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THE WIRELESSWORLD

THE OFFICIAL ORGAN OFTHE WIRELESS SOCIETY OF LONDON

A MAGAZINE DEVOTED TO WIRELESSTELEGRAPHY AND TELEPHONY.

Registered at the G.P.O. for transmission by MagazinePost to Canada and Newfoundiand.

CONTENTSTECHNICAL ARTICLES.

PAGENotes on the Physics of the Thermionic

Valve 686Digest of Wireless Literature 691The New Marconi Distress Calling Device 695How to make a Telephone Transformer C99Notes on the Design and Construction of

Valve Amplifiers 701Proceedings of the Wireless Society of

London (A Portable Set, and someproperties of C.W. Circuits) 711

Aircraft Wireless Section 729The Construction of Amateur Wireless

Apparatus

Continued on page x.

733

SEA,LAND& AIR

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CONTENTS-continuedGENERAL ARTICLES.

PA GEWireless Telegraphy in the Red Sea during

the War (79Personalities in the Wireless World 684Stray Waves 693The Amateur's Guide to the Anther 705The New Volume 707The Competition Results 708Notes of the Month 709Wireless Club Notes 721Aviation Notes 727The Library Table 732

MISCELLANEOUS.The Radio Research Board 692Questions and Answers 736

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March, 1920. x Please mention the Wireless World

:7_'1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111LL=

THE

WIRELESS WORLDNo. 84

Vol. VII

A1111111111111111111111111 111111111111111

MARCH1920

II11111111111r

Wireless Telegraphy in theRed Sea during the WarBy COMMAN DER G. MONTEFINALE (Royal Italian Navy).

THE Christmas of 1916 wasapproaching when I re-ceived an appointment forRadio service in the Red Seaand was obliged to leave my

wireless work at Brindisi, and manyAllied and Italian comrades, and the harddaily duty of wireless communicationsacross the Lower Adriatic, the Ionianand Aegean Seas.

The intensified campaign of Hunpiracy in the Aegean and the OtrantoChannel obliged the Allies to estab-lish many Wireless D.F. stations, of thewells -known Bellini-Tosi type, alongthe coasts of the Adriatic and IonianSeas, at Malta and in some bases of theNear East, and for many months, ingood and bad fortune, British andItalian radiotelegraphists had worked to-gether in the daily routine of the fleetas well as in the hunt for enemy sub-marines.

The mail steamship that carried meto Dark Africa went circumspectly outfrom the harbour of Syracuse, escorted

by two Italian destroyers. Many enemysubmarines were reported at work in thehigh seas and we received instructions

for Corinth Canal. We en-tered safely the Patrasso Gulf as thesun sank amongst the Morea Islands.The following day we passed betweenthe rocky walls of the Canal andwhen later we were in the open sea wefound a very dangerous Archipelago,with a freezing, northerly breeze andheavy sea. These constituted the bestassurances against the Hun's attacks.

For two long days we steamed alone,dominated by uncertainty, while manyenemy pirates were reported by ourwireless operator to be in the vicinity.Several times a day the Captain wasobliged to alter the course of the vessel.

At last, in a pale, fresh day -break,tinted with some of the characteristiccolours of the oriental skies, the pas-sengers crowded on the deck cheeredthe long -desired land of Egypt. Coast-ing at full speed along the mouths ofthe Nile, we dressed our bow to the

679

THE WIRELESS WORLD MARCH, 1920

white tower of the Port Said lighthousearising from the sands, and I read inevery passenger's face a profound senseof joy and satisfaction when, passingthe Lesseps statue, we left behind usthe faithless Mediterranean ! But alas!A big Russian cruiser, just clearing theharbour, struck a mine and blew upat a short distance from the beach andsank with all hands! Our joy was verysoon changed to sadness, at this unex-pected event.

It was the seventh time that I hadpassed through the Suez Canal bound toEast Africa, but I took the same inter-est in the beautiful scenery and life ofthe great water -way. In the winter of1917 the signs of the Great War in theCanal zone were not so imposing as in1918, in the course of which year apowerful military base sprang up onthe sands of El Kantara. Many cargo -boats were steaming along the Canal orwaiting in the Ismailia lake, but one metvery few mail and passenger liners andthese were crowded with white and col-oured soldiers instead of happy home-ward -bound civilians. Some wirelzssmasts rose from the sands amongst thefar distant hills of the desert showingwhere the Australian and English

trenches for the defence of the Canalzone were situated; gun -boats and moni-tors of the R.N., carrying huge guns onboard and fitted with large aerials, wereinspecting the Canal and Bitter Lakesshores at low speed, while their W/T.stations maintained constant communi-cation with the Army field stations.Squadrons of the Indian Cavalry pat-rolled the plains, and in the ravineswhere the barbed wires extended theirramifications, the Australian soldierscasually took their baths.

Entering the Suez roads we met abig three -funnelled British cruiser boundnorth. The passengers and a crowdof native soldiers on our deck cheeredthe flag of our gallant allies. The cheerwas renewed when we passed the Italianwarship, Calabria, lying at anchorbefore the picturesque beach of PortTewfik.

In the peaceful Suez roads I foundand could admire once more thecharming coloured Egyptian sunsets andthe brightness of the sub -tropical nights.I saw, as in peace time, big liners anddeep -bellied cargo boats passing by myship : the former crowded with Indianand Australian troops, the latter filledwith the Karachi and Industan corn and

A ship in ire Suez Canil.

680

WIRELESS IN THE RED SEA DURING THE WAR

A British Cruiser going North through the Suez Canal.

the rice of the Far East. No more, asin the piping times of peace, the shiningof electric lights on the decks, and thesaloons peopled with passengers; nomore the echoing orchestras on theplacid waters of the Gulf. Silence anddiscipline ruled those vessels as thetrenches of war ruled the world.

When the steamer went beyondCape Zaffarana one splendid morningwhen the rocky chain of Gebel waspainted a living red by a brilliant sun-rise over holy Sinai, we entered the openRed Sea, in a good winter breeze fromthe North. We then began to hear inour crystal receivers the feeble voicesof British and Italian shore stations.The first was that of Port Sudan, giv-ing to the ships in the Red Sea and tothe opposite station of Jeddah a "PressBulletin" of the war. Then we couldread the signals of Massawa, launchingon her four thousand metres wave theItalian Official, and the Aden Marconistation, transmitting Reuter news.

From that day-January 10th,1917,-and for two long years, thosewar bulletins became familiar to meand my companions, during our hardwireless work in that tropical climate,and they were the only recreation whichrelieved the monotony of our life.

When we reached Massawa, a pic-turesque little town, hidden at the bot-tom of the Dahlac Channels and builton some coral islands at the foot of theAbyssinian highlands, it was possible toobserve all the changes imposed by theGreat War on the local life and trades.The fine harbour was quite empty ofsteamers and of those characteristicdhows, fitted with lateen sails andhandled by natives, that in ordinarypeace times crossed the Red Sea in alldirections, trading with the ports ofAfrica and the Arabian coasts.

Now that trade had ceased as a con-sequence of the British blockade of theYemen and Asir coasts, and of the guer-rilla warfare in the interior of Arabia.

681


It was my Particular task to organ-ise the Wireless -telegraphy service ofthe Italian naval and shore stations, inconjunction with the Senior Naval Offi-cers and the Resident Naval Officers ofAden and Suez, following the rules ofthe inter -allied books.

The Massawa High -Power stationwas linked with the Marconi stations ofAden and Abu -Zabel (Cairo), whichlatter was in direct communication withRome (Centocelle). The station ofMogadiscio in Italian Somaliland (fittedwith 100 kw. Marconi set), which hadbeen linked with Massawa in 1911, wasput in communication with British sta-tions and authorities in Juhaland and theB.E.A. settlements. This organisationwas very useful for the rapid signallingof the presence of German corsairs inthe waters of the Indian Ocean. Theallied flotillas in the Red Sea and in theGulf of' Aden received even more use-ful services from the 30 k.w. Marconistation of Assab, constructed just at thebeginning of the war, by the ItalianNavy, under enormous difficulties.

The Naval Radio Station of Assahacted as a relay between the English

and Italian cruisers at sea and the shorestations of Massawa and Aden. For longweary months, in the cool and in thehot seasons, through good and bad for-tune, British and Italian operators, inthe common round of the daily work ofwireless communication, became fami-liar with each other by means of thextheric link between them. Far fromtheir menaced countries, in a climatewhich is always unhealthy for whitepeople, they accomplished difficult taskslike their companions in the Mediter-ranean and the Adriatic, but with muchmore modesty in what was, perhaps, be-lieved not to be a real war -zone. Main-taining continuous radio communicationat short and long distances is an un-common duty for radiotelegraphists inthe tropics, but this duty became abso-lutely arduous in the Southern zone ofthe Red Sea, which is included be-tween the Sana highlands on the East-ern side and the Erythrean and Abys-sinian ranges on the West. Here theatmospheric disturbances due to the ter-rific storms of the rainy seasons addtheir effect to the " strays " which Dr.De Groot affirms to be of an extra-

Massawa. A picturesque town built on coral islands.

WIRELESS IN THE RED SEA DURING THE WAR

The Massawa Wireless Station. 15o K. TV . Marconi type.

atmospheric origin, and which are moreintense in the afternoons and in thesummer season.

In March, 1917, the Massawa station,which was already linked with the Mar-coni High -Power station of Coltano,near Pisa, was put in touch witha newly -opened station at Tarantowhich was fitted with the Poulsen arc.In the summer the same station wasput in communication with the newcontinuous -wave station of Rodi. Bymeans of Taranto and Rodi the com-munications with Italy were more effi-cient, especially in the bad season.

