtwistandsoldereachonetooneoftheaerialwires;thenslipthemthroughthehardrubbertubesintheleading-inspreader,bringtheirfreeendstogetherasatCandtwistandsolderthemtoalengthofwirelongenoughtoreachtoyourlightningswitchorinstruments.
MakingaGoodGround.--Whereyouhavetomakeagroundyoucandosoeitherby(1)buryingsheetsofzincorcopperinthemoistearth;(2)buryinganumberofwiresinthemoistearth,or(3)usingacounterpoise.Tomakeagroundofthefirstkindtakehalfadozenlargesheetsofcopperorzinc,cutthemintostripsafootwide,solderthemalltogetherwithotherstripsandburythemdeeplyintheground.
Itiseasiertomakeawireground,sayofasmanyormorewiresasyouhaveinyouraerialandconnectthemtogetherwithcrosswires.Toputsuchagroundintheearthyouwillhavetouseaplowtomakethefurrowsdeepenoughtoinsurethemalwaysbeingmoist.Inthecounterpoisegroundyoumakeupasystemofwiresexactlylikeyouraerial,thatis,youinsulatethemjustascarefully;thenyousupportthemsothattheywillbeasclosetothegroundaspossibleandyetnottouchitoranythingelse.Thisandtheothertwogroundsjustdescribedshouldbeplaceddirectlyundertheaerialwireifthebestresultsaretobehad.Inusingacounterpoiseyoumustbringthewirefromituptoandthroughanotherleading-ininsulatortoyourinstruments.
CHAPTERIII
SIMPLETELEGRAPHANDTELEPHONERECEIVINGSETS
Withacrystaldetectorreceivingsetyoucanreceiveeithertelegraphicdotsanddashesortelephonicspeechandmusic.Youcanbuyareceivingsetalreadyassembledoryoucanbuythedifferentpartsandassemblethemyourself.Anassembledsetislessbotherinthebeginningbutifyouliketoexperimentyoucanhookup,thatis,connecttheseparatepartstogetheryourselfanditisperhapsalittlecheapertodoitthisway.Thenagain,bysodoingyougetalotofvaluableexperienceinwirelessworkandanunderstandingoftheworkingsofwirelessthatyoucannotgetinanyotherway.
AssembledWirelessReceivingSets.--Thecheapestassembledreceivingset[Footnote:TheMarvel,madebytheRadioMfg.Co.,NewYorkCity.]advertisedisoneinwhichthedetectorandtuningcoilismountedinabox.Itcosts$15.00,andcanbeboughtofdealersinelectricsuppliesgenerally.
Thispricealsoincludesacrystaldetector,anadjustabletuningcoil,asingletelephonereceiverwithhead-bandandthewire,porcelaininsulators,lightningswitchandgroundclampfortheaerialwiresystem.Itwillreceivewirelesstelegraphandtelephonemessagesoverarangeoffrom10to25miles.
Anothercheapunitreceptor,thatis,acompletewirelessreceivingsetalreadymountedwhichcanbeusedwithasingleaerialissoldfor$25.00.[Footnote:TheAeriolaJr.,madebytheWestinghouseCompany,Pittsburgh,Pa.]Thissetincludesacrystaldetector,avariabletuningcoil,afixedcondenserandapairofheadtelephonereceivers.Itcanalsobeusedtoreceiveeithertelegraphortelephonemessagesfromdistancesupto25miles.Theaerialequipmentisnotincludedinthisprice,butitcanbeboughtforabout$2.50extra.
AssemblingYourOwnReceivingSet.--Inthischapterweshallgoonlyintotheapparatususedfortwosimplereceivingsets,bothofwhichhaveacrystaldetector.Thefirstsetincludesadouble-slidetuningcoilandthesecondsetemploysaloose-coupledtuningcoil,orloosecoupler,asitiscalledforshort.Foreithersetyoucanuseapairof2,000-or3,000-ohmheadphones.
Photographunavailableoriginal©UnderwoodandUnderwood.
GeneralPershingListeningIn.
TheCrystalDetector.--Acrystaldetectorconsistsof:(1)theframe,(2)thecrystal,and(3)thewirepoint.Thereareanynumberofdifferentdesignsforframes,theideabeingtoprovideadevicethatwill(a)holdthesensitivecrystalfirmlyinplace,andyetpermitofitsremoval,(b)topermitthewirepoint,orelectrode,tobemovedinanydirectionsothatthefreepointofitcanmakecontactwiththemostsensitivespotonthecrystaland(c)tovarythepressureofthewireonthecrystal.
Asimpledetectorframeisshowninthecross-sectionatAinFig.10;thecrystal,whichmaybegalena,siliconorironpyrites,isheldsecurelyinaholderwhilethephosphor-bronzewirepointwhichmakescontactwithit,isfixedtooneendofathreadedrodontheotherendofwhichisaknob.
Thisrodscrewsintoandthroughasleevefixedtoaballthatsetsbetweentwobrassstandardsandthispermitsanupanddownorasidetosideadjustmentofthemetalpointwhilethepressureofitonthecrystalisregulatedbythescrew.
Acrystalofthiskindisoftenenclosedinaglasscylinderandthismakesitretainitssensitivenessforamuchlongertimethanifitwereexposedtodustandmoisture.Anuprighttypeofthisdetectorcanbeboughtfor$2.25,whileahorizontaltype,asshownatB,canbeboughtfor$2.75.Galenaisthecrystalthatisgenerallyused,for,whileitisnotquiteassensitiveassiliconandironpyrites,itiseasiertoobtainasensitivepiece.
TheTuningCoil.--Itiswiththetuningcoilthatyoutuneinandtuneoutdifferentstationsandthisyoudobyslidingthecontactstoandfroovertheturnsofwire;inthiswayyouvarytheinductanceandcapacitance,thatis,theconstantsofthereceivingcircuitsandsomakethemreceiveelectricwaves,thatis,wirelesswaves,ofdifferentlengths.
TheDoubleSlideTuningCoil.--Withthistuningcoilyoucanreceivewavesfromanystationupto1,000metersinlength.OneoftheendsofthecoilofwireconnectswiththebindingpostmarkedainFig.11,andtheotherendconnectswiththeotherbindingpostmarkedb,whileoneoftheslidingcontactsisconnectedtothebindingpostc,andtheotherslidingcontactisconnectedwiththebindingpostd.
Whenconnectinginthetuningcoil,onlythepostaorthepostbisusedasmaybemostconvenient,
buttheotherendofthewirewhichisconnectedtoapostisleftfree;justbearthispointinmindwhenyoucometoconnectthetuningcoilupwiththeotherpartsofyourreceivingset.ThetuningcoilisshowncompleteatBanditcosts$3.00or$4.00.Atripleslidetuningcoilconstructedlikethedoubleslidetunerjustdescribed,onlywithmoreturnsofwireonit,makesitpossibletoreceivewavelengthsupto1,500meters.Itcostsabout$6.00.
TheLooseCoupledTuningCoil.--Withaloosecoupler,asthiskindofatuningcoiliscalledforshort,veryselectivetuningispossible,whichmeansthatyoucantuneinastationverysharply,anditwillreceiveanywavelengthsaccordingtosizeofcoils.Theprimarycoiliswoundonafixedcylinderanditsinductanceisvariedbymeansofaslidingcontactlikethedoubleslidetuningcoildescribedabove.Thesecondarycoiliswoundonacylinderthatslidesinandoutoftheprimarycoil.Theinductanceofthiscoilisvariedbymeansofaswitchthatmakescontactwiththefixedpoints,eachofwhichisconnectedwitheverytwentiethturnofwireasshowninthediagramAinFig.12.Theloosecoupler,whichisshowncompleteatB,costsintheneighborhoodof$8.00or$10.00.
FixedandVariableCondensers.--Youdonotrequireacondenserforasimplereceivingset,butifyouwillconnectafixedcondenseracrossyourheadphonesyouwillgetbetterresults,whileavariablecondenserconnectedintheclosedcircuitofadirectcoupledreceivingset,thatis,onewhereadoubleslidetuningcoilisused,makesiteasytotuneverymuchmoresharply;avariablecondenserisabsolutelynecessarywherethecircuitsareinductivelycoupled,thatis,wherealoosecoupledtunerisused.
Afixedcondenserconsistsofanumberofsheetsofpaperwithleavesoftin-foilinbetweenthemandsobuiltupthatoneendofeveryotherleafoftin-foilprojectsfromtheoppositeendofthepaperasshownatAinFig.13.Thepaperandtin-foilarethenpressedtogetherandimpregnatedwithaninsulatingcompound.Afixedcondenseroftheexactcapacitancerequiredforconnectingacrosstheheadphonesismountedinabasefittedwithbindingposts,asshownatB,andcosts75cents.(Paperones25cents.)
Avariablecondenser,seeC,oftherotatingtypeisformedofasetoffixedsemi-circularmetalplateswhichareslightlyseparatedfromeachotherandbetweentheseasimilarsetofmovablesemi-circularmetalplatesismadetointerleave;thelatteraresecuredtoashaftonthetopendofwhichisaknobandbyturningitthecapacitanceofthecondenser,and,hence,ofthecircuitinwhichitisconnected,isvaried.Thiscondenser,whichisshownatD,ismadeintwosizes,thesmalleronebeinglargeenoughforallordinarywavelengthswhilethelargeroneisforproportionatelylongerwavelengths.Thesecondenserscost$4.00and$5.00respectively.
AboutTelephoneReceivers.--Thereareanumberofmakesofheadtelephonereceiversonthemarketthataredesignedespeciallyforwirelesswork.Thesephonesarewoundtoresistancesoffrom75ohmsto8,000ohms,andcostfrom$1.25forareceiverwithoutacordorheadbandto$15.00forapairofphoneswithacordandheadband.Youcangetareceiverwoundtoanyresistanceinbetweentheabovevaluesbutforeitherofthesimplereceivingsetssuchasdescribedinthischapteryououghttohaveapairwoundtoatleast2,000ohmsandthesewillcostyouabout$5.00.ApairofheadphonesofthistypeisshowninFig.14.
ConnectingUptheParts--ReceivingSetNo.1.--Forthissetget(1)acrystaldetector,(2)atwo-slidetuningcoil,(3)afixedcondenser,and(4)apairof2,000ohmheadphones.Mountthedetectorontheright-handsideofaboardandthetuningcoilontheleft-handside.ScrewintwobindingpostsforthecordendsofthetelephonereceiversataandbasshownatAinFig.15.Thisdoneconnectoneoftheendbindingpostsofthetuningcoilwiththegroundwireandapostofoneofthecontactslideswiththelightningarresterorswitchwhichleadstotheaerialwire.
Nowconnectthepostoftheothercontactslidetooneofthepostsofthedetectorandtheotherpostofthelatterwiththebindingposta,thenconnectthebindingpostbtothegroundwireandsolderthejoint.Nextconnecttheendsofthetelephonereceivercordtothepostsaandbandconnectafixedcondenseralsowiththeseposts,allofwhichareshowninthewiringdiagramatB,andyouarereadytoadjustthesetforreceiving.
ReceivingSetNo.2.--UsethesamekindofadetectorandpairofheadphonesasforSetNo.1,butget(1)aloosecoupledtuningcoil,and(2)avariablecondenser.Mounttheloosecoupleratthebackofaboardontheleft-handsideandthevariablecondenserontheright-handside.Thenmountthedetectorinfrontofthevariablecondenserandscrewtwobindingposts,aandb,infrontofthetuningcoilasshownatAinFig.16.
Nowconnectthepostoftheslidingcontactoftheloosecouplerwiththewirethatrunstothelightningswitchandthencetotheaerial;connectthepostoftheprimarycoil,whichistheoutsidecoil,withthegroundwire;thenconnectthebindingpostleadingtotheswitchofthesecondarycoil,whichistheinsidecoil,withoneofthepostsofthevariablecondenser,andfinally,connectthepostthatisjoinedtooneendofthesecondarycoilwiththeotherpostofthevariablecondenser.
Thisdone,connectoneofthepostsofthecondenserwithoneofthepostsofthedetector,theotherpostofthedetectorwiththebindingposta,andthepostbtotheotherpostofthevariablecondenser.Nextconnectafixedcondensertothebindingpostsaandbandthenconnectthetelephonereceiverstothesesameposts,allofwhichisshowninthewiringdiagramatB.Youarenowreadytoadjusttheinstruments.InmakingtheconnectionsuseNo.16or18insulatedcopperwireandscrapetheendscleanwheretheygointothebindingposts.See,also,thatalloftheconnectionsaretightandwhereyouhavetocrossthewireskeepthemapartbyaninchorsoandalwayscrossthematrightangles.
AdjustingtheNo.1Set--TheDetector.--Thefirstthingtodoistotestthedetectorinordertofindoutifthepointofthecontactwireisonasensitivespotofthecrystal.Todothisyouneedabuzzer,aswitchandadrycell.Anelectricbellfromwhichthegonghasbeenremovedwilldoforthebuzzer,butyoucangetonethatismadespeciallyforthepurpose,for75cents,whichgivesoutaclear,high-pitchednotethatsoundslikeahigh-powerstation.
Connectoneofthebindingpostsofthebuzzerwithonepostoftheswitch,theotherpostofthelatterwiththezincpostofthedrycellandthecarbonpostofthistotheotherpostofthebuzzer.Thenconnectthepostofthebuzzerthatisjoinedtothevibrator,tothegroundwireasshowninthewiringdiagram,Fig.17.Nowclosetheswitchofthebuzzercircuit,putonyourheadphones,andmovethewirepointofthedetectortovariousspotsonthecrystaluntilyouhearthesparksmadebythebuzzer
inyourphones.
Thenvarythepressureofthepointonthecrystaluntilyouhearthesparksasloudaspossible.Afteryouhavemadetheadjustmentopentheswitchanddisconnectthebuzzerwirefromthegroundwireofyourset.Thisdone,beverycarefulnottojarthedetectororyouwillthrowitoutofadjustmentandthenyouwillhavetodoitalloveragain.Youarenowreadytotunethesetwiththetuningcoilandlistenin.
TheTuningCoil.--TotunethissetmovetheslideAofthedouble-slidetuner,seeBinFig.15,overtotheendofthecoilthatisconnectedwiththegroundwireandtheslideBneartheoppositeendofthecoil,thatis,theonethathasthefreeend.NowmovetheslideAtowardtheBslideandwhenyouhearthedotsanddashes,orspeechormusic,thatiscominginasloudasyoucanmovetheBslidetowardtheAslideuntilyouhearstillmoreloudly.Averyfewtrialsonyourpartandyouwillbeabletotuneinortuneoutanystationyoucanhear,ifnottoocloseorpowerful.
Photographunavailableoriginal©UnderwoodandUnderwood.
TheWorld'sLargestRadioReceivingStation.OwnedbytheRadioCorporationofAmericaatRocky
PointnearPointJefferson,L.I.
AdjustingtheNo.2Set.--FirstadjustthecrystaldetectorwiththebuzzersetasdescribedabovewithSetNo.1,thenturntheknobofyourvariablecondensersothatthemovableplatesarejusthalf-wayin,pullthesecondarycoilofyourloose-coupledtunerhalfwayout;turntheswitchleveronituntilitmakesacontactwiththemiddlecontactpointandsettheslideroftheprimarycoilhalfwaybetweentheends.
Nowlisteninfortelegraphicsignalsortelephonicspeechormusic;whenyouhearoneortheotherslidethesecondarycoilinandoutoftheprimarycoiluntilthesoundsareloudest;nowmovethecontactswitchoverthepointsforthandbackuntilthesoundsarestilllouder,thenmovetheslidertoandfrountilthesoundsareyetlouderand,finally,turntheknobofthecondenseruntilthesoundsareclearandcrisp.Whenyouhavedoneallofthesethingsyouhave,intheparlanceofthewirelessoperator,tunedinandyouarereadytoreceivewhateverisbeingsent.
CHAPTERIV
SIMPLETELEGRAPHSENDINGSETS
Awirelesstelegraphtransmittingsetcanbeinstalledforaverysmallamountofmoneyprovidedyouarecontentwithonethathasalimitedrange.Largerandbetterinstrumentscan,ofcourse,behadformoremoney,buthowevermuchyouarewillingtospendstillyouarelimitedinyoursendingradiusbytheGovernment'srulesandregulations.Thebestway,andthecheapestintheend,toinstallatelegraphsetistobuytheseparatepartsandhookthemupyourself.
Theusualtypeofwirelesstelegraphtransmitteremploysadisruptivedischarge,orspark,asitiscalled,forsettinguptheoscillatingcurrentsintheaerialwiresystemandthisisthetypeofapparatusdescribedinthischapter.Therearetwowaystosetupthesparksandtheseare:(1)withaninductioncoil,orspark-coil,asitiscommonlycalled,and(2)withanalternatingcurrenttransformer,orpowertransformer,asitissometimescalled.Whereyouhavetogeneratethecurrentwithabatteryyoumustuseasparkcoil,butifyouhavea110-voltdirectoralternatinglightingcurrentinyourhomeyoucanuseatransformerwhichwillgiveyoumorepower.
ACheapTransmittingSet(No.1).--Forthissetyouwillneed:(1)aspark-coil,(2)abatteryofdrycells,(3)atelegraphkey,(4)asparkgap,(5)ahigh-tensioncondenser,and(6)anoscillationtransformer.Therearemanydifferentmakesandstylesofthesepartsbutinthelastanalysisallofthemarebuiltonthesameunderlyingbasesandworkonthesamefundamentalprinciples.
TheSpark-Coil.--Sparkcoilsforwirelessworkaremadetogivesparksfrom1/4inchinlengthupto6inchesinlength,butasasparkcoilthatgiveslessthana1-inchsparkhasaverylimitedoutputitisbesttogetacoilthatgivesatleasta1-inchspark,asthisonlycostsabout$8.00,andifyoucangeta2-ora4-inchsparkcoilsomuchthebetter.TherearetwogeneralstylesofsparkcoilsusedforwirelessandtheseareshownatAandBinFig.18.
Asparkcoilofeitherstyleconsistsof(a)asoftironcoreonwhichiswound(b)acoupleoflayersofheavyinsulatedwireandthisiscalledtheprimarycoil,(c)whileoverthis,butinsulatedfromit,iswoundalargenumberofturnsofveryfineinsulatedcopperwirecalledthesecondarycoil;(d)aninterrupter,orvibrator,asitiscommonlycalled,and,finally,(e)acondenser.Thecore,primaryandsecondarycoilsformaunitandthesearesetinaboxormountedontopofahollowwoodenbase.Thecondenserisplacedinthebottomofthebox,oronthebase,whilethevibratorismountedononeendoftheboxorontopofthebase,anditistheonlypartofthecoilthatneedsadjusting.
Thevibratorconsistsofastiff,flatspringfixedatoneendtotheboxorbasewhileitcarriesapieceofsoftironcalledanarmatureonitsfreeendandthissetsclosetooneendofthesoftironcore.Insulatedfromthisspringisastandardthatcarriesanadjustingscrewonthesmallendofwhichisaplatinumpointandthismakescontactwithasmallplatinumdiskfixedtothespring.ThecondenserisformedofalternatesheetsofpaperandtinfoilbuiltupinthesamefashionasthereceivingcondenserdescribedunderthecaptionofFixedandVariableCondensers,inChapterIII.
ThewiringdiagramCshowshowthesparkcoiliswiredup.Oneofthebatterybindingpostsisconnectedwithoneendoftheprimarycoilwhiletheotherendofthelatterwhichiswoundonthesoftironcoreconnectswiththespringofthevibrator.Theotherbatterybindingpostconnectswiththestandardthatsupportstheadjustingscrew.Thecondenserisshuntedacrossthevibrator,thatis,oneendofthecondenserisconnectedwiththespringandtheotherendofthecondenserisconnectedwiththeadjustingscrewstandard.Theendsofthesecondarycoilleadtotwobindingposts,whichareusuallyplacedontopofthesparkcoilanditistothesethatthesparkgapisconnected.
TheBattery.--Thiscanbeformedofdrycellsoryoucanuseastoragebatterytoenergizeyourcoil.Forallcoilsthatgivelessthana1-inchsparkyoushoulduse5drycells;for1-and2-inchsparkcoilsuse6or8drycells,andfor3to4-inchsparkcoilsuse8to10drycells.Thewaythedrycellsareconnectedtogethertoformabatterywillbeshownpresently.AdrycellisshownatAinFig,19.
TheTelegraphKey.--YoucanuseanordinaryMorsetelegraphkeyforthesendingsetandyoucangetonewithajapannedironbasefor$1.50(orbetter,onemadeofbrassandwhichhas1/8-inchsilvercontactpointsfor$3.00.AkeyofthelatterkindisshownatB).
TheSparkgap.--Itisinthesparkgapthatthehightensionsparktakesplace.Theapparatusinwhichthesparktakesplaceisalsocalledthesparkgap.Itconsistsofapairofzincplugs,calledelectrodes,fixedtotheendsofapairofthreadedrods,withknobsontheotherends,andthesescrewintoandthroughapairofstandardsasshownatc.Thisiscalledafixed,orstationarysparkgapandcostsabout$1.00.
TheTuningCoil.--Thetransmittinginductance,orsendingtuningcoil,consistsof20to30turnsofNo.8or9harddrawncopperwirewoundonaslottedinsulatedformandmountedonawoodenbase.Itisprovidedwithclipssothatyoucancutinandcutoutasmanyturnsofwireasyouwishandsotunethesendingcircuitstosendoutwhateverwavelengthyoudesire.Itisshownatd,andcostsabout$5.00.SeealsoOscillationTransformer,page63[ChapterIV].
TheHighTensionCondenser.--Hightensioncondensers,thatis,condenserswhichwillstandupunderhighpotentials,orelectricpressures,canbeboughtinunitsorsections.Thesecondensersaremadeupofthinbrassplatesinsulatedwithaspecialcompoundandpressedintoacompactform.Thecapacitance[Footnote:Thisisthecapacityofthecondenser.]ofonesectionisenoughforatransmittingsetusingasparkcoilthatgivesa2inchsparkorlessandtwosectionsconnectedtogethershouldbeusedforcoilsgivingfrom2to4inchsparks.Itisshownate.
ConnectingUptheApparatus.--Yoursendingsetshouldbemountedonatable,orabench,whereitneednotbemoved.Placethekeyinaboutthemiddleofthetableanddowninfront,andthesparkcoiltotheleftandwelltothebackbutsothatthevibratorendwillbetotheright,asthiswillenableyoutoadjustiteasily.Placethebatterybackofthesparkcoilandthetuningcoil(oscillationtransformer)totherightofthesparkcoilandbackofthekey,allofwhichisshowninthelayoutatAinFig.20.
Forthelowvoltagecircuit,thatisthebatterycircuit,useNo.12or14insulatedcopperwire.Connectallofthedrycellstogetherinseries,thatis,connectthezincofonecellwiththecarbonofthenextandsoonuntilallofthemareconnectedup.Thenconnectthecarbonoftheendcellwithoneofthe
postsofthekey,thezincoftheotherendcellwithoneoftheprimarypostsofthesparkcoilandtheotherprimarypostofthesparkcoilwiththeotherpostofthekey,whentheprimarycircuitwillbecomplete.
Forthehightensioncircuits,thatis,theoscillationcircuits,youmayuseeitherbareorinsulatedcopperwirebutyoumustbecarefulthattheydonottouchthetable,eachother,oranypartoftheapparatus,except,ofcourse,thepoststheyareconnectedwith.Connectoneofthepostsofthesecondarycoilofthesparkcoilwithoneofthepostsofthesparkgap,andtheotherpostwithoneofthepostsofthecondenser;thenconnecttheotherpostofthecondenserwiththelowerspringclipofthetuningcoilandalsoconnectthisclipwiththeground.Thisdone,connectthemiddlespringclipwithoneofthepostsofthesparkgap,and,finally,connectthetopclipwiththeaerialwireandyourtransmittingsetisreadytobetuned.AwiringdiagramoftheconnectionsisshownatB.AsthissetistunedinthesamewayasSetNo.2whichfollows,youarereferredtotheendofthischapter.
ABetterTransmittingSet(No.2).--Theapparatusforthissetincludes:(1)analternatingcurrenttransformer,(2)awirelesstelegraphkey,(3)afixed,arotary,oraquenchedsparkgap,(4)acondenser,and(5)anoscillationtransformer.Ifyouhavea110voltdirectlightingcurrentinyourhomeinsteadof110voltalternatingcurrent,thenyouwillalsoneed(6)anelectrolyticinterrupter,forinthiscasetheprimarycircuitofthetransformermustbemadeandbrokenrapidlyinordertosetupalternatingcurrentsinthesecondarycoil.
TheAlternatingCurrentTransformer.--Analternatingcurrent,orpower,transformerismadeonthesameprincipleasasparkcoil,thatis,ithasasoftironcore,aprimarycoilformedofacoupleoflayersofheavywire,andasecondarycoilwoundupofalargenumberofturnsofveryfinewire.Unlikethesparkcoil,however,whichhasanopenmagneticcoreandwhosesecondarycoiliswoundontheprimarycoil,thetransformerhasaclosedmagneticcore,withtheprimarycoilwoundononeofthelegsofthecoreandthesecondarywoundontheotherleg.Ithasneitheravibratornoracondenser.AplaintransformerisshownatAinFig.21.
Atransformerofthiskindcanbeboughteither(a)unmounted,thatis,justthebaretransformer,or(b)fullymounted,thatis,fittedwithanironstand,mountedonaninsulatingbaseonwhichareapairofprimarybindingposts,whilethesecondaryisprovidedwithasafetysparkgap.Therearethreesizesoftransformersofthiskindmadeandtheyareratedat1/4,1/2and1kilowatt,respectively,theydeliverasecondarycurrentof9,000,11,000and25,000volts,accordingtosize,andcost$16.00,$22.00and$33.00whenfullymounted;areductionof$3.00,$4.00and$5.00ismadewhentheyareunmounted.Allofthesetransformersoperateon110volt,60cyclecurrentandcanbeconnecteddirectlytothesourceofalternatingcurrent.
TheWirelessKey.--ForthistransmittingsetastandardwirelesskeyshouldbeusedasshownatB.Itismadeaboutthesameasaregulartelegraphkeybutitismuchheavier,thecontactpointsarelargerandinsteadofthecurrentbeingledthroughthebearingsasinanordinarykey,itiscarriedbyheavyconductorsdirectlytothecontactpoints.Thiskeyismadeinthreesizesandthefirstwillcarryacurrentof5amperes[Footnote:SeeAppendixfordefinition.]andcosts$4.00,thesecondwillcarryacurrentof10amperesandcosts$6.50,whilethethirdwillcarryacurrentof20amperesandcosts$7.50.
TheSparkGap.--Eitherafixed,arotary,oraquenchedsparkgapcanbeusedwiththisset,buttheformerisseldomusedexceptwithspark-coilsets,asitisveryhardtokeepthesparksfromarcingwhenlargecurrentsareused.Arotarysparkgapcomprisesawheel,drivenbyasmallelectricmotor,withprojectingplugs,orelectrodes,onitandapairofstationaryplugsoneachsideofthewheelas
shownatC.Thenumberofsparkspersecondcanbevariedbychangingthespeedofthewheelandwhenitisrotatedrapidlyitsendsoutsignalsofahighpitchwhichareeasytoreadatthereceivingend.Arotarygapwitha110-voltmotorcostsabout$25.00.
Aquenchedsparkgapnotonlyeliminatesthenoiseoftheordinarygapbut,whenproperlydesigned,itincreasestherangeofaninductioncoilsetsome200percent.A1/4kilowattquenchedgapcosts$10.00.[Footnote:SeeAppendixfordefinition.]
TheHighTensionCondenser.--Since,ifyouareanamateur,youcanonlysendoutwavesthatare200metersinlength,youcanonlyuseacondenserthathasacapacitanceof.007microfarad.[Footnote:SeeAppendixfordefinition.]AsectionalhightensioncondenserliketheonedescribedinconnectionwithSetNo.1canbeusedwiththissetbutitmusthaveacapacitanceofnotmorethan.007microfarad.Acondenserofthisvaluefora1/4-kilowatttransformercosts$7.00;fora1/2-kilowatttransformer$14.00,andfora1-kilowatttransformer$21.00.SeeE,Fig.19.
TheOscillationTransformer.--Withanoscillationtransformeryoucantunemuchmoresharplythanwithasingleinductancecoiltuner.Theprimarycoilisformedof6turnsofcopperstrip,orNo.9copperwire,andthesecondaryisformedof9turnsofstrip,orwire.Theprimarycoil,whichistheoutsidecoil,ishingedtothebaseandcanberaisedorloweredlikethelidofabox.Whenitisloweredtheprimaryandsecondarycoilsareinthesameplaneandwhenitisraisedthecoilssetatanangletoeachother.ItisshownatDandcosts$5.00.
ConnectingUptheApparatus.ForAlternatingCurrent.--Screwthekeytothetableaboutthemiddleofitandnearthefrontedge;placethehightensioncondenserbackofitandtheoscillationtransformerbackofthelatter;setthealternatingcurrenttransformertotheleftoftheoscillationtransformerandplacetherotaryorquenchedsparkgapinfrontofit.
NowbringapairofNo.12or14insulatedwiresfromthe110voltlightingleadsandconnectthemwithasingle-throw,double-poleswitch;connectonepoleoftheswitchwithoneofthepostsoftheprimarycoilofthealternatingpowertransformerandconnecttheotherpostofthelatterwithoneofthepostsofyourkey,andtheotherpostofthiswiththeotherpoleoftheswitch.Nowconnectthemotoroftherotarysparkgaptothepowercircuitandputasingle-pole,single-throwswitchinthemotorcircuit,allofwhichisshownatAinFig.22.
Nextconnectthepostsofthesecondarycoiltothepostsoftherotaryorquenchedsparkgapandconnectonepostofthelattertoonepostofthecondenser,theotherpostofthistothepostoftheprimarycoiloftheoscillationtransformer,whichistheinsidecoil,andtheclipoftheprimarycoiltotheothersparkgappost.Thiscompletestheclosedoscillationcircuit.Finallyconnectthepostofthesecondarycoiloftheoscillationtransformertothegroundandtheclipofittothewireleadingtotheaerialwhenyouarereadytotunetheset.AwiringdiagramoftheconnectionsisshownatB.
ForDirectCurrent.--Whereyouhave110voltdirectcurrentyoumustconnectinanelectrolyticinterrupter.Thisinterrupter,whichisshownatAandBinFig.23,consistsof(1)ajarfilledwithasolutionof1partofsulphuricacidand9partsofwater,(2)aleadelectrodehavingalargesurfacefastenedtothecoverofsurfacethatsetsinaporcelainsleeveandwhoseendrestsonthebottomofthejar.
Whentheseelectrodesareconnectedinserieswiththeprimaryofalargesparkcoiloranalternatingcurrenttransformer,seeC,andadirectcurrentoffrom40to110voltsismadetopassthroughit,thecurrentismadeandbrokenfrom1,000to10,000timesaminute.Byraisingorloweringthesleeve,thusexposingmoreorlessoftheplatinum,oralloypoint,thenumberofinterruptionsperminutecanbevariedatwill.Astheelectrolyticinterrupterwillonlyoperateinonedirection,youmustconnectitwithitsplatinum,oralloyanode,tothe+orpositivepowerleadandtheleadcathodetothe-ornegativepowerlead.Youcanfindoutwhichiswhichbyconnectingintheinterrupterandtryingit,oryoucanuseapolarityindicator.Anelectrolyticinterruptercanbeboughtforaslittleas$3.00.
HowtoAdjustYourTransmitter.TuningWithaHotWireAmmeter.--Atransmittercanbetunedintwodifferentwaysandtheseare:(1)byadjustingthelengthofthesparkgapandthetuningcoilsothatthegreatestamountofenergyissetupintheoscillatingcircuits,and(2)byadjustingtheapparatussothatitwillsendoutwavesofagivenlength.
Toadjustthetransmittersothatthecircuitswillbeintuneyoushouldhaveahotwireammeter,orradiationammeter,asitiscalled,whichisshowninFig.24.Itconsistsofathinplatinumwire
throughwhichthehigh-frequencycurrentssurgeandtheseheatit;theexpansionandcontractionofthewiremovesaneedleoverascalemarkedoffintofractionsofanampere.Whenthesparkgapandtuningcoilofyoursetareproperlyadjusted,theneedlewillswingfarthesttotherightoverthescaleandyouwillthenknowthattheaerialwiresystem,oropenoscillationcircuit,andtheclosedoscillationcircuitareintuneandradiatingthegreatestamountofenergy.
ToSendOuta200MeterWaveLength.--Ifyouareusingacondenserhavingacapacitanceof.007microfarad,whichisthelargestcapacityvaluethattheGovernmentwillallowanamateurtouse,thenifyouhaveahotwireammeterinyouraerialandtunetheinductancecoilorcoilsuntiltheammetershowsthelargestamountofenergyflowingthroughityouwillknowthatyourtransmitteristunedandthattheaerialissendingoutwaveswhoselengthis200meters.Totunetodifferentwavelengthsyoumusthaveawave-meter.
TheUseoftheAerialSwitch.--Whereyouintendtoinstallbothatransmitterandareceptoryouwillneedathrowoverswitch,oraerialswitch,asitiscalled.Anordinarydouble-pole,double-throwswitch,asshownatAinFig.25,canbeused,oraswitchmadeespeciallyforthepurposeasatBishandierbecausethearcofthethrowismuchless.
AerialSwitchforaCompleteSendingandReceivingSet.--Youcanbuyadouble-pole,double-throwswitchmountedonaporcelainbaseforabout75centsandthiswillserveforSetNo.1.Screwthisswitchonyourtablebetweenthesendingandreceivingsetsandthenconnectoneofthemiddlepostsofitwiththegroundwireandtheothermiddlepostwiththelightningswitchwhichconnectswiththeaerial.Connectthepostofthetuningcoilwithoneoftheendpostsoftheswitchandtheclipofthetuningcoilwiththeotherandcomplementarypostoftheswitch.Thisdone,connectoneoftheoppositeendpostsoftheswitchtothepostofthereceivingtuningcoilandconnecttheslidingcontactofthelatterwiththeotherandcomplementarypostoftheswitchasshowninFig.26.
ConnectingintheLightningSwitch.--Theaerialwireconnectswiththemiddlepostofthelightningswitch,whileoneoftheendpostsleadtooneofthemiddlepostsoftheaerialswitch.Theotherendpostofthelightningswitchleadstoaseparategroundoutsidethebuilding,asthewiringdiagramsFigs.26and27show.
CHAPTERV
ELECTRICITYSIMPLYEXPLAINED
Itiseasytounderstandhowelectricitybehavesandwhatitdoesifyougettherightideaofitatthestart.Inthefirstplace,ifyouwillthinkofelectricityasbeingafluidlikewateritsfundamentalactionswillbegreatlysimplified.Bothwaterandelectricitymaybeatrestorinmotion.Whenatrest,undercertainconditions,eitheronewilldeveloppressure,andthispressurewhenreleasedwillcausethemtoflowthroughtheirrespectiveconductorsandthusproduceacurrent.
ElectricityatRestandinMotion.--Anywireoraconductorofanykindcanbechargedwithelectricity,butaLeydenjar,orothercondenser,isgenerallyusedtoholdanelectricchargebecauseithasamuchlargercapacitance,asitscapacityiscalled,thanawire.Asasimpleanalogueofacondenser,supposeyouhaveatankofwaterraisedaboveasecondtankandthattheseareconnectedtogetherbymeansofapipewithavalveinit,asshownatAinFig.28.
Photographunavailableoriginal©UnderwoodandUnderwood.
FirstWirelessCollegeintheWorld,atTuftsCollege,Mass.
Nowifyoufilltheuppertankwithwaterandthevalveisturnedoff,nowatercanflowintothelowertankbutthereisadifferenceofpressurebetweenthem,andthemomentyouturnthevalveonacurrentofwaterwillflowthroughthepipe.Inverymuchthesamewaywhenyouhaveacondenserchargedwithelectricitythelatterwillbeunderpressure,thatis,adifferenceofpotentialwillbesetup,foroneofthesheetsofmetalwillbechargedpositivelyandtheotherone,whichisinsulatedfromit,willbechargednegatively,asshownatB.Onclosingtheswitchtheoppositechargesrushtogetherandformacurrentwhichflowstoandfrobetweenthemetalplates.[Footnote:Strictlyspeakingitisthedifferenceofpotentialthatsetsuptheelectromotiveforce.]
TheElectricCurrentandItsCircuit.--Justaswaterflowingthroughapipehasquantityandpressure
backofitandthepipeoffersfrictiontoitwhichtendstoholdbackthewater,so,likewise,doeselectricityflowinginacircuithave:(1)quantity,orcurrentstrength,orjustcurrent,asitiscalledforshort,oramperage,and(2)pressure,orpotentialdifference,orelectromotiveforce,orvoltage,asitisvariouslycalled,andthewire,orcircuit,inwhichthecurrentisflowinghas(3)resistancewhichtendstoholdbackthecurrent.
Adefiniterelationexistsbetweenthecurrentanditselectromotiveforceandalsobetweenthecurrent,electromotiveforceandtheresistanceofthecircuit;andifyouwillgetthisrelationshipclearlyinyourmindyouwillhaveaverygoodinsightintohowdirectandalternatingcurrentsact.Tokeepaquantityofwaterflowinginaloopofpipe,whichwewillcallthecircuit,pressuremustbeappliedtoitandthismaybedonebyarotarypumpasshownatAinFig.29;inthesameway,tokeepaquantityofelectricityflowinginaloopofwire,orcircuit,abattery,orothermeansforgeneratingelectricpressuremustbeused,asshownatB.
Ifyouhaveaclosedpipeconnectedwithapistonpump,asatC,asthepistonmovestoandfrothewaterinthepipewillmovefirstonewayandthentheother.Soalsowhenanalternatingcurrentgeneratorisconnectedtoawirecircuit,asatD,thecurrentwillflowfirstinonedirectionandthenintheother,andthisiswhatiscalledanalternatingcurrent.
CurrentandtheAmpere.--Theamountofwaterflowinginaclosedpipeisthesameatallpartsofitandthisisalsotrueofanelectriccurrent,inthatthereisexactlythesamequantityofelectricityatonepointofthecircuitasthereisatanyother.
Theamountofelectricity,orcurrent,flowinginacircuitinasecondismeasuredbyaunitcalledtheampere,[Footnote:FordefinitionofampereseeAppendix.]anditisexpressedbythesymbolI.[Footnote:ThisisbecausetheletterCisusedforthesymbolofcapacitance]Justtogiveyouanideaofthequantityofcurrentanampereiswewillsaythatadrycellwhenfreshgivesacurrentofabout20amperes.Tomeasurethecurrentinamperesaninstrumentcalledanammeterisused,asshownatAinFig.30,andthisisalwaysconnectedinserieswiththeline,asshownatB.
ElectromotiveForceandtheVolt.--Whenyouhaveapipefilledwithwateroracircuitchargedwithelectricityandyouwanttomakethemflowyoumustuseapumpinthefirstcaseandabatteryoradynamointhesecondcase.Itisthebatteryordynamothatsetsuptheelectricpressureasthecircuititselfisalwayschargedwithelectricity.
Themorecellsyouconnecttogetherinseriesthegreaterwillbetheelectricpressuredevelopedandthemorecurrentitwillmovealongjustastheamountofwaterflowinginapipecanbeincreasedbyincreasingthepressureofthepump.Theunitofelectromotiveforceisthevolt,andthisistheelectricpressurewhichwillforceacurrentof1amperethrougharesistanceof1ohm;itisexpressedbythesymbolE.Afreshdrycellwilldeliveracurrentofabout1.5volts.Tomeasurethepressureofacurrentinvoltsaninstrumentcalledavoltmeterisused,asshownatCinFig.30,andthisisalwaysconnectedacrossthecircuit,asshownatD.
ResistanceandtheOhm.--Justasawaterpipeoffersacertainamountofresistancetotheflowofwaterthroughit,soacircuitopposestheflowofelectricityinitandthisiscalledresistance.Further,inthesamewaythatasmallpipewillnotallowalargeamountofwatertoflowthroughit,so,too,athinwirelimitstheflowofthecurrentinit.
Ifyouconnectaresistancecoilinacircuititactsinthesamewayaspartlyclosingthevalveinapipe,asshownatAandBinFig.31.Theresistanceofacircuitismeasuredbyaunitcalledtheohm,anditisexpressedbythesymbolR.ANo.10,BrownandSharpegaugesoftcopperwire,1,000feetlong,hasaresistanceofabout1ohm.Tomeasuretheresistanceofacircuitanapparatuscalledaresistancebridgeisused.Theresistanceofacircuitcan,however,beeasilycalculated,asthefollowingshows.
WhatOhm'sLawIs.--If,now,(1)youknowwhatthecurrentflowinginacircuitisinamperes,andtheelectromotiveforce,orpressure,isinvolts,youcantheneasilyfindwhattheresistanceisinohmsofthecircuitinwhichthecurrentisflowingbythisformula:
VoltsE
---------=Ohms,or---=R
AmperesI
Thatis,ifyoudividethecurrentinamperesbytheelectromotiveforceinvoltsthequotientwillgiveyoutheresistanceinohms.