One of the more appreciable benefitsof long distance radio -telegraphy dur-ing the War was the possibility of re-ceiving, in savage Africa, the OfficialBulletins and all other news radiatedby Allied and enemy long-range stationsin Europe. At Massawa it was possibleto receive every day official and pressmessages transmitted by Malta, Horsea,Carnarvon, Paris, Lyons, Coltano, etc.,as well as the propaganda telegrams ofNauen, Eilvese, Pol; Sayville and

Tuckerton. All the war news receivedin the course of the day was gatheredtogether in a small official newspaperprinted by the Erythrean Governmentand widely distributed amongst theItalian and native people of the Colony.Some extracts from it were daily wire-lessed to the Italian Somaliland stations,to ships at sea and also to the ItalianLegation in Addis Abeba, where I hadestablished the first W/T. receiving sta-tion of the Abyssinian Empire.

In November, 1917, the powerfulvoice of the new big station of Rome(San Paolo) first reached the aerials ofthe Red Sea and Indian Ocean stations.

As a consequence of the new facili-ties offered by radio -telegraphic connec-tion with the Motherland, the .trafficaugmented rapidly at the Massawa sta-tion, and it was necessary, therefore, toerect a receiving duplex station at As-mara, the capital city of Erythrea. Inthis construction I followed the samesystems employed with excellent resultsin other high -power Marconi stations,using a long directive Marconi aerial.

683

LICUT.-COLO.VL eilDR.L1.91C F. H. SIMPSON, C.M.G.

684

Personalities in the Wireless WorldLIEUT. -COLONEL ADRIAN F. H. SIMPSON, C.M.G., (late)

R.E., was born in 1880; the son of Surgeon -General SirBenjamin Simpson, K.C.I.E. Educated at Clifton College andthe Royal Military College at Sandhurst, he entered the Armyin 1900 and was gazetted to the 31st East Surrey Regiment,which was at the time stationed at Lucknow. In the followingyear he joined the Hyderabad Contingent of the Indian Staff

Corps and served in the Bengal, Bombay, and Madras Residencies,afterwards obtaining command of a detachment of Native Troops . incharge of one of the Prisoner Camps which had been formed inconnection with the South African War. He also took up his share of"the white man's burden" by serving on plague duty in Central India.

In 1903 he proceeded to Russia and in 1906 succeeded in passingthe Military examination for a Russian Interpretership. He alsoobtained Government awards for proficiency in Persian and Hindustani.

In 1907 he retired from the Army in order to devote himself tothe study of Electrical Engineering and, in particular, WirelessTelegraphy. He was the Directeur Administrateur of the SocieteRusse des Telegraphes et Telephones Sans Fils, Petrograd, and Directorof the Telephone Construction Company of oscow and the MoscowElectrotechnical -Works.

Lieut.-Colonel Simpson is widely travelled and has visited atvarious times Cashmere, Finland, Scandinavia; and is well acquaintedwith India and Russia.

On the outbreak of war he at once rejoined the forces and was senton a special mission to Russia. Here he served with the CaucasianCavalry Division and was A.D.C. to the Grand Duke MichaelAlexandrovich in the Galician Campaign of 1914-15. He transferredto the R.E. in 1915 and served on the general staff at the War Officein 1916. Lieut.-Colonel Simpson has recently been appointed Directorof Wireless Telegraphy under the Government of India. His long andclose connection with Wireless Telegraphy in England and various partsof the Continent, and with a number of firms such as the English DeForest Wireless Telegraph Syndicate, Ltd., the Amalgamated RadioTelegraph Co., Ltd. (owning the Poulsen Patents), the Lepel WirelessTelegraph Co., Ltd., Marconi's Wireless Telegraph Co., Ltd., and theRussian Company of Wireless Telegraphy and Telephony of which hewas Managing Director, his wide experience of men and affairs, and hislinguistic attainments all furnish guarantees that he will carry out his newduties with distinction.

He is a Chevalier of the Order of St. Anne, 3rd degree, and of theOrder of St. Stanislas, 2nd degree with Crossed Swords, and anAssociate Member of the Institution of Electrical Engineers.

685

IL_i_11 111111111111111111111 1 11 11111 [11 1 1 1 11111111111111111111 II I III 1111 111111111111111111111

__. Notes on the Physics of==-- the Thermionic Valve== By T. G. PETERSEN. =

(Continued from February Number.)

EXHAUSTION METHODS.

WHEN discussing Tung-sten as an emitter forvalve work it was re-marked that " it isnecessary (f) to attainan exceedingly high de-

gree of vacuum and (2) to maintainsuch degree of vacuum" (WIRELESSWORLD, Jan. 1920). The attainmentof the low degree of pressure necessaryin hard valves, was not, at onetime, an easy matter. Althoughgauges on the pumping circuits indi-cated extremely low pressures, valvesexhausted showed no consistency intheir behaviour. Occasionally it wasfound possible to produce a valve inwhich the necessary vacuum had beenattained, but which on running in acircuit as a radio device, rapidly showedsigns of lowered vacuum. This lower-ing of vacuum frequently rendered suchvalves quite useless.

In the manufacture of the modernTungsten filament lamp, for lightingpurposes, satisfactory results may beobtained when a well -designed mechani-cal pump is used as the only means ofevacuation. The degree of pressure insuch lamps will often reach as low as0.000001 mm. of mercury after a run ofa few hundred hours, but it should beborne in mind that the nickel or othermetal supports are never sufficientlyhot to cause them to throw off vapours,the heat area being largely confined tothe Tungsten filament itself. This highdegree of vacuum is therefore due toabsorption of gases by the filament, asalready explained.

Pumps of various designs which hadbeen used successfully in the manufac-ture of electric lamps completely failed

to produce the high degrees of vacuonecessary in valves employing a pureelectron discharge. Since the function-ing of these pumps is, in the main,dependent upon the diffusion of gasesfrom the vacuous space into the pumpitself, a limit is reached when thediffusion outward is less than the backdiffusion from the pump. Unless meansare taken to prevent back diffusionthere must always be a limit to thedegree of vacuum obtainable with sucha device.

For instance, in the Sprengel type ofpump (Fig. 18) columns of mercury arecaused to pass an aperture of the vesselwhich is to be exhausted of gases, andin doing so to carry with them the gasesdiffused into their path from this aper-ture. Apart from the inherent limita-tions of such a pump mercury vapouris liable to diffuse back into the vesselunder treatment, at a quicker rate than

686

MERCURY TO BACKINGINLETS (pump

TAP

TO VESSEL TO BEEXHAUSTED

FALLTUBES

PHYSICS OF THE THERMIONIC VALVEthe gases diffuse outwards. In addition,this pump is extremely slow in opera-tion and much auxiliary gear is required.

The Gaede mercury diffusion pump,although of greater speed, and capableof giving higher degrees of vacuo, hasyet an inherent weak point whichmakes it unsuitable for use in evacuatingvalves. Instead of a continual suc-cession of small columns of mercury,a blast of mercury vapour is caused topass the aperture of the vessel. Thewidth of the aperture, however, isaccurately calculated from Gaede'stheory that the maximum speed of thepump is reached when the aperturewidth is equal to the mean free path ofthe gases tending to diffuse back intothe vacuous space. Whilst the blastof mercury vapour is very effective incarrying away the outward diffusedgases (i.e., those leaving the vessel tobe exhausted), the vapour atoms willnot all necessarily have vertical velocitycomponents, but some will be movingtowards the walls of the pump, and onstriking that comparatively cold surfacewill condense. The heat thus generatedwill, however, be sufficient to causesome of them to re -evaporate as quicklyas they condense. On becoming freeonce more they are just as likely todiffuse out through the aperture againstthose gases leaving the vacuous vessel.An attempt has been made to show thisin Fig. 19.

THE LANGMUIR CONDENSATION PUMP.*

In designing his condensation pumpLangmuir was aware of this limitation,and sought to remove it by the carefuldesign of the flare of the vapour blastfunnel, and the dimensions of theaperture, but mainly by cooling at thedesired points. The universal usage,at the present time, in respect of pumpsembodying the water-cooling device assuggested by Langmuir, is sufficientevidence that he has been highly suc-cessful in his efforts at eliminating thedefects of the mercury vapour pumpas investigated by Gaede. Some ideaof the operation of this pump will be

* " Physical Review," July, 1916.

MERCURY VAPOURBLAST

lirVESSELUNDERGOINGEXHAUSTION

A-- REGION OFCONDENSEDMERCURYVAPOUR

Fig. x9

grasped from the following. In Fig. 20are depicted a Langmuir CondensationPump, the liquid -air trap and a trans-mitting valve, with the voltage sourcesfor filament and anode. The mercuryat the base of the pump is heated ex-ternally, with the result that a blast ofvapour is forced up towards the de-flector D. Owing to the flare of thefunnel the blast increases in intensity inits upward motion. On hitting thedeflector the blast is sent downwards,and outwards against the water-cooledsides of the pump. Owing to the cur-vature of the deflector the majority ofmercury vapour atoms will travel down-wards, carrying with them the gasesdiffusing from the valve. Those atomswhich have a transverse direction ofmovement will condense, and since thesides are water-cooled, re -evaporationwill not take place, but the condensedmercury will return to the reservoir atthe bottom of the pump. In this respectthe condensation pump is much superiorto the Gaede diffusion pump, in which,as has already been explained, re -evaporation does take place, with theconsequent back diffusion and the limit-ation in degree of vacuum obtainable.

The gas brought down by the ver-tical blast will now be carried off bythe backing pump working at A. Thevapour blast increases in intensity as itnears the bottom and, owing to theconstriction at this point, is caused tocome under the influence of the con -

687

CC

4

THE WIRELESS WORLD

LIQUIDAIR

fr.-TO BACKINGOR ASSISTINGPUMP

A

algr PERFORATEDTRAY

MERCURY

Fig. 20.

denser and thus falls back into thereservoir, ready for further cycles ofevaporation and condensation.

There is, therefore, no theoreticallower limit to which this pump canexhaust, as the flow of diffused gasinto the pump from the vacuous vesselis always greater than that tending todiffuse back. Pressures as low as10-5 bar (1 bar = approximately .one -thousandth of a millimetre of mercurypressure) have been obtained by meansof this form of pump ; the measurementwas, however, recorded on a gauge ofspecial design introduced by A. W.Hull.