Or(2)ifyouknowwhattheelectromotiveforceofthecurrentisinvoltsandtheresistanceofthecircuitisinohmsthenyoucanfindwhatthecurrentflowinginthecircuitisinamperes,thus:
VoltsE
-----=Amperes,or---=I
OhmsR
Thatis,bydividingtheresistanceofthecircuitinohms,bytheelectromotiveforceofthecurrentyouwillgettheamperesflowinginthecircuit.
Finally(3)ifyouknowwhattheresistanceofthecircuitisinohmsandthecurrentisinamperesthenyoucanfindwhattheelectromotiveforceisinvoltssince:
OhmsxAmperes=Volts,orRxI=E
Thatis,ifyoumultiplytheresistanceofthecircuitinohmsbythecurrentinamperestheresultwillgiveyoutheelectromotiveforceinvolts.
Fromthisyouwillseethatifyouknowthevalueofanytwooftheconstantsyoucanfindthevalueoftheunknownconstantbyasimplearithmeticalprocess.ThisrelationbetweenthesethreeconstantsisknownasOhm'sLawandastheyareveryimportantyoushouldmemorizethem.
WhattheWattandKilowattAre.--JustashorsepowerorH.P.,istheunitofworkthatsteamhasdoneorcando,sothewattistheunitofworkthatanelectriccurrenthasdoneorcando.Tofindthewattsacurrentdevelopsyouneedonlytomultiplytheamperesbythevolts.Thereare746wattsto1horsepower,and1,000wattsareequalto1kilowatt.
ElectromagneticInduction.--Toshowthatacurrentofelectricitysetsupamagneticfieldaroundityouhaveonlytoholdacompassoverawirewhoseendsareconnectedwithabatterywhentheneedlewillswingatrightanglestothelengthofthewire.Bywindinganinsulatedwireintoacoilandconnectingtheendsofthelatterwithabatteryyouwillfind,ifyoutestitwithacompass,thatthecoilismagnetic.
ThisisduetothefactthattheenergyofanelectriccurrentflowinginthewireispartlychangedintomagneticlinesofforcewhichrotateatrightanglesaboutitasshownatAinFig.32.Themagneticfieldproducedbythecurrentflowinginthecoilispreciselythesameasthatsetupbyapermanentsteelmagnet.Conversely,whenamagneticlineofforceissetupapartofitsenergygoestomakeupelectriccurrentswhichwhirlaboutinalikemanner,asshownatB.
Self-inductionorInductance.--Whenacurrentismadetoflowinacoilofwirethemagneticlinesofforceproducedareconcentrated,asatC,justasalensconcentratesraysoflight,andthisformsanintensemagneticfield,asitiscalled.Nowifabarofsoftironisbroughtclosetooneendofthecoilofwire,or,betterstill,ifitispushedintothecoil,itwillbemagnetizedbyelectromagneticinduction,seeD,anditwillremainamagnetuntilthecurrentiscutoff.
MutualInduction.--Whentwoloopsofwire,orbetter,twocoilsofwire,areplacedclosetogethertheelectromagneticinductionbetweenthemisreactive,thatis,whenacurrentismadetoflowthroughoneofthecoilsclosedmagneticlinesofforcearesetupandwhenthesecuttheotherlooporturnsofwireoftheothercoil,theyinturnproduceelectriccurrentsinit.
Itisthemutualinductionthattakesplacebetweentwocoilsofwirewhichmakesitpossibletotransformlowvoltagecurrentsfromabatteryora110voltsourceofcurrentintohighpressurecurrents,orhighpotentialcurrents,astheyarecalled,bymeansofasparkcoiloratransformer,aswellastostepupandstepdownthepotentialofthehighfrequencycurrentsthataresetupinsendingandreceivingoscillationtransformers.Softironcoresarenotusedinoscillationinductancecoilsandoscillationtransformersforthereasonthatthefrequencyofthecurrentissohightheironwouldnothavetimetomagnetizeanddemagnetizeandsowouldnothelpalongthemutualinductiontoanyappreciableextent.
High-FrequencyCurrents.--Highfrequencycurrents,orelectricoscillationsastheyarecalled,arecurrentsofelectricitythatsurgetoandfroinacircuitamilliontimes,moreorless,persecond.Currentsofsuchhighfrequencieswilloscillate,thatis,surgetoandfro,inanopencircuit,suchasanaerialwiresystem,aswellasinaclosedcircuit.
Nowthereisonlyonemethodbywhichcurrentsofhighfrequency,orradio-frequency,astheyaretermed,canbesetupbysparktransmitters,andthisisbydischargingachargedcondenserthroughacircuithavingasmallresistance.Tochargeacondenserasparkcoiloratransformerisusedandtheendsofthesecondarycoil,whichdeliversthehighpotentialalternatingcurrent,areconnectedwiththecondenser.Todischargethecondenserautomaticallyaspark,oranarc,ortheflowofelectronsinavacuumtube,isemployed.
ConstantsofanOscillationCircuit.--Anoscillationcircuit,aspointedoutbefore,isoneinwhichhighfrequencycurrentssurgeoroscillate.Nowthenumberoftimesahighfrequencycurrentwillsurgeforthandbackinacircuitdependsuponthreefactorsofthelatterandthesearecalledtheconstantsofthecircuit,namely:(1)itscapacitance,(2)itsinductanceand(3)itsresistance.
WhatCapacitanceIs.--Thewordcapacitancemeanstheelectrostaticcapacityofacondenseroracircuit.Thecapacitanceofacondenseroracircuitisthequantityofelectricitywhichwillraiseitspressure,orpotential,toagivenamount.Thecapacitanceofacondenseroracircuitdependsonitssizeandformandthevoltageofthecurrentthatischargingit.
Thecapacitanceofacondenseroracircuitisdirectlyproportionaltothequantityofelectricitythatwillkeepthechargeatagivenpotential.Thefarad,whosesymbolisM,istheunitofcapacitanceandacondenseroracircuittohaveacapacitanceofonefaradmustbeofsuchsizethatonecoulomb,whichistheunitofelectricalquantity,willraiseitschargetoapotentialofonevolt.Sincethefaradisfartoolargeforpracticalpurposesamillionthofafarad,ormicrofarad,whosesymbolismfd.,isused.
WhatInductanceIs.--Underthesub-captionofSelf-inductionandInductanceinthebeginningofthischapteritwasshownthatitwastheinductanceofacoilthatmakesacurrentflowingthroughitproduceastrongmagneticfield,andhere,asoneoftheconstantsofanoscillationcircuit,itmakesahigh-frequencycurrentactasthoughitpossessedinertia.
Inertiaisthatpropertyofamaterialbodythatrequirestimeandenergytosetinmotion,orstop.Inductanceisthatpropertyofanoscillationcircuitthatmakesanelectriccurrenttaketimetostartandtimetostop.Becauseoftheinductance,whenacurrentflowsthroughacircuititcausestheelectricenergytobeabsorbedandchangesalargepartofitintomagneticlinesofforce.Wherehighfrequencycurrentssurgeinacircuittheinductanceofitbecomesapowerfulfactor.ThepracticalunitofinductanceisthehenryanditisrepresentedbythesymbolL.
WhatResistanceIs.--Theresistanceofacircuittohigh-frequencycurrentsisdifferentfromthatforlowvoltagedirectoralternatingcurrents,astheformerdonotsinkintotheconductortonearlysogreatanextent;infact,theystickpracticallytothesurfaceofit,andhencetheirflowisopposedtoaverymuchgreaterextent.Theresistanceofacircuittohighfrequencycurrentsisgenerallyfoundinthesparkgap,arcgap,orthespacebetweentheelectrodesofavacuumtube.Theunitofresistanceis,asstated,theohm,anditssymbolisR.
TheEffectofCapacitance,InductanceandResistanceonElectricOscillations.--Ifanoscillationcircuitinwhichhighfrequencycurrentssurgehasalargeresistance,itwillsoopposetheflowofthecurrentsthattheywillbedampedoutandreachzerogradually,asshownatAinFig.33.Butiftheresistanceofthecircuitissmall,andinwirelesscircuitsitisusuallysosmallastobenegligible,thecurrentswilloscillate,untiltheirenergyisdampedoutbyradiationandotherlosses,asshownatB.
Asthecapacitanceandtheinductanceofthecircuit,whichmaybemadeofanyvalue,thatisamount,youwish,determinesthetimeperiod,thatis,thelengthoftimeforacurrenttomakeonecompleteoscillation,itmustbeclearthatbyvaryingthevaluesofthecondenserandtheinductancecoilyoucanmakethehighfrequencycurrentoscillateasfastorasslowasyouwishwithincertainlimits.Wheretheelectricoscillationsthataresetupareveryfast,thewavessentoutbytheaerialwillbeshort,and,conversely,wheretheoscillationsareslowthewavesemittedwillbelong.
CHAPTERVI
HOWTHETRANSMITTINGANDRECEIVINGSETSWORK
Theeasiestwaytogetaclearconceptionofhowawirelesstransmittersendsoutelectricwavesandhowawirelessreceptorreceivesthemistotakeeachoneseparatelyandfollow:(1)inthecaseofthetransmitter,thetransformationofthelowvoltagedirect,oralternatingcurrentintohighpotentialalternatingcurrents;thenfindouthowthesechargethecondenser,howthisisdischargedbythesparkgapandsetsuphigh-frequencycurrentsintheoscillationcircuits;then(2)inthecaseofthereceptor,tofollowthehighfrequencycurrentsthataresetupintheaerialwireandlearnhowtheyaretransformedintooscillationsoflowerpotentialwhentheyhavealargercurrentstrength,howtheseareconvertedintointermittentdirectcurrentsbythedetectorandwhichthenflowintoandoperatethetelephonereceiver.
HowTransmittingSetNo.1Works.TheBatteryandSparkCoilCircuit.--Whenyoupressdownontheknobofthekeythesilverpointsofitmakecontactandthisclosesthecircuit;thelowvoltagedirectcurrentfromthebatterynowflowsthroughtheprimarycoilofthesparkcoilandthismagnetizesthesoftironcore.Theinstantitbecomesmagneticitpullsthespringofthevibratorovertoitandthisbreaksthecircuit;whenthistakesplacethecurrentstopsflowingthroughtheprimarycoil;thiscausesthecoretoloseitsmagnetismwhenthevibratorspringfliesbackandagainmakescontactwiththeadjustingscrew;thenthecycleofoperationsisrepeated.
Acondenserisconnectedacrossthecontactpointsofthevibratorsincethisgivesamuchhighervoltageattheendsofthesecondarycoilthanwherethecoilisusedwithoutit;thisisbecause:(1)theself-inductionoftheprimarycoilmakesthepressureofthecurrentriseandwhenthecontactpointsclosethecircuitagainitdischargesthroughtheprimarycoil,and(2)whenthebreaktakesplacethecurrentflowsintothecondenserinsteadofarcingacrossthecontactpoints.
ChangingthePrimarySparkCoilCurrentIntoSecondaryCurrents.--Noweverytimethevibratorcontactpointsclosetheprimarycircuittheelectriccurrentintheprimarycoilischangedintoclosedmagneticlinesofforceandasthesecutthroughthesecondarycoiltheysetupinitamomentarycurrentinonedirection.Thentheinstantthevibratorpointsbreakaparttheprimarycircuitisopenedandtheclosedmagneticlinesofforcecontractandastheydosotheycuttheturnsofwireinthesecondarycoilintheoppositedirectionandthissetsupanothermomentarycurrentinthesecondarycoilintheotherdirection.Theresultisthatthelowvoltagedirectcurrentofthebatteryischangedintoalternatingcurrentswhosefrequencyispreciselythatofthespringvibrator,butwhilethefrequencyofthecurrentsislowtheirpotential,orvoltage,isenormouslyincreased.
WhatRatioofTransformationMeans.--Tomakeasparkcoilstepupthelowvoltagedirectcurrentintohighpotentialalternatingcurrenttheprimarycoiliswoundwithacoupleoflayersofthickinsulatedcopperwireandthesecondaryiswoundwithathousand,moreorless,numberofturnswithveryfineinsulatedcopperwire.Iftheprimaryandsecondarycoilswerewoundwiththesamenumberofturnsofwirethenthepressure,orvoltage,ofthesecondarycoilatitsterminalswouldbethesameasthatofthecurrentwhichflowedthroughtheprimarycoil.Undertheseconditionstheratiooftransformation,asitiscalled,wouldbeunity.
Theratiooftransformationisdirectlyproportionaltothenumberofturnsofwireontheprimaryandsecondarycoilsand,sincethisisthecase,ifyouwind10turnsofwireontheprimarycoiland1,000turnsofwireonthesecondarycoilthenyouwillget100timesashighapressure,orvoltage,attheterminalsofthesecondaryasthatwhichyoucausedtoflowthroughtheprimarycoil,but,naturally,thecurrentstrength,oramperage,willbeproportionatelydecreased.
TheSecondarySparkCoilCircuit.--Thisincludesthesecondarycoilandthesparkgapwhichareconnectedtogether.Whenthealternating,buthighpotential,currentswhicharedevelopedbythesecondarycoil,reachtheballs,orelectrodes,ofthesparkgapthelatterarealternatelychargedpositivelyandnegatively.
Nowtakeagiveninstantwhenoneelectrodeischargedpositivelyandtheotheroneischargednegatively,thenwhentheyarechargedtoahighenoughpotentialtheelectricstrainbreaksdowntheairgapbetweenthemandthetwochargesrushtogetherasdescribedinthechapterbeforethisoneinconnectionwiththedischargeofacondenser.Whenthechargesrushtogethertheyformacurrentwhichburnsouttheairinthegapandthisgivesrisetothespark,andastheheatedgapbetweenthetwoelectrodesisaverygoodconductortheelectriccurrentsurgesforthandbackwithhighfrequency,perhapsadozentimes,beforetheairreplacesthatwhichhasburnedout.Itistheinrushingairtofillthevacuumofthegapthatmakesthecracklingnoisewhichaccompaniesthedischargeoftheelectricspark.
Inthiswaythenelectricoscillationsoftheorderofamillion,moreorless,areproducedandifanaerialandagroundwireareconnectedtothesparkballs,orelectrodes,theoscillationswillsurgeupanddownitandtheenergyoftheseinturn,arechangedintoelectricwaveswhichtraveloutintospace.Anopencircuittransmitterofthiskindwillsendoutwavesthatarefourtimesaslongastheaerialitself,butasthewavesitsendsoutarestronglydampedtheGovernmentwillnotpermitittobeused.
TheClosedOscillationCircuit.--Byusingaclosedoscillationcircuitthetransmittercanbetunedtosendoutwavesofagivenlengthandwhilethewavesarenotsostronglydampedmorecurrentcanbesentintotheaerialwiresystem.Theclosedoscillationcircuitconsistsof:(1)asparkgap,(2)acondenserand(3)anoscillationtransformer.Thehighpotentialalternatingcurrentdeliveredbythesecondarycoilnotonlychargesthesparkgapelectrodeswhichnecessarilyhaveaverysmallcapacitance,butitchargesthecondenserwhichhasalargecapacitanceandthevalueofwhichcanbechangedatwill.
Nowwhenthecondenserisfullychargeditdischargesthroughthesparkgapandthentheelectricoscillationssetupsurgetoandfrothroughtheclosedcircuit.Asaclosedcircuitisaverypoorradiatorofenergy,thatis,theelectricoscillationsarenotfreelyconvertedintoelectricwavesbyit,theysurgeupto,andthroughtheaerialwire;nowastheaerialwireisagoodradiatornearlyalloftheenergyoftheelectricoscillationswhichsurgethroughitareconvertedintoelectricwaves.
HowTransmittingSetNo.2Works.WithAlternatingCurrent.Theoperationofatransmittingsetthatusesanalternatingcurrenttransformer,orpowertransformer,asitissometimescalled,isevenmoresimplethanoneusingasparkcoil.Thetransformerneedsnovibratorwhenusedwithalternatingcurrent.Thecurrentfromageneratorflowsthroughtheprimarycoilofthetransformerandthealternationsoftheusuallightingcurrentis60cyclespersecond.Thiscurrentsetsupanalternatingmagneticfieldinthecoreofthetransformerandasthesemagneticlinesofforceexpandandcontract
theysetupalternatingcurrentsofthesamefrequencybutofmuchhighervoltageattheterminalsofthesecondarycoilaccordingtotheratiooftheprimaryandsecondaryturnsofwireasexplainedunderthesub-captionofRatioofTransformation.
WithDirectCurrent.--Whena110voltdirectcurrentisusedtoenergizethepowertransformeranelectrolyticinterruptorisneededtomakeandbreaktheprimarycircuit,justasavibratorisneededforthesamepurposewithasparkcoil.Whentheelectrodesareconnectedinserieswiththeprimarycoilofatransformerandasourceofdirectcurrenthavingapotentialof40to110volts,bubblesofgasareformedontheendoftheplatinum,oralloyanode,whichpreventthecurrentfromflowinguntilthebubblesbreakandthenthecurrentflowsagain,inthiswaythecurrentisrapidlymadeandbrokenandthebreakisverysharp.
Wherethistypeofinterrupterisemployedthecondenserthatisusuallyshuntedaroundthebreakisnotnecessaryastheinterrupteritselfhasacertaininherentcapacitance,duetoelectrolyticaction,andwhichiscalleditselectrolyticcapacitance,andthisislargeenoughtobalancetheself-inductionofthecircuitsincethegreaterthenumberofbreaksperminutethesmallerthecapacitancerequired.
TheRotarySparkGap.--Inthistypeofsparkgapthetwofixedelectrodesareconnectedwiththeterminalsofthesecondarycoilofthepowertransformerandalsowiththecondenserandprimaryoftheoscillationtransformer.Nowwheneveranypairofelectrodesontherotatingdiskareinalinewiththepairoffixedelectrodesasparkwilltakeplace,hencethepitchofthenotedependsonthespeedofthemotordrivingthedisk.Thiskindofarotaryspark-gapiscallednon-synchronousanditisgenerallyusedwherea60cyclealternatingcurrentisavailablebutitwillworkwithotherhigherfrequencies.
TheQuenchedSparkGap.--Ifyoustrikeapianostringasinglequickblowitwillcontinuetovibrateaccordingtoitsnaturalperiod.Thisisverymuchthewayinwhichaquenchedsparkgapsetsuposcillationsinacoupledclosedandopencircuit.Theoscillationssetupintheprimarycircuitbyaquenchedsparkmakeonlythreeorfoursharpswingsandinsodoingtransferalloftheirenergyovertothesecondarycircuit,whereitwilloscillatesomefiftytimesormorebeforeitisdampedout,becausethehighfrequencycurrentsarenotforced,butsimplyoscillatetothenaturalfrequencyofthecircuit.Forthisreasontheradiatedwavesapproachsomewhattheconditionofcontinuouswaves,andsosharpertuningispossible.
TheOscillationTransformer.--InthissetthecondenserintheclosedcircuitischargedanddischargedandsetsuposcillationsthatsurgethroughtheclosedcircuitasinSetNo.1.Inthisset,however,anoscillationtransformerisusedandastheprimarycoilofitisincludedintheclosedcircuittheoscillationssetupinitproducestrongoscillatingmagneticlinesofforce.Themagneticfieldthusproducedsetsupinturnelectricoscillationsinthesecondarycoiloftheoscillationtransformerandthesesurgethroughtheaerialwiresystemwheretheirenergyisradiatedintheformofelectricwaves.
Thegreatadvantageofusinganoscillationtransformerinsteadofasimpleinductancecoilisthatthecapacitanceoftheclosedcircuitcanbeverymuchlargerthanthatoftheaerialwiresystem.Thispermitsmoreenergytobestoredupbythecondenserandthisisimpressedontheaerialwhenitisradiatedaselectricwaves.
HowReceivingSetNo.IWorks.--Whentheelectricwavesfromadistantsendingstationimpingeon
thewireofareceivingaerialtheirenergyischangedintoelectricoscillationsthatareofexactlythesamefrequency(assumingthereceptoristunedtothetransmitter)butwhosecurrentstrength(amperage)andpotential(voltage)areverysmall.Theseelectricwavessurgethroughtheclosedcircuitbutwhentheyreachthecrystaldetectorthecontactofthemetalpointonthecrystalpermitsmorecurrenttoflowthroughitinonedirectionthanitwillallowtopassintheotherdirection.Forthisreasonacrystaldetectorissometimescalledarectifier,whichitreallyis.
Thusthehighfrequencycurrentswhichthesteelmagnetcoresofthetelephonereceiverwouldchokeoffarechangedbythedetectorintointermittentdirectcurrentswhichcanflowthroughthemagnetcoilsofthetelephonereceiver.Sincethetelephonereceiverchokesofftheoscillations,asmallcondensercanbeshuntedarounditsothatacompleteclosedoscillationcircuitisformedandthisgivesbetterresults.
Whentheintermittentrectifiedcurrentflowsthroughthecoilsofthetelephonereceiveritenergizesthemagnetaslongasitlasts,whenitisde-energized;thiscausesthesoftirondisk,ordiaphragmasitiscalled,whichsetsclosetotheendsofthepolesofthemagnet,tovibrate;andthisinturngivesforthsoundssuchasdotsanddashes,speechormusic,accordingtothenatureoftheelectricwavesthatsentthemoutatthedistantstation.
HowReceivingSetNo.2Works.--Whentheelectricoscillationsthataresetupbytheincomingelectricwavesontheaerialwiresurgethroughtheprimarycoiloftheoscillationtransformertheyproduceamagneticfieldandasthelinesofforceofthelattercutthesecondarycoil,oscillationsofthesamefrequencyaresetupinit.Thepotential(voltage)oftheseoscillationsare,however,steppeddowninthesecondarycoiland,hence,theircurrentstrength(amperes)isincreased.
TheoscillationsthenflowthroughtheclosedcircuitwheretheyarerectifiedbythecrystaldetectorandtransformedintosoundwavesbythetelephonereceiverasdescribedinconnectionwithSetNo.1.Thevariablecondensershuntedacrosstheclosedcircuitpermitsfinersecondarytuningtobedonethanispossiblewithoutit.Whereyouarereceivingcontinuouswavesfromawirelesstelephonetransmitter(speechormusic)youhavetotunesharperthanispossiblewiththetuningcoilaloneandtodothisavariablecondenserconnectedinparallelwiththesecondarycoilisnecessary.
CHAPTERVII
MECHANICALANDELECTRICALTUNING
Thereisastrikinglycloseresemblancebetweensoundwavesandthewaytheyaresetupintheairbyamechanicallyvibratingbody,suchasasteelspringoratuningfork,andelectricwavesandthewaytheyaresetupintheetherbyacurrentoscillatinginacircuit.Asitiseasytograspthewaythatsoundwavesareproducedandbehavesomethingwillbetoldabouttheminthischapterandalsoanexplanationofhowelectricwavesareproducedandbehaveandthusyouwillbeabletogetaclearunderstandingofthemandoftuningingeneral.
DampedandSustainedMechanicalVibrations.--IfyouwillplaceoneendofaflatsteelspringinaviceandscrewituptightasshownatAinFig.34,andthenpullthefreeendoverandletitgoitwillvibratetoandfrowithdecreasingamplitudeuntilitcomestorestasshownatB.Whenyoupullthespringoveryoustoreupenergyinitandwhenyouletitgothestoredupenergyischangedintoenergyofmotionandthespringmovesforthandback,orvibratesaswecallit,untilallofitsstoredupenergyisspent.
Ifitwerenotfortheairsurroundingitandotherfrictionallosses,thespringwouldvibrateforaverylongtimeasthestoredupenergyandtheenergyofmotionwouldpracticallyoffseteachotherandsotheenergywouldnotbeusedup.Butasthespringbeatstheairthelatterissentoutinimpulsesandtheconversionofthevibrationsofthespringintowavesintheairsoonusesuptheenergyyouhaveimpartedtoitanditcomestorest.
Inordertosendoutcontinuouswavesintheairinsteadofdampedwavesaswithaflatsteelspringyoucanuseanelectricdriventuningfork,seeC,inwhichanelectromagnetisfixedontheinsideoftheprongsandwhenthisisenergizedbyabatterycurrentthevibrationsoftheprongsoftheforkarekeptgoing,oraresustained,asshowninthediagramatD.
DampedandSustainedElectricOscillations.--Thevibratingsteelspringdescribedaboveisaverygoodanalogueofthewaythatdampedelectricoscillationswhichsurgeinacircuitsetupandsendoutperiodicelectricwavesintheetherwhiletheelectricdriventuningforkjustdescribedislikewiseagoodanalogueofhowsustainedoscillationssurgeinacircuitandsetupandsendoutcontinuouselectricwavesintheetherasthefollowingshows.
NowtheinductanceandresistanceofacircuitsuchasisshownatAinFig.35,slowsdown,andfinallydampsoutentirely,theelectricoscillationsofthehighfrequencycurrents,seeB,wherethesearesetupbytheperiodicdischargeofacondenser,preciselyasthevibrationsofthespringaredampedoutbythefrictionoftheairandotherresistancesthatactuponit.Astheelectricoscillationssurgetoandfrointhecircuititisopposedbytheactionoftheetherwhichsurroundsitandelectricwavesaresetupinandsentoutthroughitandthistransformationsoonusesuptheenergyofthecurrentthatflowsinthecircuit.
Tosendoutcontinuouswavesintheethersuchasareneededforwirelesstelephonyinsteadofdampedwaveswhichare,atthepresentwriting,generallyusedforwirelesstelegraphy,anelectricoscillationarcoravacuumtubeoscillatormustbeused,seeC,insteadofasparkgap.Whereasparkgapisusedthecondenserinthecircuitischargedperiodicallyandwithconsiderablelapsesoftimebetweeneachofthechargingprocesses,when,ofcourse,thecondenserdischargesperiodicallyandwiththesametimeelementbetweenthem.WhereanoscillationarcoravacuumtubeisusedthecondenserischargedasrapidlyasitisdischargedandtheresultistheoscillationsaresustainedasshownatD.
AboutMechanicalTuning.--Atuningforkisbetterthanaspringorastraightsteelbarforsettingupmechanicalvibrations.Asamatteroffactatuningforkissimplyasteelbarbentinthemiddlesothatthetwoendsareparallel.Ahandleisattachedtomiddlepointoftheforksothatitcanbeheldeasilyandwhichalsoallowsittovibratefreely,whentheendsoftheprongsalternatelyapproachandrecedefromoneanother.Whentheprongsvibratethehandlevibratesupanddowninunisonwithit,andimpartsitsmotiontothesoundingbox,orresonancecaseasitissometimescalled,whereoneisused.
If,now,youwillmounttheforkonasoundingboxwhichistunedsothatitwillbeinresonancewiththevibrationsoftheforktherewillbeadirectreinforcementofthevibrationswhenthenoteemittedbyitwillbeaugmentedinstrengthandquality.Thisiscalledsimpleresonance.Further,ifyoumountapairofforks,eachonaseparatesoundingbox,andhavetheforksofthesamesize,toneandpitch,andtheboxessynchronized,thatis,tunedtothesamefrequencyofvibration,thensetthetwoboxesafootorsoapart,asshownatAinFig.36,whenyoustrikeoneoftheforkswitharubberhammeritwillvibratewithadefinitefrequencyand,hence,sendoutsoundwavesofagivenlength.Whenthelatterstrikethesecondforktheimpactofthemoleculesofairofwhichthesoundwavesareformedwillsetitsprongstovibratinganditwill,inturn,emitsoundwavesofthesamelengthandthisiscalledsympatheticresonance,oraswewouldsayinwirelesstheforksareintune.
Tuningforksaremadewithadjustableweightsontheirprongsandbyfixingthesetodifferentpartsofthemthefrequencywithwhichtheforksvibratecanbechangedsincethefrequencyvariesinverselywiththesquareofthelengthanddirectlywiththethickness[Footnote:Thislawisforforkshavingarectangularcross-section.Thosehavingaroundcross-sectionvaryastheradius.]oftheprongs.Nowbyadjustingoneoftheforkssothatitvibratesatafrequencyof,say,16persecondandadjustingtheotherforksothatitvibratesatafrequencyof,say,18or20persecond,thentheforkswillnotbeintunewitheachotherand,hence,ifyoustrikeoneofthemtheotherwillnotrespond.Butifyoumaketheforksvibrateatthesamefrequency,say16,20or24persecond,whenyoustrikeoneofthemtheotherwillvibrateinunisonwithit.
AboutElectricTuning.--ElectricresonanceandelectrictuningareverylikethoseofacousticresonanceandacoustictuningwhichIhavejustdescribed.Justasacousticresonancemaybesimple
orsympatheticsoelectricresonancemaybesimpleorsympathetic.Simpleacousticresonanceisthedirectreinforcementofasimplevibrationandthisconditionishadwhenatuningforkismountedonasoundingbox.Insimpleelectricresonanceanoscillatingcurrentofagivenfrequencyflowinginacircuithavingtheproperinductanceandcapacitancemayincreasethevoltageuntilitisseveraltimesgreaterthanitsnormalvalue.Tuningthereceptorcircuitstothetransmittercircuitsareexamplesofsympatheticelectricresonance.AsademonstrationifyouhavetwoLeydenjars(capacitance)connectedincircuitwithtwoloopsofwire(inductance)whoseinductancecanbevariedasshownatBinFig.36,whenyoumakeasparkpassbetweentheknobsofoneofthembymeansofasparkcoilthenasparkwillpassinthegapoftheotheroneprovidedtheinductanceofthetwoloopsofwireisthesame.Butifyouvarytheinductanceoftheoneloopsothatitislargerorsmallerthanthatoftheotherloopnosparkwilltakeplaceinthesecondcircuit.
Whenatuningforkismadetovibrateitsendsoutwavesintheair,orsoundwaves,inalldirectionsandjustsowhenhighfrequencycurrentssurgeinanoscillationcircuittheysendoutwavesintheether,orelectricwaves,thattravelinalldirections.Forthisreasonelectricwavesfromatransmittingstationcannotbesenttooneparticularstation,thoughtheydogofurtherinonedirectionthaninanother,accordingtothewayyouraerialwirepoints.
Sincetheelectricwavestraveloutinalldirectionsanyreceivingsetproperlytunedtothewavelengthofthesendingstationwillreceivethewavesandtheonlylimitonyourabilitytoreceivefromhigh-powerstationsthroughouttheworlddependsentirelyonthewavelengthandsensitivityofyourreceivingset.Asfortuning,justaschangingthelengthandthethicknessoftheprongsofatuningforkvariesthefrequencywithwhichitvibratesand,hence,thelengthofthewavesitsendsout,so,too,byvaryingthecapacitanceofthecondenserandtheinductanceofthetuningcoilofthetransmitterthefrequencyoftheelectricoscillationssetupinthecircuitmaybechangedand,consequently,thelengthoftheelectricwavestheysendout.Likewise,byvaryingthecapacitanceandtheinductanceofthereceptorthecircuitscanbetunedtoreceiveincomingelectricwavesofwhateverlengthwithinthelimitationoftheapparatus.
CHAPTERVIII
ASIMPLEVACUUMTUBEDETECTORRECEIVINGSET
WhileyoucanreceivedotsanddashesfromsparkwirelesstelegraphstationsandhearspokenwordsandmusicfromwirelesstelephonestationswithacrystaldetectorreceivingsetsuchasdescribedinChapterIII,youcangetstationsthataremuchfartherawayandhearthembetterwithavacuumtubedetectorreceivingset.
Thoughthevacuumtubedetectorrequirestwobatteriestooperateitandthereceivingcircuitsaresomewhatmorecomplicatedthanwhereacrystaldetectorisusedstilltheformerdoesnothavetobeconstantlyadjustedasdoesthelatterandthisisanotherverygreatadvantage.Takenallinallthevacuumtubedetectoristhemostsensitiveandthemostsatisfactoryofthedetectorsthatareinuseatthepresenttime.
Notonlyisthevacuumtubeadetectorofelectricwavesignalsandspeechandmusicbutitcanalsobeusedtoamplifythem,thatis,tomakethemstrongerand,hence,louderinthetelephonereceiverandfurtheritspowersofamplificationaresogreatthatitwillreproducethembymeansofaloudspeaker,justasahornamplifiesthesoundsofaphonographreproducer,untiltheycanbeheardbyaroomoranauditoriumfullofpeople.Therearetwogeneraltypesofloudspeakers,thoughbothusetheprincipleofthetelephonereceiver.Theconstructionoftheseloudspeakerswillbefullydescribedinalaterchapter.
AssembledVacuumTubeReceivingSets.--Youcanbuyareceivingsetwithavacuumtubedetectorfromtheverysimplesttype,whichisdescribedinthischapter,tothosethatareprovidedwithregenerativecircuitsandamplifyingtubesorboth,whichweshalldescribeinlaterchapters,fromdealersinelectricalapparatusgenerally.Whileoneofthesesetscostsmorethanyoucanassembleasetforyourself,still,especiallyinthebeginning,itisagoodplantobuyanassembledoneforitisfittedwithapanelonwhichtheadjustingknobsoftherheostat,tuningcoilandcondenseraremountedandthismakesitpossibletooperateitassoonasyougetithomeandwithouttheslightesttroubleonyourpart.
Youcan,however,buyallthevariouspartsseparatelyandmountthemyourself.Ifyouwantthereceptorsimplyforreceivingthenitisagoodschemetohaveallofthepartsmountedinaboxorenclosedcase,butifyouwantitforexperimentalpurposesthenthepartsshouldbemountedonabaseorapanelsothatalloftheconnectionsareinsightandaccessible.
ASimpleVacuumTubeReceivingSet.--Forthissetyoushoulduse:(1)aloosecoupledtuningcoil,(2)avariablecondenser,(3)avacuumtubedetector,(4)anAorstoragebatterygiving6volts,(5)aBordrycellbatterygiving22-1/2volts,(6)arheostatforvaryingthestoragebatterycurrent,and(7)apairof2,000-ohmheadtelephonereceivers.Theloosecoupledtuningcoil,thevariablecondenserandthetelephonereceiversarethesameasthosedescribedinChapterIII.
TheVacuumTubeDetector.WithTwoElectrodes.--AvacuumtubeinitssimplestformconsistsofaglassbulblikeanincandescentlampinwhichawirefilamentandametalplatearesealedasshowninFig.37,Theairisthenpumpedoutofthetubeandavacuumleftorafteritisexhausteditisfilled
withnitrogen,whichcannotburn.
Whenthevacuumtubeisusedasadetector,thewirefilamentisheatedred-hotandthemetalplateischargedwithpositiveelectricitythoughitremainscold.Thewirefilamentisformedintoalooplikethatofanincandescentlampanditsoutsideendsareconnectedwitha6-voltstoragebattery,whichiscalledtheAbattery;thenthe+orpositiveterminalofa22-1/2voltdrycellbattery,calledtheBbattery,isconnectedtothemetalplatewhilethe-ornegativeterminalofthebatteryisconnectedtooneoftheterminalsofthewirefilament.Thediagram,Fig.37,simplyshowshowthetwoelectrodevacuumtube,theAordrybattery,andtheBorstoragebatteryareconnectedup.
ThreeElectrodeVacuumTubeDetector.--ThethreeelectrodevacuumtubedetectorshownatAinFig.38,ismuchmoresensitivethanthetwoelectrodetubeandhas,inconsequence,allbutsupplantedit.Inthismorerecenttypeofvacuumtubethethirdelectrode,orgrid,asitiscalled,isplacedbetweenthewirefilamentandthemetalplateandthisallowsthecurrenttobeincreasedordecreasedatwilltoaveryconsiderableextent.
ThewaythethreeelectrodevacuumtubedetectorisconnectedwiththebatteriesisshownatB.Theplate,theAordrycellbatteryandoneterminalofthefilamentareconnectedinseries--thatis,oneaftertheother,andtheendsofthefilamentareconnectedtotheBorstoragebattery.Inassemblingareceivingsetyoumust,ofcourse,haveasocketforthevacuumtube.Avacuumtubedetectorcostsfrom$5.00to$6.00.
TheDryCellandStorageBatteries.--Thereasonthatastoragebatteryisusedforheatingthefilamentofthevacuumtubedetectorisbecausethecurrentdeliveredisconstant,whereaswhenadrycellbatteryisusedthecurrentsoonfallsoffand,hence,theheatofthefilamentgraduallygrowsless.ThesmallestAor6voltstoragebatteryonthemarkethasacapacityof20to40amperehours,weighs13poundsandcostsabout$10.00.ItisshownatAinFig.39.TheBordrycellbatteryforthevacuumtubeplatecircuitthatgives22-1/2voltscanbeboughtalreadyassembledinsealedboxes.Thesmallsizeisfittedwithapairofterminalswhilethelargersizeisprovidedwithtapssothatthevoltagerequiredbytheplatecanbeadjustedastheproperoperationofthetuberequirescarefulregulationoftheplatevoltage.AdrycellbatteryforaplatecircuitisshownatB.
TheFilamentRheostat.--Anadjustableresistance,calledarheostat,mustbeusedinthefilamentandstoragebatterycircuitsothatthecurrentflowingthroughthefilamentcanbecontrolledtoanicety.Therheostatconsistsofaninsulatingandaheatresistingformonwhichiswoundanumberofturnsofresistancewire.Amovablecontactarmthatslidesoverandpressesontheturnsofwireisfixedtotheknobontopoftherheostat.Arheostatthathasaresistanceof6ohmsandacurrentcarryingcapacityof1.5ampereswhichcanbemountedonapanelboardistherightkindtouse.ItisshownatAandBinFig.40andcosts$1.25.
AssemblingtheParts.--Beginbyplacingalloftheseparatepartsofthereceivingsetonaboardorabaseofothermaterialandsetthetuningcoilonthelefthandsidewiththeadjustableswitchendtowardtherighthandsidesothatyoucanreachiteasily.Thensetthevariablecondenserinfrontofit,setthevacuumtubedetectorattherighthandendofthetuningcoilandtherheostatinfrontofthedetector.Placethetwosetsofbatteriesbackoftheinstrumentsandscrewacoupleofbindingpostsa
andbtotherighthandloweredgeofthebaseforconnectingintheheadphonesallofwhichisshownatAinFig.41.
ConnectingUptheParts.--Towireupthedifferentpartsbeginbyconnectingtheslidingcontactof
theprimarycoiloftheloosecoupledtuningcoil(thisyouwillrememberistheoutsideonethatiswoundwithfinewire)totheupperpostofthelightningswitchandconnectoneterminalofthiscoilwiththewaterpipe.Nowconnectthefreeendofthesecondarycoilofthetuningcoil(thisistheinsidecoilthatiswoundwithheavywire)tooneofthebindingpostsofthevariablecondenserandconnectthemovablecontactarmoftheadjustableswitchoftheprimaryofthetuningcoilwiththeotherpostofthevariablecondenser.
NextconnectthegridofthevacuumtubetooneofthepostsofthecondenserandthenconnecttheplateofthetubetothecarbonterminaloftheBordrycellbatterywhichisthe+orpositivepoleandconnectthezincterminalofthe-ornegativepoletothebindingposta,connectthepostbtotheothersideofthevariablecondenserandthenconnecttheterminalsoftheheadphonestothebindingpostsaandb.Whateveryoudobecarefulnottogettheplateconnectionsofthebatteryreversed.
Nowconnectoneofthepostsoftherheostattooneterminalofthefilamentandtheotherterminalofthefilamenttothe-ornegativeterminaloftheAorstoragebatteryandthe+orpositiveterminaloftheAorstoragebatterytotheotherpostoftherheostat.Finallyconnectthe+orpositiveterminaloftheAorstoragebatterywiththewirethatrunsfromtheheadphonestothevariablecondenser,allofwhichisshowninthewiringdiagramatBinFig.41.
AdjustingtheVacuumTubeDetectorReceivingSet.--AvacuumtubedetectoristunedexactlyinthesamewayastheCrystalDetectorSetNo.2describedinChapterIII,in-so-farasthetuningcoilandvariablecondenserareconcerned.Thesensitivityofthevacuumtubedetectorreceivingsetand,hence,thedistanceoverwhichsignalsandothersoundscanbehearddependsverylargelyonthesensitivityofthevacuumtubeitselfandthisinturndependson:(1)therightamountofheatdevelopedbythefilament,orfilamentbrilliancyasitiscalled,(2)therightamountofvoltageappliedtotheplate,and(3)theextenttowhichthetubeisexhaustedwherethiskindofatubeisused.
TovarythecurrentflowingfromtheAorstoragebatterythroughthefilamentsothatitwillbeheatedtotherightdegreeyouadjusttherheostatwhileyouarelisteningintothesignalsorothersounds.Bycarefullyadjustingtherheostatyoucaneasilyfindthepointatwhichitmakesthetubethemostsensitive.Arheostatisalsousefulinthatitkeepsthefilamentfromburningoutwhenthecurrentfromthebatteryfirstflowsthroughit.YoucanveryoftenincreasethesensitivenessofavacuumtubeafteryouhaveuseditforawhilebyrechargingtheAorstoragebattery.
Thedegreetowhichavacuumtubehasbeenexhaustedhasaverypronouncedeffectonitssensitivity.Thelongerthetubeisusedtheloweritsvacuumgetsandgenerallythelesssensitiveitbecomes.Whenthistakesplace(andyoucanonlyguessatit)youcanveryoftenmakeitmoresensitivebywarmingitovertheflameofacandle.Vacuumtubeshavingagascontent(inwhichcasetheyare,ofcourse,nolongervacuumtubesinthestrictsense)makebetterdetectorsthantubesfromwhichtheairhasbeenexhaustedandwhicharesealedoffinthisevacuatedconditionbecausetheirsensitivenessisnotdependentonthedegreeofvacuumasinthelattertubes.Moreover,atubethatiscompletelyexhaustedcostsmorethanonethatisfilledwithgas.
CHAPTERIX
VACUUMTUBEAMPLIFIERRECEIVINGSETS
Thereasonavacuumtubedetectorismoresensitivethanacrystaldetectorisbecausewhilethelattermerelyrectifiestheoscillatingcurrentthatsurgesinthereceivingcircuits,theformeractsasanamplifieratthesametime.Thevacuumtubecanbeusedasaseparateamplifierinconnectionwitheither:(1)acrystaldetectoror(2)avacuumtubedetector,and(a)itwillamplifyeithertheradiofrequencycurrents,thatisthehighfrequencyoscillatingcurrentswhicharesetupintheoscillationcircuitsor(b)itwillamplifytheaudiofrequencycurrents,thatis,thelowfrequencyalternatingcurrentsthatflowthroughtheheadphonecircuit.
Tousetheamplifiedradiofrequencyoscillatingcurrentsoramplifiedaudiofrequencyalternatingcurrentsthataresetupbyanamplifiertubeeitherahighresistance,calledagridleak,oranamplifyingtransformer,withorwithoutanironcore,mustbeconnectedwiththeplatecircuitofthefirstamplifiertubeandthegridcircuitofthenextamplifiertubeordetectortube,orwiththewirepointofacrystaldetector.Wheretwoormoreamplifiertubesarecoupledtogetherinthiswaytheschemeisknownascascadeamplification.
Whereeitheraradiofrequencytransformer,thatisonewithouttheironcore,oranaudiofrequencytransformer,thatisonewiththeironcore,isusedtocoupletheamplifiertubecircuitstogetherbetterresultsareobtainedthanwhereahighresistancegridleakisused,buttheamplifyingtubeshavetobemorecarefullyshieldedfromeachotherortheywillreactandsetupahowlingnoiseintheheadphones.Ontheotherhandgridleakscostlessbuttheyaremoretroublesometouseasyouhavetofindoutforyourselftheexactresistancevaluetheymusthaveandthisyoucandoonlybytestingthemout.
AGridLeakAmplifierReceivingSet.WithCrystalDetector.--Theapparatusyouneedforthissetincludes:(1)aloosecoupledtuningcoil,(2)avariablecondenser,(3)twofixedcondensers,(4)acrystaldetector,orbetteravacuumtubedetector,(5)anAor6voltstoragebattery,(6)arheostat,(7)aBor22-1/2voltdrycellbattery,(8)afixedresistanceunit,orleakgridasitiscalled,and(9)apairofhead-phones.Thetuningcoil,variablecondenser,fixedcondensers,crystaldetectorsandhead-phonesareexactlythesameasthosedescribedinSetNo.2inChapterIII.TheAandBbatteriesareexactlythesameasthosedescribedinChapterVIII.Thevacuumtubeamplifierandthegridleakaretheonlynewpiecesofapparatusyouneedandnotdescribedbefore.
TheVacuumTubeAmplifier.--ThisconsistsofathreeelectrodevacuumtubeexactlylikethevacuumtubedetectordescribedinChapterVIIIandpicturedinFig.38,exceptthatinsteadofbeingfilledwithanon-combustiblegasitisevacuated,thatis,theairhasbeencompletelypumpedoutofit.Thegasfilledtube,however,canbeusedasanamplifierandeitherkindoftubecanbeusedforeitherradiofrequencyoraudiofrequencyamplification,thoughwiththeexhaustedtubeitiseasiertoobtaintherightplateandfilamentvoltagesforgoodworking.
TheFixedResistanceUnit,orGridLeak.--Gridleaksaremadeindifferentwaysbutallofthemhaveanenormouslyhighresistance.Onewayofmakingthemconsistsofdepositingathinfilmofgoldonasheetofmicaandplacinganothersheetofmicaontoptoprotectitthewholebeingenclosedina
glasstubeasshownatAinFig.42.Thesegridleaksaremadeinunitsoffrom50,000ohms(.05megohm)to5,000,000ohms(5megohms)andcostfrom$1to$2.
Asthevalueofthegridleakyouwillneeddependsverylargelyupontheconstructionofthedifferentpartsofyourreceivingsetandonthekindofaerialwiresystemyouusewithityouwillhavetotryoutvariousresistancesuntilyouhittherightone.Theresistancethatwillgivethebestresults,however,liessomewherebetween500,000ohms(1/2amegohm)and3,000,000ohms(3megohms)andtheonlywayforyoutofindthisoutistobuy1/2,1and2megohmgridleakresistancesandconnectthemupindifferentways,asshownatB,untilyoufindtherightvalue.
AssemblingthePartsforaCrystalDetectorSet.--Beginbylayingthevariouspartsoutonabaseorapanelwiththeloosecoupledtuningcoilonthelefthandside,butwiththeadjustableswitchofthesecondarycoilontherighthandendorinfrontaccordingtothewayitismade.Thenplacethevariablecondenser,therheostat,thecrystaldetectorandthebindingpostsfortheheadphonesinfrontofandinalinewitheachother.SetthevacuumtubeamplifierbackoftherheostatandtheAandBbatteriesbackofthepartsorinanyotherplacethatmaybeconvenient.Thefixedcondensersandthegridleakcanbeplacedanywheresothatitwillbeeasytoconnecttheminandyouarereadytowireuptheset.
ConnectingUpthePartsforaCrystalDetector.--Firstconnecttheslidingcontactoftheprimaryofthetuningcoiltotheleading-inwireandoneoftheendwiresoftheprimarytothewaterpipe,asshowninFig.43.Nowconnecttheadjustablearmthatmakescontactwithoneendofthesecondaryofthetuningcoiltooneofthepostsofthevariablecondenser;thenconnecttheotherpostofthelatter
withapostofthefixedcondenserandtheotherpostofthiswiththegridoftheamplifyingtube.
Connectthefirstpostofthevariablecondensertothe+orpositiveelectrodeoftheAbatteryandits-ornegativeelectrodewiththerotatingcontactarmoftherheostat.Nextconnectoneendoftheresistancecoiloftherheostattooneofthepostsoftheamplifiertubethatleadstothefilamentandtheotherfilamentposttothe+orpositiveelectrodeoftheAbattery.Thisdoneconnectthenegative,thatis,thezincpoleoftheBbatterytothepositiveelectrodeoftheAbatteryandconnectthepositive,orcarbonpoleoftheformerwithoneendofthegridleakandconnecttheotherendofthistotheplateoftheamplifiertube.
Totheendofthegridleakconnectedwiththeplateoftheamplifiertubeconnectthemetalpointofyourcrystaldetector,thecrystalofthelatterwithonepostoftheheadphonesandtheotherpostofthemwiththeotherendofthegridleakand,finally,connectafixedcondenserinparallelwith--thatisacrosstheendsofthegridleak,allofwhichisshowninthewiringdiagraminFig.43.
AGridLeakAmplifyingReceivingSetWithVacuumTubeDetector.--Abetteramplifyingreceivingsetcanbemadethantheonejustdescribedbyusingavacuumtubedetectorinsteadofthecrystaldetector.ThissetisbuiltupexactlylikethecrystaldetectordescribedaboveandshowninFig.43uptoandincludingthegridleakresistance,butshuntedacrossthelatterisavacuumtubedetector,whichismadeandwireduppreciselyliketheoneshownatAinFig.41inthechapteraheadofthisone.Thewayagridleakandvacuumtubedetectorwithaone-stepamplifierareconnectedupisshownatAinFig.44.Whereyouhaveavacuumtubedetectorandoneormoreamplifyingtubesconnectedup,orincascadeasitiscalled,youcanuseanA,orstoragebatteryof6voltsforallofthemasshownatBinFig.44,butforeveryvacuumtubeyouuseyoumusthaveaBor22-1/2voltdrybatterytochargetheplatewith.
ARadioFrequencyTransformerAmplifyingReceivingSet.--Insteadofusingagridleakresistancetocoupleuptheamplifieranddetectortubecircuitsyoucanusearadiofrequencytransformer,thatis,atransformermadelikealoosecoupledtuningcoil,andwithoutanironcore,asshowninthewiringdiagramatAinFig.45.Inthisset,whichgivesbetterresultsthanwhereagridleakisused,theamplifiertubeisplacedinthefirstoscillationcircuitandthedetectortubeinthesecondcircuit.
Sincetheradiofrequencytransformerhasnoironcorethehighfrequency,orradiofrequencyoscillatingcurrents,astheyarecalled,surgethroughitandarenotchangedintolowfrequency,oraudiofrequencypulsatingcurrents,untiltheyflowthroughthedetector.Sincethediagramshowsonlyoneamplifierandoneradiofrequencytransformer,itisconsequentlyaonestepamplifier;however,two,threeormore,amplifyingtubescanbeconnectedupbymeansofanequalnumberofradiofrequencytransformerswhenyouwillgetwonderfulresults.Whereasixstepamplifier,thatis,wheresixamplifyingtubesareconnectedtogether,orincascade,thefirstthreeareusuallycoupledupwithradiofrequencytransformersandthelastthreewithaudiofrequencytransformers.AradiofrequencytransformerisshownatBandcosts$6to$7.
AnAudioFrequencyTransformerAmplifyingReceivingSet.--Whereaudiofrequencytransformersareusedforsteppingupthevoltageofthecurrentofthedetectorandamplifiertubes,theradiofrequencycurrentdoesnotgetintotheplatecircuitofthedetectoratallforthereasonthattheironcoreofthetransformerchokesthemoff,hence,thesucceedingamplifiersoperateataudiofrequencies.AnaudiofrequencytransformerisshownatAinFig.46andawiringdiagramshowinghowthetubesare
connectedincascadewiththetransformersisshownatB;itisthereforeatwo-stepaudiofrequencyreceivingset.
ASixStepAmplifierReceivingSetWithaLoopAerial.--Byusingareceivingsethavingathreestepradiofrequencyandathreestepaudiofrequency,thatis,asetinwhichtherearecoupledthreeamplifyingtubeswithradiofrequencytransformersandthreeamplifyingtubeswithaudiofrequencytransformersasdescribedunderthecaptionARadioFrequencyTransformerReceivingSet,youcanusealoopaerialinyourroomthusgettingaroundthedifficulties--ifsuchtherebe--inerectinganout-dooraerial.Youcaneasilymakealoopaerialbywinding10turnsofNo.14or16copperwireabout1/16inchapartonawoodenframetwofeetonthesideasshowninFig.47.Withthissixstepamplifiersetandloopaerialyoucanreceivewavelengthsof150to600metersfromvarioushighpowerstationswhichareatconsiderabledistancesaway.
HowtoPreventHowling.--Whereradiofrequencyoraudiofrequencyamplifiersareusedtocoupleyouramplifiertubesincascadeyoumusttakeparticularpainstoshieldthemfromoneanotherinordertopreventthefeedbackofthecurrentsthroughthem,whichmakestheheadphonesorloudspeakerhowl.Toshieldthemfromeachotherthetubesshouldbeenclosedinmetalboxesandplacedatleast6inchesapartwhilethetransformersshouldbesetsothattheircoresareatrightanglestoeachotherandthesealsoshouldbenotlessthansixinchesapart.
CHAPTERX
REGENERATIVEAMPLIFICATIONRECEIVINGSETS
Whileavacuumtubedetectorhasanamplifyingactionofitsown,andthisaccountsforitsgreatsensitiveness,itsamplifyingactioncanbefurtherincreasedtoanenormousextentbymakingtheradiofrequencycurrentsthataresetupintheoscillationcircuitsreactonthedetector.
Suchcurrentsarecalledfeed-backorregenerativecurrentsandwhencircuitsaresoarrangedastocausethecurrentstoflowbackthroughthedetectortubetheamplificationkeepsonincreasinguntilthecapacityofthetubeitselfisreached.Itislikeusingsteamoverandoveragaininasteamturbineuntilthereisnomoreenergyleftinit.AsystemofcircuitswhichwillcausethisregenerativeactiontotakeplaceisknownastheArmstrongcircuitsandissocalledaftertheyoungmanwhodiscoveredit.
Sincetheregenerativeactionoftheradiofrequencycurrentsisproducedbythedetectortubeitselfandwhichsetsupanamplifyingeffectwithouttheadditionofanamplifyingtube,thistypeofreceivingsethasfoundgreatfavorwithamateurs,whileincombinationwithamplifyingtubesitmultipliestheirpowerproportionatelyanditisinconsequenceusedinoneformoranotherinallthebettersets.
Therearemanydifferentkindsofcircuitswhichcanbeusedtoproducetheregenerativeamplificationeffectwhilethevariouskindsoftuningcoilswillserveforcouplingthem;forinstanceatwoorthreeslidesingletuningcoilwillanswerthepurposebutasitdoesnotgivegoodresultsitisnotadvisabletospendeithertimeormoneyonit.Abetterschemeistousealoosecouplerformedoftwoorthreehoneycomborothercompactcoils,whileavariocoupleroravariometerortwowillproducethemaximumregenerativeaction.
TheSimplestTypeofRegenerativeReceivingSet.WithLooseCoupledTuningCoil.--Whilethisregenerativesetisthesimplestthatwillgiveanythinglikefairresultsitisheredescribednotonaccountofitsdesirability,butbecauseitwillservetogiveyouthefundamentalideaofhowthefeed-backcircuitisformed.
Forthissetyouneed:(1)aloose-coupledtuningcoilsuchasdescribedinChapterIII,(2)avariablecondenserof.001mfd.(microfarad)capacitance;(3)onefixedcondenserof.001mfd.;(4)onefixedcondenserforthegridleakcircuitof.00025mfd.;(5)agridleakof1/2to2megohmsresistance;(6)avacuumtubedetector;(7)anA6voltbattery;(8)arheostat;(9)aB221/2voltbattery;and(10)apairof2000ohmheadphones.
ConnectingUptheParts.--Beginbyconnectingtheleading-inwireoftheaerialwiththebindingpostendoftheprimarycoiloftheloosecouplerasshowninthewiringdiagramFig.48andthenconnecttheslidingcontactwiththewaterpipeorotherground.Connectthebindingpostendoftheprimarycoilwithonepostofthevariablecondenser,connecttheotherpostofthiswithoneofthepostsofthe.00025mfd.condenserandtheotherendofthiswiththegridofthedetectortube;thenaroundthiscondensershuntthegridleakresistance.
Nextconnecttheslidingcontactoftheprimarycoilwiththeotherpostofthevariablecondenserandfromthisleadawireonovertooneoftheterminalsofthefilamentofthevacuumtube;totheotherterminalofthefilamentconnectoneofthepostsoftherheostatandconnecttheotherposttothe-ornegativeelectrodeoftheAbatteryandthenconnectthe+orpositiveelectrodeofittotheotherterminalofthefilament.
Connectthe+orpositiveelectrodeoftheAbatterywithonepostofthe.001mfd.fixedcondenserandconnecttheotherpostofthistooneoftheendsofthesecondarycoilofthetuningcoilandwhichisnowknownastheticklercoil;thenconnecttheotherendofthesecondary,orticklercoiltotheplateofthevacuumtube.Inthewiringdiagramthesecondary,orticklercoilisshownaboveandinalinewiththeprimarycoilbutthisisonlyforthesakeofmakingtheconnectionsclear;inrealitythesecondary,orticklercoilslidestoandfrointheprimarycoilasshownanddescribedinChapterIII.Finallyconnectthenegative,orzincpoleoftheBbatterytoonesideofthefixedcondenser,thepositive,orcarbon,poletooneoftheterminalsoftheheadphonesandtheotherterminalofthistotheotherpostofthefixedcondenserwhenyourregenerativesetiscomplete.
AnEfficientRegenerativeReceivingSet.WithThreeCoilLooseCoupler.--Toconstructareallygoodregenerativesetyoumustusealoosecoupledtunerthathasthreecoils,namelyaprimary,asecondaryandaticklercoil.AtunerofthiskindismadelikeanordinaryloosecoupledtuningcoilbutithasathirdcoilasshownatAandBinFig.49.Themiddlecoil,whichisthesecondary,isfixedtothebase,andthelargeoutsidecoil,whichistheprimary,ismovable,thatisitslidestoandfrooverthemiddlecoil,whilethesmallinsidecoil,whichisthetickler,isalsomovableandcanslideinoroutofthemiddlecoil.Noneofthesecoilsisvariable;allarewoundtoreceivewavesupto360metersinlengthwhenusedwithavariablecondenserof.001mfd.capacitance.Inotherwordsyou
slidethecoilsinandouttogettherightamountofcouplingandyoutunebyadjustingthevariablecondensertogettheexactwavelengthyouwant.
WithCompactCoils.--Compactcoiltunersareformedofthreefixedinductanceswoundinflatcoils,andthesearepivotedinamountingsothatthedistancebetweenthemand,therefore,thecoupling,canbevaried,asshownatAinFig.50.Thesecoilsarewoundupbythemakersforvariouswavelengthsrangingfromasmallonethatwillreceivewavesofanylengthupto360meterstoalargeonethathasamaximumof24,000meters.Foranamateursetgetthreeofthesmallestcoilswhenyoucannotonlyhearamateurstationsthatsendona200meterwavebutbroadcastingstationsthatsendona360meterwave.
Thesethreecoilsaremountedwithpanelplugswhichlatterfitintoastand,ormounting,sothatthemiddlecoilisfixed,thatis,stationary,whilethetwooutsidecoilscanbeswungtoandfrolikeadoor;thisschemepermitssmallvariationsofcouplingtobehadbetweenthecoilsandthiscanbedoneeitherbyhandlesorbymeansofknobsonapanelboard.WhileIhavesuggestedtheuseofthesmallestsizecoils,youcangetandusethosewoundforanywavelengthyouwanttoreceiveandwhenthoseareconnectedwithvariometersandvariablecondensers,andwithaproperaerial,youwillhaveahighlyefficientreceptorthatwillworkoverallrangesofwavelengths.Thesmallestsizecoilscostabout$1.50apieceandthemountingcostsabout$6or$7each.
TheABatteryPotentiometer.--Thisdeviceissimplyaresistanceliketherheostatdescribedinconnectionwiththeprecedingvacuumtubereceivingsetsbutitiswoundto200or300ohmsresistanceasagainst1-1/2to6ohmsoftherheostat.Itis,however,usedaswellastherheostat.Withavacuumtubedetector,andespeciallywithonehavingagas-content,apotentiometerisverynecessaryasitisonlybymeansofitthatthepotentialoftheplateofthedetectorcanbeaccuratelyregulated.Theresultofproperregulationisthatwhenthecriticalpotentialvalueisreachedthereisamarkedincreaseintheloudnessofthesoundsthatareemittedbytheheadphones.
AsyouwillseefromAinFig.51ithasthreetaps.ThetwotapswhichareconnectedwiththeendsoftheresistancecoilareshuntedaroundtheAbatteryandthethirdtap,whichisattachedtothemovablecontactarm,isconnectedwiththeBbatterytap,seeB,atwhichthisbatterygives18volts.SincetheAbatterygives6voltsyoucanvarythepotentialoftheplatefrom18to24volts.ThepotentiometermustneverbeshuntedaroundtheBbatteryorthelatterwillsoonrundown.Apotentiometercostsacoupleofdollars.
ThePartsandHowtoConnectThemUp.--Forthisregenerativesetyouwillneed:(1)ahoneycomborothercompactthree-coiltuner,(2)twovariable(.001and.0005mfd.)condensers;(3)a.00025mfd.fixedcondenser;(4)a1/2to2megohmgridleak;(5)atubedetector;(6)a6voltAbattery;(7)arheostat;(8)apotentiometer;(9)an18or20voltBbattery;(10)afixedcondenserof.001mfd.fixedcondenser;and(11)apairof2000ohmheadphones.
Towireupthepartsconnecttheleading-inwireoftheaerialwiththeprimarycoil,whichisthemiddleoneofthetuner,andconnecttheotherterminalwiththeground.Connecttheendsofthesecondarycoil,whichisthemiddleone,withthepostsofthevariablecondenserandconnectoneofthepostsofthelatterwithonepostofthefixed.00025mfd.condenserandtheotherpostofthiswiththegrid;thenshuntthegridleakaroundit.Nextconnecttheotherpostofthevariablecondensertothe-ornegativeelectrodeoftheAbattery;the+orpositiveelectrodeofthistooneterminalofthedetectorfilamentandtheotherendofthelattertotheelectrodeoftheAbattery.
Nowconnectoneendoftheticklercoilwiththedetectorplateandtheotherposttothefixed.001mfd.condenser,thentheotherendofthistothepositiveorcarbonpoleoftheBbattery.
ThisdoneshuntthepotentiometeraroundtheAbatteryandrunawirefromthemovablecontactofit(thepotentiometer)overtothe18volttap,(seeB,Fig.51),oftheBbattery.Finally,shunttheheadphonesandthe.001mfd.fixedcondenserandyouarereadytotryoutconclusions.
ARegenerativeAudioFrequencyAmplifierReceivingSet.--Theuseofamateurregenerativecascadeaudiofrequencyreceivingsetsisgettingtobequitecommon.Togetthegreatestamplificationpossiblewithamplifyingtubesyouhavetokeepanegativepotentialonthegrids.Youcan,however,getverygoodresultswithoutanyspecialchargingarrangementbysimplyconnectingonepostoftherheostatwiththenegativeterminalofthefilamentandconnectingthelowpotentialendofthesecondaryofthetuningcoilwiththe-ornegativeelectrodeoftheAbattery.Thisschemewillgivethegridsanegativebiasofabout1volt.Youdonotneedtobotherabouttheseaddedfactorsthatmakeforhighefficiencyuntilafteryouhavegotyourreceivingsetinworkingorderandunderstand
allaboutit.
ThePartsandHowtoConnectThemUp.--Exactlythesamepartsareneededforthissetastheonedescribedabove,butinadditionyouwillwant:(1)twomorerheostats;(2)twomoresetsofB22-1/2voltbatteries;(3)twoamplifiertubes,and(4)twoaudiofrequencytransformersasdescribedinChapterIXandpicturedatAinFig.46.
Towireupthepartsbeginbyconnectingtheleading-inwiretooneendoftheprimaryofthetuningcoilandthenconnecttheotherendofthecoilwiththeground.Avariablecondenserof.001mfd.capacitancecanbeconnectedinthegroundwire,asshowninFig.52,togoodadvantagealthoughitisnotabsolutelyneeded.Nowconnectoneendofthesecondarycoiltoonepostofa.001mfd.variablecondenserandtheotherendofthesecondarytotheotherpostofthecondenser.
Nextbringalead(wire)fromthefirstpostofthevariablecondenserovertothepostofthefirstfixedcondenserandconnecttheotherpostofthelatterwiththegridofthedetectortube.Shunt1/2to2megohmgridleakresistancearoundthefixedcondenserandthenconnectthesecondpostofthevariablecondensertooneterminalofthedetectortubefilament.Runthiswireonoverandconnectitwiththefirstpostofthesecondrheostat,thesecondpostofwhichisconnectedwithoneterminalofthefilamentofthefirstamplifyingtube;thenconnectthefirstpostoftherheostatwithoneendofthesecondarycoilofthefirstaudiofrequencytransformer,andtheotherendofthiscoilwiththegridofthefirstamplifiertube.
Connecttheleadthatrunsfromthesecondpostofvariablecondensertothefirstpostofthethirdrheostat,thesecondpostofwhichisconnectedwithoneterminalofthesecondamplifyingtube;thenconnectthefirstpostoftherheostatwithoneendofthesecondarycoilofthesecondaudiofrequencytransformerandtheotherendofthiscoilwiththegridofthesecondamplifiertube.
Thisdoneconnectthe-ornegativeelectrodeoftheAbatterywiththesecondpostofthevariablecondenserandconnectthe+orpositiveelectrodewiththefreepostofthefirstrheostat,theotherpostofwhichconnectswiththefreeterminalofthefilamentofthedetector.Fromthisleadtapoffawireandconnectittothefreeterminalofthefilamentofthefirstamplifiertube,andfinallyconnecttheendoftheleadwiththefreeterminalofthefilamentofthesecondamplifiertube.
NextshuntapotentiometeraroundtheAbatteryandconnectthethirdpost,whichconnectswiththeslidingcontact,tothenegativeorzincpoleofaBbattery,thenconnectthepositiveorcarbonpoleofittothenegativeorzincpoleofasecondBbatteryandthepositiveorcarbonpoleofthelatterwithoneendoftheprimarycoilofthesecondaudiofrequencytransformerandtheotherendofittotheplateofthefirstamplifyingtube.Runtheleadonoverandconnectittooneoftheterminalsofthesecondfixedcondenserandtheotherterminalofthiswiththeplateofthesecondamplifyingtube.Thenshunttheheadphonesaroundthecondenser.
FinallyconnectoneendoftheticklercoilofthetunerwiththeplateofthedetectortubeandconnecttheotherendoftheticklertooneendoftheprimarycoilofthefirstaudiofrequencytransformerandtheotherendofittothewirethatconnectsthetwoBbatteriestogether.
CHAPTERXI
SHORTWAVEREGENERATIVERECEIVINGSETS
Ashortwavereceivingsetisonethatwillreceivearangeofwavelengthsoffrom150to600meterswhilethedistanceoverwhichthewavescanbereceivedaswellastheintensityofthesoundsreproducedbytheheadphonesdependson:(1)whetheritisaregenerativesetand(2)whetheritisprovidedwithamplifyingtubes.
High-graderegenerativesetsdesignedespeciallyforreceivingamateursendingstationsthatmustuseashortwavelengtharebuiltontheregenerativeprinciplejustlikethosedescribedinthelastchapterandfurtheramplificationcanbehadbytheuseofamplifiertubesasexplainedinChapterIX,butthenewfeatureofthesesetsistheuseofthevariocouplerandoneormorevariometers.Thesetuningdevicescanbeconnectedupindifferentwaysandareverypopularwithamateursatthepresenttime.
Differingfromtheordinaryloosecouplerthevariometerhasnomovablecontactswhilethevariometerisprovidedwithtapssothatyoucanconnectitupforthewavelengthyouwanttoreceive.Allyouhavetodoistotunetheoscillationcircuitstoeachotheristoturntherotor,whichisthesecondarycoil,aroundinthestator,astheprimarycoiliscalledinordertogetaveryfinevariationofthewavelength.Itisthisconstructionthatmakessharptuningwiththesesetspossible,bywhichismeantthatallwavelengthsaretunedoutexcepttheonewhichthereceivingsetistunedfor.
AShortWaveRegenerativeReceiver--WithOneVariometerandThreeVariableCondensers.--Thissetalsoincludesavariocouplerandagridcoil.Thewaythatthepartsareconnectedtogethermakesitasimpleandatthesametimeaveryefficientregenerativereceiverforshortwaves.Whilethissetcanbeusedwithoutshieldingthepartsfromeachotherthebestresultsarehadwhenshieldsareused.
Thepartsyouneedforthissetinclude:(1)onevariocoupler;(2)one.001microfaradvariablecondenser;(3)one.0005microfaradvariablecondenser;(4)one.0007microfaradvariablecondenser;(5)one2megohmgridleak;(6)onevacuumtubedetector;(7)one6voltAbattery;(8)one6ohm,1-1/2ampererheostat;(9)one200ohmpotentiometer;(10)one22-1/2voltBbattery;(11)one.001microfaradfixedcondenser,(12)onepairof2,000ohmheadphones,and(13)avariometer.
TheVariocoupler.--Avariocouplerconsistsofaprimarycoilwoundontheoutsideofatubeofinsulatingmaterialandtocertainturnsofthistapsareconnectedsothatyoucanfixthewavelengthwhichyouraerialsystemistoreceivefromtheshortestwave;i.e.,150metersonupbystepstothelongestwave,i.e.,600meters,whichistherangeofmostamateurvariocouplersthataresoldintheopenmarket.Thisisthepartofthevariocouplerthatiscalledthestator.
Thesecondarycoiliswoundonthesectionofaballmountedonashaftandthisisswunginbearingsonthestatorsothatitcanturninit.Thispartofthevariocoupleriscalledtherotorandisarrangedsothatitcanbemountedonapanelandadjustedbymeansofaknoboradial.AdiagramofavariocouplerisshownatAinFig.53,andthecoupleritselfatB.Therearevariousmakesandmodificationsofvariocouplersonthemarketbutallofthemareaboutthesamepricewhichis$6.00or$8.00.
TheVariometer.--Thisdeviceisquitelikethevariocoupler,butwiththesedifferences:(1)therotorturnsinthestator,whichisalsothesectionofaball,and(2)oneendoftheprimaryisconnectedwithoneendofthesecondarycoil.Tobereallyefficientavariometermusthaveasmallresistanceandalargeinductanceaswellasasmalldielectricloss.Tosecurethefirsttwoofthesefactorsthewireshouldbeformedofanumberoffine,purecopperwireseachofwhichisinsulatedandthewholestrandthencoveredwithsilk.Thiskindofwireisthebestthathasyetbeendevisedforthepurposeandissoldunderthetradenameoflitzendraht.
Anewtypeofvariometerhaswhatisknownasabasketweave,orwavywoundstatorandrotor.Thereisnowood,insulatingcompoundorotherdielectricmaterialsinlargeenoughquantitiestoabsorbtheweakcurrentsthatflowbetweenthem,henceweakersoundscanbeheardwhenthiskindofavariometerisused.Withityoucantunesharplytowavesunder200metersinlengthanduptoandincludingwavelengthsof360meters.Whenamateurstationsofsmallpoweraresendingontheseshortwavesthisstyleofvariometerkeepstheelectricoscillationsattheirgreateststrengthand,hence,thereproducedsoundswillbeofmaximumintensity.AwiringdiagramofavariometerisshownatAinFig.54andabasketballvariometerisshowncompleteatB.
ConnectingUptheParts.--Tohook-upthesetconnecttheleading-inwiretooneendoftheprimarycoil,orstator,ofthevariocouplerandsolderawiretooneofthetapsthatgivesthelongestwavelengthyouwanttoreceive.Connecttheotherendofthiswirewithonepostofa.001microfaradvariablecondenserandconnecttheotherpostwiththegroundasshowninFig.55.Nowconnectoneendofthesecondarycoil,orrotor,toonepostofa.0007mfd.variablecondenser,theotherpostofthistooneendofthegridcoilandtheotherendofthiswiththeremainingendoftherotorofthevariocoupler.
Nextconnectonepostofthe.0007mfd.condenserwithoneoftheterminalsofthedetectorfilament;thenconnecttheotherpostofthiscondenserwithonepostofthe.0005mfd.variablecondenserandtheotherpostofthiswiththegridofthedetector,thenshuntthemegohmgridleakaroundthelattercondenser.Thisdoneconnecttheotherterminalofthefilamenttoonepostoftherheostat,theotherpostofthistothe-ornegativeelectrodeofthe6voltAbatteryandthe+orpositiveelectrodeofthelattertotheotherterminalofthefilament.
ShuntthepotentiometeraroundtheAbatteryandconnecttheslidingcontactwiththe-orzincpoleoftheBbatteryandthe+orcarbonpolewithoneterminaloftheheadphone;connecttheotherterminaltooneofthepostsofthevariometerandtheotherpostofthevariometertotheplateofthedetector.Finallyshunta.001mfd.fixedcondenseraroundtheheadphones.IfyouwanttoamplifythecurrentwithavacuumtubeamplifierconnectintheterminalsoftheamplifiercircuitshownatAinFigs.44or45atthepointwheretheyareconnectedwiththesecondarycoiloftheloosecoupledtuningcoil,inthosediagramswiththebindingpostsofFig.55wherethephonesareusuallyconnectedin.
ShortWaveRegenerativeReceiver.WithTwoVariometersandTwoVariableCondensers.--Thistypeofregenerativereceptorisverypopularwithamateurswhoareusinghigh-gradeshort-wavesets.Whenyouconnectupthisreceptoryoumustkeepthevariouspartswellseparated.Screwthevariocouplertothemiddleofthebaseboardorpanel,andsecurethevariometersoneithersideofitsothatthedistancebetweenthemwillbe9or10inches.Bysoplacingthemthecouplingwillbethesameonbothsidesandbesidesyoucanshieldthemfromeachothereasier.
Fortheshielduseasheetofcopperonthebackofthepanelandplaceasheetofcopperbetweentheparts,orbetter,enclosethevariometersanddetectorandamplifyingtubesifyouusethelatterinsheetcopperboxes.Whenyousetupthevariometersplacethemsothattheirstatorsareatrightanglestoeachotherforotherwisethemagneticlinesofforcesetupbythecoilsofeachonewillbemutuallyinductiveandthiswillmaketheheadphonesorloudspeakerhowl.Whatevertendencythereceptorhastohowlwiththisarrangementcanbeovercomebyputtinginagridleakoftherightresistanceandadjustingthecondenser.
ThePartsandHowtoConnectThemUp.--Forthissetyourequire:(1)onevariocoupler;(2)twovariometers;(3)one.001microfaradvariablecondenser;(4)one.0005microfaradvariablecondenser;(5)one2megohmgridleakresistance;(6)onevacuumtubedetector;(7)one6voltAbattery;(8)one200ohmpotentiometer;(9)one22-1/2voltBbattery;(10)one.001microfaradfixedcondenser,and(11)onepairof2,000ohmheadphones.
Towireupthesetbeginbyconnectingtheleading-inwiretothefixedendoftheprimarycoil,orstator,ofthevariocoupler,asshowninFig.56,andconnectonepostofthe.001mfd.variablecondensertothestatorbysolderingashortlengthofwiretothetapofthelatterthatgivesthelongestwaveyouwanttoreceive.Nowconnectoneendofthesecondarycoil,orrotor,ofthevariocouplerwithonepostofthe.0005mfd.variablecondenserandtheotherparttothegridofthedetectortube.Connecttheotherendoftherotorofthevariocouplertooneofthepostsofthefirstvariometerandtheotherpostofthistooneoftheterminalsofthedetectorfilament.
Connectthisfilamentterminalwiththe-ornegativeelectrodeoftheAbatteryandthe+orpositiveelectrodeofthiswithonepostoftherheostatandleadawirefromtheotherposttothefreeterminalofthefilament.ThisdoneshuntthepotentialaroundtheAbatteryandconnecttheslidingcontacttothe-orzincpoleoftheBbatteryandthe+orcarbonpoleofthistooneterminaloftheheadphones,whiletheotherterminalofthisleadstooneofthepostsofthesecondvariometer,theotherpostofwhichisconnectedtotheplateofthedetectortube.Ifyouwanttoaddanamplifiertubethenconnectittothepostsinsteadoftheheadphonesasdescribedintheforegoingset.
CHAPTERXII
INTERMEDIATEANDLONGWAVEREGENERATIVERECEIVINGSETS
Allreceivingsetsthatreceiveoverarangeofwavelengthsoffrom150metersto3,000metersarecalledintermediatewavesetsandallsetsthatreceivewavelengthsoverarangeofanythingmorethan3,000metersarecalledlongwavesets.Therangeofintermediatewavereceptorsissuchthattheywillreceiveamateur,broadcasting,shipandshoreNavy,commercial,Arlington'stimeandallotherstationsusingsparktelegraphdampedwavesorarcorvacuumtubetelephonecontinuouswavesbutnotcontinuouswavetelegraphsignals,unlessthesehavebeenbrokenupintogroupsatthetransmittingstation.Toreceivecontinuouswavetelegraphsignalsrequiresreceivingsetsofspecialkindandthesewillbedescribedinthenextchapter.
IntermediateWaveReceivingSets.--Therearetwochiefschemesemployedtoincreasetherangeofwavelengthsthatasetcanreceiveandthesearebyusing:(1)loadingcoilsandshuntcondensers,and(2)bank-woundcoilsandvariablecondensers.Ifyouhaveashort-wavesetandplantoreceiveintermediatewaveswithitthenloadingcoilsandfixedcondensersshuntedaroundthemaffordsyouthewaytodoit,butifyouprefertobuyanewreceptorthenthebetterwayistogetonewithbank-woundcoilsandvariablecondensers;thislatterwaypreservestheelectricalbalanceoftheoscillationcircuitsbetter,theelectricallossesarelessandthetuningeasierandsharper.
IntermediateWaveSetWithLoadingCoils.--Forthisintermediatewavesetyoucanuseeitheroftheshort-wavesetsdescribedintheforegoingchapter.Fortheloadingcoilsusehoneycombcoils,orothergoodcompactinductancecoils,asshowninChapterXandhavingarangeofwhateverwavelengthyouwishtoreceive.Thefollowingtableshowstherangeofwavelengthofthevarioussizedcoilswhenusedwithavariablecondenserhavinga.001microfaradcapacitance,theapproximateinductanceofeachcoilinmillihenriesandpricesatthepresentwriting:
TABLEOFCHARACTERISTICSOFHONEYCOMBCOILS
ApproximateWave
LengthinMetersin
Millihenries
Inductance.001mfd.VariableMounted
Appx.AirCondenser.onPlug
.040130--375$1.40
.075180--5151.40
.15240--7301.50
.3330--10301.50
.6450--14601.55
1.3660--22001.60
2.3930--28501.65
4.51300--40001.70
6.51550--48001.75
11.2050--63001.80
20.3000--85002.00
40.4000--120002.15
65.5000--150002.35
100.6200--190002.60
125.7000--210003.00
175.8200--240003.50
Theseandotherkindsofcompactcoilscanbeboughtatelectricalsupplyhousesthatsellwirelessgoods.Ifyouraerialisnotveryhighorlongyoucanuseloadingcoils,buttogetanythinglikeefficientresultswiththemyoumusthaveanaerialoflargecapacitanceandtheonlywaytogetthisistoputupahighandlongonewithtwoormoreparallelwiresspacedagoodlydistanceapart.
ThePartsandHowtoConnectThemUp.--Get(1)twohoneycomborothercoilsofthegreatestwavelengthyouwanttoreceive,forinordertoproperlybalancetheaerial,orprimaryoscillationcircuit,andtheclosed,orsecondaryoscillationcircuit,youhavetotunethemtothesamewavelength;(2)two.001mfd.variablecondensers,thoughfixedcondenserswilldo,and(3)twosmallsingle-throwdouble-poleknifeswitchesmountedonporcelainbases.
Tousetheloadingcoilsallyouhavetodoistoconnectoneofthemintheaerialabovetheprimarycoiloftheloosecoupler,orvariocouplerasshowninthewiringdiagraminFig.57,thenshuntoneofthecondensersarounditandconnectoneoftheswitchesaroundthis;thisswitchenablesyoutocutinorouttheloadingcoilatwill.Likewiseconnecttheotherloadingcoilinonesideoftheclosed,orsecondarycircuitbetweenthevariable.0007mfd.condenserandthesecondarycoiloftheloosecouplerorvariocouplerasshowninFig.53.TheotherconnectionsareexactlythesameasshowninFigs.44and45.
AnIntermediateWaveSetWithVariocouplerInductanceCoils.--Byusingthecoilwoundontherotorofthevariocouplerastheticklerthecouplingbetweenthedetectortubecircuitsandtheaerialwiresystemincreasesasthesetistunedforgreaterwavelengths.Thisschememakesthecontroloftheregenerativecircuitfarmorestablethanitiswhereanordinaryloosecoupledtuningcoilisused.
Whenthevariocouplerisadjustedforreceivingverylongwavestherotorsetsatrightanglestothestatorand,sincewhenitisinthispositionthereisnomutualinductionbetweenthem,theticklercoilservesasaloadingcoilforthedetectorplateoscillationcircuit.Inductancecoilsforshortwavelengthsareusuallywoundinsinglelayersbutbank-woundcoils,astheyarecalledarenecessarytogetcompactnesswherelongwavelengthsaretobereceived.Bywindinginductancecoilswithtwoormorelayersthehighestinductancevaluescanbeobtainedwiththeleastresistance.AwiringdiagramofamultipointinductancecoilisshowninFig.58.Youcanbuythisintermediatewavesetassembledandreadytouseorgetthepartsandconnectthemupyourself.
ThePartsandHowtoConnectThemUp.--Forthisregenerativeintermediatewavesetget:(1)one12sectiontriplebank-woundinductancecoil,(2)onevariometer,and(3)alltheotherpartsshowninthediagramFig.58exceptthevariocoupler.Firstconnectthefreeendofthecondenserintheaerialtooneoftheterminalsofthestatorofthevariocoupler;thenconnecttheotherterminalofthestatorwithoneoftheendsofthebank-woundinductancecoilandconnectthemovablecontactofthiswiththeground.