THE MCLEOD GAUGE.Gauges reading as low as 10-' bar

are not, however, absolutely necessaryin practice, the McLeod gauge beingrobust and, quite adequate to indicatethe degree of vacuum at which gas -free-ing of the electrodes may be commenced.

A simplified diagram of a McLeodgauge is shown in Fig. 21. When it isdesired to ascertain the pressure arrivedat during pumping, the movable reser-voir of mercury is lifted up, thus forcingthe mercury up both C and B. Thelevel in C will be higher than that inB, since the gases in the former are

MARCH, 1920

ANODETO BEGASFREED

1F

practically unconfined, whereas thosein B are compressed by reason of thetube's sealed end.' The difference ofthese heights is a measure of thepressure in C. The volume of thegases in B is measured by the gradua-tions along it. The total volume of Aand the tube B above the point ofjunction with C is also known. If this

688

TO VACUOUSSPACE

MERCURY HEIGHTOF WHICH CANBE ALTERED ATWILL

MOVABLE RESERVOIR OF MERCURY

F . 21.

PHYSICS OF THE THERMIONIC VALVEvolume be represented by V, the volumeof the gas confined in B by v, andthe pressure indicated by the differencein level of C and B by P, then thepressure in millimetres of mercury, ofthe vacuous space to be measured isgiven by

p = PvV

In practice such a calculation is notmade, but a scale is attached fromwhich a rough indication may be ob-tained, or the pressure is read directlyin millimetres of mercury.

LIQUID AIR.Returning to the consideration of

Fig. 20 it will be noticed thatbetween the valve and the condensa-tion pump a liquid -air trap inter-venes. In this trap any mercuryvapour that may have diffused backfrom the pump will be brought to sucha low temperature as to make thepressure due to its presence a negligiblequantity. For instance, if it be sup-posed that the inner surface of the traphas a temperature of -1800 C (thetemperature at which liquid air com-mences to boil) then the pressure dueto the mercury will be 2.3 x 10_27millimetres of mercury, a negligiblequantity.

The use of liquid air is very neces-sary, for, if the temperature be notlower than, say, - C, althoughmercury freezes at this point thepressure it exerts is equivalent to.0000023 millimetres of mercury, whichmay not be a value to be ignored.

ELECTRONIC BOMBARDMENT AS A GAS -FREEING PROCESS.

It will be noted that in Fig. 20there are shown means of heating thefilament and of maintaining the anodeat a high potential with respect to thefilament. Although great care be takento render gas -free the units comprisingthe electrodes and their supports beforeinserting them in the bulb, much re-mains to be done by reason of imperfectgas -freeing in the first place, and theabsorption of gases by .these coin-

ponents during the time after gas -freeing and before evacuation. Themethod employed to effect final elimina-tion of gases from the metal parts isthat of electronic bombardment.

In practice the anode is maintainedat a high potential with respect to thefilament throughout the process of ex-haustion. This may be done either bymeans of an alternating or a directvoltage. Of the two the latter is moredesirable and is easily obtained byusing a high voltage transformer inconjunction with valve rectifiers, inwhich case it is necessary to connectthe rectifier in one leg of the trans-former secondary in such a way thatone side of its filament is connected tothe anode of the valve to be exhausted,thus maintaining this electrode at ahigh positive potential.

As will be obvious later, it is im-perative that the filament of the valveto be pumped be kept dull. In theevent of the high voltage availablebeing insufficient, the bombardmentmay be assisted by the application of apositive potential on the grid, as shownin the figure.

When the McLeod gauge indicatesa sufficiently high degree of vacuum,the filaments are brightened up and ablue fluorescence is produced through-out the bulb and down the circuittubes. Simultaneously the anode be-comes reddened, although this may notbe apparent until the filament is dulledagain. The process of alternatelybrightening and dulling the filament,with periods for cooling the anode, isemployed until little or no fluorescenceresults.

This phenomenon of electronic bom-bardment, which manifests itself bythe blue glow and by the reddening ofthe anode, puts a severe strain on thefilament. During the periods in whichthe filament is dull the number ofelectrons hitting the anode is insuf-ficient, in spite of their velocity, to heatit up to any appreciable extent. When,however, the emission is increased suf-ficiently, heat is produced on the plateby the bombardment of its surface by

689


the stream of cathode rays caused bythe strong electric field. Provided theheat produced is great enough, gasesoccluded in the electrode (i.e., heldwithin the metal or on its surface) willbe released and drawn away by thecontinuous action of the pump. Someof the gases come within the path ofthe cathode rays from the filament andare in consequence split up or ionized.An immediate result is the release ofadditional electrons and the formationof positive ions of molecular dimensions.These additional electrons then assistin the bombardment of the anode,whilst the positive ions, attracted bythe high negative potential, bombardthe filament.

Now the filament is already at aconsiderable temperature (approachingthat of its melting point), and coupledwith the fact that it is fragile, the bom-bardment is very liable to disintegrateit, if allowed to become excessive.

In practice great care is required inthis process, for much previous goodworkmanship may be spoilt by an un-necessarily long or too severe a periodof bombardment.

It has been stated that it is impera-tive to keep the filament dull through-out the early stages of exhaustion. Itwill be obvious that if the bombard-ment is commenced when too muchgas remains, the positive bombardmentof the filament will be so great as tocompletely destroy that electrode.

If it ever becomes possible to pro-duce the original emission by other thanthermal means, such as photo -electricmethods, the cathode might be robustenough to withstand this bombardment.The stage will then have been reachedwhen much higher anode voltages maybe safely used.

MINOR EXHAUSTION DETAILS.In the case of small receiving valves

it is possible to arrange that a numbermay be simultaneously gas -freed by theprocess outlined. This method con-siderably reduces the total time ofexhaustion. With this type of valvedifficulties are encountered during bom-bardment because of the close proximity

of the electrodes, the static pull causedby the high potential on the platefrequently being sufficient to bow thefilament to such a degree as to force itinto contact with the grid. Assumingthat the grid had been previously con-nected to the filament externally (i.e. ithad zero difference of potential withrespect to it), the screening effect nowbecomes entirely destroyed, and in con-sequence an excessive current flowsthrough the valve-with disastrousresults.

The total period of exhaustion, inspite of a lengthy bombardment doesnot in the case of small receiving valvesusually exceed two hours. Further, asmany as twelve valves may be ex-hausted simultaneously, so that thisbrings down the length of time for eachvalve to be exhausted, to ten minutes.

The larger variety have usually to beexhausted singly or, at the most, inpairs, and take from 3 to 5 hours in theexhaustion operation, even when arapid pump is used.IONIZATION IN VALVES DURING USE AS

RADIO DEVICES.The process of gas - elimination

from the metal parts can, however,never be absolutely complete, and thatthis is so becomes apparent during theoperation of the valve as a radio device.Especially is this true with respect totransmitters, where large electronic cur-rents are present. If, however, keyingarrangements are made which breakand make these large currents, thedanger of ionization is greatly lessened,since the spaces of time interveningbetween and in the Morse characters,are adequate to preventing undue ac-cumulation of heat on the anode.

When such interruption is not prac-ticable the anode may attain a tem-perature sufficient to release a littlegas, in which case ionization by col-lision will take place, and if the valveis not immediately cooled (by dullingthe filament or otherwise decreasingthe flow of electronic current), thevacuum may be brought so low andthe filament disintegrated so badly, asto render the valve of no further use.

690

=-Llii11111111111111111111111iiii11111111MiiiiiIIIIHMI IIIIIIIIIIIIIiiIIillliillllllllllllllllIII I'=

Digest of Wireless Literature

ZWEI MIT HILFE DER NEUENVERSTARKER ENTDECKTE

ERSHEINUNGEN.BY H. BARKHAUSEN.

Physikalische Zeitschrift, Sept. 1919.(1) NOISES FROM THE DEMAGNETISA-

TION OF IRON.

With the recently developed vacuumtube amplifiers it is easily possible toobtain a current amplification of 10,000which is equivalent to an energy ampli-fication of 100,000,000. By means ofthese instruments small changes in elec-tric or magnetic fields which wouldotherwise escape our notice can be madeperceptible. One can regard their helpas being that of a new type of electricalmicroscope which magnifies things tenthousand times. Quite recently Scholtkyhas shown that, by using enormous am-plification the electrons of a vacuum tubecan be heard in their flight as the cur-rent executes spontaneous variations inaccordance with the laws of the kinetictheory of gases.

A similar phenomenon has been dis-covered by the writer and Herr Dr.Tuczek in the case of iron. It hasbeen found that iron produces a" noise" on being demagnetised.When the magneto -motive force isaltered th'e mdlecu,lar magnets settledown rapidly in their new positions andin so doing generate in a surrounding coilirregular electrical impulses which can

be heard as a noise in the telephone.Fig. 1 shows the simple experimentalarrangement employed. The iron coreE is surrounded by a coil S of 25 mm.diameter and 300 turns. The ends ofthe coil are connected to a telephonethrough an amplifier. By moving thehorse -shoe magnet M and so alteringthe induction the noises in the tele-phone can be produced.

It has been found that the thickerthe iron core the weaker is the noiseproduced. For example a core 20mm.thick gives no sound at all. From agreat number of experiments it has alsobeen found that the softer the iron thegreater is the intensity of the noise.Hard steel gives hardly any effect whilethe noise with soft iron is particularlymarked. It is desirable that many fur-ther and more detailed experimentsshould be performed on this subject asit seems probable that there is some con-nection between this phenomenon andthe action of the Marconi magneticdetector.

(2) MUSICAL SOUNDS FROM THEEARTH.

During the war amplifiers were usedon both sides of the front for the inter-ception of enemy telephone messages.The telephone currents were detectedpartly by electromagnetic induction andpartly by means of the stray earth cur-rents which escaped from the telephonewires at points of defective insulation.Although these currents are extremelyfeeble the enormous ampificationavailable could be utilised to make themaudible. The listening circuit nor-mally used is shown in Fig. 2. Thetwo earth electrodes A and B whichare usually 100 metres apart are ledthrough an amplifier to the telephone

691

A


On many days these earth soundswere so strong and numerous that or-dinary interception could not be carriedon at the same time. The phenomenonseems to be correlated with atmosphericconditions and was particularly notice-able on the mornings of the warmerdays of May and June. It differedcompletely from the normal atmos-pheric strays which produce onlycrackling or bubbling noises in thetelephones.B

Fig. 2.