Nextconnectawiretotheaerialbetweenthevariablecondenserandthestatorandconnectthistoonepostofa.0005microfaradfixedcondenser,thenconnecttheotherpostofthiswiththegridofthedetectorandshunta2megohmgridleakaroundit.Connectawiretothegroundwirebetweenthebank-woundinductancecoilandthegroundproper,i.e.,theradiatororwaterpipe,connecttheotherendofthistothe+electrodeoftheAbatteryandconnectthisendalsotooneoftheterminalsofthe
filament.Thisdoneconnecttheotherterminalofthefilamenttoonepostoftherheostatandtheotherpostofthistothe-ornegativesideoftheAbattery.
Tothe+electrodeoftheAbatteryconnectthe-orzincpoleoftheBbatteryandconnectthe+orcarbonpoleofthelatterwithonepostofthefixed.001microfaradcondenser.Thisdoneconnectoneterminaloftheticklercoilwhichisontherotorofthevariometertotheplateofthedetectorandtheotherterminaloftheticklertotheotherpostofthe.001condenserandaroundthisshuntyourheadphones.Orifyouwanttouseoneormoreamplifyingtubesconnectthecircuitofthefirstone,seeFig.45,tothepostsoneithersideofthefixedcondenserinsteadoftheheadphones.
ALongWaveReceivingSet.--ThevividimaginationofJulesVerneneverconceivedanythingsofascinatingasthereceptionofmessageswithoutwiressentoutbystationshalfwayroundtheworld;andinthesedaysofhighpowercablelessstationsonthefivecontinentsyoucanlisten-intothemessagesandhearwhatisbeingsentoutbytheLyons,ParisandotherFrenchstations,byGreatBritain,Italy,GermanyandevenfaroffRussiaandJapan.
Alongwavesetforreceivingthesestationsmustbeabletotunetowavelengthsupto20,000meters.Differingfromthewayinwhichtheregenerativeactionoftheshortwavesetsdescribedintheprecedingchapterissecuredandwhichdependsonaticklercoilandthecouplingactionofthedetectorinthislongwaveset,[Footnote:Alloftheshortwaveandintermediatewavereceiversdescribed,areconnectedupaccordingtothewiringdiagramusedbytheA.H.GrebeCompany,RichmondHill,LongIsland,N.Y.]thisactionisobtainedbytheuseofaticklercoilintheplatecircuitwhichisinductivelycoupledtothegridcircuitandthisfeedsbackthenecessaryamountofcurrent.Thisisaverygoodwaytoconnectupthecircuitsforthereasonthat:(1)thewiringissimplified,and(2)itgivesasinglevariableadjustmentfortheentirerangeofwavelengthsthereceptorisintendedtocover.
ThePartsandHowtoConnectThemUp.--Thetwochieffeaturesasfarasthepartsareconcernedofthislongwavelengthreceivingsetare(1)thevariablecondensers,and(2)thetuninginductancecoils.Thevariablecondenserusedinserieswiththeaerialwiresystemhas26platesandisequaltoacapacitanceof.0008mfd.whichisthenormalaerialcapacitance.Thecondenserusedinthesecondarycoilcircuithas14platesandthisisequaltoacapacitanceof.0004mfd.
Thereareanumberofinductancecoilsandthesearearrangedsothattheycanbeconnectedinorcutoutandcombinationsarethusformedwhichgiveahighefficiencyandyetallowthemtobecompactlymounted.Theinductancecoilsoftheaerialwiresystemandthoseofthesecondarycoilcircuitarepracticallyalike.Forwavelengthsupto2,200metersbanklitz-woundcoilsareusedandthesearewoundupin2,4and6banksinordertogivetheproperdegreeofcouplingandinductancevalues.
Wherewavelengthsofmorethan2,200metersaretobereceivedcoto-coilsareusedasthesearethe"lastword"ininductancecoildesign,andareespeciallyadaptedformediumaswellaslongwavelengths.[Footnote:CanbehadoftheCotoCoilCo.,Providence,R.I.]Thesevariouscoilsarecutinandoutbymeansoftwofive-pointswitcheswhichareprovidedwithauxiliaryleversandcontactorsfordead-endingtherightamountofthecoils.Incuttingincoilsforincreasedwavelengths,thatisfrom10,000to20,000meters,allofthecoilsoftheaerialareconnectedinseriesaswellasallofthecoilsofthesecondarycircuit.TheconnectionsforalongwavereceptorareshowninthewiringdiagraminFig.59.
CHAPTERXIII
HETERODYNEORBEATLONGWAVETELEGRAPHRECEIVINGSET
Anyofthereceivingsetsdescribedintheforegoingchapterswillrespondtoeither:(1)awirelesstelegraphtransmitterthatusesasparkgapandwhichsendsoutperiodicelectricwaves,orto(2)awirelesstelephonetransmitterthatusesanarcoravacuumtubeoscillatorandwhichsendsoutcontinuouselectricwaves.Toreceivewirelesstelegraphsignals,however,fromatransmitterthatusesanarcoravacuumtubeoscillatorandwhichsendsoutcontinuouswaves,eitherthetransmitterorthereceptormustbesoconstructedthatthecontinuouswaveswillbebrokenupintogroupsofaudiofrequencyandthisisdoneinseveraldifferentways.
Therearefourdifferentwaysemployedatthepresenttimetobreakupthecontinuouswavesofawirelesstelegraphtransmitterintogroupsandtheseare:(a)theheterodyne,orbeat,method,inwhichwavesofdifferentlengthsareimpressedonthereceivedwavesandsoproducesbeats;(b)thetikker,orchoppermethod,inwhichthehighfrequencycurrentsarerapidlybrokenup;(c)thevariablecondensermethod,inwhichthemovableplatesaremadetorapidlyrotate;(d)thetonewheel,orfrequencytransformer,asitisoftencalled,andwhichisreallyamodifiedformofandanimprovementonthetikker.Theheterodynemethodwillbedescribedinthischapter.
WhattheHeterodyneorBeatMethodIs.--ThewordheterodynewascoinedfromtheGreekwordsheteroswhichmeansother,ordifferent,anddynewhichmeanspower;inotherwordsitmeanswhenusedinconnectionwithawirelessreceptorthatanotheranddifferenthighfrequencycurrentisusedbesidestheonethatisreceivedfromthesendingstation.Inmusicabeatmeansaregularlyrecurrentswellingcausedbythereinforcementofasoundandthisissetupbytheinterferenceofsoundwaveswhichhaveslightlydifferentperiodsofvibrationas,forinstance,whentwotonestakeplacethatarenotquiteintunewitheachother.This,then,istheprincipleoftheheterodyne,orbeat,receptor.
Intheheterodyne,orbeatmethod,separatesustainedoscillations,thatarejustaboutasstrongasthoseoftheincomingwaves,aresetupinthereceivingcircuitsandtheirfrequencyisjustalittlehigheroralittlelowerthanthosethataresetupbythewavesreceivedfromthedistanttransmitter.Theresultisthattheseoscillationsofdifferentfrequenciesinterfereandreinforceeachotherwhenbeatsareproduced,theperiodofwhichisslowenoughtobeheardintheheadphones,hencetheincomingsignalscanbeheardonlywhenwavesfromthesendingstationarebeingreceived.AfullerexplanationofhowthisisdonewillbefoundinChapterXV.
TheAutodyneorSelf-HeterodyneLong-WaveReceivingSet.--Thisisthesimplesttypeofheterodynereceptoranditwillreceiveperiodicwavesfromsparktelegraphtransmittersorcontinuouswavesfromanarcorvacuumtubetelegraphtransmitter.Inthistypeofreceptorthedetectortubeitselfismadetosetuptheheterodyneoscillationswhichinterferewiththosethatareproducedbytheincomingwavesthatarealittleoutoftunewithit.
Withalongwaveautodyne,orself-heterodynereceptor,asthistypeiscalled,andatwo-stepaudio-frequencyamplifieryoucanclearlyhearmanyofthecablelessstationsofEuropeandothersthatsendoutlongwaves.Forreceivinglongwavestations,however,youmusthavealongaerial--asinglewire200ormorefeetinlengthwilldo--andthehigheritisthelouderwillbethesignals.
Whereitisnotpossibletoputtheaerialupahundredfeetormoreabovetheground,youcanusealoweroneandstillgetmessagesinInternationalMorsefairlystrong.
ThePartsandConnectionsofanAutodyne,orSelf-Heterodyne,ReceivingSet.--Forthislongwavereceivingsetyouwillneed:(1)onevariocouplerwiththeprimarycoilwoundonthestatorandthesecondarycoilandticklercoilwoundontherotor,oryoucanusethreehoneycomborothergoodcompactcoilsofthelongestwaveyouwanttoreceive,atableofwhichisgiveninChapterXII;(2)two.001mfd.variablecondensers;(3)one.0005mfd.variablecondenser;(4)one.5to2megohmgridleakresistance;(5)onevacuumtubedetector;(6)oneAbattery;(7)onerheostat;(8)oneBbattery;(9)onepotentiometer;(10)one.001mfd.fixedcondenserand(11)onepairofheadphones.Forthetwo-stepamplifieryoumust,ofcourse,havebesidestheabovepartstheamplifiertubes,variablecondensers,batteriesrheostats,potentiometersandfixedcondensersasexplainedinChapterIX.Theconnectionsfortheautodyne,orself-heterodyne,receivingsetareshowninFig.60.
TheSeparateHeterodyneLongWaveReceivingSet.--Thisisabetterlongwavereceptorthantheselfheterodynesetdescribedaboveforreceivingwirelesstelegraphsignalssentoutbyacontinuouslongwavetransmitter.Thegreatadvantageofusingaseparatevacuumtubetogeneratetheheterodyneoscillationsisthatyoucanmakethefrequencyoftheoscillationsjustwhatyouwantittobeandhenceyoucanmakeitalittlehigheroralittlelowerthantheoscillationssetupbythereceivedwaves.
ThePartsandConnectionsofaSeparateHeterodyneLongWaveReceivingSet.--Thepartsrequiredforthislongwavereceivingsetare:(1)fourhoneycomborothergoodcompactinductancecoilsofthelongestwavelengththatyouwanttoreceive;(2)three.001mfd.variablecondensers;(3)one.0005mfd.variablecondenser;(4)one1megohmgridleakresistance;(5)onevacuumtubedetector;(6)oneAbattery;(7)tworheostats;(8)twoBbatteries,oneofwhichissuppliedwithtaps;(9)onepotentiometer;(10)onevacuumtubeamplifier,forsettinguptheheterodyneoscillations;(11)apair
ofheadphonesand(12)allofthepartsforatwo-stepamplifierasdetailedinChapterIX,thatisifyouaregoingtouseamplifiers.TheconnectionsareshowninFig.61.
InusingeitheroftheseheterodynereceiversbesuretocarefullyadjusttheBbatterybymeansofthepotentiometer.
[Footnote:Theamplifiertubeinthiscaseisusedasageneratorofoscillations.]
CHAPTERXIV
HEADPHONESANDLOUDSPEAKERS
WirelessHeadphones.--AtelephonereceiverforawirelessreceivingsetismadeexactlyonthesameprincipleasanordinaryBelltelephonereceiver.Theonlydifferencebetweenthemisthattheformerismadeflatandcompactsothatapairofthemcanbefastenedtogetherwithabandandwornonthehead(whenitiscalledaheadset),whilethelatterislongandcylindricalsothatitcanbeheldtotheear.Afurtherdifferencebetweenthemisthatthewirelessheadphoneismadeassensitiveaspossiblesothatitwillrespondtoveryfeeblecurrents,whiletheordinarytelephonereceiverisfarfrombeingsensitiveandwillrespondonlytocomparativelylargecurrents.
HowaBellTelephoneReceiverIsMade.--Anordinarytelephonereceiverconsistsofthreechiefpartsandtheseare:(1)ahard-rubber,orcomposition,shellandcap,(2)apermanentsteelbarmagnetononeendofwhichiswoundacoiloffineinsulatedcopperwire,and(3)asoftirondisk,ordiaphragm,allofwhichareshowninthecross-sectioninFig.62.Thebarmagnetissecurelyfixedinsideofthehandlesothattheoutsideendcomestowithinabout1/32ofaninchofthediaphragmwhenthisislaidontopoftheshellandthecapisscrewedon.
Photographunavailableoriginal©UnderwoodandUnderwood.
AlexanderGrahamBell,InventoroftheTelephone,nowanardentRadioEnthusiast.
Theendsofthecoilofwireareconnectedwithtwobindingpostswhichareintheendoftheshell,butareshowninthepictureatthesidesforthesakeofclearness.Thiscoilusuallyhasaresistanceofabout75ohmsandthemeaningoftheohmicresistanceofareceiveranditsbearingonthesensitivenessofitwillbeexplainedalittlefartheralong.Afterthedisk,ordiaphragm,whichis
generallymadeofthin,softsheetironthathasbeentinnedorjapanned,[Footnote:Adiskofphotographictin-typeplateisgenerallyused.]isplacedovertheendofthemagnet,thecap,whichhasasmallopeninginit,isscrewedonandthereceiverisreadytouse.
HowaWirelessHeadphoneIsMade.--Forwirelessworkareceiverofthewatch-casetypeisusedandnearlyalwaystwosuchreceiversareconnectedwithaheadband.ItconsistsofapermanentbarmagnetbentsothatitwillfitintotheshellofthereceiverasshownatAinFig.63.
Theendsofthismagnet,whicharecalledpoles,arebentup,andhencethistypeiscalledabipolarreceiver.Themagnetsarewoundwithfineinsulatedwireasbeforeandthediaphragmisheldsecurelyinplaceoverthembyscrewingonthecap.
AboutResistance,TurnsofWireandSensitivityofHeadphones.--Ifyouareabeginnerinwirelessyouwillhearthosewhoareexperiencedspeakofatelephonereceiverashavingaresistanceof75ohms,1,000ohms,2,000or3,000ohms,asthecasemaybe;fromthisyouwillgatherthatthehighertheresistanceofthewireonthemagnetsthemoresensitivethereceiveris.Inasensethisistrue,butitisnottheresistanceofthemagnetcoilsthatmakesitsensitive,infact,itcutsdownthecurrent,butitisthenumberofturnsofwireonthemthatdeterminesitssensitiveness;itiseasytoseethatthisisso,forthelargerthenumberofturnsthemoreoftenwillthesamecurrentflowroundthecoresofthemagnetandsomagnetizethemtoagreaterextent.
Buttowindalargenumberofturnsofwirecloseenoughtothecorestobeeffectivethewiremustbeverysmallandso,ofcourse,thehighertheresistancewillbe.NowthewireusedforwindinggoodreceiversisusuallyNo.40,andthishasadiameterof.0031inch;consequently,whenyouknowtheohmicresistanceyougetanideaofthenumberofturnsofwireandfromthisyougatherinageneralwaywhatthesensitivityofthereceiveris.
Areceiverthatissensitiveenoughforwirelessworkshouldbewoundtonotlessthan1,000ohms(thismeanseachearphone),whilethoseofabettergradearewoundtoashighas3,000ohmsfor
eachone.Ahigh-gradeheadsetisshowninFig.64.Eachphoneofaheadsetshouldbewoundtothesameresistance,andtheseareconnectedinseriesasshown.Wheretwoormoreheadsetsareusedwithonewirelessreceivingsettheymustallbeofthesameresistanceandconnectedinseries,thatis,thecoilsofoneheadsetareconnectedwiththecoilsofthenextheadsetandsoontoformacontinuouscircuit.
TheImpedanceofHeadphones.--Whenacurrentisflowingthroughacircuitthematerialofwhichthewireismadenotonlyopposesitspassage--thisiscalleditsohmicresistance--butacounter-electromotiveforcetothecurrentissetupduetotheinductiveeffectsofthecurrentonitselfandthisiscalledimpedance.Whereawireiswoundinacoiltheimpedanceofthecircuitisincreasedandwhereanalternatingcurrentisusedtheimpedancegrowsgreaterasthefrequencygetshigher.Theimpedanceofthemagnetcoilsofareceiverissogreatforhighfrequencyoscillationsthatthelattercannotpassthroughthem;inotherwords,theyarechokedoff.
HowtheHeadphonesWork.--Asyouwillseefromthecross-sectionsinFigs.62and63thereisnoconnection,electricalormechanical,betweenthediaphragmandtheotherpartsofthereceiver.Nowwheneitherfeebleoscillations,whichhavebeenrectifiedbyadetector,orsmallcurrentsfromaBbattery,flowthroughthemagnetcoilsthepermanentsteelmagnetisenergizedtoagreaterextentthanwhennocurrentisflowingthroughit.Thisaddedmagneticenergymakesthemagnetattractthediaphragmmorethanitwoulddobyitsownforce.If,ontheotherhand,thecurrentiscutoffthepullofthemagnetislessenedandasitsattractionforthediaphragmisdecreasedthelatterspringsbacktoitsoriginalposition.Whenvaryingcurrentsflowthroughthecoilsthediaphragmvibratesaccordinglyandsendsoutsoundwaves.
AboutLoudSpeakers.--Thesimplestacousticinstrumenteverinventedisthemegaphone,whichlatterisaGreekwordmeaninggreatsound.ItisaveryprimitivedeviceandourIndiansmadeitoutofbirch-barkbeforeColumbusdiscoveredAmerica.Initssimplestformitconsistsofacone-shapedhornandasthespeakertalksintothesmallendtheconcentratedsoundwavespassoutofthelargeendinwhateverdirectionitisheld.
Nowaloudspeakerofwhateverkindconsistsoftwochiefpartsandtheseare:(1)atelephone
receiver,and(2)amegaphone,orhornasitiscalled.Aloudspeakerwhenconnectedwithawirelessreceivingsetmakesitpossibleforaroom,oranauditorium,fullofpeople,oranoutdoorcrowd,tohearwhatisbeingsentoutbyadistantstationinsteadofbeinglimitedtoafewpersonslistening-inwithheadphones.Tousealoudspeakeryoushouldhaveavacuumtubedetectorreceivingsetandthismustbeprovidedwithaone-stepamplifieratleast.
Togetreallygoodresultsyouneedatwo-stepamplifierandthenenergizetheplateofthesecondvacuumtubeamplifierwitha100voltBbattery;orifyouhaveathree-stepamplifierthenusethehighvoltageontheplateofthethirdamplifiertube.Amplifyingtubesaremadetostandaplatepotentialof100voltsandthisisthekindyoumustuse.Nowitmayseemcurious,butwhenthecurrentflowsthroughthecoilsofthetelephonereceiverinonedirectionitgivesbetterresultsthanwhenitflowsthroughintheotherdirection;tofindoutthewaythecurrentgivesthebestresultstryitoutbothwaysandthisyoucandobysimplyreversingtheconnections.
TheSimplestTypeofLoudSpeaker.--Thisloudspeaker,whichiscalled,theArkay,[Footnote:MadebytheRiley-KlotzMfg.Co.,Newark,N.J.]willworkonaone-ortwo-stepamplifier.Itconsistsofabrasshornwithacurveinitandinthebottomthereisanadapter,orframe,withasetscrewinitsothatyoucanfitinoneofyourheadphonesandthisisallthereistoit.Theconstructionisrigidenoughtopreventovertones,ordistortionofspeechormusic.ItisshowninFig.65.
AnotherSimpleKindofLoudSpeaker.--Anotherloudspeaker,seeFig.66,isknownastheAmplitone[Footnote:MadebytheAmericanPattern,FoundryandMachineCo.,82ChurchStreet,N.Y.C.]anditlikewisemakesuseoftheheadphonesasthesoundproducer.Thisdevicehasacastmetalhornwhichimprovesthequalityofthesound,andallyouhavetodoistosliptheheadphonesontheinlettubesofthehornanditisreadyforuse.Thetwoheadphonesnotonlygivealongervolumeofsoundthanwhereasingleoneisusedbutthereisacertainblendedqualitywhichresultsfromonephonesmoothingouttheimperfectionsoftheother.
AThirdKindofSimpleLoudSpeaker.--TheoperationoftheAmplitron,[Footnote:MadebytheRadioServiceCo.,110W.40thStreet,N.Y.]asthisloudspeakeriscalled,isslightlydifferentfromothersusedforthesamepurpose.Thesoundssetupbytheheadphoneareconveyedtotheapexofaninvertedcopperconewhichis7incheslongand10inchesindiameter.Hereitisreflectedbyaparabolicmirrorwhichgreatlyamplifiesthesounds.Theamplificationtakesplacewithoutdistortion,thesoundsremainingasclearandcrispaswhenprojectedbythetransmittingstation.Byremovingthecapfromthereceivertheshellisscrewedintoareceptacleontheendoftheloudspeakerandtheinstrumentisreadyforuse.ItispicturedinFig.67.
ASuperLoudSpeaker.--Thisloudspeaker,whichisknownastheMagnavoxTelemegafone,wastheinstrumentusedbyLt.HerbertE.Metcalf,3,000feetintheair,andwhichstartledtheCityofWashingtononApril2,1919,byrepeatingPresidentWilson'sVictoryLoanMessagefromanairplaneinflightsothatitwasdistinctlyheardby20,000peoplebelow.
ThiswonderfulachievementwasaccomplishedthroughtheinstallationoftheMagnavoxand
amplifiersinfrontoftheTreasuryBuilding.EverywordLt.MetcalfspokeintohiswirelesstelephonetransmitterwascaughtandswelledinvolumebytheTelemegafonesbelowandpersonsblocksawaycouldhearthemessageplainly.Twokindsoftheseloudspeakersaremadeandtheseare:(1)asmallloudspeakerfortheuseofoperatorssothatheadphonesneednotbeworn,and(2)alargeloudspeakerforauditoriumandout-dooraudiences.
Photographunavailableoriginal©UnderwoodandUnderwood.
World'sLargestLoudSpeakerevermade.InstalledinLytlePark,Cincinnati,Ohio,topermitPresidentHarding'sAddressatPointPleasant,Ohio,duringtheGrantCentenaryCelebrationtobe
heardwithinaradiusofonesquare.
Eitherkindmaybeusedwithaone-ortwo-stepamplifierorwithacascadeofhalfadozenamplifiers,accordingtothedegreeofloudnessdesired.TheTelemegafoneitselfisnotanamplifierinthetruesenseinasmuchasitcontainsnoelementswhichwilllocallyincreasetheincomingcurrent.Itdoes,however,transformthevariableelectriccurrentsofthewirelessreceivingsetintosoundvibrationsinamostwonderfulmanner.
Atelemegafoneofeitherkindisformedof:(1)atelephonereceiveroflargeproportions,(2)astep-downinductioncoil,and(3)a6voltstoragebatterythatenergizesapowerfulelectromagnetwhichworksthediaphragm.Anelectromagnetisusedinsteadofapermanentmagnetandthisisenergizedbya6-voltstoragebatteryasshowninthewiringdiagramatAinFig.68.Oneendofthecoreofthismagnetisfixedtotheironcaseofthespeakerandtogethertheseformtheequivalentofahorseshoemagnet.Amovablecoilofwireissupportedfromthecenterofthediaphragmtheedgeofwhichisrigidlyheldbetweenthecaseandthesmallendofthehorn.Thiscoilisplacedovertheupperendofthemagnetanditsterminalsareconnectedtothesecondaryoftheinductioncoil.Nowwhenthecoilisenergizedbythecurrentfromtheamplifiersitandthecoreactlikeasolenoidinthatthecoiltendstosuckthecoreintoit;butsincethecoreisfixedandthecoilismovablethecoredrawsthecoildowninstead.Theresultisthatwitheveryvariationofthecurrentthatflowsthroughthecoilitmovesupanddownandpullsandpushesthediaphragmdownandupwithit.Thelargeamplitudeofthevibrationsofthelattersetuppowerfulsoundwaveswhichcanbeheardseveralblocksawayfromthehorn.Inthiswaythenarethefaintincomingsignals,speechandmusicwhicharereceivedbytheamplifyingreceivingsetreproducedandmagnifiedenormously.TheTelemegafoneisshowncompleteatB.
CHAPTERXV
OPERATIONOFVACUUMTUBERECEPTORS
Fromtheforegoingchaptersyouhaveseenthatthevacuumtubecanbeusedeitherasadetectororanamplifierorasageneratorofelectricoscillations,asinthecaseoftheheterodynereceivingset.Tounderstandhowavacuumtubeactsasadetectorandasanamplifieryoumustfirstknowwhatelectronsare.ThewayinwhichthevacuumtubesetsupsustainedoscillationswillbeexplainedinChapterXVIIIinconnectionwiththeOperationofVacuumTubeTransmitters.
WhatElectronsAre.--Scienceteachesusthatmassesofmatteraremadeupofmolecules,thateachoftheseismadeupofatoms,andeachofthese,inturn,ismadeupofacentralcoreofpositiveparticlesofelectricitysurroundedbynegativeparticlesofelectricityasshownintheschematicdiagram,Fig.69.Thelittleblackcirclesinsidethelargecirclerepresentpositiveparticlesofelectricityandthelittlewhitecirclesoutsideofthelargecirclerepresentnegativeparticlesofelectricity,orelectronsastheyarecalled.
Itisthenumberofpositiveparticlesofelectricityanatomhasthatdeterminesthekindofanelementthatisformedwhenenoughatomsofthesamekindarejoinedtogethertobuilditup.Thushydrogen,whichisthelightestknownelement,hasonepositiveparticleforitsnucleus,whileuranium,theheaviestelementnowknown,has92positiveparticles.Nowbeforeleavingtheatompleasenotethatitisasmuchsmallerthanthediagramasthelatterissmallerthanoursolarsystem.
WhatIsMeantbyIonization.--Ahydrogenatomisnotonlylighterbutitissmallerthantheatomofanyotherelementwhileanelectronismorethanathousandtimessmallerthantheatomofwhichitisapart.Nowaslongasalloftheelectronsremainattachedtothesurfaceofanatomitspositiveandnegativechargesareequalizedanditwill,therefore,beneitherpositivenornegative,thatis,itwillbe
perfectlyneutral.When,however,oneormoreofitselectronsareseparatedfromit,andthereareseveralwaysbywhichthiscanbedone,theatomwillshowapositivechargeanditisthencalledapositiveion.
Inotherwordsapositiveionisanatomthathaslostsomeofitsnegativeelectronswhileanegativeionisonethathasacquiredsomeadditionalnegativeelectrons.Whenanumberofelectronsarebeingconstantlygivenbytheatomsofanelement,whichletussupposeisametal,andarebeingattractedtoatomsofanotherelement,whichwewillsayisalsoametal,aflowofelectronstakesplacebetweenthetwooppositelychargedelementsandformacurrentofnegativeelectricityasrepresentedbythearrowsatAinFig.70.
Whenastreamofelectronsisflowingbetweentwometalelements,asafilamentandaplateinavacuumtubedetector,oranamplifier,theyactascarriersformorenegativeelectronsandthesearesuppliedbyabatteryasweshallpresentlyexplain.Ithasalwaysbeencustomaryforustothinkofacurrentofelectricityasflowingfromthepositivepoleofabatterytothenegativepoleofitandhencewehavecalledthisthedirectionofthecurrent.Sincetheelectronictheoryhasbeenevolvedithasbeenshownthattheelectrons,ornegativechargesofelectricity,flowfromthenegativetothepositivepoleandthattheionizedatoms,whicharemorepositivethannegative,flowintheoppositedirectionasshownatB.
HowElectronsareSeparatedfromAtoms.--Thenextquestionthatarisesishowtomakeametalthrowoffsomeoftheelectronsoftheatomsofwhichitisformed.Thereareseveralwaysthatthiscanbedonebutinanyeventeachatommustbegivenagood,hardblow.Asimplewaytodothisistoheatametaltoincandescencewhentheatomswillbombardeachotherwithterrificforceandmanyoftheelectronswillbeknockedoffandthrownoutintothesurroundingspace.
Butall,ornearlyall,ofthemwillreturntotheatomsfromwhencetheycameunlessameansofsomekindisemployedtoattractthemtotheatomsofsomeotherelement.Thiscanbedonebygivingthelatterpieceofmetalapositivecharge.Ifnowthesetwopiecesofmetalareplacedinabulbfromwhichtheairhasbeenexhaustedandthefirstpieceofmetalisheatedtobrilliancywhilethesecondpieceofmetaliskeptpositivelyelectrifiedthenastreamofelectronswillflowbetweenthem.
ActionoftheTwoElectrodeVacuumTube.--Nowinavacuumtubedetectorawirefilament,likethatofanincandescentlamp,isconnectedwithabatteryandthisformsthehotelementfromwhichtheelectronsarethrownoff,andametalplatewithaterminalwiresecuredtoitisconnectedtothe
positiveorcarbontapofadrybattery;nowconnectthenegativeorzinctapofthiswithoneendofatelephonereceiverandtheotherendofthiswiththeterminalsofthefilamentasshownatAinFig.71.IfnowyouheatthefilamentandholdthephonetoyourearyoucanhearthecurrentfromtheBbatteryflowingthroughthecircuit.
Sincetheelectronsarenegativechargesofelectricitytheyarenotonlythrownoffbythehotwirebuttheyareattractedbythepositivechargedmetalplateandwhenenoughelectronspass,orflow,fromthehotwiretotheplatetheyformaconductingpathandsocompletethecircuitwhichincludesthefilament,theplateandtheBorplatebattery,whenthecurrentcanthenflowthroughit.Asthenumberofelectronsthatarethrownoffbythefilamentisnotgreatandthevoltageoftheplateisnothighthecurrentthatflowsbetweenthefilamentandtheplateisalwaysquitesmall.
HowtheTwoElectrodeTubeActsasaDetector.--Astheactionofatwoelectrodetubeasadetector[Footnote:Thethreeelectrodevacuumtubehasentirelytakentheplaceofthetwoelectrodetype.]issimplerthanthatofthethreeelectrodevacuumtubeweshalldescribeitfirst.Thetwoelectrode
vacuumtubewasfirstmadebyMr.EdisonwhenhewasworkingontheincandescentlampbutthatitwouldserveasadetectorofelectricwaveswasdiscoveredbyProf.Fleming,ofOxfordUniversity,London.Asamatteroffact,itisnotreallyadetectorofelectricwaves,butitactsas:(1)arectifieroftheoscillationsthataresetupinthereceivingcircuits,thatis,itchangesthemintopulsatingdirectcurrentssothattheywillflowthroughandaffectatelephonereceiver,and(2)itactsasarelayandthefeeblereceivedoscillatingcurrentcontrolsthelargerdirectcurrentfromtheBbatteryinverymuchthesamewaythatatelegraphrelaydoes.Thislatterrelayactionwillbeexplainedwhenwecometoitsoperationasanamplifier.
Wehavejustlearnedthatwhenthestreamofelectronsflowfromthehotwiretothecoldpositiveplateinthetubetheyformaconductingpaththroughwhichthebatterycurrentcanflow.Nowwhentheelectricoscillationssurgethroughtheclosedoscillationcircuit,whichincludesthesecondaryofthetuningcoil,thevariablecondenser,thefilamentandtheplateasshownatBinFig.71thepositivepartofthempassesthroughthetubeeasilywhilethenegativepartcannotgetthrough,thatis,thetop,orpositive,partofthewave-formremainsintactwhilethelower,ornegative,partiscutoffasshowninthediagramatC.AsthereceivedoscillationsareeitherbrokenupintowavetrainsofaudiofrequencybythetelegraphtransmitteroraremodulatedbyatelephonetransmittertheycarrythelargerimpulsesofthedirectcurrentfromtheBbatteryalongwiththemandtheseflowthroughtheheadphones.Thisisthereasonthevacuumtubeamplifiesaswellasdetects.
HowtheThreeElectrodeTubeActsasaDetector.--ThevacuumtubeasadetectorhasbeenmadeverymuchmoresensitivebytheuseofathirdelectrodeshowninFig.72.Inthistypeofvacuumtubethethirdelectrode,orgrid,isplacedbetweenthefilamentandtheplateandthiscontrolsthenumberofelectronsflowingfromthefilamenttotheplate;inpassingbetweenthesetwoelectrodestheyhavetogothroughtheholesformedbythegridwires.
Ifnowthegridischargedtoahighernegativevoltagethanthefilamenttheelectronswillbestoppedbythelatter,seeA,thoughsomeofthemwillgothroughtotheplatebecausetheytravelatahighrateofspeed.Thehigherthenegativechargeonthegridthesmallerwillbethenumberofelectronsthatwillreachtheplateand,ofcourse,thesmallerwillbetheamountofcurrentthatwillflowthroughthetubeandtheheadphonesfromtheBbattery.
Ontheotherhandifthegridischargedpositively,seeB,thenmoreelectronswillstriketheplatethanwhenthegridisnotusedorwhenitisnegativelycharged.ButwhenthethreeelectrodetubeisusedasadetectortheoscillationssetupinthecircuitschangethegridalternatelyfromnegativetopositiveasshownatCandhencethevoltageoftheBbatterycurrentthatisallowedtoflowthroughthedetectorfromtheplatetothefilamentrisesandfallsinunisonwiththevoltageoftheoscillatingcurrents.Thewaythepositiveandnegativevoltagesoftheoscillationswhicharesetupbytheincomingwaves,
energizethegrid;howtheoscillatortubeclipsoffthenegativepartsofthem,and,finally,howthesecarrythebatterycurrentthroughthetubeareshowngraphicallybythecurvesatD.
HowtheVacuumTubeActsasanAmplifier.--Ifyouconnectupthefilamentandtheplateofathreeelectrodetubewiththebatteriesanddonotconnectinthegrid,youwillfindthattheelectronswhicharethrownoffbythefilamentwillnotgetfartherthanthegridregardlessofhowhighthevoltageisthatyouapplytotheplate.Thisisduetothefactthatalargenumberofelectronswhicharethrownoffbythefilamentstrikethegridandgiveitanegativecharge,andconsequently,theycannotgetanyfarther.SincetheelectronsdonotreachtheplatethecurrentfromtheBbatterycannotflowbetweenitandthefilament.
Nowwithaproperlydesignedamplifiertubeaverysmallnegativevoltageonthegridwillkeepaverylargepositivevoltageontheplatefromsendingacurrentthroughthetube,andoppositely,averysmallpositivevoltageonthegridwillletaverylargeplatecurrentflowthroughthetube;thisbeingtrueitfollowsthatanysmallvariationofthevoltagefrompositivetonegativeonthegridandtheotherwayaboutwillvaryalargecurrentflowingfromtheplatetothefilament.
IntheMorsetelegraphtherelaypermitsthesmallcurrentthatisreceivedfromthedistantsendingstationtoenergizeapairofmagnets,andthesedrawanarmaturetowardthemandcloseasecondcircuitwhenalargecurrentfromalocalbatteryisavailableforworkingthesounder.Theamplifiertubeisavariablerelayinthatthefeeblecurrentssetupbytheincomingwavesconstantlyandproportionatelyvaryalargecurrentthatflowsthroughtheheadphones.Thisthenistheprincipleonwhichtheamplifyingtubeworks.
TheOperationofaSimpleVacuumTubeReceivingSet.--Thewayasimplevacuumtubedetectorreceivingsetworksislikethis:whenthefilamentisheatedtobrilliancyitgivesoffelectronsaspreviouslydescribed.Nowwhentheelectricwavesimpingeontheaerialwiretheysetuposcillationsinitandthesesurgethroughtheprimarycoiloftheloosecoupledtuningcoil,adiagramofwhichisshownatBinFig.41.
Theenergyoftheseoscillationssetsuposcillationsofthesamefrequencyinthesecondarycoilandthesehighfrequencycurrentswhosevoltageisfirstpositiveandthennegative,surgeintheclosedcircuitwhichincludesthesecondarycoilandthevariablecondenser.Atthesametimethealternatingpositiveandnegativevoltageoftheoscillatingcurrentsisimpressedonthegrid;ateachchangefrom+to-andbackagainitallowstheelectronstostriketheplateandthenshutsthemoff;astheelectronsformtheconductingpathbetweenthefilamentandtheplatethelargerdirectcurrentfromtheBbatteryispermittedtoflowthroughthedetectortubeandtheheadphones.
OperationofaRegenerativeVacuumTubeReceivingSet.--ByfeedingbackthepulsatingdirectcurrentfromtheBbatterythroughtheticklercoilitsetsupotherandstrongeroscillationsinthesecondaryofthetuningcoilwhentheseactonthedetectortubeandincreaseitssensitivenesstoaremarkableextent.Theregenerative,orfeedback,actionofthereceivingcircuitsusedwillbeeasilyunderstoodbyreferringbacktoBinFig.47.
Whenthewavessetuposcillationsintheprimaryofthetuningcoiltheenergyofthemproduceslikeoscillationsintheclosedcircuitwhichincludesthesecondarycoilandthecondenser;thealternatingpositiveandnegativevoltagesoftheseareimpressedonthegridandthese,aswehaveseenbefore,causesimilarvariationsofthedirectcurrentfromtheBbatterywhichactsontheplateandwhich
flowsbetweenthelatterandthefilament.
Thisvaryingdirectcurrent,however,ismadetoflowbackthroughthethird,orticklercoilofthetuningcoilandsetsupinthesecondarycoilandcircuitsotherandlargeroscillatingcurrentsandtheseaugmenttheactionoftheoscillationsproducedbytheincomingwaves.TheseextraandlargercurrentswhicharetheresultofthefeedbackthenactonthegridandcausestilllargervariationsofthecurrentintheplatevoltageandhenceofthecurrentoftheBbatterythatflowsthroughthedetectorandtheheadphones.Atthesametimethetubekeepsonrespondingtothefeebleelectricoscillationssetupinthecircuitsbytheincomingwaves.Thisregenerativeactionofthebatterycurrentaugmentstheoriginaloscillationsmanytimesandhenceproducesoundsintheheadphonesthataremanytimesgreaterthanwherethevacuumtubedetectoraloneisused.
OperationofAutodyneandHeterodyneReceivingSets.--Onpage109[ChapterVII]wediscussedandatAinFig.36isshownapictureoftwotuningforksmountedonsoundingboxestoillustratetheprincipleofelectricaltuning.Whenapairoftheseforksaremadetovibrateexactlythesamenumberoftimespersecondtherewillbeacondensationoftheairbetweenthemandthesoundwavesthataresentoutwillbeaugmented.Butifyouadjustoneoftheforkssothatitwillvibrate256timesasecondandtheotherforksothatitwillvibrate260timesasecondthentherewillbeaphasedifferencebetweenthetwosetsofwavesandthelatterwillaugmenteachother4timeseverysecondandyouwillheartheserisingandfallingsoundsasbeats.
Nowelectricoscillationssetupintwocircuitsthatarecoupledtogetheractinexactlythesamewayassoundwavesproducedbytwotuningforksthatareclosetoeachother.Sincethisistrueifyoutuneoneoftheclosedcircuitssothattheoscillationsinitwillhaveafrequencyofa1,000,000andtunetheothercircuitsothattheoscillationsinithaveafrequencyof1,001,000asecondthentheoscillationswillaugmenteachother1,000timeseverysecond.
AstheserisingandfallingcurrentsactonthepulsatingcurrentsfromtheBbatterywhichflowthroughthedetectortubeandtheheadphonesyouwillhearthemasbeats.Agraphicrepresentationoftheoscillatingcurrentssetupbytheincomingwaves,thoseproducedbytheheterodyneoscillatorandthebeatstheyformisshowninFig.73.Toproducethesebeatsareceptorcanuse:(1)asinglevacuumtubeforsettinguposcillationsofbothfrequencieswhenitiscalledanautodyne,orself-heterodynereceptor,or(2)aseparatevacuumtubeforsettinguptheoscillationsforthesecondcircuitwhenitiscalledaheterodynereceptor.
TheAutodyne,orSelf-HeterodyneReceivingSet.--Whereonlyonevacuumtubeisusedforproducingbothfrequenciesyouneedonlyaregenerative,orfeed-backreceptor;thenyoucantunetheaerialwiresystemtotheincomingwavesandtunetheclosedcircuitofthesecondarycoilsothatitwillbeoutofstepwiththeformerby1,000oscillationspersecond,moreorless,theexactnumberdoesnotmatterintheleast.Fromthisyouwillseethatanyregenerativesetcanbeusedforautodyne,orself-heterodyne,reception.
TheSeparateHeterodyneReceivingSet.--Thebetterway,however,istouseaseparatevacuumtubeforsettinguptheheterodyneoscillations.Thelatterthenactontheoscillationsthatareproducedbytheincomingwavesandwhichenergizethegridofthedetectortube.Notethatthevacuumtubeusedforproducingtheheterodyneoscillationsisageneratorofelectricoscillations;thelatterareimpressedonthedetectorcircuitsthroughthevariablecoupling,thesecondaryofwhichisinserieswiththeaerialwireasshowninFig.74.ThewayinwhichthetubeactsasageneratorofoscillationswillbetoldinChapterXVIII.
CHAPTERXVI
CONTINUOUSWAVETELEGRAPHTRANSMITTINGSETSWITHDIRECTCURRENT
Inthefirstpartofthisbookwelearnedaboutspark-gaptelegraphsetsandhowtheoscillationstheysetuparedampedandthewavestheysendoutareperiodic.Inthisandthenextchapterweshallfindouthowvacuumtubetelegraphtransmittersaremadeandhowtheysetuposcillationsthataresustainedandradiatewavesthatarecontinuous.
Sendingwirelesstelegraphmessagesbycontinuouswaveshasmanyfeaturestorecommenditasagainstsendingthembyperiodicwavesandamongthemostimportantofthesearethatthetransmittercanbe:(1)moresharplytuned,(2)itwillsendsignalsfartherwiththesameamountofpower,and(3)itisnoiselessinoperation.Thedisadvantageousfeaturesarethat:(1)abatterycurrentisnotsatisfactory,(2)itscircuitsaresomewhatmorecomplicated,and(3)theoscillatortubesburnoutoccasionally.Thereis,however,agrowingtendencyamongamateurstousecontinuouswavetransmittersandtheyarecertainlymoreup-to-dateandinterestingthansparkgapsets.
Nowtherearetwopracticalwaysbywhichcontinuouswavescanbesetupforsendingeithertelegraphicsignalsortelephonicspeechandmusicandthesearewith:(a)anoscillationarclamp,and(b)avacuumtubeoscillator.Theoscillationarcwastheearliestknownwayofsettingupsustainedoscillations,anditisnowlargelyusedforcommercialhighpower,longdistancework.Butsincethevacuumtubehasbeendevelopedtoahighdegreeofefficiencyandistheschemethatisnowinvogueforamateurstationsweshallconfineoureffortsheretoexplainingtheapparatusnecessaryandhowtowirethevariouspartstogethertoproduceseveralsizesofvacuumtubetelegraphtransmitters.
SourcesofCurrentforTelegraphTransmittingSets.--Differingfromaspark-gaptransmitteryoucannotgetanyappreciableresultswithalowvoltagebatterycurrenttostartwith.ForapurelyexperimentalvacuumtubetelegraphtransmitteryoucanuseenoughBbatteriestooperateitbutthecurrentstrengthofthesedropssofactwhentheyareinuse,thattheyarenotatallsatisfactoryforthework.
Youcan,however,use110voltdirectcurrentfromalightingcircuitasyourinitialsourceofpowertoenergizetheplateofthevacuumtubeoscillatorofyourexperimentaltransmitter.Whereyouhavea110voltdirectcurrentlightingserviceinyourhomeandyouwantahighervoltageforyourplate,youwillthenhavetouseamotor-generatorsetandthiscostsmoney.Ifyouhave110voltalternatingcurrentlightingserviceathandyourtroublesareoversofarascostisconcernedforyoucanstepituptoanyvoltageyouwantwithapowertransformer.Inthischapterwillbeshownhowtouseadirectcurrentforyoursourceofinitialpowerandinthenextchapterhowtouseanalternatingcurrentfortheinitialpower.
AnExperimentalContinuousWaveTelegraphTransmitter.--YouwillrememberthatinChapterXVwelearnedhowtheheterodynereceiverworksandthatintheseparateheterodynereceivingsetthesecondvacuumtubeisusedsolelytosetuposcillations.Nowwhilethisextratubeisusedasageneratorofoscillationstheseare,ofcourse,veryweakandhenceadetectortubecannotbeusedto
generateoscillationsthatareusefulforotherpurposesthanheterodynereceptorsandmeasurements.
Thereisavacuumtubeamplifier[Footnote:ThisistheradiationUV-201,madebytheRadioCorporationofAmerica,WoolworthBldg.,NewYorkCity.]madethatwillstandaplatepotentialof100volts,andthiscanbeusedasageneratorofoscillationsbyenergizingitwitha110voltdirectcurrentfromyourlightingservice.OrinapinchyoucanusefivestandardBbatteriestodeveloptheplatevoltage,butthesewillsoonrundown.Butwhateveryoudo,neveruseacurrentfromalightingcircuitonatubeofanykindthathasaratedplatepotentialoflessthan100volts.
TheApparatusYouNeed.--Forthisexperimentalcontinuouswavetelegraphtransmittergetthefollowingpiecesofapparatus:(1)onesinglecoiltunerwiththreeclips;(2)one.002mfd.fixedcondenser;(3)three.001mfd.condensers;(4)oneadjustablegridleak;(5)onehot-wireammeter;(6)onebuzzer;(7)onedrycell;(8)onetelegraphkey;(9)one100voltplatevacuumtubeamplifier;(10)one6voltstoragebattery;(11)onerheostat;(12)oneoscillationchokecoil;(13)onepanelcut-outwithasingle-throw,double-poleswitch,andapairoffusesocketsonit.
TheTuningCoil.--Youcaneithermakethistuningcoilorbuyone.Tomakeitgettwodisksofwood3/4-inchthickand5inchesindiameterandfourstripsofhardwood,orbetter,hardrubberorcompositionstrips,suchasbakelite,1/2-inchthick,1inchwideand5-3/4incheslong,andscrewthemtothedisksasshownatAinFig.75.Nowwraponthisformabout25turnsofNo.8or10,BrownandSharpegauge,barecopperwirewithaspaceof1/8-inchbetweeneachturn.Getthreeofthesmallestsizeterminalclips,seeB,andclipthemontothedifferentturns,whenyourtuningcoilisreadyforuse.Youcanbuyacoilofthiskindfor$4.00or$5.00.
TheCondensers.--Fortheaerialseriescondensergetonethathasacapacitanceof.002mfd.andthatwillstandapotentialof3,000volts.[Footnote:TheUC-1014FaradoncondensermadebytheRadioCorporationofAmericawillservethepurpose.]ItisshownatC.Theotherthreecondensers,seeD,arealsoofthefixedtypeandmayhaveacapacitanceof.001mfd.;[Footnote:ListNo.266;fixedreceivingcondenser,soldbytheManhattanElectricalSupplyCo.]theblockingcondensershouldpreferablyhaveacapacitanceof1/2amfd.Inthesecondenserstheleavesofthesheetmetalareembeddedincomposition.Theaerialcondenserwillcostyou$2.00andtheothers75centseach.
TheAerialAmmeter.--Thisinstrumentisalsocalledahot-wireammeterbecausetheoscillatingcurrentsflowingthroughapieceofwireheatitaccordingtotheircurrentstrengthandasthewirecontractsandexpandsitmovesaneedleoverascale.Theammeterisconnectedintheaerialwiresystem,eitherintheaerialsideorthegroundside--thelatterplaceisusuallythemostconvenient.Whenyoutunethetransmittersothattheammetershowsthelargestamountofcurrentsurgingintheaerialwiresystemyoucanconsiderthattheoscillationcircuitsareintune.Ahot-wireammeterreadingto2.5ampereswillserveyourneeds,itcosts$6.00andisshownatEinFig.75.
PhotographunavailableUnitedStatesNavalHighPowerStation,ArlingtonVa.GeneralviewofPowerRoom.AttheleftcanbeseentheControlSwitchboards,andoverhead,thegreat30K.W.ArcTransmitterwithAccessories.
TheBuzzerandDryCell.--Whileaheterodyne,orbeat,receptorcanreceivecontinuouswavetelegraphsignalsanordinarycrystalorvacuumtubedetectorreceivingsetcannotreceivethemunlesstheyarebrokenupintotrainseitheratthesendingstationoratthereceivingstation,anditisconsideredthebetterpracticetodothisattheformerratherthanatthelatterstation.ForthissmalltransmitteryoucanuseanordinarybuzzerasshownatF.Adrycellortwomustbeusedtoenergizethebuzzer.Youcangetoneforabout75cents.
TheTelegraphKey.--Anykindofatelegraphkeywillservetobreakupthetrainsofsustainedoscillationsintodotsanddashes.ThekeyshownatGismountedonacompositionbaseandisthecheapestkeymade,costing$1.50.
TheVacuumTubeOscillator.--Asexplainedbeforeyoucanuseanyamplifyingtubethatismadeforaplatepotentialof100volts.Thecurrentrequiredforheatingthefilamentisabout1ampereat6volts.Aporcelainsocketshouldbeusedforthistubeasitisthebestinsulatingmaterialforthepurpose.AnamplifiertubeofthistypeisshownatHandcosts$6.50.
TheStorageBattery.--Astoragebatteryisusedtoheatthefilamentofthetube,justasitiswithadetectortube,anditcanbeofanymakeorcapacityaslongasitwilldevelop6volts.Thecheapest6voltstoragebatteryonthemarkethasa20to40ampere-hourcapacityandsellsfor$13.00.
TheBatteryRheostat.--Aswiththereceptorsarheostatisneededtoregulatethecurrentthatheatsthefilament.ArheostatofthiskindisshownatIandislistedat$1.25.
TheOscillationChokeCoil.--Thiscoilisconnectedinbetweentheoscillationcircuitsandthesourceofcurrentwhichfeedstheoscillatortubetokeeptheoscillationssetupbythelatterfromsurgingbackintotheservicewireswheretheywouldbreakdowntheinsulation.Youcanmakeanoscillationchokecoilbywindingsay100turnsofNo.28BrownandSharpegaugedoublecottoncoveredmagnetwireonacardboardcylinder2inchesindiameterand2-1/2incheslong.
TransmitterConnectors.--Forconnectingupthedifferentpiecesofapparatusofthetransmitteritisagoodschemetousecopperbraid;thisismadeofbraidedcopperwireinthreesizesandsellsfor7,15and20centsafootrespectively.ApieceofitispicturedatJ.
ThePanelCut-Out.--Thisisusedtoconnectthecordofthe110-voltlampsocketwiththetransmitter.Itconsistsofapairofplugcutoutsandasingle-throw,double-poleswitchmountedonaporcelainbaseasshownatK.Insomelocalitiesitisnecessarytoplacetheseinanironboxtoconformtotherequirementsofthefireunderwriters.
ConnectingUptheTransmittingApparatus.--Thewaythevariouspiecesofapparatusareconnectedtogetherisshowninthewiringdiagram.Fig.76.Beginbyconnectingonepostoftheammeterwiththewirethatleadstotheaerialandtheotherpostofittooneendofthetuningcoil;connectclip1tooneterminalofthe.002mfd.3,000voltaerialcondenserandtheotherpostofthiswiththeground.
Nowconnecttheendofthetuningcoilthatleadstotheammeterwithoneendofthe.001mfd.gridcondenserandtheotherendofthiswiththegridofthevacuumtube.Connectthetelegraphkey,thebuzzerandthedrycellinseriesandthenshuntthemaroundthegridcondenser.Nextconnecttheplateofthetubewithoneendofthe.001mfd.blockingcondenserandtheotherendofthiswiththeclip2onthetuningcoil.
Connectoneendofthefilamentwiththe+orpositiveelectrodeofthestoragebattery,the-ornegativeelectrodeofthiswithonepostoftherheostatandtheotherpostofthelatterwiththeotherendofthefilament;thenconnectclip3withthe+orpositivesideofthestoragebattery.Thisdoneconnectoneendofthechokecoiltotheconductorthatleadstotheplateandconnecttheotherendofthechokecoiltooneofthetapsoftheswitchonthepanelcut-out.Connectthe+orpositiveelectrodeofthestoragebatterytotheotherswitchtapandbetweentheswitchandthechokecoilconnecttheprotectivecondenseracrossthe110voltfeedwires.Finallyconnectthelampcordfromthesockettotheplugfusetapswhenyourexperimentalcontinuouswavetelegraphtransmitterisreadytouse.
A100MileC.W.TelegraphTransmitter.--Hereisacontinuouswavetelegraphtransmitterthatwillcoverdistancesupto100milesthatyoucanrelyon.Itisbuiltonexactlythesamelinesastheexperimentaltransmitterjustdescribed,butinsteadofusinga100voltplateamplifierasamakeshiftgeneratorofoscillationsitemploysavacuumtubemadeespeciallyforsettinguposcillationsandinsteadofhavingalowplatevoltageitisenergizedwith350volts.
TheApparatusYouNeed.--Forthistransmitteryourequire:(1)oneoscillationtransformer;(2)onehot-wireammeter;(3)oneaerialseriescondenser;(4)onegridleakresistance;(5)onechopper;(6)
onekeycircuitchokecoil;(7)one5wattvacuumtubeoscillator;(8)one6voltstoragebattery;(9)onebatteryrheostat;(10)onebatteryvoltmeter;(11)oneblockingcondenser;(12)onepowercircuitchokecoil,and(13)onemotor-generator.
TheOscillationTransformer.--Thetuningcoil,oroscillationtransformerasthisoneiscalled,isaconductivelycoupledtuner--thatis,theprimaryandsecondarycoilsformonecontinuouscoilinsteadoftwoseparatecoils.Thistunerismadeupof25turnsofthincopperstrip,3/8inchwideandwithitsedgesrounded,andthisissecuredtoawoodbaseasshownatAinFig.77.Itisfittedwithonefixedtapandthreeclipstoeachofwhichalengthofcopperbraidisattached.Ithasadiameterof6-1/4inches,aheightof7-7/8inchesandalengthof9-3/8inches,anditcosts$11.00.
TheAerialCondenser.--Thiscondenserismadeupofthreefixedcondensersofdifferentcapacitances,namely.0003,.0004and.0005mfd.,andthesearemadetostandapotentialof7500volts.Thecondenseristhereforeadjustableand,asyouwillseefromthepictureB,ithasoneterminalwireatoneendandthreeterminalwiresattheotherendsothatone,twoorthreecondenserscanbeusedinserieswiththeaerial.Acondenserofthiskindcosts$5.40.
TheAerialAmmeter.--Thisisthesamekindofahot-wireammeteralreadydescribedinconnectionwiththeexperimentalset,butitreadsto5amperes.
TheGridandBlockingCondensers.--Eachoftheseisafixedcondenserof.002mfd.capacitanceandisratedtostand3,000volts.Itismadeliketheaerialcondenserbuthasonlytwoterminals.Itcosts$2.00.
TheKeyCircuitApparatus.--Thisconsistsof:(1)thegridleak;(2)thechopper;(3)thechokecoil,and(4)thekey.Thegridleakisconnectedintheleadfromthegridtotheaerialtokeepthevoltageonthegridattherightpotential.Ithasaresistanceof5000ohmswithamid-tapat2500ohmsasshownatC.Itcosts$2.00.
Thechopperissimplyarotaryinterrupterdrivenbyasmallmotor.Itcomprisesawheelofinsulatingmaterialinwhich30ormoremetalsegmentsaresetinaninsulatingdiskasshownatD.Ametalcontactcalledabrushisfixedoneithersideofthewheel.Itcostsabout$7.00andthemotortodriveitisextra.Thechokecoiliswoundupofabout250turnsofNo.30BrownandSharpegaugecottoncoveredmagnetwireonaspoolwhichhasadiameterof2inchesandalengthof3-1/4inches.
The5WattOscillatorVacuumTube.--Thistubeismadeliketheamplifiertubedescribedforusewiththeprecedingexperimentaltransmitter,butitislarger,hasamoreperfectvacuum,andwillstandaplatepotentialof350voltswhiletheplatecurrentis.045ampere.Thefilamenttakesacurrentofalittlemorethan2amperesat7.5volts.Astandard4-tapbaseisusedwithit.Thetubecosts$8.00andtheporcelainbaseis$1.00extra.ItisshownatE.
TheStorageBatteryandRheostat.--Thismustbea5-cellbatterysothatitwilldevelop10volts.Astoragebatteryofanycapacitycanbeusedbutthelowestpricedonecostsabout$22.00.Therheostatforregulatingthebatterycurrentisthesameasthatusedintheprecedingexperimentaltransmitter.
TheFilamentVoltmeter.--Togetthebestresultsitisnecessarythatthevoltageofthecurrentwhichheatsthefilamentbekeptatthesamevalueallofthetime.Forthistransmitteradirectcurrentvoltmeterreadingfrom0to15voltsisused.ItisshownatFandcosts$7.50.
TheOscillationChokeCoil.--Thisismadeexactlyliketheonedescribedinconnectionwiththeexperimentaltransmitter.
TheMotor-GeneratorSet.--Whereyouhaveonlya110ora220voltdirectcurrentavailableasasourceofpoweryouneedamotor-generatortochangeitto350volts,andthisisanexpensivepieceofapparatus.Itconsistsofasinglearmaturecorewithamotorwindingandageneratorwindingonitandeachofthesehasitsowncommutator.Wherethelowvoltagecurrentflowsintooneofthewindingsitdrivesitsasamotorandthisinturngeneratesthehighervoltagecurrentintheotherwinding.Geta100watt350voltmotor-generator;itisshownatFandcostsabout$75.00.
ThePanelCut-Out.--Thisswitchandfuseblockisthesameasthatusedintheexperimentalset.
TheProtectiveCondenser.--Thisisafixedcondenserhavingacapacitanceof1mfd.andwillstand750volts.Itcosts$2.00.
ConnectingUptheTransmittingApparatus.--Fromallthathasgonebeforeyouhaveseenthateachpieceofapparatusisfittedwithterminal,wires,tapsorbindingposts.ToconnectupthepartsofthistransmitteritisonlynecessarytomaketheconnectionsasshowninthewiringdiagramFig.78.
A200MileC.W.TelegraphTransmitter.--Tomakeacontinuouswavetelegraphtransmitterthatwillcoverdistancesupto200milesallyouhavetodoistousetwo5wattvacuumtubesinparallel,alloftherestoftheapparatusbeingexactlythesame.Connectingtheoscillatortubesupinparallelmeansthatthetwofilamentsareconnectedacrosstheleadsofthestoragebattery,thetwogridsonthesameleadthatgoestotheaerialandthetwoplatesonthesameleadthatgoestothepositivepoleofthegenerator.Wheretwoormoreoscillatortubesareusedonlyonestoragebatteryisneeded,buteachfilamentmusthaveitsownrheostat.ThewiringdiagramFig.79showshowthetwotubesareconnectedupinparallel.
A500MileC.W.TelegraphTransmitter.--Forsendingtodistancesofover200milesandupto500milesyoucanuseeither:(1)threeorfour5wattoscillatortubesinparallelasdescribedabove,or(2)one50wattoscillatortube.Muchoftheapparatusfora50watttubesetisexactlythesameasthatusedforthe5wattsets.Someoftheparts,however,mustbeproportionatelylargerthoughthedesignallthewaythroughremainsthesame.
TheApparatusandConnections.--Theaerialseriescondenser,theblockingcondenser,thegridcondenser,thetelegraphkey,thechopper,thechokecoilinthekeycircuit,thefilamentvoltmeterandtheprotectivecondenserinthepowercircuitareidenticalwiththosedescribedforthe5watttransmittingset.
The50WattVacuumTubeOscillator.--Thisisthesizeoftubegenerallyusedbyamateursforlongdistancecontinuouswavetelegraphy.Asingletubewilldevelop2to3amperesinyouraerial.Thefilamenttakesa10voltcurrentandaplatepotentialof1,000voltsisneeded.OneofthesetubesisshowninFig.80andthecostis$30.00.Atubesockettofititcosts$2.50extra.
TheAerialAmmeter.--Thisshouldreadto5amperesandthecostis$6.25.
TheGridLeakResistance.--Ithasthesameresistance,namely5,000ohmsastheoneusedwiththe5
watttubetransmitter,butitisalittlelarger.Itislistedat$1.65.
TheOscillationChokeCoil.--Thechokecoilinthepowercircuitismadeofabout260turnsofNo.30B.&S.cottoncoveredmagnetwirewoundonaspool2-1/4inchesindiameterand3-1/4incheslong.
TheFilamentRheostat.--Thisismadetotakecareofa10voltcurrentanditcosts$10.00.
TheFilamentStorageBattery.--Thismustdevelop12voltsandonehavinganoutputof40ampere-hourscostsabout$25.00.
TheProtectiveCondenser.--Thiscondenserhasacapacitanceof1mfd.andcosts$2.00.
TheMotor-Generator.--Whereyouuseone50wattoscillatortubeyouwillneedamotor-generatorthatdevelopsaplatepotentialof1000voltsandhasanoutputof200watts.Thismachinewillstandyouabout$100.00.
ThedifferentpiecesofapparatusforthissetareconnectedupexactlythesameasshowninthewiringdiagraminFig.78.
A1000MileC.W.TelegraphTransmitter.--Allofthepartsofthistransmittingsetarethesameasforthe500miletransmitterjustdescribedexceptthemotorgeneratorandwhilethisdevelopsthesameplatepotential,i.e.,1,000volts,itmusthaveanoutputof500watts;itwillcostyouintheneighborhoodof$175.00.Forthislongdistancetransmitteryouusetwo50wattoscillatortubesinparallelandallofthepartsareconnectedtogetherexactlythesameasforthe200miletransmittershowninthewiringdiagraminFig.79.
CHAPTERXVII
CONTINUOUSWAVETELEGRAPHTRANSMITTINGSETSWITHALTERNATINGCURRENT
Withinthelastfewyearsalternatingcurrenthaslargelytakentheplaceofdirectcurrentforlight,heatandpowerpurposesinandaroundtownsandcitiesandifyouhavealternatingcurrentserviceinyourhomeyoucaninstallalongdistancecontinuouswavetelegraphtransmitterwithverylittletroubleandatacomparativelysmallexpense.
A100MileC.W.TelegraphTransmittingSet.--Theprincipalpiecesofapparatusforthistransmitterarethesameasthoseusedforthe100MileContinuousWaveTelegraphTransmittingSetdescribedandpicturedintheprecedingchapterwhichuseddirectcurrent,exceptthatanalternatingcurrentpowertransformerisemployedinsteadofthemorecostlymotor-generator.
TheApparatusRequired.--Thevariouspiecesofapparatusyouwillneedforthistransmittingsetare:(1)onehot-wireammeterfortheaerialasshownatEinFig.75,butwhichreadsto5amperesinsteadofto2.5amperes;(2)onetuningcoilasshownatAinFig.77;(3)oneaerialcondenserasshownatBinFig.77;(4)onegridleakasshownatCinFig.77;(5)onetelegraphkeyasshownatGinFig.75;(6)onegridcondenser,madeliketheaerialcondenserbuthavingonlytwoterminals;(7)one5wattoscillatortubeasshownatEinFig.77;(8)one.002mfd.3,000voltby-passcondenser,madeliketheaerialandgridcondensers;(9)onepairofchokecoilsforthehighvoltagesecondarycircuit;(10)onemilli-ammeter;(11)oneA.C.powertransformer;(12)onerheostatasshownatIinFig.75,and(13)onepanelcut-outasshownatKinFig.75.
TheChokeCoils.--Eachoftheseismadebywindingabout100turnsofNo.28,BrownandSharpegauge,cottoncoveredmagnetwireonaspool2inchesindiameterand2-1/2incheslong,whenitwillhaveaninductanceofabout0.5millihenry[Footnote:Amillihenryis1/1000thpartofahenry.]at1,000cycles.
TheMilli-ammeter.--Thisisanalternatingcurrentammeterandreadsfrom0to250milliamperes;[Footnote:Amilliampereisthe1/1000thpartofanampere.]andisusedformeasuringthesecondarycurrentthatenergizestheplateoftheoscillatortube.Itlooksliketheaerialammeterandcostsabout$7.50.
TheA.C.PowerTransformer.--Differingfromthemotorgeneratorsetthepowertransformerhasnomovingparts.Forthistransmittingsetyouneedatransformerthathasaninputof325volts.Itismadetoworkona50to60cyclecurrentat102.5to115volts,whichistherangeofvoltageoftheordinaryalternatinglightingcurrent.Thisadjustmentforvoltageismadebymeansoftapsbroughtoutfromtheprimarycoiltoarotaryswitch.
Thehighvoltagesecondarycoilwhichenergizestheplatehasanoutputof175wattsanddevelopsapotentialoffrom350to1,100volts.Thelowvoltagesecondarycoilwhichheatsthefilamenthasanoutputof175wattsanddevelops7.5volts.Thistransformer,whichisshowninFig.81,islargeenoughtotakecareoffromonetofour5wattoscillatortubes.Itweighsabout15poundsandsellsfor$25.00.
PhotographunavailableTheTransformerandTuneroftheWorld'sLargestRadioStation.OwnedbytheRadioCorporation
ofAmericaatRockyPointnearPortJeffersonL.I.
ConnectingUptheApparatus.--ThewiringdiagramFig.82showsclearlyhowalloftheconnectionsaremade.Itwillbeobservedthatastoragebatteryisnotneededasthesecondarycoilofthetransformersuppliesthecurrenttoheatthefilamentoftheoscillator.Thefilamentvoltmeterisconnectedacrossthefilamentsecondarycoilterminals,whiletheplatemilli-ammeterisconnectedtothemid-tapsoftheplatesecondarycoilandthefilamentsecondarycoil.
A200to500MileC.W.TelegraphTransmittingSet.--Distancesoffrom200to500milescanbesuccessfullycoveredwithatelegraphtransmitterusingtwo,threeorfour5wattoscillatortubesinparallel.Theapparatusneededisidenticalwiththatusedforthe100miletransmitterjustdescribed.ThetubesareconnectedinparallelasshowninthewiringdiagraminFig.83.
A500to1,000MileC.W.TelegraphTransmittingSet.--Withtheapparatusdescribedfortheabovesetandasingle50wattoscillatortubeadistanceofupwardsof500milescanbecovered,whilewithtwo50wattoscillatortubesinparallelyoucancoveradistanceof1,000mileswithoutdifficulty,andnearly2,000mileshavebeencoveredwiththisset.
TheApparatusRequired.--AlloftheapparatusforthisC.W.telegraphtransmittingsetisthesameasthatdescribedforthe100and200milesetsbutyouwillneed:(1)oneortwo50wattoscillatortubeswithsockets;(2)onekeycondenserthathasacapacitanceof1mfd.,andaratedpotentialof1,750volts;(3)one0to500milli-ammeter;(4)oneaerialammeterreadingto5amperes,and(5)anA.C.powertransformerforoneortwo50watttubes.
Photographunavailable
BroadcastingGovernmentReportsbyWirelessfromWashington.ThisshowsMr.GaleatworkwithhissetinthePostOfficeDepartment.
TheAlternatingCurrentPowerTransformer.--Thispowertransformerismadeexactlyliketheonedescribedinconnectionwiththepreceding100miletransmitterandpicturedinFig.81,butitisconsiderablylarger.Likethesmallerone,however,itismadetoworkwitha50to60cyclecurrentat102.5to115voltsand,hence,canbeusedwithanyA.C.lightingcurrent.
Ithasaninputof750voltsandthehighvoltagesecondarycoilwhichenergizestheplatehasanoutputof450wattsanddevelops1,500to3,000volts.Thelowvoltagesecondarycoilwhichheatsthefilamentdevelops10.5volts.Thistransformerwillsupplycurrentforoneortwo50-wattoscillatortubesanditcostsabout$40.00.
ConnectingUptheApparatus.--WhereasingleoscillatortubeisusedthepartsareconnectedasshowninFig.82,andwheretwotubesareconnectedinparallelthevariouspiecesofapparatusarewiredtogetherasshowninFig.83.Theonlydifferencebetweenthe5watttubetransmitterandthe50watttubetransmitterisinthesizeoftheapparatuswithoneexception;whereoneortwo50watttubesareusedasecondcondenseroflargecapacitance(1mfd.)isplacedinthegridcircuitandthetelegraphkeyisshuntedarounditasshowninthediagramFig.83.
CHAPTERXVIII
WIRELESSTELEPHONETRANSMITTINGSETSWITHDIRECTANDALTERNATINGCURRENTS
Intimepastthemostdifficultofallelectricalapparatusfortheamateurtomake,installandworkwasthewirelesstelephone.Thiswasbecauseitrequiredadirectcurrentofnotlessthan500voltstosetupthesustainedoscillationsandallordinarydirectcurrentforlightingpurposesisusuallygeneratedatapotentialof110volts.
Nowasyouknowitiseasytostep-upa110voltalternatingcurrenttoanyvoltageyouwishwithapowertransformerbutuntilwithincomparativelyrecentyearsanalternatingcurrentcouldnotbeusedfortheproductionofsustainedoscillationsfortheverygoodreasonthatthestateofthearthadnotadvancedthatfar.Intheneworderofthingsthesedifficultieshaveallbutvanishedandwhileawirelesstelephonetransmitterstillrequiresahighvoltagedirectcurrenttooperateitthisiseasilyobtainedfrom110voltsourceofalternatingcurrentbymeansofvacuumtuberectifiers.
Thepulsatingdirectcurrentsarethenpassedthroughafilteringreactancecoil,calledareactor,andoneormorecondensers,andthesesmooththemoutuntiltheyapproximateacontinuousdirectcurrent.Thelatteristhenmadetoflowthroughavacuumtubeoscillatorwhenitisconvertedintohighfrequencyoscillationsandthesearevaried,ormodulated,asitiscalled,byamicrophonetransmittersuchasisusedforordinarywiretelephony.Theenergyofthesesustainedmodulatedoscillationsisthenradiatedintospacefromtheaerialintheformofelectricwaves.
Thedistancethatcanbecoveredwithawirelesstelephonetransmitterisaboutone-fourthasgreatasthatofawirelesstelegraphtransmitterhavingthesameinputofinitialcurrent,butitislongenoughtosatisfythemostenthusiasticamateur.Forinstancewithawirelesstelephonetransmitterwhereanamplifiertubeisusedtosetuptheoscillationsandwhichismadeforaplatepotentialof100volts,distancesupto10or15milescanbecovered.
Withasingle5wattoscillatortubeenergizedbyadirectcurrentof350voltsfromeitheramotor-generatororfromapowertransformer(afterithasbeenrectifiedandsmoothedout)speechandmusiccanbetransmittedtoupwardsof25miles.Wheretwo5watttubesconnectedinparallelareusedwirelesstelephonemessagescanbetransmittedtodistancesof40or50miles.Further,asingle50wattoscillatortubewillsendtodistancesof50to100mileswhiletwoofthesetubesinparallelwillsendfrom100to200miles.Finally,wherefourorfiveoscillatortubesareconnectedinparallelproportionatelygreaterdistancescanbecovered.
AShortDistanceWirelessTelephoneTransmittingSet-With110VoltDirectLightingCurrent.--Forthisverysimple,shortdistancewirelesstelephonetransmittingsetyouneedthesameapparatusasthatdescribedandpicturedinthebeginningofChapterXVIforaShortDistanceC.W.TelegraphTransmitter,exceptthatyouuseamicrophonetransmitterinsteadofatelegraphkey.Ifyouhavea110voltdirectlightingcurrentinyourhomeyoucanputupthisshortdistancesetforverylittlemoneyanditwillbewellworthyourwhiletodoso.
TheApparatusYouNeed.--Forthissetyourequire:(1)onetuningcoilasshownatAandBinFig.75;
(2)oneaerialammeterasshownatCinFig.75;(3)oneaerialcondenserasshownatCinFig.75;(4)onegrid,blockingandprotectivecondenserasshownatDinFig.75;(5)onegridleakasshownatCinFig.77;(6)onevacuumtubeamplifierwhichisusedasanoscillator;(7)one6voltstoragebattery;(8)onerheostatasshownatIinFig.75;(9)oneoscillationchokecoil;(10)onepanelcut-outasshownatKinFig.75andanordinarymicrophonetransmitter.
TheMicrophoneTransmitter.--ThebestkindofamicrophonetousewiththisandothertelephonetransmittingsetsisaWesternElectricNo.284-W.[Footnote:MadebytheWesternElectricCompany,Chicago,Ill.]ThisisknownasasolidbacktransmitterandisthestandardcommercialtypeusedonalllongdistanceBelltelephonelines.Itarticulatessharplyanddistinctlyandtherearenocurrentvariationstodistortthewaveformofthevoiceanditwillnotbuzzorsizzle.ItisshowninFig.84andcosts$2.00.Anyothergoodmicrophonetransmittercanbeusedifdesired.
ConnectingUptheApparatus.--Beginbyconnectingtheleading-inwirewithoneoftheterminalsofthemicrophonetransmitter,asshowninthewiringdiagramFig.85,andtheotherterminalofthistooneendofthetuningcoil.Nowconnectclip1ofthetuningcoiltooneofthepostsofthehot-wireammeter,theotherpostofthistooneendofaerialcondenserand,finally,theotherendofthelatterwiththewaterpipeorotherground.Themicrophonecanbeconnectedinthegroundwireandtheammeterintheaerialwireandtheresultswillbepracticallythesame.
Nextconnectoneendofthegridcondensertothepostofthetuningcoilthatmakesconnectionwiththemicrophoneandtheotherendtothegridofthetube,andthenshuntthegridleakaroundthecondenser.Connectthe+orpositiveelectrodeofthestoragebatterywithoneterminalofthefilamentofthevacuumtube,theotherterminalofthefilamentwithonepostoftherheostatandtheotherpostofthiswiththe-ornegativeelectrodeofthebattery.Thisdone,connectclip2ofthetuningcoiltothe+orpositiveelectrodeofthebatteryandbringaleadfromittooneoftheswitchtapsofthepanelcut-out.
Nowconnectclip3ofthetuningcoilwithoneendoftheblockingcondenser,theotherendofthiswithoneterminalofthechokecoilandtheotherterminalofthelatterwiththeotherswitchtapofthecut-out.Connecttheprotectivecondenseracrossthedirectcurrentfeedwiresbetweenthepanelcut-outandthechokecoil.Finallyconnecttheendsofalampcordtothefusesockettapsofthecut-out,andconnecttheotherendstoalampplugandscrewitintothelampsocketofthefeedwires.Screwinapairof5amperefuseplugs,closetheswitchandyouarereadytotunethetransmitterandtalktoyourfriends.
A25to50MileWirelessTelephoneTransmitter--WithDirectCurrentMotorGenerator.--Whereyouhavetostartwith110or220voltdirectcurrentandyouwanttotransmittoadistanceof25milesormoreyouwillhavetoinstallamotor-generator.Tomakethistransmitteryouwillneedexactlythesameapparatusasthatdescribedandpicturedforthe100MileC.W.TelegraphTransmittingSetinChapterXVI,exceptthatyoumustsubstituteamicrophonetransmitterandatelephoneinductioncoil,oramicrophonetransformer,orstillbetter,amagneticmodulator,forthetelegraphkeyandchopper.
TheApparatusYouNeed.--Toreiterate;thepiecesofapparatusyouneedare:(1)oneaerialammeterasshownatEinFig.75;(2)onetuningcoilasshownatAinFig.77;(3)oneaerialcondenserasshownatBinFig.77;(4)onegridleakasshownatCinFig.77;(5)onegrid,blockingandprotectivecondenser;(6)one5wattoscillatortubeasshownatEinFig.77;(7)onerheostatasshownatIinFig.75;(8)one10volt(5cell)storagebattery;(9)onechokecoil;(10)onepanelcut-outasshownatKinFig.75,and(11)amotor-generatorhavinganinputof110or220voltsandanoutputof350volts.
Inadditiontotheaboveapparatusyouwillneed:(12)amicrophonetransmitterasshowninFig.84;(13)abatteryoffourdrycellsora6voltstoragebattery,andeither(14)atelephoneinductioncoilasshowninFig.86;(15)amicrophonetransformerasshowninFig.87;oramagneticmodulatorasshowninFig.88.Allofthesepartshavebeendescribed,assaidabove,inChapterXVI,exceptthemicrophonemodulators.
TheTelephoneInductionCoil.--Thisisalittleinductioncoilthattransformsthe6-voltbatterycurrentafterithasflowedthroughandbeenmodulatedbythemicrophonetransmitterintoalternatingcurrentsthathaveapotentialof1,000voltsofmore.ItconsistsofaprimarycoilofNo.20B.andS.gaugecottoncoveredmagnetwirewoundonacoreofsoftironwireswhilearoundtheprimarycoiliswoundasecondarycoilofNo.30magnetwire.Getastandardtelephoneinductioncoilthathasaresistanceof500or750ohmsandthiswillcostyouacoupleofdollars.
TheMicrophoneTransformer.--Thisdeviceisbuiltonexactlythesameprincipleasthetelephoneinductioncoiljustdescribedbutitismoreeffectivebecauseitisdesignedespeciallyformodulatingtheoscillationssetupbyvacuumtubetransmitters.Aswiththetelephoneinductioncoil,themicrophonetransmitterisconnectedinserieswiththeprimarycoilanda6voltdryorstoragebattery.
Inthebettermakesofmicrophonetransformer,thereisathirdwinding,calledasidetonecoil,towhichaheadphonecanbeconnectedsothattheoperatorwhoisspeakingintothemicrophonecanlisten-inandsolearnifhistransmitterisworkinguptostandard.
TheMagneticModulator.--Thisisasmallclosedironcoretransformerofpeculiardesignandhavingaprimaryandasecondarycoilwoundonit.Thisdeviceisusedtocontrolthevariationsoftheoscillatingcurrentsthataresetupbytheoscillatortube.Itismadeinthreesizesandforthetransmitterheredescribedyouwantthesmallestsize,whichhasanoutputof1/2to1-1/2amperes.Itcostsabout$10.00.
HowtheApparatusIsConnectedUp.--Thedifferentpiecesofapparatusareconnectedtogetherinexactlythesamewayasthe100MileC.W.TelegraphSetinChapterXVIexceptthatthemicrophonetransmitterandmicrophonemodulator(whicheverkindyouuse)issubstitutedforthetelegraphkeyandchopper.
Nowtherearethreedifferentwaysthatthemicrophoneanditsmodulatorcanbeconnectedincircuit.TwoofthebestwaysareshownatAandBinFig.89.InthefirstwaythesecondaryterminalsofthemodulatorareshuntedaroundthegridleakinthegridcircuitasatA,andinthesecondthesecondaryterminalsareconnectedintheaerialasatB.Whereaninductioncoiloramicrophonetransformerisusedtheyareshuntedaroundacondenser,butthisisnotnecessarywiththemagneticmodulator.WhereasecondtubeisusedasinFig.90thenthemicrophoneanditsmodulatorareconnectedwiththegridcircuitandclip3ofthetuningcoil.
A50to100MileWirelessTelephoneTransmitter--WithDirectCurrentMotorGenerator.--Astheinitialsourceofcurrentavailableistakentobea110or220voltdirectcurrentamotor-generatorhavinganoutputof350voltsmustbeusedasbefore.Theonlydifferencebetweenthistransmitterandtheprecedingoneisthat:(1)two5watttubesareused,thefirstservingasanoscillatorandthesecondasamodulator;(2)anoscillationchokecoilisusedintheplatecircuit;(3)areactancecoilorreactor,isusedintheplatecircuit;and(4)areactorisusedinthegridcircuit.
TheOscillationChokeCoil.--Youcanmakethischokecoilbywindingabout275turnsofNo.28B.andS.gaugecottoncoveredmagnetwireonaspool2inchesindiameterand4incheslong.Giveitagoodcoatofshellacvarnishandletitdrythoroughly.
ThePlateandGridCircuitReactanceCoils.--Whereasingletubeisusedasanoscillatorandasecondtubeisemployedasamodulator,areactor,whichisacoilofwirewoundonanironcore,isusedintheplatecircuittokeepthehighvoltagedirectcurrentofthemotor-generatorthesameatalltimes.Likewisethegridcircuitreactorisusedtokeepthevoltageofthegridataconstantvalue.ThesereactorsaremadealikeandapictureofoneofthemisshowninFig.91andeachonewillcostyou$5.75.
ConnectinguptheApparatus.--AllofthedifferentpiecesofapparatusareconnectedupasshowninFig.89.Oneoftheendsofthesecondaryoftheinductioncoil,orthemicrophonetransformer,orthemagneticmodulatorisconnectedtothegridcircuitandtheotherendtoclip3ofthetuningcoil.
A100to200MileWirelessTelephoneTransmitter--WithDirectCurrentMotorGenerator.--ByusingthesameconnectionsshowninthewiringdiagramsinFig.89andasingle50wattoscillatortubeyourtransmitterwillthenhavearangeof100milesorso,whileifyouconnectuptheapparatusasshowninFig.90andusetwo50watttubesyoucanworkupto200miles.Muchoftheapparatusfora50wattoscillatorsetwhereeitheroneortwotubesareusedisofthesamesizeanddesignasthatjustdescribedforthe5wattoscillatorsets,but,asintheC.W.telegraphsets,someofthepartsmustbeproportionatelylarger.Therequiredpartsare(1)the50watttube;(2)thegridleakresistance;(3)thefilamentrheostat;(4)thefilamentstoragebattery;and(5)themagneticmodulator.Alloftheseparts,exceptthelatter,aredescribedindetailundertheheadingofa500MileC.W.TelegraphTransmittingSetinChapterXVI,andarealsopicturedinthatchapter.
Itisnotadvisabletouseaninductioncoilforthemodulatorforthisset,butuse,instead,eitheratelephonetransformer,orbetter,amagneticmodulatorofthesecondsizewhichhasanoutputof
from1-1/2to3-1/2amperes.Themagneticmodulatorisdescribedandpicturedinthischapter.