T. With such a circuit a most remark-able piping note is heard at times. Atthe front operators usually refer tothese noises as " flying grenades." itis difficult to imitate the sound by aword but the spoken word " piou "gives a slight idea of what is heard.Physically the note appears to be thatdue to an oscillation of practically con-stant amplitude but of quickly varyingfrequency, the frequency at the begin-ning of the sound being the highestaudible and dropping rapidly to thedeepest audible tones. On account ofthe properties of the amplifier (designof telephone, etc.), the note is particu-larly strong when the frequency is1,000. The whole phenomenon lastsabout a second.

The earth electrodes which arethe origin of occasional noises canscarcely be regarded as the source ofthese sounds; neither is it probable thatthe effect is due to some meteorologicalinfluence on the deeply buried earthwires. Much more likely is the sug-gestion that the amplifier itself, ener-gised by a particularly strong atmos-pheric generates these oscillations.But all experiments tried in the labor-atory to imitate this phenomenon haveso far failed. Various types of elec-trical impulses and spark flashes havebeen tried but with no result. Thus nocomplete theory can be advanced forthe cause of these weak alternating cur-rents which originate so freely in theearth.

THE RADIO RESEARCH BOARD.

The Department of Scientific andIndustrial Research has appointed aRadio Research Board to co-ordinateand develop researches in wireless tele-graphy and telephony, which are at pre-sent being prosecuted by Governmentdepartments. The Board is' composed asfollows :-Chairman, Admiral of theFleet, Sir Henry B. Jackson, G.C.B.,

K.C.V.O., F.R.S.; Comdr. J. S. Sal-mond, R.N. (representing the Ad-miralty); Lt. -Col. A. G. T. Cusins,C.M.G. (War Office); Wing Com-mander A. D. Warrington Morris,C.M.G., O.B.E. (Air*Ministry); Mr.E. H. Shaughnessy, O.B.E (PostOffice), Prof. J. E. Petavel, F.R.S., andProf. Sir E. Rutherford, F.R.S.

692

LUI11111111111111111111111111111111i11111111111111111111111111111111111111111111111111111111111111111L'

= Stray Waves _-= =71111111111111111111111111111111111111111111111111111111111l11111111111111111111111111111111111111111r7

THE AMATEUR POSITION.s0 far as the progress of the

Amateur Club movement is

concerned matters improvesteadily month by month. Wehave received news of the for-mation of several new clubs,

shoals of enquiries as to where clubsexist, and a number of letters intimatingthe writers' willingness to start clubs. Weare gratified, too, to note that the schemeto form an affiliation of the provincialclubs with the Wireless Society of Lon-don is meeting with great success. Un-der Wireless Club Notes will be foundthe definite proposals formulated by thelast-named Society.

Professor E. W. Marchant, D.Sc.,in his address as Chairman of the Liver-pool Sub -centre of the I.E.E. on j_nuary19th, said " of all the branchesof this problem the one which Liver-pool people must fully appreciate is

Wireless Telegraphy." " Liverpool is

a centre which lends itself particularlywell to the study of wireless problems,and it is hoped that the activities of re-search in this direction will be consider-able." Now the Liverpool WirelessAssociation is trying to resume its acti-vities, and we hope Liverpool amateurswill rally round the Secretary, Mr. S.Frith, 6, Cambridge Road, Crossley,and assist him to make the Associationworthy of Liverpool.

* * *

WIRELESS SIMPLIFIED.An article entitled " Wireless and the

Press," which appeared in The News-paper TV arid of January 3rd, describeswhat appears to be the last word in wire-less receivers and X -stoppers. Afterstating the times at which news is trans-

mitted by certain stations, the articleproceeds to explain that : "Contact isestablished with these stations at theabove hours by bringing a switch intocontact with a metal stud representingthe wavelength of the particular station,whilst the rotation of a knob eliminatesundesirable noises."

MESSAGES FROM MARS.When the pure journalism is separ-

ated from certain recent articles in thedaily press the fact emerges that Sena -tore Marconi is about to prosecute someresearches in wireless phenomena whichare observable on wavelengths of the or-der of hundreds of miles. Apparentlysignals have been heard on wavelengthsmuch greater than any employed byknown stations, and are deemed to meritinvestigation. The signals may bemere x's. or they may represent deliber-ate attempts at signalling from anotherplanet. In the present state of ourknowledge one is at a loss to express anopinion on this question, especially as itbrings up others, such as whether intelli-gent beings exist on Mars, and whethertheir intelligence has developed alongthe same lines as our own.

The following letter from Mr. Mar-coni appears in the Electrician of Jan.30th :-

Sir,-I desire to protest against the in-terpretation that appears to have been putupon statements which I have made at in-tervals during the last few years withregard to the possible sources of whatare being termed " mysterious messagesfrom the unknown." Wireless mes-sages are transmitted through the etherby the agency of electromagnetic wavesof definite lengths which can be ad -

693


justed, and in order to receive such mes-sages the receivers should be tuned to theparticular wavelength that is being usedfor transmission.

At times signals are received whichare apparently due to electromagneticwaves of great length (up to hundredsof miles), and these signals are not of thesame character as those commonlycalled " X's " or " strays." Occasionallysuch signals can be imagined to cor-respond to the Morse signals for certain'letters, and these signals occur at all sea-sons and irregularly.

The sources of such signals are un-known. They may be in the atmo-sphere or outside it, and due to electricaldisturbances. If outside the atmosphere,they may arise in any point of inter-planetary space, possibly in the sun,where it is well known that electricaldisturbances occur.

Obviously, since the planet Mars issituated somewhere near in interplane-tary space, the source of such signalsmight be on it or on any other planet.There is NOTHING, however, to showthat this is the case, nor must any purelyfanciful speculations of mine be inter-preted to mean that I have asserted hav-ing received any intelligible or unintelli-gible messages from Mars or from anyother point in space outside the earth.

I am, etc.,G. MARCONI.

London, Jan. 28th.

THE EFFECT OF GASES ONTHE EMISSION OF ELEC-TRONS FROM HEATED

FILAMENTS.La Nature of January 10th last

contains an interesting article whichdeals incidentally with the intimate re-lation between the electronic emissionfrom heated filaments and the chemicalactivity of the filament.

The writer states that the emission ofelectrons from a filament is generally

lowered by the formation on the fila-ment of a layer of gas when traces ofthe particular gas are present.

He proceeds to say that experienceshows that with tungsten in all caseswhere it has been employed with achemically inert gas, the emission ofelectrons by the heated filament wasnot modified or choked, whilst in casesof gases which combine with tungstenthis emission was diminished, and thatit is reasonable to conclude from thisthat this action is due to the gase-ous layer on the filament. Accordingto the writer of the article, the layershave a thickness of one molecule, rarelyof two or more.

In Archiv fur Elektrotechnik, July24, 1919, M. Abraham deals in an in-teresting manner with the effect onradiation of compound antenn. Twoaerials, erected in close proximity,radiating synchronously, and havingtheir capacity to earth mainly concen-trated in the horizontal portions, willrequire an amount of energy to main-tain them in oscillation greater than thesum of the amounts required for eachindividually, as each aerial will inducecurrents in the other. This increase ofenergy results in increased radiation,through the superposition of the twofields, but it vanishes when the oscilla-tions of the two aerials are displaced inphase by a quarter of a period.

The interaction between the aerialsaffects, of course, the radiation resist-ance of each and also the frequenciesof the respective antenna currents.

By using, at a given distance, asecondary aerial, excited only by the in-fluence of the main transmitting aerial(and tuned to the same frequency) acomplete shadow is thrown by the for-mer and the radiation is at the sametime increased in the opposite directionby a kind of mirror action.

A secondary antenna may also beused in a receiving station to screen themain antenna from certain radiations.

694

i_1111111111111111111111111111111111111111111111111111111 -111111111111111111111111111111111111111111111L

The NewMarconi Distress Calling Device

11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111IFF

THE readers of the WIRE-LESS WORLD will have seenin various newspapers anaccount of a demonstrationconducted between Chelms-

ford and Shelford (Cambridge), inwhich the station at Shelford rang anordinary electric bell and explodedsmall mines at Chelmsford, by meansof special wireless signals.

Some ships carry only one operatorand he cannot spend anything liketwenty-four hours per diem " listen-ing in " on the offchance of hearing adistress call,, and if such a call is madeduring his " watch below " it goes un-heard by his ship.

To amend this state of affairs, andto make certain that distress calls wouldnot pass unheeded, a little while agothe Research Laboratory of Marconi'sWireless Telegraph Company was in-structed to carry out certain experimentson distant control. It was desired to beable to ring a bell at a distance by meansof Wireless Telegraphy, and the objectunderlying the investigation was to con-tribute to the greater safety of life at sea.

The predetermined signal is a seriesof dots regularly transmitted at the rateof 180 per minute. This number waschosen as being not too fast for theoperator to count and time, and as tooslow to be interfered with by ordinarytransmissions.

The first thing was to make a relaywhich would respond only to the pre-determined signal, and which could beoperated by the change in current pro-duced by the reception of such a signal.The change in current with the valves

695

in use in the receiver was never morethan half a milliampere.

Many relays were made, and triedout, and for various reasons were re-jected. The final design is as shownin Fig. 1, and in construction is not un-like the ordinary moving needle gal-vanometer. In brief the description isas follows : -Two rectangular hollowformers each wound with many hun-dreds of turns of very fine wire areplaced one above the other on a brassbase, the windings being connected inseries, and the free ends being taken totwo insulated terminals in the base. Inthe rectangular orifice of the coilsswings a small ring magnet, pivoted atits centre and supported in jewelledbearings which are carried by two verti-cal brass pillars screwed to the base. Thepivot also carries a small circular phos-

Fig.'.


phor-bronze spring, one end of whichis attached to a brass collet on the pivot,the other end being soldered to a ton-gued brass washer clamped to one of thebrass pillars. This tongued washerserves the same purpose as the zero ad-justment on an indicating instrument.By twisting it about its centre the po-sition of the magnet can be alteredand the best working position obtainei.Besides these two details the pivot hasfixed at right angles to itself a fine plati-num -tipped steel arm. This arm is onepole of a switch and is connected byway of the brass pillar, spring,and pivot, to the base of the instru-ment. The other pole of the switch isa small piece of hard carbon, fixed toone end of a strip of flexible copper, theother end of which is supported on asmall pillar and connected to a terminalinsulated from the base. A glass frontis provided in the case of the instrument,so that the action can be inspected fromwithout, and the whole case screwsdown on to the brass base, renderingthe interior dust -proof. Two gauze -capped leaden tubes containing a dryingagent will be seen in Fig. 1. The wholeinstrument is swung in gimbals.

By adjusting the length of the phos-phor -bronze spring it is possible to ar-range that the wheel magnet, pivot, andarm oscillate at the rate of 180 com-plete periods per minute.

The resistance of the coils and thecurrent available are sufficient to preventa single dash, or series of mixed dots anddashes, such as are received in an ordin-ary telegraphic communication fromswinging the moving system far enoughto cause the two contacts of the tinyswitch to touch. It is only by theregularly -delivered impulses arriving atthe right moment that the swing can bebuilt up from zero to full, and contactestablished.

Some trouble was experienced with

this tiny switch. In the original modelboth contacts were made of platinum andsometimes they did not strike with suf-ficient force to make good contact at thefirst time. To overcome this fault Dr.Fleming's Patent No. 112544 of 1918was employed. The modified connec-tions of this patent are as shown in Fig.2. In Fig. 2, Pt is a contact of platinum

Pt C

(15-6MB

I'llFig. 2.

or other noble metal, C is a hard car-bon contact, K a condenser, L an in-ductance, T an instrument which it isdesired to operate by the battery B onclosing the switch Pt. C. The batterycharges the condenser, and when theswitch closes the condenser dischargesthrough the inductance and oscillationspass across the points Pt C and improvesthe contact at those points.

The point next to be considered wasan arrangement for permanently closingthe alarm circuit once the contact hadbeen struck, and the instrument shownin Fig. 3 was designed.

This instrument consists of two coilswith soft iron cores mounted on a softiron plate, forming an electromagnet.

696

Fig. 3.

NEW MARCONI DISTRESS CALLING DEVICE

Above these coils is placed a soft ironarmature connected with a flat steelspring at one end to a brass standard,the other end being free. At the freeend is carried a small insulator, which,when the electromagnet is energised,will depress a short platinum -tippedsteel spring on to a similar one; also ata little distance from the free end is fixeda manipulating key contact which canstrike a similar one situated immediatelybeneath it.

The action is as follows :-Theplatinum -carbon switch of the receiv-ing relay, is connected in series witha twenty-four volt battery and the coilsof this electromagnet; the two platinum -tipped steel springs are connected inparallel with the platinum -carbonswitch. When this switch makes con-tact the electromagnet is energised andthe armature is drawn down and closesthe switch formed by the two steelsprings. This switch being closedand in parallel with the first switch themagnet will remain energised, andthe armature depressed, until the batteryis switched off. Fig. 4 shows theseconnections. Neglecting the resistanceof the connections, it will be seen thatas long as the electromagnet is energisedthere will be a P.D. of about twenty-four volts at its terminals. The alarmbell, which is an ordinary high -powerbell working off twenty-four volts isconnected in parallel with the electro-

RECEIVINGRELAY CONTACTS

magnet, and so long as the latter is

energised the bell will ring.The adopted automatic transmitter is

as shown in Fig. 5. The instrumentconsists of two iron -cored coils mountedon a yoke, the whole forming an elec-tromagnet. Between the poles of thismagnet swings a heavy brass ring witha soft iron diametric bar. To the shaftcarrying the ring are attached a spiralsteel spring, like a clock spring, and alight flexible steel arm tipped with plati-num. Below this arm is a small platinumcontact, supported by a helical springcontained in a tube. The free end of the

F g. 5.

clock spring is clamped to a projectionon the wheel of a worm gear, and ahandle is provided on the screw of thisgear, so that the distance of travel be-tween the moving contact on the shaft,and the spring -supported contact, can bevaried. The variation of this travelcontrols the period of the transmitter,and it is found that the shorter the tra-vel the shorter the period. Three ter-minals are brought through the base andthe whole instrument is mounted ingimbals.

697

T

THE WIRELESS WORLD

TO \

RECEIVER

-4---11111G VOLTS 24 VOLTS

TAPPING KEY

MARCH, 1920

ril-- o 0 86 K L SHUNT

RECEIVE

RECEIVINGRELAY

KEYRELAY

Fig. 6.

For transmission a series circuit is

made comprising a twenty-four volt bat-tery, the coils and contacts of the trans-mitter, and the coils of the instrumentshown in Fig. 3; a small tapping key isconnected in parallel with the trans-mitter contacts. To start the instru-ment this key is pressed and immediatelyreleased. By thus closing the circuitthe electromagnets of both instrumentsare energised and the iron bar of thewheel swings towards the magnet. Thecircuit being broken and the magnet de-magnetised the wheel is urged by theclock spring past its position of rest, andon until the contacts of the transmittertouch; attraction starts again and thecircuit is again broken, and so the cycleof events is repeated as long as the bat -

BELL KEY

tery is switched on. Each time thewheel transmitter is energised the elec-tromagnet shown in Fig. 3 is energised,the armature is drawn down, and theheavy key contacts meet. These contactsare in parallel with those of the mani-pulating key of the ship set, so providedthat the generator is running, spark-ing occurs at every striking of the con-tacts. By means of a watch and theworm gear previously referred to, theoperator can adjust the frequency of hissignal to a nicety, and when once thisis adjusted it is unlikely to vary.

Fig. 6 shows the complete diagramof connections from the last valve of thereceiver to the contacts of the mani-pulating key.

698

rm

JJI 1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111

How to make a TelephoneTransformer

By A. D. KENT.

Here, at last, is the article for which so many amateurs have asked.

:T1111111111111111111111111111111111111111111111111111111111111H1111111111111111i1111111111111111111117;

IT is a common practice when through bad insulation in their tele-using a crystal as a detector toemploy telephones having a re-sistance of the order of 3,000wto 4,000to each. The reason of

this is, that in order to increase to a maxi-mum the magnetomotive force of thetelephone field coils, the latter arewound with as many turns of wire as ispossible. Therefore, the finest copperwire is used. This means that thetelephones will have a very high resist-ance-about 8,000(a; this does notmatter very much, however, consideringthat the resistance of the crystal at itsmost sensitive point is about 10,000a).It is therefore obviously inefficient to uselow resistance telephones of about 150cain a circuit which already has a resistanceof at least 10,000o).

For the benefit of amateurs who onlypossess low resistance telephones and towhom the purchase of high resistancetelephones is a big item, and also ofamateurs who are in doubt as to whichto buy-high or low resistance tele-phones,-I intend to describe the simpleconstruction of a telephone transformer-the use of which in conjunction withlow resistance telephones will give re-sults equivalent to those obtained withhigh resistance telephones.

Apart from any other considerations,the use of a telephone transformer in avalve receiver circuit is most essential,for the telephones are then well insulatedfrom all the other circuits. Amateurswho possess valve receivers will doubt-less have experienced the troubles caused

phones.

CONSTRUCTION OFTELEPHONE TRANSFORMER.

To commence building the trans-former the following materials will berequired : -6 ozs. No. 30 single silkcovered copper wire, 3 ozs. No. 44single silk covered copper wire, 6 ozs.No. 24 soft iron wire, bare, 2 pieces ofhard wood, 21" x 2" x ,4", 4 brass ter-minals and nuts, insulating tape, waxedpaper, paraffin wax and 12" of rubbervalve tubing.

To build up the core, cut the ironwire up into sufficient 3" lengths tomake up a circular iron core "i" in dia-meter, which must be firmly bound withinsulating tape. The tape will servethe double purpose of securing the wireand insulating the secondary windingfrom the core.

The two pieces of wood we will useas the two flanges or cheeks of the bob-bin, and to mount the terminals upon.

Fig. 1 shows quite clearly the methodof mounting and fixing the core into thewood, preparatory to winding. TheNo. 30, or thick winding, we will callthe secondary and will wind it direct onto the iron core which we have insulated.Proceed as follows : -Drill a small holein the wood cheek just above the core,large enough to allow the wire with afew inches of valve rubber on it to gothrough. This wire can he secured toone terminal, but before proceeding towind bind the first turn on to the core

699

THE WIRELESS WORLD

Fig.with cotton in order to take the strain offthe wire connections. Winding cannow proceed, care being taken to windevenly and not to damage the insulationof the wire as it is guided through thefingers. It will be found easiest to windover the bobbin, i.e., turn the trans-former bobbin clockwise, feeding thewire through finger and thumb, the reelof wire being mounted on a spindle andfree to turn, not too easily, betweenyourself and the transformer bobbin.

The completed

When the end of the -layer is reached. commence another layer winding from

right to left and so on, always windingin the same direction until the 6 ozs. ofwire are used up. The last turn shouldbe tied off with cotton and the end, in-sulated with rubber tube, should bebrought through the wood cheek andsecured to a terminal.

The two terminals should now bemarked S. Before winding the prim-ary wire on, wrap a few turns of waxedpaper, not more than three, round thesecondary. This will serve as insula-tion and also to give a fresh even sur-

MARCH, 1920

I.face upon which to commence windingagain. Proceed to wind as in the caseof the secondary, taking every precautionto protect the insulation of the wire dur-ing the proCess, as with these fine wiresthe insulation is easily rubbed off. Fastenthe two ends of the wires to the remain-ing two terminals and mark them P.