A50to100MileWirelessTelephoneTransmittingSet--With110VoltAlternatingCurrent.--Ifyouhavea110volt[Footnote:Alternatingcurrentforlightingpurposesrangesfrom102.5voltsto115volts,sowetakethemedianandcallit110volts.]alternatingcurrentavailableyoucanuseitfortheinitialsourceofenergyforyourwirelesstelephonetransmitter.Thechiefdifferencebetweenawirelesstelephonetransmittingsetthatusesanalternatingcurrentandonethatusesadirectcurrentisthat:(1)apowertransformerisusedforsteppingupthevoltageinsteadofamotor-generator,and(2)avacuumtuberectifiermustbeusedtoconvertthealternatingcurrentintodirectcurrent.
TheApparatusYouNeed.--Forthistelephonetransmittingsetyouneed:(1)oneaerialammeter;(2)onetuningcoil;(3)onetelephonemodulator;(4)oneaerialseriescondenser;(5)one4celldrybatteryora6voltstoragebattery;(6)onemicrophonetransmitter;(7)onebatteryswitch;(8)onegridcondenser;(9)onegridleak;(10)two5wattoscillatortubeswithsockets;(11)oneblockingcondenser;(12)oneoscillationchokecoil;(13)twofiltercondensers;(14)onefilterreactancecoil;(15)analternatingcurrentpowertransformer,and(16)two20wattrectifiervacuumtubes.
Alloftheabovepiecesofapparatusarethesameasthosedescribedforthe100MileC.W.TelegraphTransmitterinChapterXVII,except:(a)themicrophonemodulator;(b)themicrophonetransmitterand(c)thedryorstoragebattery,allofwhicharedescribedinthischapter;andthenewpartswhichare:(d)therectifiervacuumtubes;(e)thefiltercondensers;and(f)thefilterreactancecoil;furtherandfinally,thepowertransformerhasathirdsecondarycoilonitanditisthisthatfeedsthealternatingcurrenttotherectifiertubes,whichinturnconvertsitintoapulsatingdirectcurrent.
TheVacuumTubeRectifier.--Thisrectifierhastwoelectrodes,thatis,ithasafilamentandaplateliketheoriginalvacuumtubedetector,Thesmallestsizerectifiertuberequiresaplatepotentialof550voltswhichisdevelopedbyoneofthesecondarycoilsofthepowertransformer.Thefilamentterminaltakesacurrentof7.5voltsandthisissuppliedbyanothersecondarycoilofthetransformer.Thisrectifiertubedeliversadirectcurrentof20wattsat350volts.Itlooksexactlylikethe5wattoscillatortubewhichispicturedatEinFig.77.Thepriceis$7.50.
TheFilterCondensers.--Thesecondensersareusedinconnectionwiththereactancecoiltosmoothoutthepulsatingdirectcurrentafterithaspassedthroughtherectifiertube.Theyhaveacapacitanceof1mfd.andwillstand750volts.Thesecondenserscostabout$2.00each.
TheFilterReactanceCoil.--ThisreactorwhichisshowninFig.92,hasaboutthesameappearanceasthepowertransformerbutitissomewhatsmaller.Itconsistsofacoilofwirewoundonasoftironcoreandhasalargeinductance,hencethecapacitanceofthefiltercondensersareproportionatelysmallerthanwhereasmallinductanceisusedwhichhasbeenthegeneralpractice.Thesizeyourequireforthissethasanoutputof160milliamperesanditwillsupplycurrentforonetofour5wattoscillatortubes.Thissizeofreactorcosts$11.50.
ConnectingUptheApparatus.--ThewiringdiagraminFig.93showshowthevariouspiecesofapparatusforthistelephonetransmitterareconnectedup.Youwillobserve:(1)thattheterminalsofthepowertransformersecondarycoilwhichdevelops10voltsareconnectedtothefilamentsoftheoscillatortubes;(2)thattheterminalsoftheothersecondarycoilwhichdevelops10voltsareconnectedwiththefilamentsoftherectifiertubes;(3)thattheterminalsofthethirdsecondarycoilwhichdevelops550voltsareconnectedwiththeplatesoftherectifiertubes;(4)thatthepairoffiltercondensersareconnectedinparallelandtheseareconnectedtothemid-tapsofthetwofilamentsecondarycoils;(5)thatthereactancecoilandthethirdfiltercondenserareconnectedtogetherinseriesandtheseareshuntedacrossthefiltercondensers,whichareinparallel;and,finally,(6)aleadconnectsthemid-tapofthe550-voltsecondarycoilofthepowertransformerwiththeconnectionbetweenthereactorandthethirdfiltercondenser.
A100to200MileWirelessTelephoneTransmittingSet--With110VoltAlternatingCurrent.--ThistelephonetransmitterisbuiltupofexactlythesamepiecesofapparatusandconnectedupinpreciselythesamewayastheonejustdescribedandshowninFig.93.
ApparatusRequired.--Theonlydifferencesbetweenthisandtheprecedingtransmitterare:(1)themagneticmodulator,ifyouuseone,shouldhaveanoutputof3-1/2to5amperes;(2)youwillneedtwo50wattoscillatortubeswithsockets;(3)two150wattrectifiertubeswithsockets;(4)anaerialammeterthatreadsto5amperes;(5)three1mfd.filtercondensersinparallel;(6)twofiltercondensersof1mfd.capacitancethatwillstand1750volts;and(6)a300milliamperefilterreactor.
TheapparatusiswiredupasshowninFig.93.
CHAPTERXIX
THEOPERATIONOFVACUUMTUBETRANSMITTERS
Thethreeforegoingchaptersexplainedindetailthedesignandconstructionof(1)twokindsofC.W.telegraphtransmitters,and(2)twokindsofwirelesstelephonetransmitters,thedifferencebetweenthembeingwhethertheyused(A)adirectcurrent,or(B)analternatingcurrentastheinitialsourceofenergy.Ofcoursethereareotherdifferencesbetweenthoseofliketypesas,forinstance,theapparatusandconnectionsused(a)inthekeycircuits,and(b)inthemicrophonecircuits.Butinallofthetransmittersdescribedofwhatevertypeorkindthesamefundamentaldeviceisusedforsettingupsustainedoscillationsandthisisthevacuumtube.
TheOperationoftheVacuumTubeOscillator.--Theoperationofthevacuumtubeinproducingsustainedoscillationsdependson(1)theactionofthetubeasavalveinsettinguptheoscillationsinthefirstplaceand(2)theactionofthegridinamplifyingtheoscillationsthussetup,bothofwhichweexplainedinChapterXIV.Inthatchapteritwasalsopointedoutthataverysmallchangeinthegridpotentialcausesacorrespondingandlargerchangeintheamountofcurrentflowingfromtheplatetothefilament;andthatifavacuumtubeisusedfortheproductionofoscillationstheinitialsourceofcurrentmusthaveahighvoltage,infactthehighertheplatevoltagethemorepowerfulwillbetheoscillations.
Tounderstandhowoscillationsaresetupbyavacuumtubewhenadirectcurrentisappliedtoit,takealookatthesimplecircuitsshowninFig.94.Nowwhenyouclosetheswitchthevoltagefromthebatterychargesthecondenserandkeepsitchargeduntilyouopenitagain;theinstantyoudothisthecondenserdischargesthroughthecircuitwhichincludesitandtheinductancecoil,andthedischargeofacondenserisalwaysoscillatory.
WhereanoscillatortubeisincludedinthecircuitsasshownatAandBinFig.94,thegridtakestheplaceoftheswitchandanyslightchangeinthevoltageofeitherthegridortheplateissufficienttostartatrainofoscillationsgoing.Astheseoscillationssurgethroughthetubethepositivepartsofthemflowfromtheplatetothefilamentandthesecarrymoreofthedirectcurrentwiththem.
Tomakeatubesetuppowerfuloscillationsthen,itisonlynecessarythatanoscillationcircuitshallbeprovidedwhichwillfeedpartoftheoscillationssetupbythetubebacktothegridcircuitandwhenthisisdonetheoscillationswillkeeponbeingamplifieduntilthetubereachesthelimitofitsoutput.
TheOperationofC.W.TelegraphTransmittersWithDirectCurrent--ShortDistanceC.W.Transmitter.--InthetransmittershowninthewiringdiagraminFig.76thepositivepartofthe110voltdirectcurrentiscarrieddownfromthelampsocketthroughonesideofthepanelcut-out,thencethroughthechokecoilandtotheplateoftheoscillatortube,whenthelatterischargedtothepositivesign.Thenegativepartofthe110voltdirectcurrentthenflowsdowntheotherwiretothefilamentsothatthereisadifferenceofpotentialbetweentheplateandthefilamentof110volts.Nowwhenthe6-voltbatterycurrentisswitchedonthefilamentisheatedtobrilliancy,andtheelectronsthrownoffbyitformaconductingpathbetweenitandtheplate;the110voltcurrentthenflowsfromthelattertotheformer.
Nowfollowthewiringfromtheplateovertotheblockingcondenser,thencetoclip3ofthetuningcoil,throughtheturnsofthelattertoclip2andovertothefilamentand,whenthelatterisheated,youhaveaclosedoscillationcircuit.Theoscillationssurginginthelattersetupotherandlikeoscillationsinthetuningcoilbetweentheendofwhichisconnectedwiththegrid,theaerialandtheclip2,andthesesurgethroughthecircuitformedbythisportionofthecoil,thegridcondenserandthefilament;thisistheamplifyingcircuitanditcorrespondstotheregenerativecircuitofareceivingset.
Whenoscillationsaresetupinitthegridisalternatelychargedtothepositiveandnegativesigns.Thesereversalsofvoltagesetupstrongerandeverstrongeroscillationsintheplatecircuitasbeforeexplained.Notonlydotheoscillationssurgeintheclosedcircuitsbuttheyruntoandfroontheaerialwirewhentheirenergyisradiatedintheformofelectricwaves.TheoscillationsarevariedbymeansofthetelegraphkeywhichisplacedinthegridcircuitasshowninFig.76.
TheOperationoftheKeyCircuit.--TheeffectinaC.W.transmitterwhenatelegraphkeyisconnectedinserieswithabuzzerandabatteryandtheseareshuntedaroundthecondenserinthegridcircuit,istorapidlychangethewaveformofthesustainedoscillations,andhence,thelengthofthewavesthataresentout.Whilenosoundcanbeheardintheheadphonesatthereceivingstationsolongasthe
pointsofthekeyarenotincontact,whentheyareincontacttheoscillationsaremodulatedandsoundsareheardintheheadphonesthatcorrespondtothefrequencyofthebuzzerinthekeycircuit.
TheOperationofC.W.TelegraphTransmitterswithDirectCurrent.--Thechiefdifferencesbetweenthelongdistancesetswhichuseadirectcurrent,i.e.,thosedescribedinChapterXVI,andtheshortdistancetransmittingsetsarethattheformeruse:(1)amotor-generatorsetforchangingthelowvoltagedirectcurrentintohighvoltagedirectcurrent,and(2)achopperinthekeycircuit.Thewaythemotor-generatorchangesthelow-intohigh-voltagecurrenthasbeenexplainedinChapterXVI.
Thechopperinterruptstheoscillationssurgingthroughthegridcircuitatafrequencythattheearcanhear,thatistosay,about800to1,000timespersecond.Whenthekeyisopen,ofcourse,thesustainedoscillationssetupinthecircuitswillsendoutcontinuouswavesbutwhenthekeyisclosedtheseoscillationsarebrokenupandthentheysendoutdiscontinuouswaves.Ifaheterodynereceivingset,seeChapterXV,isbeingusedattheotherendyoucandispensewiththechopperandthekeycircuitneededisverymuchsimplified.Theoperationofkeycircuitsofthelatterkindwillbedescribedpresently.
TheOperationofC.W.TelegraphTransmitterswithAlternatingCurrent--WithaSingleOscillatorTube.--Whereanoscillatortubetelegraphtransmitterisoperatedbya110voltalternatingcurrentastheinitialsourceofenergy,abuzzer,chopperorotherinterruptorisnotneededinthekeycircuit.Thisisbecauseoscillationsaresetuponlywhentheplateisenergizedwiththepositivepartofthealternatingcurrentandthisproducesanintermittentmusicaltoneintheheadphones.Hencethiskindofasendingsetiscalledatonetransmitter.
Sinceoscillationsaresetuponlybythepositivepartorvoltageofanalternatingcurrentitisclearthat,asamatteroffact,thiskindofatransmitterdoesnotsendoutcontinuouswavesandthereforeitisnotaC.W.transmitter.ThisisgraphicallyshownbythecurveofthewaveformofthealternatingcurrentandtheoscillationsthataresetupbythepositivepartofitinFig.95.Wheneverthepositivehalfofthealternatingcurrentenergizestheplatethenoscillationsaresetupbythetubeand,conversely,whenthenegativehalfofthecurrentchargestheplatenooscillationsareproduced.
Youwillalsoobservethattheoscillationssetupbythepositivepartofthecurrentarenotofconstantamplitudebutstartatzerotheinstantthepositivepartbeginstoenergizetheplateandtheykeeponincreasinginamplitudeasthecurrentrisesinvoltageuntilthelatterreachesitsmaximum;thenasitgraduallydropsagaintozerotheoscillationsdecreaseproportionatelyinamplitudewithit.
HeatingtheFilamentwithAlternatingCurrent.--Whereanalternatingcurrentpowertransformerisusedtodevelopthenecessaryplatevoltageasecondsecondarycoilisgenerallyprovidedforheatingthefilamentoftheoscillationtube.Thisisbetterthanadirectcurrentforitaddstothelifeofthefilament.Whenyouuseanalternatingcurrenttoheatthefilamentkeepitatthesamevoltageratherthanatthesameamperage(currentstrength).Todothisyouneedonlytouseavoltmeteracrossthefilamentterminalsinsteadofanammeterinserieswithit;thenregulatethevoltageofthefilamentwitharheostat.
TheOperationofC.W.TelegraphTransmitterswithAlternatingCurrent--WithTwoOscillatorTubes.--ByusingtwooscillatortubesandconnectingthemupwiththepowertransformerandoscillatingcircuitsasshowninthewiringdiagraminFig.83theplatesarepositivelyenergizedalternatelywitheveryreversalofthecurrentand,consequently,thereisnotimeperiodbetweentheendingoftheoscillationssetupbyonetubeandthebeginningoftheoscillationssetupbytheothertube.Inotherwordstheseoscillationsaresustainedbutasinthecaseofthoseofasingletube,theiramplituderisesandfalls.Thiskindofasetiscalledafullwaverectificationtransmitter.
Thewavesradiatedbythistransmittercanbereceivedbyeitheracrystaldetectororaplainvacuum-tubedetectorbuttheheterodynereceptorwillgiveyoubetterresultsthaneitheroftheforegoingtypes.
TheOperationofWirelessTelephoneTransmitterswithDirectCurrent--ShortDistanceTransmitter.--Theoperationofthisshortdistancewirelesstelephonetransmitter,awiringdiagramofwhichisshowninFig.85isexactlythesameasthatoftheDirectCurrentShortDistanceC.W.TelegraphTransmitteralreadyexplainedinthischapter.Theonlydifferenceintheoperationofthesesetsisthesubstitutionofthemicrophonetransmitterforthetelegraphkey.
TheMicrophoneTransmitter.--Themicrophonetransmitterthatisusedtovary,ormodulate,thesustainedoscillationssetupbytheoscillatortubeandcircuitsisshowninFig.84.ByreferringtothediagramatAinthisfigureyouwillreadilyunderstandhowitoperates.Whenyouspeakintothemouthpiecethesoundwaves,whicharewavesintheair,impingeuponthediaphragmandthesesetitintovibration--thatis,theymakeitmovetoandfro.
Whenthediaphragmmovestowardthebackofthetransmitteritforcesthecarbongranulesthatareinthecupclosertogether;thislowerstheirresistanceandallowsmorecurrentfromthebatterytoflowthroughthem;whenthepressureoftheairwavesisremovedfromthediaphragmitspringsbacktowardthemouth-pieceandthecarbongranulesloosenupwhentheresistanceofferedbythemisincreasedandlesscurrentcanflowthroughthem.Wheretheoscillationcurrentintheaerialwireissmallthetransmittercanbeconnecteddirectlyinserieswiththelatterwhentheformerwillsurgethroughit.Asyouspeakintothemicrophonetransmitteritsresistanceisvariedandthecurrentstrengthoftheoscillationsisvariedaccordingly.
TheOperationofWirelessTelephoneTransmitterswithDirectCurrent--LongDistanceTransmitters.--Inthewirelesstelephonetransmittersforlongdistanceworkwhichwereshownanddescribedintheprecedingchapterabatteryisusedtoenergizethemicrophonetransmitter,andthesetwoelementsareconnectedinserieswithamicrophonemodulator.Thislatterdevicemaybeeither(1)atelephoneinductioncoil,(2)amicrophonetransformer,or(3)amagneticmodulator;thefirsttwoofthesedevicesstep-upthevoltageofthebatterycurrentandtheamplifiedvoltagethusdevelopedisimpressedontheoscillationsthatsurgethroughtheclosedoscillationcircuitortheaerialwire
systemaccordingtotheplacewhereyouconnectit.Thethirddeviceworksonadifferentprincipleandthiswillbedescribedalittlefartheralong.
TheOperationofMicrophoneModulators--TheInductionCoil.--Thisdeviceisreallyaminiaturetransformer,seeAinFig.86,anditspurposeistochangethe6voltdirectcurrentthatflowsthroughthemicrophoneinto100voltsalternatingcurrent;inturn,thisisimpressedontheoscillationsthataresurgingineither(1)thegridcircuitasshownatAinFig.89,andinFig.90,(2)theaerialwiresystem,asshownatBinFig.89andFig.93.Whenthecurrentfromthebatteryflowsthroughtheprimarycoilitmagnetizesthesoftironcoreandasthemicrophonevariesthestrengthofthecurrentthehighvoltagealternatingcurrentssetupinthesecondarycoiloftheinductioncoilarelikewisevaried,whentheyareimpresseduponandmodulatetheoscillatingcurrents.
TheMicrophoneTransformer.--Thisisaninductioncoilthatisdesignedespeciallyforwirelesstelephonemodulation.Theironcoreofthistransformerisalsooftheopenmagneticcircuittype,seeAinFig.87,andtheratiooftheturns[Footnote:SeeChapterVI]oftheprimaryandthesecondarycoilissuchthatwhenthesecondarycurrentisimpresseduponeitherthegridcircuitortheaerialwiresystemitcontrolstheoscillationsflowingthroughitwiththegreatestefficiency.
TheMagneticModulator.--Thispieceofapparatusisalsocalledamagneticamplifier.Theironcoreisformedofverythinplates,orlaminationsastheyarecalled,andthispermitshigh-frequencyoscillationstosurgeinacoilwoundonit.Inthistransformer,seeAinFig.88,thecurrentflowingthroughthemicrophonevariesthemagneticpermeabilityofthesoftironcorebythemagneticsaturationofthelatter.Sincethemicrophonecurrentisabsolutelydistinctfromtheoscillatingcurrentssurgingthroughthecoilofthetransformeraverysmalldirectcurrentflowingthroughacoilonthelatterwillvaryormodulateverylargeoscillatingcurrentssurgingthroughtheformer.ItisshownconnectedintheaerialwiresystematAinFig.88,andinFig.93.
OperationoftheVacuumTubeasaModulator.--Whereamicrophonemodulatoroftheinductioncoilormicrophonetransformertypeisconnectedinthegridcircuitoraerialwiresystemthemodulationisnotveryeffective,butbyusingasecondtubeasamodulator,asshowninFig.90,anefficientdegreeofmodulationcanbehad.Nowtherearetwomethodsbywhichavacuumtubecanbeusedasamodulatorandtheseare:(1)bytheabsorptionoftheenergyofthecurrentsetupbytheoscillatortube,and(2)byvaryingthedirectcurrentthatenergizestheplateoftheoscillatortube.
Thefirstofthesetwomethodsisnotusedbecauseitabsorbstheenergyoftheoscillatingcurrentproducedbythetubeanditisthereforewasteful.Thesecondmethodisanefficientone,asthedirectcurrentisvariedbeforeitpassesintotheoscillatortube.Thisissufficientreasonfordescribingonlythesecondmethod.Thevoltageofthegridofthemodulatortubeisvariedbythesecondarycoiloftheinductioncoilormicrophonetransformer,abovedescribed.Inthiswaythemodulatortubeactslikeavariableresistancebutitamplifiesthevariationsimpressedontheoscillationssetupbytheoscillatortube.Asthemagneticmodulatordoesthesamethingavacuumtubeusedasamodulatorisnotneededwheretheformerisemployed.Forthisreasonamagneticmodulatoristhecheapestinthelongrun.
TheOperationofWirelessTelephoneTransmitterswithAlternatingCurrent.--Whereaninitialalternatingcurrentisusedforwirelesstelephony,thecurrentmustberectifiedfirstandthensmoothedoutbeforepassingintotheoscillatortubetobeconvertedintooscillations.Furthersothattheoscillationswillbesustained,twooscillatortubesmustbeused,and,finally,inorderthatthe
oscillationsmaynotvaryinamplitudethealternatingcurrentmustbefirstchangedintodirectcurrentbyapairofrectifiervacuumtubes,asshowninFig.93.Whenthisisdonetheplateswillbepositivelychargedalternatelywitheveryreversalofthecurrentinwhichcasetherewillbenobreakinthecontinuityoftheoscillationssetupandthereforeinthewavesthataresentout.
TheOperationofRectifierVacuumTubes.--Thevacuumtuberectifierissimplyatwoelectrodevacuumtube.ThewayinwhichitchangesacommercialalternatingcurrentintopulsatingdirectcurrentisthesameasthatinwhichatwoelectrodevacuumtubedetectorchangesanoscillatingcurrentintopulsatingdirectcurrentsandthishasbeenexplainedindetailundertheheadingofTheOperationofaTwoElectrodeVacuumTubeDetectorinChapterXII.IntheC.W.TelegraphTransmittingSetsdescribedinChapterXVII,theoscillatortubesactasrectifiersaswellasoscillatorsbutforwirelesstelephonythealternatingcurrentmustberectifiedfirstsothatacontinuousdirectcurrentwillresult.
TheOperationofReactorsandCondensers.--Areactorisasinglecoilofwirewoundonanironcore,seeFig.90andAinFig.91,anditshouldpreferablyhavealargeinductance.ThereactorfortheplateandgridcircuitofawirelesstelephonetransmitterwhereoneormoretubesareusedasmodulatorsasshowninthewiringdiagraminFig.90,andthefilterreactorshowninFig.92,operateinthesameway.
Whenanalternatingcurrentflowsthroughacoilofwirethereversalsofthecurrentsetupacounterelectromotiveforceinitwhichopposes,thatisreacts,onthecurrent,andthehigherthefrequencyofthecurrentthegreaterwillbethereactance.Whenthepositivehalfofanalternatingcurrentismadetoflowthroughalargeresistancethecurrentissmoothedoutbutatthesametimealargeamountofitsenergyisusedupinproducingheat.
Butwhenthepositivehalfofanalternatingcurrentismadetoflowthroughalargeinductanceitactslikealargeresistanceasbeforeandlikewisesmoothsoutthecurrent,butnoneofitsenergyiswastedinheatandsoacoilhavingalargeinductance,whichiscalledaninductivereactance,orjustreactorforshort,isusedtosmoothout,orfilter,thealternatingcurrentafterithasbeenchangedintoapulsatingdirectcurrentbytherectifiertubes.
Acondenseralsohasareactanceeffectonanalternatingcurrentbutdifferentfromaninductioncoilthelowerthefrequencythegreaterwillbethereactance.Forthisreasonbothafilterreactorandfiltercondensersareusedtosmoothoutthepulsatingdirectcurrents.
CHAPTERXX
HOWTOMAKEARECEIVINGSETFOR$5.00ORLESS
InthechaptersonReceptorsyouhavebeentoldhowtobuilduphigh-gradesets.Buttherearethousandsofboys,and,probably,notafewmen,whocannotaffordtoinvest$25.00,moreorless,inareceivingsetandwouldliketoexperimentinasmallway.
Thefollowingsetisinexpensive,andwiththischeap,littleportablereceptoryoucangettheMorsecodefromstationsahundredmilesdistantandmessagesandmusicfrombroadcastingstationsifyoudonotlivetoofarawayfromthem.Allyouneedforthissetare:(1)acrystaldetector,(2)atuningcoiland(3)anearphone.Youcanmakeacrystaldetectoroutofacoupleofbindingposts,abitofgalenaandapieceofbrasswire,or,better,youcanbuyoneallreadytousefor50cents.
PhotographunavailableWirelessReceptor,thesizeofaSafetyMatchBox.AYouthfulGeniusinthepersonofKennethR.Hinman,Whoisonlytwelveyearsold,hasmadeaWirelessReceivingSetthatfitsneatlyintoa
SafetyMatchBox.WiththisInstrumentandaPairofOrdinaryReceivers,HeisabletocatchnotonlyCodeMessagesbuttheregularBroadcastingProgramsfromStationsTwentyandThirtyMiles
Distant.
TheCrystalDetector.--ThisisknownastheRascobabydetectoranditismadeandsoldbytheRadioSpecialtyCompany,96ParkPlace,NewYorkCity.ItisshowninFig.96.Thebaseismadeofblackcompositionandonitismountedastandardinwhicharodslidesandononeendofthisthereisfixedahardrubberadjustingknobwhiletheotherendcarriesathinpieceofphosphor-bronzewire,calledacat-whiskerTosecurethegalenacrystalinthecupyousimplyunscrewtheknurledcap,placeitinthecavityofthepostandscrewthecapbackonagain.Thefreeendofthecat-whiskerwireisthenadjustedsothatitwillrestlightlyontheexposedpartofthegalena.
TheTuningCoil.--Youwillhavetomakethistuningcoil,whichyoucandoatacostoflessthan$1.00,asthecheapesttuningcoilyoucanbuycostsatleast$3.00,andweneedtherestofour$5.00toinvestintheearphone.Getacardboardtube,suchasisusedformailingpurposes,2inchesindiameterand3incheslong,seeAinFig.97.Nowwindon250turnsofNo.40BrownandSharpegaugeplainenameledmagnetwire.YoucanuseNo.40doublecottoncoveredmagnetwire,inwhichcaseyouwillhavetoshellacthetubeandthewireafteryougetiton.
Asyouwindonthewiretakeoffatapatevery15thturn,thatis,scrapethewireandsolderonapieceabout7incheslong,asshowninFig.99;anddothisuntilyouhave6tapstakenoff.Insteadofleavingthewiresoutsideofthetubebringthemtotheinsideofitandthenoutthroughoneoftheopenends.Nowbuyaroundwood-baseswitchwith7contactpointsonitasshownatBinFig.97.Thiswillcostyou25or50cents.
TheHeadphone.--AnordinaryBelltelephonereceiverisofsmalluseforwirelessworkasitiswoundtotoolowaresistanceandthediaphragmismuchtoothick.IfyouhappentohaveaBellphoneyoucanrewinditwithNo.40singlecoveredsilkmagnetwire,orenameledwireofthesamesize,whenitssensitivitywillbeverygreatlyimproved.Thenyoumustgetathindiaphragmandthisshouldnotbeenameled,asthistendstodampenthevibrationsofit.Youcangetadiaphragmoftherightkindfor5cents.
Thebetterway,though,istobuyanearphonemadeespeciallyforwirelesswork.Youcangetonewoundto1000ohmsresistancefor$1.75andthispriceincludesacord.[Footnote:ThisisMesco,No.470wirelessphone.SoldbytheManhattanElectricalSupplyCo.,ParkPlace,N.Y.C.]For$1.00extrayoucangetahead-bandforit,andthenyourphonewilllookliketheonepicturedinFig.98.
HowtoMounttheParts.--Nowmountthecoilonawoodbase,1/2or1inchthick,3-1/2incheswideand5-1/2incheslong,andthenconnectoneendofthecoiltooneoftheendpointsontheswitch,andconnecteachsucceedingtaptooneoftheswitchpoints,asshownschematicallyinFig.99anddiagrammaticallyinFig.100.Thisdone,screwtheswitchdowntothebase.Finallyscrewthedetectortothebaseandscrewtwobindingpostsinfrontofthecoil.Thesearefortheearphone.
TheCondenser.--Youdonothavetoconnectacondenseracrosstheearphonebutifyoudoyouwillimprovethereceivingqualitiesofthereceptor.
HowtoConnectUptheReceptor.--NowconnectupallthepartsasshowninFigs.99and100,thenconnecttheleading-inwireoftheaerialwiththeleveroftheswitch;andconnectthefreeendofthetuningcoilwiththeground.Ifyouhavenoaerialwiretryhookingituptoarainpipethatisnotgroundedorthesteelframeofanumbrella.Foragroundyoucanuseawaterpipe,anironpipedrivenintotheground,orahydrant.Putonyourheadphone,adjustthedetectorandmovetheleverovertheswitchcontactsuntilitisinadjustmentandthen,ifallyourconnectionsareproperlymade,youshouldbeabletopickupmessages.
PhotographunavailableWirelessSetmadeintoaRing,designedbyAlfredG.Rinehart,ofElizabeth,NewJersey.ThislittleReceptorisaPracticalSet;itwillreceiveMessages,Concerts,etc.,Measures1"by5/8"by7/8".An
ordinaryUmbrellaisusedasanAerial.
APPENDIX
USEFULINFORMATION
ABBREVIATIONSOFUNITS
UnitAbbreviation
ampereamp.
ampere-hoursamp.-hr.
centimetercm.
centimeter-gram-secondc.g.s.
cubiccentimeterscm.^3
cubicinchescu.in.
cyclespersecond~
degreesCentigrade°C.
degreesFahrenheit°F.
feetft.
foot-poundsft.-lb.
gramsg.
henriesh.
inchesin.
kilogramskg.
kilometerskm.
kilowattskw.
kilowatt-hourskw.-hr.
kilovolt-ampereskv.-a.
metersm.
microfarads[Greek:mu]f.
micromicrofarads[Greek:mumu]f.
millihenriesmh.
millimetersmm.
poundslb.
secondssec.
squarecentimeterscm.^2
squareinchessq.in.
voltsv.
wattsw.
PREFIXESUSEDWITHMETRICSYSTEMUNITS
PrefixAbbreviationMeaning
micro[Greek:mu].1millionth
millim.1thousandth
centic.1hundredth
decid.1tenth
dekadk.10
hektoh.1hundred
kilok.1thousand
megam.1million
SYMBOLSUSEDFORVARIOUSQUANTITIES
QuantitySymbol
capacitanceC
conductanceg
couplingco-efficientk
current,instantaneousi
current,effectivevalueI
decrement[Greek:delta]
dielectricconstant[Greek:alpha]
electricfieldintensity[Greek:epsilon]
electromotiveforce,
instantaneousvalueE
electromotiveforce,
effectivevalueF
energyW
forceF
frequencyf
frequencyx2[Greek:pi][Greek:omega]
impedanceZ
inductance,selfL
inductance,mutualM
magneticfieldintensityA
magneticflux[Greek:Phi]
magneticinductionB
periodofacomplete
oscillationT
potentialdifferenceV
quantityofelectricityQ
ratioofthe
circumferenceofa
circletoitsdiameter
=3.1416[Greek:pi]
reactanceX
resistanceR
timet
velocityv
velocityoflightc
wavelength[Greek:lambda]
wavelengthinmeters[Greek:lambda]m
workW
permeability[Greek:mu]
Squareroot[Math:squareroot]
TABLEOFENAMELEDWIRE
No.ofTurnsTurnsOhmsper
Wire,perperCubicInch
B.&S.LinearSquareof
GaugeInchInchWinding
2030885.748
223714001.88
244621604.61
2658346011.80
2873540029.20
3091826070.90
3211621,0007547.00
3414513,4302968.00
3617831,8201098.00
3823254,080456.00
4029486,500183.00
TABLEOFFREQUENCYANDWAVELENGTHS
W.L.--WaveLengthsinMeters.
F.--NumberofOscillationsperSecond.
O.orsquarerootL.C.iscalledOscillationConstant.
C.--CapacityinMicrofarads.
L.--InductanceinCentimeters.
1000Centimeters=1Microhenry.
W.L.FOL.C.
506,000,000.839.7039
1003,000,0001.682.82
1502,000,0002.526.35
2001,500,0003.3611.29
2501,200,0004.1917.55
3001,000,0005.0525.30
350857,1005.8734.46
400750,0006.7145.03
450666,7007.5557.00
500600,0008.3970.39
550545,4009.2385.19
600500,00010.07101.41
700428,60011.74137.83
800375,00013.42180.10
900333,30015.10228.01
1,000300,00016.78281.57
1,100272,73018.45340.40
1,200250,00020.13405.20
1,300230,76021.81475.70
1,400214,38023.49551.80
1,500200,00025.17633.50
1,600187,50026.84720.40
1,700176,46028.52813.40
1,800166,67030.20912.00
1,900157,80031.881,016.40
2,000150,00033.551,125.60
2,100142,85035.231,241.20
2,200136,36036.911,362.40
2,300130,43038.591,489.30
2,400125,00040.271,621.80
2,500120,00041.951,759.70
2,600115,38043.621,902.60
2,700111,11045.302,052.00
2,800107,14046.892,207.00
2,900103,45048.662,366.30
3,000100,00050.332,533.20
4,00075,00067.114,504.00
5,00060,00083.897,038.00
6,00050,000100.710,130.00
7,00041,800117.313,630.00
8,00037,500134.118,000.00
9,00033,300151.022,820.00
10,00030,000167.928,150.00
11,00027,300184.834,150.00
12,00025,000201.540,600.00
13,00023,100218.347,600.00
14,00021,400235.055,200.00
15,00020,000252.063,500.00
16,00018,750269.072,300.00
PRONUNCIATIONOFGREEKLETTERS
ManyofthephysicalquantitiesuseGreeklettersforsymbols.ThefollowingistheGreekalphabetwiththewaythelettersarepronounced:
aalpha
bbeta
ggamma
ddelta
eepsilon
zzeta
aeeta
ththeta
iiota
kkappa
llambda
mmu
nnu
xXi(Zi)
oomicron
ppi
rrho
ssigma
ttau
uupsilon
phphi
chchi
pspsi
oomega
TABLEOFSPARKINGDISTANCES
InAirforVariousVoltagesbetweenNeedlePoints
VoltsDistance
InchesCentimeter
5,000.225.57
10,000.4701.19
15,000.7251.84
20,0001.0002.54
25,0001.3003.30
30,0001.6254.10
35,0002.0005.10
40,0002.4506.20
45,0002.957.50
50,0003.559.90
60,0004.6511.8
70,0005.8514.9
80,0007.1018.0
90,0008.3521.2
100,0009.6024.4
110,00010.7527.3
120,00011.8530.1
130,00012.9532.9
140,00013.9535.4
150,00015.0038.1
FEETPERPOUNDOFINSULATEDMAGNETWIRE
No.ofSingleDoubleSingleDouble
B.&S.Cotton,Cotton,Silk,Silk,Enamel
Gauge4-Mils8-Mils1-3/4-Mils4-Mils
20311298319312320
21389370408389404
22488461503498509
23612584636631642
24762745800779810
259579031,0059661,019
261,1921,1181,2651,2021,286
271,4881,4221,5901,5431,620
281,8521,7591,9721,9172,042
292,3752,2072,5702,4352,570
302,8602,5343,1452,9003,240
313,8002,7683,9433,6834,082
324,3753,7374,9504,6545,132
335,5904,6976,1805,6896,445
346,5006,1687,7407,1118,093
358,0506,7379,6008,58410,197
369,8207,87712,00010,03912,813
3711,8609,30915,00010,66616,110
3814,30010,63618,66014,22220,274
3917,13011,90723,15016,51625,519
4021,59014,22228,70021,33332,107
INTERNATIONALMORSECODEANDCONVENTIONALSIGNALS
TOBEUSEDFORALLGENERALPUBLICSERVICERADIOCOMMUNICATION
1. Adashisequaltothreedots.2. Thespacebetweenpartsofthesameletterisequaltoonedot.3. Thespacebetweentwolettersisequaltothreedots.4. Thespacebetweentwowordsisequaltofivedots.
[Note:perioddenotesMorsedot,hyphendenotesMorsedash]
A.-
B-...
C-.-.
D-..
E.
F..-.
G--.
H....
I..
J.---
K-.-
L.-..
M--
N-.
O---
P.--.
Q--.-
R.-.
S...
T-
U..-
V...-
W.--
X-..-
Y-.--
Z--..
Ä(German).-.-
ÁorÅ(Spanish-Scandinavian).--.-
CH(German-Spanish)----
É(French)..-..
Ñ(Spanish)--.--
Ö(German)---.
Ü(German)..--
1.----
2..---
3...--
4....-
5.....
6-....
7--...
8---..
9----.
0-----
Period......
Semicolon-.-.-.
Comma-.-.-.
Colon---...
Interrogation..--..
Exclamationpoint--..--
Apostrophe.----.
Hyphen-....-
Barindicatingfraction-..-.
Parenthesis-.--.-
Invertedcommas.-..-.
Underline..--.-
Doubledash-...-
DistressCall...---...
Attentioncalltoprecedeeverytransmission-.-.-
Generalinquirycall-.-.--.-
From(de)-...
Invitationtotransmit(goahead)-.-
Warning--highpower--..--
Question(pleaserepeatafter...)--interruptinglongmessages..--..
Wait.-...
Break(Bk.)(doubledash)-...-
Understand...-.
Error........
Received(O.K.).-.
Positionreport(toprecedeallpositionmessages)-.-.
Endofeachmessage(cross).-.-.
Transmissionfinished(endofwork)(conclusionofcorrespondence)...-.-
INTERNATIONALRADIOTELEGRAPHICCONVENTION
LISTOFABBREVIATIONSTOBEUSEDINRADIOCOMMUNICATION
ABBREVIATIONQUESTIONANSWERORREPLY
PRBDoyouwishtocommunicateIwishtocommunicatebymeans
bymeansoftheInternationaloftheInternationalSignalCode.
SignalCode?
QRAWhatshiporcoaststationisThisis....
that?
QRBWhatisyourdistance?Mydistanceis....
QRCWhatisyourtruebearing?Mytruebearingis....
QRDWhereareyouboundfor?Iamboundfor....
QRFWhereareyouboundfrom?Iamboundfrom....
QRGWhatlinedoyoubelongto?Ibelongtothe...Line.
QRHWhatisyourwavelengthinMywavelengthis...meters.
meters?
QRJHowmanywordshaveyoutosend?Ihave...wordstosend.
QRKHowdoyoureceiveme?Iamreceivingwell.
QRLAreyoureceivingbadly?Iamreceivingbadly.Please
ShallIsend20?send20.
...-....-.
foradjustment?foradjustment.
QRMAreyoubeinginterferedwith?Iambeinginterferedwith.
QRNAretheatmosphericsstrong?Atmosphericsareverystrong.
QROShallIincreasepower?Increasepower.
QRPShallIdecreasepower?Decreasepower.
QRQShallIsendfaster?Sendfaster.
QRSShallIsendslower?Sendslower.
QRTShallIstopsending?Stopsending.
QRUHaveyouanythingforme?Ihavenothingforyou.
QRVAreyouready?Iamready.Allrightnow.
QRWAreyoubusy?Iambusy(or:Iambusywith...).
Pleasedonotinterfere.
QRXShallIstandby?Standby.Iwillcallyouwhen
required.
QRYWhenwillbemyturn?YourturnwillbeNo....
QRZAremysignalsweak?Yousignalsareweak.
QSAAremysignalsstrong?Yousignalsarestrong.
QSBIsmytonebad?Thetoneisbad.
Ismysparkbad?Thesparkisbad.
QSCIsmyspacingbad?Yourspacingisbad.
QSDWhatisyourtime?Mytimeis....
QSFIstransmissiontobeinTransmissionwillbein
alternateorderorinseries?alternateorder.
QSGTransmissionwillbeina
seriesof5messages.
QSHTransmissionwillbeina
seriesof10messages.
QSJWhatrateshallIcollectfor...?Collect....
QSKIsthelastradiogramcanceled?Thelastradiogramiscanceled.
QSLDidyougetmyreceipt?Pleaseacknowledge.
QSMWhatisyourtruecourse?Mytruecourseis...degrees.
QSNAreyouincommunicationwithland?Iamnotincommunicationwithland.
QSOAreyouincommunicationwithIamincommunicationwith...
anyshiporstation(through...).
(or:with...)?
QSPShallIinform...thatyouareInform...thatIamcallinghim.
callinghim?
QSQIs...callingme?Youarebeingcalledby....
QSRWillyouforwardtheradiogram?Iwillforwardtheradiogram.
QSTHaveyoureceivedthegeneralGeneralcalltoallstations.
call?
QSUPleasecallmewhenyouhaveWillcallwhenIhavefinished.
finished(or:at...o'clock)?
QSVIspubliccorrespondencebeingPubliccorrespondenceisbeing
handled?handled.Pleasedonotinterfere.
[Footnote:Publiccorrespondenceisanyradiowork,officialorprivate,handledoncommercialwavelengths.]
QSWShallIincreasemysparkIncreaseyoursparkfrequency.
frequency?
QSXShallIdecreasemysparkDecreaseyoursparkfrequency.
frequency?
QSYShallIsendonawavelengthLetuschangetothewavelength
of...meters?of...meters.
QSZSendeachwordtwice.Ihave
difficultyinreceivingyou.
QTARepeatthelastradiogram.
Whenanabbreviationisfollowedbyamarkofinterrogation,itreferstothequestionindicatedforthatabbreviation.
UsefulInformation
SymbolsUsedForApparatus
alternatorammeteraerialarcbatterybuzzercondenservariablecondenserconnectionofwiresnoconnectioncoupledcoils
variablecouplingdetectorgap,plaingap,quenchedgroundhotwireammeterinductorvariableinductorkeyresistorvariableresistorswitchs.p.s.t."s.p.d.t."d.p.s.t."d.p.d.t."reversingphonereceiver"transmitterthermoelementtransformervacuumtubevoltmeterchokecoil
DEFINITIONSOFELECTRICANDMAGNETICUNITS
Theohmistheresistanceofathreadofmercuryatthetemperatureofmeltingice,14.4521gramsinmass,ofuniformcross-sectionandalengthof106.300centimeters.
Theampereisthecurrentwhichwhenpassedthroughasolutionofnitrateofsilverinwateraccordingtocertainspecifications,depositssilverattherateof0.00111800ofagrampersecond.
Thevoltistheelectromotiveforcewhichproducesacurrentof1amperewhensteadilyappliedtoaconductortheresistanceofwhichis1ohm.
Thecoulombisthequantityofelectricitytransferredbyacurrentof1amperein1second.
Theampere-houristhequantityofelectricitytransferredbyacurrentof1amperein1hourandis,therefore,equalto3600coulombs.
Thefaradisthecapacitanceofacondenserinwhichapotentialdifferenceof1voltcausesittohaveachargeof1coulombofelectricity.
Thehenryistheinductanceinacircuitinwhichtheelectromotiveforceinducedis1voltwhentheinducingcurrentvariesattherateof1amperepersecond.
Thewattisthepowerspentbyacurrentof1ampereinaresistanceof1ohm.
ThejouleistheenergyspentinIsecondbyaflowof1amperein1ohm.
Thehorse-powerisusedinratingsteammachinery.Itisequalto746watts.
Thekilowattis1,000watts.
Theunitsofcapacitanceactuallyusedinwirelessworkarethemicrofarad,whichisthemillionthpartofafarad,becausethefaradistoolargeaunit;andtheC.G.S.electrostaticunitofcapacitance,whichisoftencalledthecentimeterofcapacitance,whichisaboutequalto1.11microfarads.
Theunitsofinductancecommonlyusedinradioworkarethemillihenry,whichisthethousandthpartofahenry;andthecentimeterofinductance,whichisoneone-thousandthpartofamicrohenry.
Note.--ForfurtherinformationaboutelectricandmagneticunitsgettheBureauofStandardsCircularNo.60,calledElectricUnitsandStandards,thepriceofwhichis15cents;alsogetScientificPaperNo.292,calledInternationalSystemofElectricandMagneticUnits,price10cents.TheseandotherinformativepaperscanbehadfromtheSuperintendentofDocuments,GovernmentPrintingOffice,Washington,D.C.
WIRELESSBOOKS
TheAdmiraltyManualofWirelessTelegraphy.1920.PublishedbyHisMajesty'sStationeryOffice,London.
RalphE.Batcher.--PreparedRadioMeasurements.1921.WirelessPress,Inc.,NewYorkCity.
ElmerE.Bucher.--PracticalWirelessTelegraphy.1918.WirelessPress,Inc.,NewYorkCity.
ElmerE.Bucher.--VacuumTubesinWirelessCommunication.1919.WirelessPress,Inc.,NewYorkCity.
ElmerE.Bucher.--TheWirelessExperimenter'sManual.1920.WirelessPress,Inc.,NewYorkCity.
1. FrederickCollins.--WirelessTelegraphy,ItsHistory,Theory,andPractice.1905.McGrawPub.Co.,NewYorkCity.
2. H.Dellinger.--PrinciplesUnderlyingRadioCommunication.3. SignalCorps,U.S.Army,Washington,D.C.4. M.Dorsett.--WirelessTelegraphyandTelephony.1920.WirelessPress,Ltd.,London.5. A.Fleming.--PrinciplesofElectricWaveTelegraphy.1919.Longmans,GreenandCo.,London.
CharlesB.Hayward.--HowtoBecomeaWirelessOperator.1918.AmericanTechnicalSociety,Chicago,Ill.
G.D.Robinson.--ManualofRadioTelegraphyandTelephony.1920.UnitedStatesNavalInstitute,Annapolis,Md.
RupertStanley.--TextbookofWirelessTelegraphy.1919.Longmans,GreenandCo.,London.
E.W.Stone.--ElementsofRadioTelegraphy.1919.D,VanNostrandCo.,NewYorkCity.
L.B.Turner.--WirelessTelegraphyandTelephony.1921.CambridgeUniversityPress.Cambridge,England.
SendtotheSuperintendentofDocuments,GovernmentPrintingOffice,Washington,D.C.,foracopyofPriceListNo.64whichliststheGovernment'sbooksandpamphletsonwireless.Itwillbesenttoyoufreeofcharge.
TheGovernmentpublishes;(1)AListofCommercialGovernmentandSpecialWirelessStations,everyyear,price15cents;(2)AListofAmateurWirelessStations,yearly,price15cents;(3)AWirelessServiceBulletinispublishedmonthly,price5centsacopy,or25centsyearly;and(4)WirelessCommunicationLawsoftheUnitedStates,theInternationalWirelessTelegraphicConventionandRegulationsGoverningWirelessOperatorsandtheUseofWirelessonShipsandLandStations,price15centsacopy.OrdersfortheabovepublicationsshouldbeaddressedtotheSuperintendentofDocuments,GovernmentPrintingOffice,Washington,D.C.
ManufacturersandDealersinWirelessApparatusandSupplies:
Adams-MorganCo.,UpperMontclair,N.J.
AmericanHardRubberCo.,11MercerStreet,NewYorkCity.
AmericanRadioandResearchCorporation,MedfordHillside,Mass.
Brach(L.S.)Mfg.Co.,127SussexAve.,Newark,N.J.
Brandes(C.)Inc.,237LafayetteSt.,NewYorkCity.
Bunnell(J.H.)Company,ParkPlace,NewYorkCity.
BurgessBatteryCompany,HarrisTrustCo.Bldg.,Chicago,Ill.
Clapp-EastmanCo.,120MainSt.,Cambridge,Mass.
ConnecticutTelephoneandTelegraphCo.,Meriden,Conn.
ContinentalFiberCo.,Newark,Del.
Coto-CoilCo.,Providence,R.I.
CrosleyMfg.Co.,Cincinnati,Ohio.
Doolittle(F.M.),817ChapelSt.,NewHaven,Conn.
Edelman(PhilipE.),9CortlandtSt.,NewYorkCity.
EdisonStorageBatteryCo.,Orange,N.J.
ElectricSpecialtyCo.,Stamford,Conn.
ElectroseMfg.Co.,60WashingtonSt.,Brooklyn,N.Y.
GeneralElectricCo.,Schenectady,N.Y.
Grebe(A.H.)andCo.,Inc.,RichmondHill,N.Y.C.
InternationalBrassandElectricCo.,176BeekmanSt.,NewYorkCity.
InternationalInsulatingCo.,25West45thSt.,NewYorkCity.
KingAmplitoneCo.,82ChurchSt.,NewYorkCity.
Kennedy(ColinB.)Co.,RialtoBldg.,SanFrancisco,Cal.
MagnavoxCo.,Oakland,Cal.
ManhattanElectricalSupplyCo.,ParkPlace,N.Y.
Marshall-GerkenCo.,Toledo,Ohio.
MichiganPaperTubeandCanCo.,2536GrandRiverAve.,Detroit,Mich.
Murdock(Wm.J.)Co.,Chelsea,Mass.
NationalCarbonCo.,Inc.,LongIslandCity,N.Y.
PittsburghRadioandApplianceCo.,112DiamondSt.,Pittsburgh,Pa,
RadioCorporationofAmerica,233Broadway,NewYorkCity.
Riley-KlotzMfg.Co.,17-19MulberrySt.,Newark,N.J.
RadioSpecialtyCo.,96ParkPlace,NewYorkCity.
Roller-SmithCo.,15BarclaySt.,NewYorkCity.
Tuska(C.D.)Co.,Hartford,Conn.
WesternElectricCo.,Chicago,Ill.
WestinghouseElectricCo.,Pittsburgh,Pa.
WestonElectricalInstrumentCo.,173WestonAve.,Newark,N.J.
WestfieldMachineCo.,Westfield,Mass.
ABBREVIATIONSOFCOMMONTERMS
A...............Aerial
A.C.............AlternatingCurrent
A.F.............AudioFrequency
B.andS........Brown&SharpeWireGauge
C...............CapacityorCapacitance
C.G.S...........Centimeter-Grain-Second
Cond............Condenser
Coup............Coupler
C.W.............ContinuousWaves
D.C.............DirectCurrent
D.P.D.T.........DoublePointDoubleThrow
D.P.S.T.........DoublePointSingleThrow
D.X.............Distance
E...............ShortforElectromotiveForce(Volt)
E.M.F...........ElectromotiveForce
F...............FilamentorFrequency
G...............Grid
Gnd.............Ground
I...............CurrentStrength(Ampere)
I.C.W...........InterruptedContinuousWaves
KW..............Kilowatt
L...............Inductance
L.C.............LooseCoupler
Litz............Litzendraht
Mfd.............Microfarad
Neg.............Negative
O.T.............OscillationTransformer
P...............Plate
Prim............Primary
Pos.............Positive
R...............Resistance
R.F.............RadioFrequency
Sec.............Secondary
S.P.D.T.........SinglePointDoubleThrow
S.P.S.T.........SinglePointSingleThrow
S.R.............SelfRectifying
T...............TelephoneorPeriod(time)ofComplete
Oscillation
Tick............Tickler
V...............PotentialDifference
Var.............Variometer
Var.Cond.......VariableCondenser
V.T.............VacuumTube
W.L.............WaveLength
X...............Reactance
GLOSSARY
ABATTERY.--SeeBatteryA.
ABBREVIATIONS,CODE.--Abbreviationsofquestionsandanswersusedinwirelesscommunication.TheabbreviationofaquestionisusuallyinthreelettersofwhichthefirstisQ.ThusQRBisthecodeabbreviationof"whatisyourdistance?"andtheanswer"Mydistanceis..."SeePage306[Appendix:ListofAbbreviations].
ABBREVIATIONS,UNITS.--Abbreviationsofvariousunitsusedinwirelesselectricity.TheseabbreviationsareusuallylowercaselettersoftheRomanalphabet,butoccasionallyGreeklettersareusedandothersigns.Thusamperesisabbreviatedamp.,micro,whichmeansonemillionth,[Greek:mu],etc.SeePage301[Appendix:UsefulAbbreviations].
ABBREVIATIONSOFWORDSANDTERMS.--Lettersusedinsteadofwordsandtermsforshorteningthemupwherethereisaconstantrepetitionofthem,asA.C.foralternatingcurrent;C.W.forcontinuouswaves;V.T.forvacuumtube,etc.SeePage312[Appendix:AbbreviationsofCommonTerms].
AERIAL.--Alsocalledantenna.Anaerialwire.Oneormorewiressuspendedintheairandinsulatedfromitssupports.Itistheaerialthatsendsoutthewavesandreceivesthem.
AERIAL,AMATEUR.--Anaerialsuitableforsendingout200meterwavelengths.Suchanaerialwiresystemmustnotexceed120feetinlengthfromthegrounduptotheaerialswitchandfromthisthroughtheleading-inwiretotheendoftheaerial.
AERIALAMMETER.--SeeAmmeter,HotWire.
AERIAL,BED-SPRINGS.--Whereanoutdooraerialisnotpracticablebed-springsareoftenmadetoservethepurpose.
AERIALCAPACITY.--SeeCapacity,Aerial.
AERIALCOUNTERPOISE.--Whereitisnotpossibletogetagoodgroundanaerialcounterpoiseorearthcapacitycanbeusedtoadvantage.Thecounterpoiseismadeliketheaerialandissupporteddirectlyunderitclosetothegroundbutinsulatedfromit.
AERIAL,DIRECTIONAL.--Aflat-toporotheraerialthatwilltransmitandreceiveovergreaterdistancestoandfromonedirectionthantoandfromanother.
AERIAL,GROUND.--Signalscanbereceivedonasinglelongwirewhenitisplacedonorburiedintheearthorimmersedinwater.Itisalsocalledagroundantennaandanundergroundaerial.
AERIAL,LOOP.--Alsocalledacoilaerial,coilantenna,loopaerial,loopantennaandwhenusedforthepurposeadirectionfinder.Acoilofwirewoundonaverticalframe.
AERIALRESISTANCE.--SeeResistance,Aerial.
AERIALSWITCH.--SeeSwitchAerial.
AERIALWIRE.--(1)Awireorwiresthatformtheaerial.(2)Wirethatisusedforaerials;thisisusuallycopperorcopperalloy.
AERIALWIRESYSTEM.--Anaerialandgroundwireandthatpartoftheinductancecoilwhichconnectsthem.Theopenoscillationcircuitofasendingorareceivingstation.
AIRCORETRANSFORMER.--SeeTransformer,AirCore.
AMATEURAERIALORANTENNA.--SeeAerial,Amateur.
ALTERNATOR.--Anelectricmachinethatgeneratesalternatingcurrent.
ALPHABET,INTERNATIONALCODE.--AmodifiedMorsealphabetofdotsanddashesoriginallyusedinContinentalEuropeand,hence,calledtheContinentalCode.Itisnowusedforallgeneralpublicservicewirelesscommunicationallovertheworldand,hence,itiscalledtheInternationalCode.Seepage305[Appendix:InternationalMorseCode].
ALTERNATINGCURRENT(A.C.)--SeeCurrent.
ALTERNATINGCURRENTTRANSFORMER.--SeeTransformer.
AMATEURGROUND.--SeeGround,Amateur.
AMMETER.--Aninstrumentusedformeasuringthecurrentstrength,intermsofamperes,thatflowsinacircuit.Ammetersusedformeasuringdirectandalternatingcurrentsmakeuseofthemagneticeffectsofthecurrents.Highfrequencycurrentsmakeuseoftheheatingeffectsofthecurrents.
AMMETER,HOT-WIRE.--Highfrequencycurrentsareusuallymeasuredbymeansofaninstrumentwhichdependsonheatingawireormetalstripbytheoscillations.Suchaninstrumentisoftencalledathermalammeter,radioammeterandaerialammeter.
AMMETER,AERIAL.--SeeAmmeter,HotWire.
AMMETER,RADIO.--SeeAmmeter,HotWire.
AMPERE.--Thecurrentwhichwhenpassedthroughasolutionofnitrateofsilverinwateraccordingtocertainspecifications,depositssilverattherateof0.00111800ofagrampersecond.
AMPERE-HOUR.--Thequantityofelectricitytransferredbyacurrentof1amperein1hourandis,therefore,equalto3600coulombs.
AMPERE-TURNS.--Whenacoiliswoundupwithanumberofturnsofwireandacurrentismadetoflowthroughit,itbehaveslikeamagnet.BThestrengthofthemagneticfieldinsideofthecoildependson(1)thestrengthofthecurrentand(2)thenumberofturnsofwireonthecoil.Thusafeeblecurrentflowingthroughalargenumberofturnswillproduceasstrongamagneticfieldasastrongcurrentflowingthroughafewturnsofwire.Thisproductofthecurrentinamperestimesthenumberofturnsofwireonthecoiliscalledtheampere-turns.
AMPLIFICATION,AUDIOFREQUENCY.--Acurrentofaudiofrequencythatisamplifiedbyanamplifiertubeorothermeans.
AMPLIFICATION,CASCADE.--SeeCascadeAmplification.
AMPLIFICATION,RADIOFREQUENCY.--Acurrentofradiofrequencythatisamplifiedbyanamplifiertubeorothermeansbeforeitreachesthedetector.
AMPLIFICATION,REGENERATIVE.--Aschemethatusesathirdcircuittofeedbackpartoftheoscillationsthroughavacuumtubeandwhichincreasesitssensitivenesswhenusedasadetectorandmultipliesitsactionasanamplifierandanoscillator.
AMPLIFIER,AUDIOFREQUENCY.--Avacuumtubeorotherdevicethatamplifiesthesignalsafterpassingthroughthedetector.
AMPLIFIER,MAGNETIC.--Adeviceusedforcontrollingradiofrequencycurrentseitherbymeansofatelegraphkeyoramicrophonetransmitter.Thecontrollingcurrentflowsthroughaseparatecircuitfromthatoftheradiocurrentandafractionofanamperewillcontrolseveralamperesintheaerialwire.
AMPLIFIERS,MULTI-STAGE.--Areceivingsetusingtwoormoreamplifiers.Alsocalledcascadeamplification.
AMPLIFIER,VACUUMTUBE.--Avacuumtubethatisusedeithertoamplifytheradiofrequencycurrentsortheaudiofrequencycurrents.
AMPLITUDEOFWAVE.--Thegreatestdistancethatapointmovesfromitspositionofrest.
AMPLIFYINGTRANSFORMER,AUDIO.--SeeTransformer,AudioAmplifying.
AMPLIFYINGMODULATORVACUUMTUBE.--SeeVacuumTube,AmplifyingModulator.
AMPLIFYINGTRANSFORMERRADIO.--SeeTransformer,RadioAmplifying.
ANTENNA,AMATEUR.--SeeAerial,Amateur.
ANTENNASWITCH.--SeeSwitch,Aerial.
APPARATUSSYMBOLS.--SeeSymbols,Apparatus.
ARMSTRONGCIRCUIT.--SeeCircuit,Armstrong.
ATMOSPHERICS.--SameasStatic,whichsee.
ATTENUATION.--InSendingwirelesstelegraphandtelephonemessagestheamplitudeoftheelectricwavesisdampedoutasthedistanceincreases.Thisiscalledattenuationanditincreasesasthefrequencyisincreased.Thisisthereasonwhyshortwavelengthswillnotcarryasfaraslongwavelengths.
AUDIOFREQUENCYAMPLIFIER.--SeeAmplifier,AudioFrequency.
AUDIOFREQUENCYAMPLIFICATION.--SeeAmplification,AudioFrequency.
AUDIBILITYMETER.--SeeMeter,Audibility.
AUDIOFREQUENCY.--SeeFrequency,Audio.
AUDIOFREQUENCYCURRENT.--SeeCurrent,AudioFrequency.
AUDION.--Anearlytradenamegiventothevacuumtubedetector.
AUTODYNERECEPTOR.--SeeReceptor,Autodyne.
AUTOTRANSFORMER.--SeeTransformer,Auto.
BAKELITE.--Amanufacturedinsulatingcompound.
BBATTERY.--SeeBatteryB.
BAND,WAVELENGTH.--SeeWaveLengthBand.
BASKETWOUNDCOILS.--SeeCoils,Inductance.
BATTERY,A.--The6-voltstoragebatteryusedtoheatthefilamentofavacuumtube,detectororamplifier.
BATTERY,B.--The22-1/2-voltdrycellbatteryusedtoenergizetheplateofavacuumtubedetectororamplifier.
BATTERY,BOOSTER.--Thisisthebatterythatisconnectedinserieswiththecrystaldetector.
BATTERY,C.--Asmalldrycellbatterysometimesusedtogivethegridofavacuumtubedetectorabiaspotential.
BATTERY,EDISONSTORAGE.--Astoragebatteryinwhichtheelementsaremadeofnickelandironandimmersedinanalkalineelectrolyte.
BATTERY,LEADSTORAGE.--Astoragebatteryinwhichtheelementsaremadeofleadandimmersedinanacidelectrolyte.
BATTERYPOLES.--SeePoles,Battery.
BATTERY,PRIMARY.--Abatterythatgeneratescurrentbychemicalaction.
BATTERY,STORAGE.--Abatterythatdevelopsacurrentafterithasbeencharged.
BEATRECEPTION.--SeeHeterodyneReception.
BEDSPRINGSAERIAL.--SeeAerial,BedSprings.
BLUBBLUB.--Overmodulationinwirelesstelephony.
BROADWAVE.--SeeWave,Broad.
BRUSHDISCHARGE.--SeeDischarge.
BUZZERMODULATION.--SeeModulation,Buzzer.
BLUEGLOWDISCHARGE.--SeeDischarge.
BOOSTERBATTERY.--SeeBattery,Booster.
BROADCASTING.--Sendingoutintelligenceandmusicfromacentralstationforthebenefitofallwholivewithinrangeofitandwhohavereceivingsets.
CAPACITANCE.--Alsocalledbytheoldernameofcapacity.Thecapacityofacondenser,inductancecoilorotherdevicecapableofretainingachargeofelectricity.Capacitanceismeasuredintermsofthemicrofarad.
CAPACITIVECOUPLING.--SeeCoupling,Capacitive.
CAPACITY.--Anyobjectthatwillretainachargeofelectricity;henceanaerialwire,acondenserorametalplateissometimescalledacapacity.
CAPACITY,AERIAL.--Theamounttowhichanaerialwiresystemcanbecharged.Thecapacitanceofasmallamateuraerialisfrom0.0002to0.0005microfarad.
CAPACITY,DISTRIBUTED.--Acoilofwirenotonlyhasinductance,butalsoacertainsmallcapacitance.Coilswoundwiththeirturnsparallelandhavinganumberoflayershaveabunchedcapacitancewhichproducesuntowardeffectsinoscillationcircuits.Inhoneycombandotherstaggerwoundcoilsthecapacitanceismoreevenlydistributed.
CAPACITYREACTANCE.--SeeReactance,Capacity.
CAPACITYUNIT.--SeeFarad.
CARBONRHEOSTATS.--SeeRheostat,Carbon.
CARBORUNDUMDETECTOR.--SeeDetector.
CARRIERCURRENTTELEPHONY.--SeeWired-Wireless.
CARRIERFREQUENCY.--SeeFrequency,Carrier.
CARRIERFREQUENCYTELEPHONY.--SeeWired-Wireless.
CASCADEAMPLIFICATION.--Twoormoreamplifyingtubeshookedupinareceivingset.
CATWHISKERCONTACT.--Along,thinwirewhichmakescontactwiththecrystalofadetector.
CENTIMETEROFCAPACITANCE.--Equalto1.11microfarads.
CENTIMETEROFINDUCTANCE.--Equaltooneone-thousandthpartofamicrohenry.
CELLULARCOILS.--SeeCoils,Inductance.
C.G.S.ELECTROSTATICUNITOFCAPACITANCE.--SeeCentimeterofCapacitance.
CHARACTERISTICS.--Thespecialbehaviorofadevice,suchasanaerial,adetectortube,etc.
CHARACTERISTICS,GRID.--SeeGridCharacteristics.
CHOKECOILS.--Coilsthatpreventthehighvoltageoscillationsfromsurgingbackintothetransformerandbreakingdowntheinsulation.
CHOPPERMODULATION.--SeeModulation,Chopper.
CIRCUIT.--Anyelectricalconductorthroughwhichacurrentcanflow.Alowvoltagecurrentrequiresaloopofwireorotherconductorbothendsofwhichareconnectedtothesourceofcurrentbeforeitcanflow.Ahighfrequencycurrentwillsurgeinawirewhichisopenatbothendsliketheaerial.
ClosedCircuit.--Acircuitthatiscontinuous.OpenCircuit.--Aconductorthatisnotcontinuous.CoupledCircuits.--Openandclosedcircuitsconnectedtogetherbyinductancecoils,condensersorresistances.Seecoupling.CloseCoupledCircuits.--Openandclosedcircuitsconnecteddirectlytogetherwithasingleinductancecoil.LooseCoupledCircuits.--Openedandclosedcurrentsconnectedtogetherinductivelybymeansofatransformer.Stand-byCircuits.--Alsocalledpick-upcircuits.Whenlistening-inforpossiblecallsfromanumberofstations,areceiverisusedwhichwillrespondtoawidebandofwavelengths.ArmstrongCircuits.--TheregenerativecircuitinventedbyMajorE.H.Armstrong.
CLOSECOUPLEDCIRCUITS.--SeeCurrents,CloseCoupled.
CLOSEDCIRCUIT.--SeeCircuit,Closed.
CLOSEDCORETRANSFORMER.--SeeTransformer,ClosedCore.
CODE.--
Continental.--SameasInternational.International.--OnthecontinentofEuropelandlinesusetheContinentalMorsealphabeticcode.ThiscodehascometobeusedthroughouttheworldforwirelesstelegraphyandhenceitisnowcalledtheInternationalcode.ItisgivenonPage305.[Appendix:InternationalMorseCode].Morse.--ThecodedevisedbySamuelF.B.MorseandwhichisusedonthelandlinesintheU.S.NationalElectric.--AsetofrulesandrequirementsdevisedbytheNationalBoardofFireUnderwritersfortheelectricalinstallationsinbuildingsonwhichinsurancecompaniescarryrisks.Thiscodealsocoverstherequirementsforwirelessinstallations.Acopymaybehadfrom
theNationalBoardofFireUnderwriters,NewYorkCity,orfromyourinsuranceagent.NationalElectricSafety.--TheBureauofStandards,Washington,D.C.,haveinvestigatedtheprecautionswhichshouldbetakenforthesafeoperationofallelectricequipment.AcopyoftheBureauofStandardsHandbookNo.3canbehadfor40centsfromtheSuperintendentofDocuments.
COEFFICIENTOFCOUPLING.--SeeCoupling,Coefficientof.
COILAERIAL.--SeeAerial,Loop.
COILANTENNA.--SeeAerial,Loop.
COIL,INDUCTION.--Anapparatusforchanginglowvoltagedirectcurrentsintohighvoltage,lowfrequencyalternatingcurrents.Whenfittedwithasparkgapthehighvoltage,lowfrequencycurrentsareconvertedintohighvoltage,highfrequencycurrents.ItisthenalsocalledasparkcoilandaRuhmkorffcoil.
COIL,LOADING.--Acoilconnectedintheaerialorclosedoscillationcircuitsothatlongerwavelengthscanbereceived.
COIL,REPEATING.--SeeRepeatingCoil.
COIL,ROTATING.--Onewhichrotatesonashaftinsteadofslidingasinaloosecoupler.Therotorofavariometerorvariocouplerisarotatingcoil.
COILS,INDUCTANCE.--Thesearethetuningcoilsusedforsendingandreceivingsets.Forsendingsetstheyareformedofoneandtwocoils,asinglesendingcoilisgenerallycalledatuninginductancecoil,whileatwo-coiltuneriscalledanoscillationtransformer.Receivingtuningcoilsaremadewithasinglelayer,singlecoil,orapairofcoils,whenitiscalledanoscillationtransformer.Sometuninginductancecoilshavemorethanonelayer,theyarethencalledlatticewound,cellular,basketwound,honeycomb,duo-lateral,staggerwound,spider-webandslabcoils.
COMMERCIALFREQUENCY.--SeeFrequency,Commercial.
CONDENSER,AERIALSERIES.--Acondenserplacedintheaerialwiresystemtocutdownthewavelength.
CONDENSER,VERNIER.--Asmallvariablecondenserusedforreceivingcontinuouswaveswhereverysharptuningisdesired.
CONDENSER.--Allconductingobjectswiththeirinsulationformcapacities,butacondenserisunderstoodtomeantwosheetsorplatesofmetalplacedcloselytogetherbutseparatedbysomeinsulatingmaterial.
AdjustableCondenser.--Wheretwoormorecondenserscanbecoupledtogetherbymeansofplugs,switchesorotherdevices.AerialCondenser.--Acondenserconnectedintheaerial.AirCondenser.--Whereaironlyseparatesthesheetsofmetal.By-PassCondenser.--Acondenserconnectedinthetransmittingcurrentssothatthehigh
frequencycurrentscannotflowbackthroughthepowercircuit.FilterCondenser.--Acondenseroflargecapacitanceusedincombinationwithafilterreactorforsmoothingoutthepulsatingdirectcurrentsastheycomefromtherectifier.FixedCondenser.--Wheretheplatesarefixedrelativelytooneanother.GridCondenser.--Acondenserconnectedinserieswiththegridlead.LeydenJarCondenser.--Whereglassjarsareused.MicaCondenser.--Wheremicaisused.OilCondenser.--Wheretheplatesareimmersedinoil.PaperCondenser.--Wherepaperisusedastheinsulatingmaterial.Protective.--Acondenseroflargecapacityconnectedacrossthelowvoltagesupplycircuitofatransmittertoformaby-pathofkick-backoscillations.VariableCondenser.--Wherealternateplatescanbemovedandsomadetointerleavemoreorlesswithasetoffixedplates.Vernier.--Asmallcondenserwithavernieronitsothatitcanbeveryaccuratelyvaried.Itisconnectedinparallelwiththevariablecondenserusedintheprimarycircuitandisusedforthereceptionofcontinuouswaveswheresharptuningisessential.
CONDENSITE.--Amanufacturedinsulatingcompound.
CONDUCTIVITY.--Theconductanceofagivenlengthofwireofuniformcrosssection.Thereciprocalofresistivity.
CONTACTDETECTORS.--SeeDetectors,Contact.
CONTINENTALCODE.--SeeCode,Continental.
COULOMB.--Thequantityofelectricitytransferredbyacurrentof1amperein1second.
CONVECTIVEDISCHARGE.--SeeDischarge.
CONVENTIONALSIGNALS.--SeeSignals,Conventional.
COUNTERELECTROMOTIVEFORCE.--SeeElectromotiveForce,Counter.
COUNTERPOISE.Aduplicateoftheaerialwirethatisraisedafewfeetabovetheearthandinsulatedfromit.Usuallynoconnectionismadewiththeearthitself.
COUPLEDCIRCUITS.--SeeCircuit,Coupled.
COUPLING.--Whentwooscillationcircuitsareconnectedtogethereitherbythemagneticfieldofaninductancecoil,orbytheelectrostaticfieldofacondenser.
COUPLING,CAPACITIVE.--Oscillationcircuitswhenconnectedtogetherbycondensersinsteadofinductancecoils.
COUPLING,COEFFICIENTOF.--Themeasureoftheclosenessofthecouplingbetweentwocoils.
COUPLING,INDUCTIVE.--Oscillationcircuitswhenconnectedtogetherbyinductancecoils.
COUPLING,RESISTANCE.--Oscillationcircuitsconnectedtogetherbyaresistance.
CRYSTALRECTIFIER.--Acrystaldetector.
CURRENT,ALTERNATING(A.C.).--Alowfrequencycurrentthatsurgestoandfroinacircuit.
CURRENT,AUDIOFREQUENCY.--Acurrentwhosefrequencyislowenoughtobeheardinatelephonereceiver.Suchacurrentusuallyhasafrequencyofbetween200and2,000cyclespersecond.
CURRENT,PLATE.--Thecurrentwhichflowsbetweenthefilamentandtheplateofavacuumtube.
CURRENT,PULSATING.--Adirectcurrentwhosevoltagevariesfrommomenttomoment.
CURRENT,RADIOFREQUENCY.--Acurrentwhosefrequencyissohighitcannotbeheardinatelephonereceiver.Suchacurrentmayhaveafrequencyoffrom20,000to10,000,000persecond.
CURRENTS,HIGHFREQUENCY.--(1)Currentsthatoscillatefrom10,000to300,000,000timespersecond.(2)Electricoscillations.
CURRENTS,HIGHPOTENTIAL.--(1)Currentsthathaveapotentialofmorethan10,000volts.(2)Highvoltagecurrents.
CYCLE.--(1)Aseriesofchangeswhichwhencompletedareagainatthestartingpoint.(2)Aperiodoftimeattheendofwhichanalternatingoroscillatingcurrentrepeatsitsoriginaldirectionofflow.
DAMPING.--Thedegreetowhichtheenergyofanelectricoscillationisreduced.Inanopencircuittheenergyofanoscillationsetupbyasparkgapisdampedoutinafewswings,whileinaclosedcircuititisgreatlyprolonged,thecurrentoscillating20timesormorebeforetheenergyisdissipatedbythesumoftheresistancesofthecircuit.
DECREMENT.--Theactorprocessofgraduallybecomingless.
DETECTOR.--Anydevicethatwill(1)changetheoscillationssetupbytheincomingwavesintodirectcurrent,thatiswhichwillrectifythem,or(2)thatwillactasarelay.
Carborundum.--Onethatusesacarborundumcrystalforthesensitiveelement.Carborundumisacrystallinesiliconcarbideformedintheelectricfurnace.CatWhiskerContact.--SeeCatWhiskerContact.Chalcopyrite.--Copperpyrites.Abrasscoloredmineralusedasacrystalfordetectors.SeeZincite.Contact.--Acrystaldetector.Anykindofadetectorinwhichtwodissimilarbutsuitablesolidsmakecontact.Ferron.--Adetectorinwhichironpyritesareusedasthesensitiveelement.Galena.--Adetectorthatusesagalenacrystalfortherectifyingelement.IronPyrites.--Adetectorthatusesacrystalofironpyritesforitssensitiveelement.Molybdenite.--Adetectorthatusesacrystalofsulphideofmolybdenumforthesensitiveelement.Perikon.--Adetectorinwhichabornitecrystalmakescontactwithazincitecrystal.Silicon.--Adetectorthatusesacrystalofsiliconforitssensitiveelement.
VacuumTube.--Avacuumtube(whichsee)usedasadetector.Zincite.--Adetectorinwhichacrystalofzinciteisusedasthesensitiveelement.
DETUNING.--Amethodofsignalingbysustainedoscillationsinwhichthekeywhenpresseddowncutsouteithersomeoftheinductanceorsomeofthecapacityandhencegreatlychangesthewavelength.
DIELECTRIC.--Aninsulatingmaterialbetweentwoelectricallychargedplatesinwhichthereissetupanelectricstrain,ordisplacement.
DIELECTRICSTRAIN.--Theelectricdisplacementinadielectric.
DIRECTIONALAERIAL.--SeeAerial,Directional.
DIRECTIONFINDER.--SeeAerial,Loop.
DISCHARGE.--(1)Afaintlyluminousdischargethattakesplacefromthepositivepointedterminalofaninductioncoil,orotherhighpotentialapparatus;istermedabrushdischarge.(2)Acontinuousdischargebetweentheterminalsofahighpotentialapparatusistermedaconvectivedischarge.(3)Thesuddenbreaking-downoftheairbetweentheballsformingthesparkgapistermedadisruptivedischarge;alsocalledanelectricspark,orjustsparkforshort.(4)Whenatubehasapoorvacuum,ortoolargeabatteryvoltage,itglowswithabluelightandthisiscalledablueglowdischarge.
DISRUPTIVEDISCHARGE.--SeeDischarge.
DISTRESSCALL.[Morsecode:]...---...(SOS).
DISTRIBUTEDCAPACITY.--SeeCapacity,Distributed.
DOUBLEHUMPRESONANCECURVE.--Aresonancecurvethathastwopeaksorhumpswhichshowthattheoscillatingcurrentswhicharesetupwhentheprimaryandsecondaryofatuningcoilarecloselycoupledhavetwofrequencies.
DUO-LATERALCOILS.--SeeCoils,Inductance.
DUPLEXCOMMUNICATION.--Awirelesstelephonesystemwithwhichitispossibletotalkbetweenbothstationsineitherdirectionwithouttheuseofswitches.Thisisknownastheduplexsystem.
EARTHCAPACITY.--Anaerialcounterpoise.
EARTHCONNECTION.--Metalplatesorwiresburiedinthegroundorimmersedinwater.Anykindofmeansbywhichthesendingandreceivingapparatuscanbeconnectedwiththeearth.
EDISONSTORAGEBATTERY.--SeeStorageBattery,Edison.
ELECTRICENERGY.--Thepowerofanelectriccurrent.
ELECTRICOSCILLATIONS.--SeeOscillations,Electric.
ELECTRICSPARK.--SeeDischarge,Spark.
ELECTRICITY,NEGATIVE.--Theoppositeofpositiveelectricity.Negativeelectricityisformedofnegativeelectronswhichmakeuptheoutsideparticlesofanatom.
ELECTRICITY,POSITIVE.--Theoppositeofnegativeelectricity.Positiveelectricityisformedofpositiveelectronswhichmakeuptheinsideparticlesofanatom.
ELECTRODES.--Usuallythepartsofanapparatuswhichdipintoaliquidandcarryacurrent.Theelectrodesofadrybatteryarethezincandcarbonelements.TheelectrodesofanEdisonstoragebatteryaretheironandnickelelements,andtheelectrodesofaleadstoragebatteryaretheleadelements.
ELECTROLYTES.--Theacidoralkalinesolutionsusedinbatteries.
ELECTROMAGNETICWAVES.--SeeWaves,Electric.
ELECTROMOTIVEFORCE.--Abbreviatedemf.Theforcethatdrivesanelectriccurrentalongaconductor.Alsolooselycalledvoltage.
ELECTROMOTIVEFORCE,COUNTER.--Theemf.thatissetupinadirectionoppositetothatinwhichthecurrentisflowinginaconductor.
ELECTRON.--(1)Anegativeparticleofelectricitythatisdetachedfromanatom.(2)Anegativeparticleofelectricitythrownofffromtheincandescentfilamentofavacuumtube.
ELECTRONFLOW.--Thepassageofelectronsbetweentheincandescentfilamentandthecoldpositivelychargedplateofavacuumtube.
ELECTRONRELAY.--SeeRelay,Electron.
ELECTRONTUBE.--Avacuumtubeoragas-contenttubeusedforanypurposeinwirelesswork.SeeVacuumTube.
ELECTROSEINSULATORS.--InsulatorsmadeofacompositionmaterialthetradenameofwhichisElectrose.
ENERGY,ELECTRIC.--SeeElectricEnergy.
ENERGYUNIT.--Thejoule,whichsee,Page308[Appendix:DefinitionsofElectricandMagneticUnits].
FADING.--Thesuddenvariationinstrengthofsignalsreceivedfromatransmittingstationwhenalltheadjustmentsofbothsendingandreceivingapparatusremainthesame.Alsocalledswinging.
FARAD.--Thecapacitanceofacondenserinwhichapotentialdifferenceof1voltcausesittohaveachargeof1coulombofelectricity.
FEED-BACKACTION.--Feedingbacktheoscillatingcurrentsinavacuumtubetoamplifyitspower.
Alsocalledregenerativeaction.
FERROMAGNETICCONTROL.--SeeMagneticAmplifier.
FILAMENT.--Thewireinavacuumtubethatisheatedtoincandescenceandwhichthrowsoffelectrons.
FILAMENTRHEOSTAT.--SeeRheostat,Filament.
FILTER.--Inductancecoilsorcondensersorbothwhich(1)preventtroublesomevoltagesfromactingonthedifferentcircuits,and(2)smoothoutalternatingcurrentsaftertheyhavebeenrectified.
FILTERREACTOR.--SeeReactor,Filter.
FIREUNDERWRITERS.--SeeCode,NationalElectric.
FIXEDGAP.--SeeGap.
FLEMINGVALVE.--Atwo-electrodevacuumtube.
FORCEDOSCILLATIONS.--SeeOscillations,Forced.
FREEOSCILLATIONS.--SeeOscillations,Free.
FREQUENCY,AUDIO.--(1)Analternatingcurrentwhosefrequencyislowenoughtooperateatelephonereceiverand,hence,whichcanbeheardbytheear.(2)Audiofrequenciesareusuallyaround500or1,000cyclespersecond,butmaybeaslowas200andashighas10,000cyclespersecond.
Carrier.--Aradiofrequencywavemodulatedbyanaudiofrequencywavewhichresultsinsettingofthreeradiofrequencywaves.Theprincipalradiofrequencyiscalledthecarrierfrequency,sinceitcarriesortransmitstheaudiofrequencywave.Commercial.--(1)Alternatingcurrentthatisusedforcommercialpurposes,namely,light,heatandpower.(2)Commercialfrequenciesnowingeneralusearefrom25to50cyclespersecond.Natural.--Thependulumandvibratingspringhaveanaturalfrequencywhichdependsonthesize,materialofwhichitismade,andthefrictionwhichithastoovercome.Likewiseanoscillationcircuithasanaturalfrequencywhichdependsuponitsinductance,capacitanceandresistance.Radio.--(1)Anoscillatingcurrentwhosefrequencyistoohightoaffectatelephonereceiverand,hence,cannotbeheardbytheear.(2)Radiofrequenciesareusuallybetween20,000and2,000,000cyclespersecondbutmaybeaslowas10,000andashighas300,000,000cyclespersecond.Spark.--Thenumberofsparkspersecondproducedbythedischargeofacondenser.
GAP,FIXED.--Onewithfixedelectrodes.