The transformer now being complete,heat up some paraffin wax until it is justliquid. Immerse the transformer in itand leave it for half an hour, keeping the

Tranformer

wax just liquid. If the transformer istaken out at the end of this period andleft to drain, all the superfluous wax willdrain out, although the windings willretain sufficient to protect the insulationfrom damp. To finish the transformeroff neatly, wrap several layers of waxedpaper round the primary and wrap onelayer of bookbinder's cloth over all tocomplete. The resistance of the windingsshould be approximately :-Primary,4,500w; secondary, 60w. The primaryshould be connected in the crystal cir-cuit of the receiver, and the secondaryconnected direct to the telephones.

700

JII IIIiIII!IIII II VIII Till 111 111111 l!I II IIIIIII!II IIII II 1111111 II IIII II III I II III I I II VIII IIIIIIIIIIIL

Notes on the Design and Construc--=-= tion of Valve Amplifiers

By JOHN SCOTT-TAGGART.

IV.-RESISTANCETHE third general class of

amplifiers embraces thosein which the coupling be-tween successive valves isobtained by means of non -

inductive resistances. This class ofreceiver has been previously describedby the Author*, but some additionalremarks here will not be out of place.

A simple two -valve circuit employ-ing a resistance coupling is shown inFig. 15. Incoming oscillations varythe potential of the grid G, whose

J . Scott -Taggart. " The use of ImpedanceCapacity and Resistance Couplings in High -Frequency Amplifiers," WIRELESS WORLD,February, 1919

2

Fig. 55.

AMPLIFIERS.

normal value is made slightly negativeby means of the potentiometer B3.This will help to ensure that the firstvacuum tube will act purely 'as anamplifier of the oscillations. A resis-tance R3, which should be devoid ofcapacity or inductance is connected inthe plate -circuit of the first tube.This resistance should be of the orderof about 8o,000 ohms when valves ofthe French or " R " type are used.The resistance R3 is usually made moreor less equal to the resistance of thevalve across filament and plate. Theresistance may be made by using suit-able high resistance material, makingconnection to a strip of paper over

GI,

R1

R

Bi

B2

Two -valve Resistance Amplifier.

701


which a pencil has been rubbed, or byother suitable means. Such resist-ances, however, do not usually give asgood results as the commercial article.

An electron current will normallyflow from the filament F1 to the plateP1, through R3 via the plate batteryH, back to the filament F1 which isheated through a rheostat R1 by pre-ferably a six -volt accumulator B1

which also heats the filament of thesecond vacuum tube.

Since an electron current is flowingthrough R3 from Z to Y, it will bedear that Z will b.t negative with res-pect to Y. Since the resistance R,is high, there will be a considerablevoltage drop across it. Consequently,we need a higher voltage plate batteryH than in ordinary valve circuits.From 8o volts to 150 volts is suitable.

To explain the action of the resist-ance amplifier, let us consider thatwith a plate battery H of too volts, thecurrent in the P, plate circuit is 0.5milliampere. The resistance of theplate circuit is consequently 100divided by 0.0005 which equals 200,000ohms. Since R, is 8o,000 ohms, theresistance of the valve under these con-ditions will be 120,000 ohms.

Since a current of 0.5 milliampere isflowing through R3 the potential acrossR, is 0.00005 x 80,000=40 volts andthis acts in such a way that Z is nega-tive. The potential of P1 will ob-viously be + 6o volts. Thus we seethat while Z is - 40 volts with respectto Y yet the opposing and greaterpotential of H makes the potential ofZ - 40 + 100 or + 6o volts with res-pect to the filaments.

Now let us imagine that a halfoscillation has made G1 positive withrespect to F1. The current throughR3 increases. Consequently the po-tential across R3 increases and Zbecomes still more negative with res-

pect to Y and this potential of Z withrespect to the filaments may fall from+ 40 volts to say, +39 volts. Thepotential of Z and also P1 has thusbecome relatively negative to theextent of I volt.

In the circuit shown, we communi-cate these voltage changes across theplate circuit of the first valve to thegrid G2 of the second. This may bedone by connecting a small condenserC2 of about .00005 mfd. between Zand G2. If Z were connected directlyto G2 the potential of G2 would nor-mally be +40 volts, a most unsuitablevalue. By using C2, however, thepotential of G2 is in the neigh-bourhood of zero volts. The conden-ser C2, however, will allow of pulsat-ing or alternating E.M.F.s to passthrough it. Consequently when thepotential of Z suddenly changes from+ 40 to + 39 volts, the grid G. ac-quires a momentary potential of -volt which will decrease the plate cur-rent of the second valve. A negativehalf cycle applied to G1 would decreasethe plate current of the first valve andso increase the resistance of the valve.The current through R3 will decreaseand so the potential across it. Thepotential of Z with respect to F willnow be, say, - 39 volts instead of - 40.The potential of Z with respect to thefilaments will he- 39+ 100= +61 volts.The potential of Z has thus becomepositive with respect to F2. Thismomentary increase will make G2positive with respect to F2 and theplate current of the second valve willtend to increase.

In this manner oscillations may bepassed on from valve to valve, eachvalve increasing the amplification.The last valve (the second in this case)may be made to act as a detector, andtelephones included in its plate circuit.In the circuit under consideration a

702

CONSTRUCTION OF VALVE AMPLIFIERShigh resistance R, of about 5 millionohms (megohms) is converted as shown.This leak prevents the accumulation of anegative charge on G2.

Fig. 16 shows a four valve receiver.The first three valves are intended tooperate as amplifiers of the oscillationsand consequently it is preferable togive their grids a slightly negativepotential. This has been accomplishedby inserting a resistance R as shown.This resistance may have a value ofabout I to 1.5 ohms and ensures thatall the three first grids will have anegative potential. This potential, itwill be noted, acts through the 5 meg-ohm grid leaks since the grid currentis negligible and consequently there isno voltage drop across these resistances.The last valve acts as a detector andmight, if desired, have a separate fila-ment rheostat.

Increased amplification is obtainableon these circuits by employing retro-action. It has been stated that when

grid is momentarily positive,the first plate becomes relatively nega-tive, the second grid negative, thesecond plate positive, and so on. Ifnow we connect a very small conden-ser between the first grid and one ofthe subsequent plates which possessesthe same potential sign at the same

e

I

moment retroactive amplification willtake place. This condenser is prefer-ably variable and should have acapacity of about 0.00005 mfd.

Retroaction may be obtained bymaking connections between any twopoints which have the same potentialsign. Thus, the condenser might beconnected across the grid of thesecond vacuum tube and the plate ofthe third or fifth tube. It is usuallypreferable to obtain the desired retro-action by making the coupling betweentwo plates of similar sign, such as theist and 3rd, 1st and 5th, 2nd and 4th,and so on.

If the degree of retroaction be suffi-ciently increased, the circuits willoscillate of their own accord at a fre-quency which may be varied by adjust-ing the aerial condenser. The ampli-fier may then be used as a continuous-wave receiver.

In place of a coupling condenser,a high resistance of about to megohmshas been suggested, but the retroactionis not then conveniently variable.

An important advantage of resistanceamplifiers over iron -core amplifiers, isthat they are quieter in action. Thisis due to the fact that the small gridcondensers offer a high resistance tothe low -frequency variations and

I

Fig. 16. Four -valve Resistance Amplifier.

703

MIN

THE WIRELESS WORLD

Fig. 17. Impedance Amplifier.

irregularities of plate curent whichusually produce the noises. On theother hand, they readily allow high -frequency potentials to be transmittedthrough them.

Resistance amplifiers :_re most effi-cient on wave -lengths lower than 600metres. This is because there is al-ways a certain unavoidable capacityacting in shunt to the plate circuitresistances. High -frequency currentwill prefer to pass across this capacitythan through the resistance. Theeffective impedance offered by the platecircuit resistance is decreased and thedegree to which it is decreased willdepend on the capacity and on thefrequency of incoming signals. Thegreater the frequency the less will bethe resistance of the capacity and theless the total impedance. Conse-quently, resistance amplifiers are notusually very efficient on short wave-lengths.

In place of non -inductive resist -

MARCH, 1920

ances, impedance coils have been used.Coils made by winding about 400 yds.of fine wire on an iron core may be"used in place of the resistances. Theseamplifiers are more suitable for lowwave -lengths since the impedance ofsuch iron core coils increases with thefrequency. The efficiency of such anamplifier would, however, vary accord-ing to the wave -length since the im-pedance depends on the frequency andthe efficiency on the impedance. Fig.17 shows such an impedance amplifier.

Since the Authorities have now madea preliminary announcement with re-gard to amateur licences we hope veryshortly to give practical dimensions anddetails of some valve receiving circuits.

. We would particularly draw the atten-tion of the amateur to the fact that it isnecessary to obtain special permissionfrom the Postmaster -General before in-stalling or using any receiving circuitsinvolving the use of three -electrodevalves.

TO APPEAR SHORTLY.A valuable article on A.C. work in connection with TriodeCircuits, by Mr. R. C. CLINKER, of the Wireless Society ofLondon.

704

The Amateur's Guide to the AetherWEATHER REPORTS FROM THE AIR MINISTRY.

'17111111111111111111111111111111111111111111111.11111111IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII1111111111

AMETEOROLOGICALprogramme is circulatedthree times daily (at 8.15a.m., 9.15 a.m., and8.15 p.m., all G.M.T.).

by the Air Ministry Wireless Station(GFA) situated at the top ofIndia House, in Kingsway, Lon-don. It is transmitted by the C.W. systemon a wavelength of 1,400 metres. Weare now able to publish particulars of thespecial code used for this programme, toenable those of our readers who may wishto intercept it, to transcribe the messagesreceived. The programme consists of aprécis of meteorological reports receivedby the Air Ministry. Station from all partsof the country.

We had the pleasure recently of visit-ing the station referred to above andshown in the illustration. It is the maincontrol station of the Air Ministry and isused chiefly for the collection and dis-semination of aviation meteorological re-ports and for controlling the British aerialservice, both R.A.F. and commercial.

The installation includes two con-tinuous wave transmitters, one of whiCh,possessing a useful wireless range of 400miles, is employed for transmitting allmessages to places in the British Isles;and the other, of higher power, with auseful range of approximately 1,500miles, is employed for communicationwith Paris, Brussels, Norway and Hol-land and many other places.