GAP,NON-SYNCHRONOUS.--Arotarysparkgaprunbyaseparatemotorwhichmaybewidelydifferentfromthatofthespeedofthealternator.
GAP,QUENCHED.--(1)Asparkgapfortheimpulseproductionofoscillatingcurrents.(2)Thismethodcanbelikenedtoonewhereaspringisstruckasinglesharpblowandthencontinuestosetupvibrations.
GAP,ROTARY.--Onehavingfixedandrotatingelectrodes.
GAP,SYNCHRONOUS.--Arotarysparkgaprunatthesamespeedasthealternatorwhichsuppliesthepowertransformer.Suchagapusuallyhasasmanyteethastherearepolesonthegenerator.Henceonesparkoccursperhalfcycle.
GAS-CONTENTTUBE.--SeeVacuumTube.
GENERATORTUBE.--Avacuumtubeusedtosetuposcillations.Asamatteroffactitdoesnotgenerateoscillations,butchangestheinitiallowvoltagecurrentthatflowsthroughitintooscillations.Alsocalledanoscillatortubeandapowertube.
GRIDBATTERY.--SeeBatteryC.
GRIDCHARACTERISTICS.--Thevariousrelationsthatcouldexistbetweenthevoltagesandcurrentsofthegridofavacuumtube,andthevalueswhichdoexistbetweenthemwhenthetubeisinoperation.Thesecharacteristicsaregenerallyshownbycurves.
GRIDCONDENSER.--SeeCondenser,Grid.
GRIDLEAK.--Ahighresistanceunitconnectedinthegridleadofbothsendingandreceivingsets.Inasendingsetitkeepsthevoltageofthegridataconstantvalueandsocontrolstheoutputoftheaerial.Inareceivingsetitcontrolsthecurrentflowingbetweentheplateandfilament.
GRIDMODULATION.--SeeModulation,Grid.
GRIDPOTENTIAL.--Thenegativeorpositivevoltageofthegridofavacuumtube.
GRIDVOLTAGE.--SeeGridPotential.
GRINDERS.--ThemostcommonformofStatic,whichsee.Theymakeagrindingnoiseintheheadphones.
GROUND.--SeeEarthConnection.
GROUND,AMATEUR.--Awater-pipeground.
GROUND,WATERPIPE.--Acommonmethodofgroundingbyamateursistousethewaterpipe,gaspipeorradiator.
GUIDEDWAVETELEPHONY.--SeeWiredWireless.
HARDTUBE.--Avacuumtubeinwhichthevacuumishigh,thatis,exhaustedtoahighdegree.
HELIX.--(1)Anycoilofwire.(2)Specificallyatransmittertuninginductancecoil.
HENRY.--Theinductanceinacircuitinwhichtheelectromotiveforceinducedis1voltwhentheinducingcurrentvariesattherateof1amperepersecond.
HETERODYNERECEPTION.--(1)Receivingbythebeatmethod.(2)Receivingbymeansofsuperposingoscillationsgeneratedatthereceivingstationontheoscillationssetupintheaerialbytheincomingwaves.
HETERODYNERECEPTOR.--SeeReceptor,Heterodyne.
HIGHFREQUENCYCURRENTS.--SeeCurrents,HighFrequency.
HIGHFREQUENCYRESISTANCE.--SeeResistance,HighFrequency.
HIGHPOTENTIALCURRENTS.--SeeCurrents,HighPotential.
HIGHVOLTAGECURRENTS.--SeeCurrents,HighPotential.
HONEYCOMBCOILS.--SeeCoils,Inductance.
HORSE-POWER.--Usedinratingsteammachinery.Itisequalto746watts.
HOTWIREAMMETER.--SeeAmmeter,HotWire.
HOWLING.--Wheremorethanthreestagesofradioamplification,ormorethantwostagesofaudioamplification,areusedhowlingnoisesareapttooccurinthetelephonereceivers.
IMPEDANCE.--Anoscillationcircuithasreactanceandalsoresistance,andwhenthesearecombinedthetotaloppositiontothecurrentiscalledimpedance.
INDUCTANCECOILS.--SeeCoils,Inductance.
INDUCTANCECOIL,LOADING.--SeeCoil,LoadingInductance.
INDUCTIVECOUPLING.--SeeCoupling,Inductive.
INDUCTIVEREACTANCE.--SeeReactance,Inductive.
INDUCTIONCOIL.--SeeCoil,Induction.
INDUCTION,MUTUAL.--Inductionproducedbetweentwocircuitsorcoilsclosetoeachotherbythemutualinteractionoftheirmagneticfields.
INSULATION.--Materialsusedonandaroundwiresandotherconductorstokeepthecurrentfromleakingaway.
INSPECTOR,RADIO.--AU.S.inspectorwhosebusinessitistoissuebothstationandoperators'licensesinthedistrictofwhichheisincharge.
INTERFERENCE.--Thecrossingorsuperposingoftwosetsofelectricwavesofthesameorslightly
differentlengthswhichtendtoopposeeachother.Itistheuntowardinterferencebetweenelectricwavesfromdifferentstationsthatmakesselectivesignalingsodifficultaproblem.
INTERMEDIATEWAVES.--SeeWaves.
IONICTUBES.--SeeVacuumTubes.
INTERNATIONALCODE.--SeeCode,International.
JAMMING.--Wavesthatareofsuchlengthandstrengththatwhentheyinterferewithincomingwavestheydrownthemout.
JOULE.--Theenergyspentin1secondbyaflowof1amperein1ohm.
JOULE'SLAW.--Therelationbetweentheheatproducedinsecondstotheresistanceofthecircuit,tothecurrentflowinginit.
KENOTRON.--ThetradenameofavacuumtuberectifiermadebytheRadioCorporationofAmerica.
KICK-BACK.--Oscillatingcurrentsthatriseinvoltageandtendtoflowbackthroughthecircuitthatissupplyingthetransmitterwithlowvoltagecurrent.
KICK-BACKPREVENTION.--SeePrevention,Kick-Back.
KILOWATT.--1,000watts.
LAMBDA.--SeePages301,302.[Appendix:UsefulAbbreviations].
LATTICEWOUNDCOILS.--SeeCoils,Inductance.
LIGHTNINGSWITCH.--SeeSwitch,Lightning.
LINERADIOCOMMUNICATION.--SeeWiredWireless.
LINERADIOTELEPHONY.--SeeTelephony,LineRadio.
LITZENDRAHT.--Aconductorformedofanumberoffinecopperwireseithertwistedorbraidedtogether.Itisusedtoreducetheskineffect.SeeResistance,HighFrequency.
LOADFLICKER.--Theflickeringofelectriclightsonlinesthatsupplywirelesstransmittingsetsduetovariationsofthevoltageonopeningandclosingthekey.
LOADINGCOIL.--SeeCoil,Loading.
LONGWAVES.--SeeWaves.
LOOPAERIAL.--SeeAerial,Loop.
LOOSECOUPLEDCIRCUITS.--SeeCircuits,LooseCoupled.
LOUDSPEAKER.--Atelephonereceiverconnectedtoahorn,oraspeciallymadeone,thatreproducestheincomingsignals,wordsormusicloudenoughtobeheardbyaroomoranauditoriumfullofpeople,orbylargecrowdsout-doors.
MAGNETICPOLES.--SeePoles,Magnetic.
MEGOHM.--Onemillionohms.
METER,AUDIBILITY.--Aninstrumentformeasuringtheloudnessofasignalbycomparisonwithanothersignal.Itconsistsofapairofheadphonesandavariableresistancewhichhavebeencalibrated.
MHO.--Theunitofconductance.Asconductanceisthereciprocalofresistanceitismeasuredbythereciprocalohmormho.
MICA.--Atransparentmineralhavingahighinsulatingvalueandwhichcanbesplitintoverythinsheets.Itislargelyusedinmakingcondensersbothfortransmittingandreceivingsets.
MICROFARAD.--Themillionthpartofafarad.
MICROHENRY.--Themillionthpartofafarad.
MICROMICROFARAD.--Themillionthpartofamicrofarad.
MICROHM.--Themillionthpartofanohm.
MICROPHONETRANSFORMER.--SeeTransformer,Microphone.
MICROPHONETRANSMITTER.--SeeTransmitter,Microphone.
MILLI-AMMETER.--Anammeterthatmeasuresacurrentbytheone-thousandthofanampere.
MODULATION.--(1)Inflectionorvaryingthevoice.(2)Varyingtheamplitudeofoscillationsbymeansofthevoice.
MODULATION,BUZZER.--Themodulationofradiofrequencyoscillationsbyabuzzerwhichbreaksupthesustainedoscillationsofatransmitterintoaudiofrequencyimpulses.
MILLIHENRY.--Thethousandthpartofahenry.
MODULATION,CHOPPER.--Themodulationofradiofrequencyoscillationsbyachopperwhichbreaksupthesustainedoscillationsofatransmitterintoaudiofrequencyimpulses.
MODULATION,GRID.--Theschemeofmodulatinganoscillatortubebyconnectingthesecondaryofatransformer,theprimaryofwhichisconnectedwithabatteryandamicrophonetransmitter,inthegridlead.
MODULATION,OVER.--SeeBlubBlub.
MODULATION,PLATE.--Modulatingtheoscillationssetupbyavacuumtubebyvaryingthecurrentimpressedontheplate.
MODULATORTUBE.--Avacuumtubeusedasamodulator.
MOTION,WAVE.--(1)Thetoandfromotionofwateratsea.(2)Wavestransmittedby,inandthroughtheair,orsoundwaves.(3)Wavestransmittedby,inandthroughtheether,orelectromagneticwaves,orelectricwavesforshort.
MOTOR-GENERATOR.--Amotorandadynamobuilttorunatthesamespeedandmountedonacommonbase,theshaftsbeingcoupledtogether.Inwirelessitisusedforchangingcommercialdirectcurrentintodirectcurrentofhighervoltagesforenergizingtheplateofavacuumtubeoscillator.
MULTI-STAGEAMPLIFIERS.--SeeAmplifiers,Multi-Stage.
MUTUALINDUCTION.--SeeInduction,Mutual.
MUSH.--Irregularintermediatefrequenciessetupbyarctransmitterswhichinterferewiththefundamentalwavelengths.
MUSHYNOTE.--Anotethatisnotclearcut,andhencehardtoread,whichisreceivedbytheheterodynemethodwhendampedwavesormodulatedcontinuouswavesarebeingreceived.
NATIONALELECTRICCODE.--SeeCode,NationalElectric.
NATIONALELECTRICSAFETYCODE.--SeeCode,NationalElectricSafety.
NEGATIVEELECTRICITY.--SeeElectricity,Negative.
NON-SYNCHRONOUSGAP.--SeeGap,Non-Synchronous.
OHM.--Theresistanceofathreadofmercuryatthetemperatureofmeltingice,14.4521gramsinmass,ofuniformcross-sectionandalengthof106.300centimeters.
OHM'SLAW.--Theimportantfixedrelationbetweentheelectriccurrent,itselectromotiveforceandtheresistanceoftheconductorinwhichitflows.
OPENCIRCUIT.--SeeCircuit,Open.
OPENCORETRANSFORMER.--SeeTransformer,OpenCore.
OSCILLATIONTRANSFORMER.--SeeTransformer,Oscillation.
OSCILLATIONS,ELECTRIC.--Acurrentofhighfrequencythatsurgesthroughanopenoraclosedcircuit.(1)Electricoscillationsmaybesetupbyasparkgap,electricarcoravacuumtube,whentheyhavenotonlyahighfrequencybutahighpotential,orvoltage.(2)Whenelectricwavesimpingeonanaerialwiretheyaretransformedintoelectricoscillationsofafrequencyequaltothosewhichemittedthewaves,butsinceaverysmallamountofenergyisreceivedtheirpotentialorvoltageislikewiseverysmall.
Sustained.--Oscillationsinwhichthedampingfactorissmall.Damped.--Oscillationsinwhichthedampingfactorislarge.Free.--Whenacondenserdischargesthroughanoscillationcircuit,wherethereisnooutsideelectromotiveforceactingonit,theoscillationsaresaidtobefree.Forced.--Oscillationsthataremadetosurgeinacircuitwhosenaturalperiodisdifferentfromthatoftheoscillationssetupinit.
OSCILLATIONTRANSFORMER.--SeeTransformer.
OSCILLATIONVALVE.--SeeVacuumTube.
OSCILLATORTUBE.--Avacuumtubewhichisusedtoproduceelectricoscillations.
OVERMODULATION.--SeeBlubBlub.
PANCAKEOSCILLATIONTRANSFORMER.--Disk-shapedcoilsthatareusedforreceivingtuninginductances.
PERMEABILITY,MAGNETIC.--Thedegreetowhichasubstancecanbemagnetized.Ironhasagreatermagneticpermeabilitythanair.
PHASE.--Acharacteristicaspectorappearancethattakesplaceatthesamepointorpartofacycle.
PICK-UPCIRCUITS.--SeeCircuits,Stand-by.
PLATECIRCUITREACTOR.--SeeReactor,PlateCircuit.
PLATECURRENT.--SeeCurrent,Plate.
PLATEMODULATION.--SeeModulation,Plate.
PLATEVOLTAGE.--SeeFoliage,Plate.
POLES,BATTERY.--Thepositiveandnegativeterminalsoftheelementsofabattery.Onastoragebatterythesepolesaremarked+and-respectively.
POLES,MAGNETIC.--Theendsofamagnet.
POSITIVEELECTRICITY.--SeeElectricity,Positive.
POTENTIALDIFFERENCE.--Theelectricpressurebetweentwochargedconductorsorsurfaces.
POTENTIOMETER.--Avariableresistanceusedforsubdividingthevoltageofacurrent.Avoltagedivider.
POWERTRANSFORMER.--SeeTransformer,Power.
POWERTUBE.--SeeGeneratorTube.
PRIMARYBATTERY.--SeeBattery,Primary.
PREVENTION,KICK-BACK.--Achokecoilplacedinthepowercircuittopreventthehighfrequencycurrentsfromgettingintothetransformerandbreakingdowntheinsulation.
QST.--Anabbreviationusedinwirelesscommunicationfor(1)thequestion"Haveyoureceivedthegeneralcall?"and(2)thenotice,"Generalcalltoallstations."
QUENCHEDGAP.--SeeGap,Quenched.
RADIATION.--Theemission,orthrowingoff,ofelectricwavesbyanaerialwiresystem.
RADIOAMMETER.--SeeAmmeter,HotWire.
RADIOFREQUENCY.--SeeFrequency,Radio.
RADIOFREQUENCYAMPLIFICATION.--SeeAmplification,RadioFrequency.
RADIOFREQUENCYCURRENT.--SeeCurrent,RadioFrequency.
RADIOINSPECTOR.--SeeInspector,Radio.
RADIOTRON.--Thetradenameofvacuumtubedetectors,amplifiers,oscillatorsandmodulatorsmadebytheRadioCorporationofAmerica.
RADIOWAVES.--SeeWaves,Radio.
REACTANCE.--Whenacircuithasinductanceandthecurrentchangesinvalue,itisopposedbythevoltageinducedbythevariationofthecurrent.
REACTANCE,CAPACITY.--Thecapacityreactanceistheoppositionofferedtoacurrentbyacapacity.Itismeasuredasaresistance,thatis,inohms.
RECEIVINGTUNINGCOILS.--SeeCoils,Inductance.
RECEIVER,LOUDSPEAKING.--SeeLoudSpeakers.
RECEIVER,WATCHCASE.--Acompacttelephonereceiverusedforwirelessreception.
REACTANCE,INDUCTIVE.--Theinductivereactanceistheoppositionofferedtothecurrentbyaninductancecoil.Itismeasuredasaresistance,thatis,inohms.
REACTOR,FILTER.--Areactancecoilforsmoothingoutthepulsatingdirectcurrentsastheycomefromtherectifier.
REACTOR,PLATECIRCUIT.--Areactancecoilusedintheplatecircuitofawirelesstelephonetokeepthedirectcurrentsupplyataconstantvoltage.
RECEIVER.--(1)Atelephonereceiver.(2)Anapparatusforreceivingsignals,speechormusic.(3)
Bettercalledareceptortodistinguishitfromatelephonereceiver.
RECTIFIER.--(1)Anapparatusforchangingalternatingcurrentintopulsatingdirectcurrent.(2)Specificallyinwireless(a)acrystalorvacuumtubedetector,and(b)atwo-electrodevacuumtubeusedforchangingcommercialalternatingcurrentintodirectcurrentforwirelesstelephony.
REGENERATIVEAMPLIFICATION.--SeeAmplification,Regenerative.
RECEPTOR.--Areceivingset.
RECEPTOR,AUTODYNE.--Areceptorthathasaregenerativecircuitandthesametubeisusedasadetectorandasageneratoroflocaloscillations.
RECEPTOR,BEAT.--Aheterodynereceptor.
RECEPTOR,HETERODYNE.--Areceivingsetthatusesaseparatevacuumtubetosetupthesecondseriesofwavesforbeatreception.
REGENERATIVEACTION.--SeeFeed-BackAction.
REGENERATIVEAMPLIFICATION.--SeeAmplification,Regenerative.
RELAY,ELECTRON.--Avacuumtubewhenusedasadetectororanamplifier.
REPEATINGCOIL.--Atransformerusedinconnectingupawirelessreceiverwithawiretransmitter.
RESISTANCE.--Theoppositionofferedbyawireorotherconductortothepassageofacurrent.
RESISTANCE,AERIAL.--Theresistanceoftheaerialwiretooscillatingcurrents.Thisisgreaterthanitsordinaryohmicresistanceduetotheskineffect.SeeResistance,HighFrequency.
RESISTANCEBOX.--SeeResistor.
RESISTANCECOUPLING.--SeeCoupling,Resistance.
RESISTANCE,HIGHFREQUENCY.--Whenahighfrequencycurrentoscillatesonawiretwothingstakeplacethataredifferentthanwhenadirectoralternatingcurrentflowsthroughit,andtheseare(1)thecurrentinsideofthewirelagsbehindthatofthecurrentonthesurface,and(2)theamplitudeofthecurrentislargestonthesurfaceandgrowssmallerasthecenterofthewireisreached.Thisunevendistributionofthecurrentisknownastheskineffectanditamountstothesamethingasreducingthesizeofthewire,hencetheresistanceisincreased.
RESISTIVITY.--Theresistanceofagivenlengthofwireofuniformcrosssection.Thereciprocalofconductivity.
RESISTOR.--Afixedorvariableresistanceunitoragroupofsuchunits.Variableresistorsarealsocalledresistanceboxesandmoreoftenrheostats.
RESONANCE.--(1)Simpleresonanceofsoundisitsincreasesetupbyonebodybythesympathetic
vibrationofasecondbody.(2)Byextensiontheincreaseintheamplitudeofelectricoscillationswhenthecircuitinwhichtheysurgehasanaturalperiodthatisthesame,ornearlythesame,astheperiodofthefirstoscillationcircuit.
RHEOSTAT.--Avariableresistanceunit.SeeResistor.
RHEOSTAT,CARBON.--Acarbonrod,orcarbonplatesorblocks,whenusedasvariableresistances.
RHEOSTAT,FILAMENT.--Avariableresistanceusedforkeepingthecurrentofthestoragebatterywhichheatsthefilamentofavacuumtubeataconstantvoltage.
ROTATINGCOIL.--SeeCoil.
ROTARYGAP.--SeeGap.
ROTOR.--Therotatingcoilofavariometeroravariocoupler.
RUHMKORFFCOIL.--SeeCoil,Induction.
SATURATION.--Themaximumplatecurrentthatavacuumtubewilltake.
SENSITIVESPOTS.--Spotsondetectorcrystalsthataresensitivetotheactionofelectricoscillations.
SHORTWAVES.--SeeWaves.
SIDEWAVES.--SeeWaveLengthBand.
SIGNALS,CONVENTIONAL.--(1)TheInternationalMorsealphabetandnumeralcode,punctuationmarks,andafewimportantabbreviationsusedinwirelesstelegraphy.(2)Dotanddashsignalsfordistresscall,invitationtotransmit,etc.Nowusedforallgeneralpublicservicewirelesscommunication.
SKINEFFECT.--SeeResistance,HighFrequency.
SOFTTUBE.--Avacuumtubeinwhichthevacuumislow,thatis,itisnothighlyexhausted.
SPACECHARGEEFFECT.--Theelectricfieldintensityduetothepressureofthenegativeelectronsinthespacebetweenthefilamentandplatewhichatlastequalsandneutralizesthatduetothepositivepotentialoftheplatesothatthereisnoforceactingontheelectronsnearthefilament.
SPARK.--SeeDischarge.
SPARKCOIL.--SeeCoil,Induction.
SPARKDISCHARGE.--SeeSpark,Electric.
SPARKFREQUENCY.--SeeFrequency,Spark.
SPARKGAP.--(1)Asparkgap,withoutthehyphen,meanstheapparatusinwhichsparkstakeplace;it
isalsocalledasparkdischarger.(2)Spark-gap,withthehyphen,meanstheair-gapbetweentheopposedfacesoftheelectrodesinwhichsparksareproduced.
Plain.--Asparkgapwithfixedelectrodes.Rotary.--Asparkgapwithapairoffixedelectrodesandanumberofelectrodesmountedonarotatingelement.Quenched.--Asparkgapformedofanumberofmetalplatesplacedcloselytogetherandinsulatedfromeachother.
SPIDERWEBINDUCTANCECOIL.--SeeCoil,SpiderWebInductance.
SPREADER.--Astickofwood,orspar,thatholdsthewiresoftheaerialapart.
STAGGERWOUNDCOILS.--SeeCoils,Inductance.
STAND-BYCIRCUITS.--SeeCircuits,Stand-By.
STATIC.--Alsocalledatmospherics,grinders,strays,X's,and,whenbadenough,byothernames.Itisanelectricaldisturbanceintheatmospherewhichmakesnoisesinthetelephonereceiver.
STATOR.--Thefixedorstationarycoilofavariometeroravariocoupler.
STORAGEBATTERY.--SeeBattery,Storage.
STRAYELIMINATION.--Amethodforincreasingthestrengthofthesignalsasagainstthestrengthofthestrays.SeeStatic.
STRAYS.--SeeStatic.
STRANDEDWIRE.--SeeWire,Stranded.
SUPER-HETERODYNERECEPTOR.--SeeHeterodyne,Super.
SWINGING.--SeeFading.
SWITCH,AERIAL.--Aswitchusedtochangeoverfromthesendingtothereceivingset,andtheotherwayabout,andconnectthemwiththeaerial.
SWITCH,LIGHTNING.--Theswitchthatconnectstheaerialwiththeoutsidegroundwhentheapparatusisnotinuse.
SYMBOLS,APPARATUS.--Alsocalledconventionalsymbols.Thesearediagrammaticlinesrepresentingvariouspartsofapparatussothatwhenawiringdiagramofatransmitterorareceptoristobemadeitisonlynecessarytoconnectthemtogether.Theyareeasytomakeandeasytoread.SeePage307[Appendix:SymbolsUsedforApparatus].
SYNCHRONOUSGAP.--SeeGap,Synchronous.
TELEPHONY,LINERADIO.--SeeWiredWireless.
THERMALAMMETER.--SeeAmmeter,HotWire.
THREEELECTRODEVACUUMTUBE.--SeeVacuumTube,ThreeElectrode.
TIKKER.--Aslippingcontactdevicethatbreaksupthesustainedoscillationsatthereceivingendintogroupssothatthesignalscanbeheardintheheadphones.Thedeviceusuallyconsistsofafinesteelorgoldwireslippinginthesmoothgrooveofarotatingbrasswheel.
TRANSFORMER.--Aprimaryandasecondarycoilforsteppingupordownaprimaryalternatingoroscillatingcurrent.
A.C.--SeePowerTransformer.AirCooled.--Atransformerinwhichthecoilsareexposedtotheair.AirCore.--Withhighfrequencycurrentsitisthegeneralpracticenottouseironcoresasthesetendtochokeofftheoscillations.Hencethecoreconsistsoftheairinsideofthecoils.Auto.--Asinglecoilofwireinwhichonepartformstheprimaryandtheotherpartthesecondarybybringingoutanintermediatetap.AudioAmplifying.--Thisisatransformerwithanironcoreandisusedforfrequenciesuptosay3,000.ClosedCore.--Atransformerinwhichthepathofthemagneticfluxisentirelythroughiron.Powertransformershaveclosedcores.Microphone.--Asmalltransformerformodulatingtheoscillationssetupbyanarcoravacuumtubeoscillator.OilCooled.--Atransformerinwhichthecoilsareimmersedinoil.OpenCore.--Atransformerinwhichthepathofthemagneticfluxispartlythroughironandpartlythroughair.Inductioncoilshaveopencores.Oscillation.--Acoilorcoilsfortransformingorsteppingdownoruposcillatingcurrents.Oscillationtransformersusuallyhavenoironcoreswhentheyarealsocalledaircoretransformers.Power.--Atransformerforsteppingdownacommercialalternatingcurrentforlightingandheatingthefilamentandforsteppingupthecommerciala.c.,forchargingtheplateofavacuumtubeoscillator.RadioAmplifying.--Thisisatransformerwithanaircore.Itdoesnotinitselfamplifybutissocalledbecauseitisusedinconnectionwithanamplifyingtube.
TRANSMITTER,MICROPHONE.--AtelephonetransmitterofthekindthatisusedintheBelltelephonesystem.
TRANSMITTINGTUNINGCOILS.--SeeCoils,Inductance.
TUNING.--Whentheopenandclosedoscillationcircuitsofatransmitterorareceptorareadjustedsothatbothoftheformerwillpermitelectricoscillationstosurgethroughthemwiththesamefrequency,theyaresaidtobetuned.Likewise,whenthesendingandreceivingstationsareadjustedtothesamewavelengththeyaresaidtobetuned.
CoarseTuning.--Thefirstadjustmentinthetuningoscillationcircuitsofareceptorismadewiththeinductancecoilandthistunesthemcoarse,orroughly.FineTuning.--Aftertheoscillationcircuitshavebeenroughlytunedwiththeinductancecoilthe
exactadjustmentisobtainedwiththevariablecondenserandthisisfinetuning.Sharp.--Whenasendingsetwilltransmitorareceivingsetwillreceiveawaveofgivenlengthonlyitissaidtobesharplytuned.Thesmallerthedecrementthesharperthetuning.
TUNINGCOILS.--SeeCoils,Inductance.
TWOELECTRODEVACUUMTUBE.--SeeVacuumTube,TwoElectrode.
VACUUMTUBE.--Atubewithtwoorthreeelectrodesfromwhichtheairhasbeenexhausted,orwhichisfilledwithaninertgas,andusedasadetector,anamplifier,anoscillatororamodulatorinwirelesstelegraphyandtelephony.
Amplifier.--SeeAmplifier,VacuumTube.AmplifyingModulator.--Avacuumtubeusedformodulatingandamplifyingtheoscillationssetupbythesendingset.GasContent.--Atubemadelikeavacuumtubeandusedasadetectorbutwhichcontainsaninertgasinsteadofbeingexhausted.Hard.--SeeHardTube.Rectifier.--(1)Avacuumtubedetector.(2)atwo-electrodevacuumtubeusedforchangingcommercialalternatingcurrentintodirectcurrentforwirelesstelephony.Soft.--SeeSoftTube.ThreeElectrode.--Avacuumtubewiththreeelectrodes,namelyafilament,agridandaplate.TwoElectrode.--Avacuumtubewithtwoelectrodes,namelythefilamentandtheplate.
VALVE.--SeeVacuumTube.
VALVE,FLEMING.--SeeFlemingValve.
VARIABLECONDENSER.--SeeCondenser,Variable.
VARIABLEINDUCTANCE.--SeeInductance,Variable.
VARIABLERESISTANCE.--SeeResistance,Variable.
VARIOCOUPLER.--Atuningdeviceforvaryingtheinductanceofthereceivingoscillationcircuits.Itconsistsofafixedandarotatablecoilwhosewindingsarenotconnectedwitheachother.
VARIOMETER.--Atuningdeviceforvaryingtheinductanceofthereceivingoscillationcurrents.Itconsistsofafixedandarotatablecoilwiththecoilsconnectedinseries.
VERNIERCONDENSER.--SeeCondenser,Vernier.
VOLT.--Theelectromotiveforcewhichproducesacurrentof1amperewhensteadilyappliedtoaconductortheresistanceofwhichisoneohm.
VOLTAGEDIVIDER.--SeePotentiometer.
VOLTAGE,PLATE.--Thevoltageofthecurrentthatisusedtoenergizetheplateofavacuumtube.
VOLTMETER.--Aninstrumentformeasuringthevoltageofanelectriccurrent.
WATCHCASERECEIVER.--SeeReceiver,WatchCase.
WATER-PIPEGROUND.--SeeGround,Water-Pipe.
WATT.--Thepowerspentbyacurrentof1ampereinaresistanceof1ohm.
WAVE,BROAD.--Awavehavingahighdecrement,whenthestrengthofthesignalsisnearlythesameoverawiderangeofwavelengths.
WAVELENGTH.--Everywaveofwhateverkindhasalength.Thewavelengthisusuallytakentomeanthedistancebetweenthecrestsoftwosuccessivewaves.
WAVELENGTHBAND.--Inwirelessreceptionwhencontinuouswavesarebeingsentoutandthesearemodulatedbyamicrophonetransmitterthedifferentaudiofrequenciessetupcorrespondingradiofrequenciesandtheenergyoftheseareemittedbytheaerial;thisresultsinwavesofdifferentlengths,orabandofwavesasitiscalled.
WAVEMETER.--Anapparatusformeasuringthelengthsofelectricwavessetupintheoscillationcircuitsofsendingandreceivingsets.
WAVEMOTION.--Disturbancessetupinthesurroundingmediumaswaterwavesinandonthewater,soundwavesintheairandelectricwavesintheether.
WAVES.--SeeWaveMotion.
WAVES,ELECTRIC.--Electromagneticwavessetupinandtransmittedbyandthroughtheether.
Continuous.AbbreviatedC.W.--Wavesthatareemittedwithoutabreakfromtheaerial.Alsocalledundampedwaves.Discontinuous.--Wavesthatareemittedperiodicallyfromtheaerial.Alsocalleddampedwaves.Damped.--SeeDiscontinuousWaves.Intermediate.--Wavesfrom600to2,000metersinlength.Long.--Wavesover2,000metersinlength.Radio.--Electricwavesusedinwirelesstelegraphyandtelephony.Short.--Wavesupto600metersinlength.Wireless.--Electricwavesusedinwirelesstelegraphyandtelephony.Undamped.--SeeContinuousWaves.
WIRELESSTELEGRAPHCODE.--SeeCode,International.
WIRE,ENAMELLED.--Wirethatisgivenathincoatofenamelwhichinsulatesit.
WIRE,PHOSPHORBRONZE.--Averystrongwiremadeofanalloyofcopperandcontainingatraceofphosphorus.
WIREDWIRELESS.--Continuouswavesofhighfrequencythataresentovertelephonewiresinsteadofthroughspace.Alsocalledlineradiocommunication;carrierfrequencytelephony,carriercurrent
telephony;guidedwavetelephonyandwiredwireless.
X'S.--SeeStatic.
ZINCITE.--SeeDetector.
WIRELESSDON'TS
AERIALWIREDON'TS
Don'tuseironwireforyouraerial.
Don'tfailtoinsulateitwellatbothends.
Don'thaveitlongerthan75feetforsendingouta200-meterwave.
Don'tfailtousealightningarrester,orbetter,alightningswitch,foryourreceivingset.
Don'tfailtousealightningswitchwithyourtransmittingset.
Don'tforgetyoumusthaveanoutsideground.
Don'tfailtohavetheresistanceofyouraerialassmallaspossible.Usestrandedwire.
Don'tfailtosoldertheleading-inwiretotheaerial.
Don'tfailtoproperlyinsulatetheleading-inwirewhereitgoesthroughthewindoworwall.
Don'tletyouraerialorleading-inwiretouchtreesorotherobjects.
Don'tletyouraerialcometooclosetooverheadwiresofanykind.
Don'trunyouraerialdirectlyunder,orover,orparallelwithelectriclightorotherwires.
Don'tfailtomakeagoodgroundconnectionwiththewaterpipeinside.
TRANSMITTINGDON'TS
Don'tattempttosenduntilyougetyourlicense.
Don'tfailtoliveuptoeveryruleandregulation.
Don'tuseaninputofmorethan1/2akilowattifyoulivewithin5nauticalmilesofanavalstation.
Don'tsendonmorethana200-meterwaveifyouhavearestrictedorgeneralamateurlicense.
Don'tusesparkgapelectrodesthataretoosmallortheywillgethot.
Don'tusetoolongortooshortasparkgap.Therightlengthcanbefoundbytryingitout.
Don'tfailtouseasafetysparkgapbetweenthegridandthefilamentterminalswheretheplatepotentialisabove2,000volts.
Don'tbuyamotor-generatorsetifyouhavecommercialalternatingcurrentinyourhome.
Don'toverloadanoscillationvacuumtubeasitwillgreatlyshortenitslife.Usetwoinparallel.
Don'toperateatransmittingsetwithoutahot-wireammeterintheaerial.
Don'tusesolidwireforconnectingupthepartsoftransmitters.Usestrandedorbraidedwire.
Don'tfailtosoldereachconnection.
Don'tusesolderingfluid,userosin.
Don'tthinkthatalloftheenergyofanoscillationtubecannotbeusedforwavelengthsof200metersandunder.Itcanbeifthetransmittingsetandaerialareproperlydesigned.
Don'trunthewiresofoscillationcircuitstooclosetogether.
Don'tcrossthewiresofoscillationcircuitsexceptatrightangles.
Don'tsetthetransformerofatransmittingsetnearerthan3feettothecondenserandtuningcoil.
Don'tusearotarygapinwhichthewheelrunsoutoftrue.
RECEIVINGDON'TS
Don'texpecttogetasgoodresultswithacrystaldetectoraswithavacuumtubedetector.
Don'tbediscouragedifyoufailtohitthesensitivespotofacrystaldetectorthefirsttime--orseveraltimesthereafter.
Don'tuseawirelargerthanNo.80forthewireelectrodeofacrystaldetector.
Don'ttrytousealoudspeakerwithacrystaldetectorreceivingset.
Don'texpectaloopaerialtogiveworthwhileresultswithacrystaldetector.
Don'thandlecrystalswithyourfingersasthisdestroystheirsensitivity.Usetweezersoracloth.
Don'timbedthecrystalinsolderastheheatdestroysitssensitivity.UseWood'smetal,orsomeotheralloywhichmeltsatornearthetemperatureofboilingwater.
Don'tforgetthatstrongstaticandstrongsignalssometimesdestroythesensitivityofcrystals.
Don'theatthefilamentofavacuumtubetogreaterbrilliancythanisnecessarytosecurethesensitivenessrequired.
Don'tuseaplatevoltagethatislessormorethanitisratedfor.
Don'tconnectthefilamenttoalightingcircuit.
Don'tusedrycellsforheatingthefilamentexceptinapinch.
Don'tuseaconstantcurrenttoheatthefilament,useaconstantvoltage.
Don'tuseavacuumtubeinahorizontalpositionunlessitismadetobesoused.
Don'tfailtoproperlyinsulatethegridandplateleads.
Don'tusemorethan1/3oftheratedvoltageonthefilamentandontheplatewhentryingitoutforthefirsttime.
Don'tfailtousealternatingcurrentforheatingthefilamentwherethisispossible.
Don'tfailtouseavoltmetertofindthepropertemperatureofthefilament.
Don'texpecttogetresultswithaloudspeakerwhenusingasinglevacuumtube.
Don'tfailtoprotectyourvacuumtubesfrommechanicalshocksandvibration.
Don'tfailtocutofftheAbatteryentirelyfromthefilamentwhenyouarethroughreceiving.
Don'tswitchontheAbatterycurrentallatoncethroughthefilamentwhenyoustarttoreceive.
Don'texpecttogetthebestresultswithagas-contentdetectortubewithoutusingapotentiometer.
Don'tconnectapotentiometeracrosstheBbatteryoritwillspeedilyrundown.
Don'texpecttogetasgoodresultswithasinglecoiltunerasyouwouldwithaloosecoupler.
Don'texpecttogetasgoodresultswithatwo-coiltuneraswithonehavingathird,ortickler,coil.
Don'tthinkyouhavetousearegenerativecircuit,thatis,onewithaticklercoil,toreceivewithavacuumtubedetector.
Don'tthinkyouaretheonlyamateurwhoistroubledwithstatic.
Don'texpecttoeliminateinterferenceiftheamateursaroundyouaresendingwithsparksets.
Don'tlayoutorassembleyoursetonapanelfirst.Connectituponaboardandfindoutifeverythingisright.
Don'ttrytoconnectupyoursetwithoutawiringdiagraminfrontofyou.
Don'tfailtoshieldradiofrequencyamplifiers.
Don'tsettheaxesofthecoresofradiofrequencytransformersinaline.Setthematrightanglestoeachother.
Don'tusewiresmallerthanNo.14forconnectingupthevariousparts.
Don'tfailtoadjusttheBbatteryafterputtinginafreshvacuumtube,asitssensitivitydependslargelyonthevoltage.
Don'tfailtoproperlyspacethepartswhereyouusevariometers.
Don'tfailtoputacoppershieldbetweenthevariometerandthevariocoupler.
Don'tfailtokeeptheleadstothevacuumtubeasshortaspossible.
Don'tthrowyourreceivingsetoutofthewindowifithowls.Tryplacingtheaudio-frequencytransformersfartherapartandthecoresofthematrightanglestoeachother.
Don'tusecondenserswithpaperdielectricsforanamplifierreceivingsetoritwillbenoisy.
Don'texpectasgoodresultswithaloopaerial,orwhen?usingthebedsprings,asanout-dooraerialwillgiveyou.
Don'tuseanamplifierhavingaplatepotentialoflessthan100voltsforthelaststepwherealoudspeakeristobeused.
Don'ttrytoassembleasetifyoudon'tknowthedifferencebetweenabindingpostandablueprint.Buyasetreadytouse.
Don'texpecttogetArlingtontimesignalsandthebigcablelessstationsifyourreceiverismadeforshortwavelengths.
Don'ttakeyourheadphonesapart.Youarejustasapttospoilthemasyouwouldawatch.
Don'texpecttogetresultswithaBelltelephonereceiver.
Don'tforgetthatthereareotheroperatorsusingtheetherbesidesyourself.
Don'tletyourBbatterygetdampanddon'tletitfreeze.
Don'ttrytorechargeyourBbatteryunlessitisconstructedforthepurpose.
STORAGEBATTERYDON'TS
Don'tconnectasourceofalternatingcurrentdirecttoyourstoragebattery.Youhavetousearectifier.
Don'tconnectthepositiveleadofthechargingcircuitwiththenegativeterminalofyourstoragebattery.
Don'tlettheelectrolytegetlowerthanthetopsoftheplatesofyourstoragebattery.
Don'tfailtolookaftertheconditionofyourstoragebatteryonceinawhile.
Don'tbuyastoragebatterythatgiveslessthan6voltsforheatingthefilament.
Don'tfailtokeepthespecificgravityoftheelectrolyteofyourstoragebatterybetween1.225and1.300Baume.Thisyoucandowithahydrometer.
Don'tfailtorechargeyourstoragebatterywhenthehydrometershowsthatthespecificgravityoftheelectrolyteiscloseto1.225.
Don'tkeepchargingthebatteryafterthehydrometershowsthatthespecificgravityis1.285.
Don'tletthestoragebatteryfreeze.
Don'tletitstandforlongerthanamonthwithoutusingunlessyouchargeit.
Don'tmonkeywiththestoragebatteryexcepttoaddalittlesulphuricacidtotheelectrolytefromtimetotime.Ifanythinggoeswrongwithitbettertakeittoaservicestationandlettheexpertdoit.
EXTRADON'TS
Don'tthinkyouhaveanup-to-datetransmittingstationunlessyouareusingC.W.
Don'tuseawirefromyourlightningswitchdowntotheoutsidegroundthatissmallerthanNo.4.
Don'ttrytooperateyoursparkcoilwith110-voltdirectlightingcurrentwithoutconnectinginarheostat.
Don'ttrytooperateyoursparkcoilwith110-voltalternatinglightingcurrentwithoutconnectinginanelectrolyticinterrupter.
Don'ttrytooperateanalternatingcurrentpowertransformerwith110-voltdirectcurrentwithoutconnectinginanelectrolyticinterruptor.
Don't--nonever--connectonesideofthesparkgaptotheaerialwireandtheothersideofthesparkgaptotheground.TheGovernmentwon'thaveit--that'sall.
Don'ttrytotuneyourtransmittertosendoutwavesofgivenlengthbyguesswork.Useawavemeter.
Don'tusehardfiberforpanels.Itisaverypoorinsulatorwherehighfrequencycurrentsareused.
Don'tthinkyouaretheonlyonewhodoesn'tknowallaboutwireless.Wirelessisaverycomplexartandtherearemanythingsthatthoseexperiencedhavestilltolearn.
THEEND.
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