The observations which are trans-mitted at the times mentioned above, aremade at 10 a.m., 7.0 a.m., and 6.0p.m. (G.M.T.) respectively.

The message is arranged in two parts,

the first part consisting of weather infor-mation from the following stations :-

101 Lejwick195 Stornoway199 Blacksod Point182 Malin Head192 Valentia166 Scilly

150 Dungeness174 Holyhead162 Portland110 Aberdeen118 Tynemouth136 Yarmouth

The identification number of eachStation is followed by two groups of fivefigures which are arranged thus : -BBBDD FwBbb, and have the followingsignificance :-BBBBarometer in ulillibars and tenths.

The initial 9 or 'to is omitted.DD-Direction of wind in points (o2-NNE

i6-S, etc.).F-Force of wind on Beaufort Scale.

(See Code I.) not m.p.h.w-Present weather in international code.

(See Code IL).B-Charactenistic of barometric tendency

(See Code III.).bb-Amount of barometric tendency during

the previous 3 hours. (50 added forfall).

The first and second parts of the mes-sage are divided by one group of fourX's.

The second part of the message con-sists of upper wind information from asmany as possible of the following sta-tions :-Scotland, N., 107, Houton Bay.Scotland, N.E., 109, Longside or 113, Fife-

ness.Scotland E., 115, East Fortune, or 117, St.

Abbs Head, or 119, Cramlington.England, N.E., 123, Flamborough Head, or

125, Howden, or 131, Cranwell.England, E., 135 Yarmouth or 137 Pulham, or

141 Orfordness, or 143 Felixstowe.England, S.E., 147, Grain, or 149, Capel, or

151, Polegate.

705


Midland Counties, 173, Turnhill, or 139, Bed-ford.

Southern Counties, 133, Calshot, or 133,Stonehenge.

Channel, 161, Portland, or 163, Plymouth.England, S.W. 163, Mullion.S. Wales, 169 Pembroke.England, N.W. & N. Wales, 173, Anglesey,

or 177, Barrow.Scotland, S.W., 179, Luce Bay, or 181, In-

chinnan.Ireland, N., 183, Malin Head.Ireland, E., 184, Baldonnel.Ireland, S.W., 191, Beerhaven, or 192, Valen-

cia, or 189, Queenstown.

The identification number of eachStation is followed by two groups of five

Photo.

figures arranged thus HDDVV and willhave the following significance :-

H-Height.DD-Wind direction in point (o2-NNE 16-

S., etc.).VV-Wind speed in miles per hour.

The first of these groups gives thewind direction and speed at either one ortwo thousand feet, the height being in-dicated by the first figure of the group.

The second group gives the winddirection and speed at a height betweenthree and ten thousand feet, the heightbeing indicated by the first figure of thegroup. Ten thousand feet is indicatedby the figure 0.

Some of the apparatus at the Air Ministry Wireless Station.

706

Photo Press.

AMATEUR'S GUIDE TO THE AETHERCODE L CODE II.

Beaufort Miles per Metres per o-Blue Sky.Number, hour. second. 1-Sky cloudy.

o Less than Less then o.31- 3 0.3- 1.5 2-Sky cloudy.

2 4- 7 1.6- 3.3 3-Sky cloudy.3 8-12 3.4- 5.4 4-Sky completely, overcast.4 13-18 5.5- 7.95 19-24 8.o-xo.7 5-Rain falling.6 25-31 I0.8-13.8 6-Snow falling.78

32-3839-46

13.9-17.117.2-20.7 7-Mist

9 47-54 20.8-24.4 8-Fog.Wind Force above 9 is sent as 9. 9-Thunder.

o-Steady.1-Unsteady.2- Rising.3-Failing.4-Falling, then rising.5Steady, then rising.

CODE III.

6-Steady, then falling.7-Falling, now steady8-Rising, now steady or falling.9-Storm indications; sudden rise with

marked change of wind and weather.

THE NEW VOLUME.THE eighth volume of THEWIRELESS WORLD, whichcommences in April, willbear in its general appear-ance and within its pages

many signs that the prevailing spirit ofreconstruction has not passed unheededover the pioneer wireless magazine ofthe British Empire.

The most far-reaching improvementwhich will be effected is that themagazine will appear fortnightly in-stead' of monthly, a change which, weare convinced, will meet with the unani-mous approval of our readers. By thismeans we shall eliminate to a large ex-tent the disabilities under which a

monthly publication labours.In its new form the WIRELESS

WORLD will contain 36 literary pagesand will be issued at sixpence per copy.

The policy of the magazine remainsunaltered in its general aims, though itsscope will be extended in certain direc-tions. First, about policy. The lattercan be defined in two words,-instruc-tion and information As regards the

first, special features will be introduced.For beginners in the study of radiowork there will be a complete article inevery issue, giving instruction in theprinciples underlying radio -communica-tion and the apparatus by which this iseffected. Although each article will becomplete in itself, its position in the serieswill be carefully arranged beforehandand with a view to rendering thestudent's conceptions orderly and co-herent. Another regular feature will bea series of complete articles by Mr. PhilipR. Coursey, B.Sc., A.M.I.E.E., dealingwith various radio topics and written in amanner similar to that known as the" popular lecture style," so that theymay be made the bases of popular lec-tures, the demand for which is increas-ing every month.

For more advanced students we shallcontinue to publish technical articles byexperts in various branches of radiowork. Most of these articles will bespecially commissioned-a procedurewhich will ensure that the magazinewill keep abreast of the march of pro-gress. The Digest of Radio Literature,

707


always a popular feature, will be mademore useful than ever by an increase inthe number of articles covered in eachissue, whilst the Book Reviews will, asbefore, deal promptly with all new booksrelating to wireless or allied subjects.

Our Questions and Answers Section,always full to overflowing, will be en-larged and made of greater interest toall readers by the inclusion of the ques-tions to which the answers refer.

The important position which theamateur wireless community has at-tained, and the increasing number andactivity of the Wireless Clubs point tothe need for an Amateur 'Wirelessmagazine especially devoted to the in-struction of novices and to the needs ofprivate experimenters and clubs in re-spect to the construction of apparatusand the design of installations. Thesefunctions will be exercised by theWIRELESS WORLD, which has alwaysendeavoured to forward the aims andinterests of amateurs. As the officialorgan of that influential body, the Wire-less Society of London, we shall publishverbatim reports of its proceedings,

which means that many important andoriginal papers will appear in our pages,together with discussions of the sameby front -rank radio workers. A gene-rous amount of space will be allotted toreports and notices of all the otherWireless Clubs, including those of othercountries.

An entirely new feature of themagazine will be the inauguration of anExchange and Mart Section, the advan-tages of which scarcely require descrip-tion.

Finally, our policy is to give our read-ers the fullest possible information aboutthe world of wireless, its personalities,its progress all over the world, its com-mercial aspects and the general trend ofthought, research and development. Itis impossible to overlook the importanceof wireless as used in conjunction withaviation, and we have, therefore, ar-ranged to publish regularly every sixweeks an article dealing with the pro-gress of commercial aircraft wireless, sothat the completed volume will contain arecord of the year's development of thisphase of the art.

COMPETITION FOR COMMERCIAL WIRELESS OPERATORSNames of Prize Winners

The competition which started in our Sep-tember issue was an attempt to stimulate thepowers of observation of Wireless Tele-graphists, and, at the same time, to gatherdata which might prove useful in the resolu-tion of .che various outstanding problems of

ther-wave phenomena. We hoped that thegenerous prizes offered and the manifold oppor-tunities for observation enjoyed by operatorswould result in a large number of entries, butthe number of competitors was not large. Per-haps the chief reasons for this are that manysea -going operators in distant parts of theworld failed to learn about the competition andmany others, on large passenger ships, weretoo busy about their wireless duties to be ableto make regular observations. Not oneattempt has been received from shore opera-tors. The names of the prize -winners are asfollow :

1st prize, Twelve Guineas, MT. J. Wil-liamson, 114, Duke Street, Leith.

2nd prize, Six Guineas, Mr. J. Cunning-ham, 35, Liverpool Street, Wal-worth, S.E.17.

Consolation prize of Books, Mr. E. A.Payne, " Hill Crest," HonywoodRoad, Colchester.

Consolation prize of Books, Mr. C. H.Beckway, 44, Blandford Road,Beckenham, Kent.

The other two consolation prizes have notbeen awarded because in no other instanceswere the papers submitted considered to con-tribute anything useful to the present stock ofknowledge.

708

Notes of the Month-,-51111111111111111111111111111111111111111111111111111111111111111111111111111i11111111111111111111111rF:

FRENCH NAVAL COASTALWIRELESS STATIONS.

AN Admiralty Notice toMariners (92 of 1920)states that the FrenchNaval coastal wireless Sta-tions established in France

and Algeria are no longer to be used forcommercial services; only the Stationsunder the administration of the Post,Telegraphs and Telephones will beused for this purpose; these Stations areas follows-

Boulogne-Ostrohove.Havre-Bleville.Ouessant (Ushant).Bordeaux-Le Bousoat.Marseilles-Jetee.Cros de Cagnes (Nice).Bonifacio.Port de l'Eau.The Direction -finding Station Barre

de l'Adour (Bayonne) can, however, beused for local commercial services byvessels bound to or from Bayonne.

The French Naval direction -findingStations will remain at the disposal ofmerchant vessels of all nationalities; thisservice will not incur any charge.

In Tunis, Morocco, and the Frenchcolonies the Naval wireless Stations willcontinue to be available for commercialservices. In Tunis, however, merchantvessels should for preference use CapeBon Station; Sidi Abdullah Station willonly intervene in case of difficulty incommunicating with Cape Bon Station.

The Naval Stations can still be utilisedby the Allied warships desiring to com-municate with the French Naval Autho-rities; they will follow the Inter -Alliedprocedure in force.

THE STEADY MARCH OFWIRELESS.

A wireless telephone equipment is

being installed by the Public ServiceCompany of Northern Illinois at its BlueIsland and Joliet Stations, which Stationsare 25 miles apart. The telephones willhave a range of about 100 miles, andwill safeguard communication in theevent of the wire lines being for any rea-son put out of commission.

We understand that a wireless tele-phone system throughout the northernterritory of Manitoba, to bring it intotouch with the cities of the West, isrecommended by the Commissioner.

Direction -finding Stations are to beemployed by the Marconi Company onan airway route for the purpose ofdemonstrating the use of wireless tele-phony in aerial navigation. Successfulexperiments in wireless telephony havealso been carried out by that Companybetween Chelmsford and a station 20Miles east of Amsterdam, with portablesets that can be carried on mules.

A demand for telephonic communi-cation in British Columbia has arisen asa result of recent gold discoveries in theYukon, and a Yukon member of theOverseas Club has asked the OverseasTrade Bureau to put him in touch witha firm which can supply wireless tele-phone sets capable of connecting Daw-son with a camp 200 miles away.

From Pittsburg comes the interestingnews that 400 owners of wireless tele-phones in that part of the United Statesenjoy concerts nightly by means of theirinstruments.

According to the Liverpool Courierof December 31st last, the U.S.Government is being asked by the

709


Admiralty for a report on a new phaseof wireless telephony, which it is claimedwill make it possible to focus radio mes-sages sent out, as well as to attract andcompel them to travel in close vicinityto the attracting wire. It is stated thatMajor -General George 0. Squier, ChiefSignal Officer of the United StatesArmy, has perfected a system permittingten or more telephone conversations tobe transmitted simultaneously.

A proposal has been mooted to erecta wireless station on the coast of BritishColumbia, having a range of 6,000 miles,which would establish direct wirelesscommunication with the Orient.

With the gradual return of normalconditions, many fresh wireless "links"are being forged. In the near future,the following services, amongst others,will be opened :

United States-Gt. Britain (ter-minal stations at Belmar, New Jersey,and Carnarvon, Wales).

United States-France (terminal sta-tions at Tuckerton, New Jersey, and,probably, Bordeaux).

United States-Scandinavia (terminalstations at Marion, New Jersey, andStavanger, Norway).

A direct wireless service betweenNorth and South America is also underconsideration.

It is announced from Rotterdam thatMessrs. L. Smit & Co.'s wireless stationat Maassluis has been re -opened.

The Uruguayan Legislative Cham-bers have been recommended by theUruguayan Council of Administration toauthorise the Department of WirelessTelegraphy to contract for a loan of$200,000 (Uruguayan gold) to enableimprovements and extensions to beeffected in the wireless services.

According to the Electrician, it isannounced that the Italian Government,having found the wireless service be-tween Carnarvon and Rome moreefficient than others, has instructed its

delegation in Paris to adopt the Carnar-von-Rome route for all its importantmessages.

GALE WARNINGS BYWIRELESS.

The Admiralty has decided to institutea wireless service of gale warnings forships at sea. The warning will be issuedby various British coast stations whenthe strength of the wind is expected toreach or exceed 40 miles per hour, andwill probably take the following form :(example): Gale probable from S.W.and W., Irish Sea and Bristol Channel."

WIRELESS DIRECTION -FINDING.

An extremely interesting and instruc-tive paper on Radio Direction and Posi-tion Finding, was read' by Capt. H. J.Round before a meeting of the Institu-tion of Electrical Engineers held at theInstitution of Civil Engineers, on Jan.14th. Captain Round dwelt on thehistory and the improvement during theWar of Direction -Finding by Wireless.

* *

BRITISH SHIPMASTERS'DINNER.

A dinner open to all British Ship-masters throughout the Kingdom will begiven at 'the Adelphi Hotel, Liverpool,on Wednesday, March 3rd. Tickets,41 Is. Od. each. Obtainable fromCaptain P. 0. Griffiths, Superintendent,Mercantile Marine Office, CanningPlace, Liverpool. It is hoped that asmany Shipmasters as possible willattend.CATALOGUE OF WIRELESS

APPARATUS.We have received an attractive cata-

logue of standard condensers and wire-less apparatus manufactured by H. W.Sullivan, Winchester House, London.An illustration of each instrument is

given, with its price and particulars ofspecial features.

710

al11111111111111111111111111111111111111111111111111111111111111111111111111111111111111i111111111111L

The Proceedingsof the Wireless Society of London T--=

==_-- Ordinary General Meeting held in the Lecture Hall of the Institutionof Civil Engineers on Thursday January 291h 1920. The President,

Campbell Swinton, in the Chair.

The SECRETARY having read the Minutes of the last meeting, and these havingbeen passed and signed as correct, the PRESIDENT called on Mr. R. C. Clinker todeliver his lecture. This was followed by a discussion and a vote of thanks to thelecturer.

The CHAIRMAN (Mr. F. Hope -Jones), withregard to the scheme for the affiliation of theprovincial and suburban clubs to the WirelessSociety of London, then said :-

Mr. President and Gentlemen,-We sent outour invitation to fifteen wireless societies-allthat we could hear of-early this month. Ofthose, I think I can say there have been norefusals of our proposals, but from three wehave received no reply. I think the reasonmust be attributed to the fact that they haveprobably not resumed their activities yet. Fivehave definitely accepted our proposals, and theremainder have asked for more precise in-formation of what we suggest.

The Committee having gone very carefullyinto the whole question of affiliation, havemade certain definite proposals which are nowbeing formulated to all. In the first place,the idea is that all members of every affiliatedsociety shall have a general invitation to ourmonthly meetings, providing themselves, ofcourse, with a note of identification fromtheir secretaries. That will mean, 1 hope,that members of various provincial societieswhen -they happen to be in town at the dateof our meeting, will be in our audience. Thcothe affiliation of the society carries -with it theoffer of a membership to one of the officialsof that society ; whether the Secretary, orChairman, or President, it is for them to say.They will make the election themselves, natu-rally. That member of each society will be-come a member of the Wireless Society ofLondon. The intention is that we haveready for the disposal of each of the affiliatedsocieties reprints of all the papers that areread before us here in London. It is intendedto give a dozen copies of each, and if noticeis given of any further number required theywill be provided at the cost of -printing andpaper.

The proposals generally have been wel-comed, and not least the suggestion that thesocieties shall add to their titles, "Affiliated to

the Wireless Society of London." The great-est advantage that I think the whole schemehas to offer is a conference ; it is proposedto hold one every year, making a beginningnext month here in London. It is as-sumed that we shall not travel from town totown like the British Association, but thatour conferences, for the present, at any rate,shall always be held in London ; and it is sug-gested that the coming month is proper, be-cause at the end of next month we are over-due with our Presidential address-which willbe the subject of our next general meeting-and I am sure you will agree with me therewill be a very fitting opportunity to invitemembers or delegates from various provincialsocieties to join us on that occasion. Thedate has been fixed for Friday, 27th February,when the President will give us his addressat the Society of Arts, for a reason which hewill explain to you. It is hoped that theconference will be called for the same after-noon, probably in the same building. Theidea is that the invitation to the conferenceis absolutely general to any member of anaffiliated provincial society who happens tobe in London. I have no doubt many socie-ties will actually appoint delegates to attendit.

I need hardly say we are alive to the desir-ability of having the very latest informationfrom the "powers that be" with regard tolegislation, and perhaps with regard to slacken-ing the rules a little bit ; but that must be leftto the Committee of the Wireless Society ofLondon, and cannot very well 'be discussed inpublic.

I ought to add that the fee for affiliationof each wireless society has been fixed at oneguinea, with an annual subscription of oneguinea. All those who have referred to ithave accepted it at once as a reasonable re-quest. I think that is all that need be saidon the subject of affiliation at the present time.You will understand I am only anticipating

711


by a post or two the official announcementthat will be communicated to each of- the-societies concerned.

The PRESIDENT : It only remains for me toannounce the fact that the next meeting willbe held on the 27th February, and that it isproposed to hold the meeting at eight o'clockbecause it is thought that is a more convenient'hour than six o'clock, the time at which themeeting must start if held in this building.It had been intended that the next meeting-should be in this building, but I thought thatprobably you would like to have some experi-ments shown you, especially the reception ofwireless signals from a distance without anyaerial-simply on a coil. Unfortunately this"building is very unsuitable for the purpose.It is entirely framed in iron girders, and ex-periment has shown that it is very difficult toget the signals an an inside aerial in this roomat all. If you are, going to show things ofthat kind to a large audience you want toget the signals fairly powerful ; but with athree -valve amplifier in this roam and a bigcoil we could not get anything at all. Outside,away from the girders, we got the signals at

once; but this room is very unsuitable. Weconsidered whether it was possible to applyte the institution of Mechanical Engineers,which is close here. That is an old building,and not built,. I think, in the way this oneis ; but unfortunately immediately at the backof it there is a very large building all framedin iron-just like this building-and I amafraid that we might there also have difficultyin getting strong signals. But the Societyof Arts building was built by the brothersAdam about 1740, before iron girders wereknown ; so I think we are fairly safe in goingthere. There is a trouble there-the alternat-ing current. Same roof experiments I havemade there show that it is not very conduciveto the desired result ; 'but I 4think we can getover that, and it is proposed the meeting shallbe held at the Society of Arts at eight o'clock.Among other -things I have got word fromGeneral Ferrie of the Eiffel Tower that hewill be pleased to do what he did befare in194-to send us a special message, which Ihope to make audible to you. The meetingis now adjourned until February 27th.

A PORTABLE SET, AND SOME PROPERTIES OF C.W. CIRCUITS.By R. C. CLINKER.

There are many members of this'Society who have had a good deal todo with valves during the last five or sixyears, and who, of course, know a great-deal about them. On the other hand, Ithink there are many members who havenot had the opportunity, and are nowbeginning to use them and to learn thevarious customs of the valve. I thoughtI would make this lecture rather elemen-tary,-at any rate to the first class, ifthey will excuse it,-because veryfamiliar things may be put in, perhaps,new ways, and discussion afterwards isalways very helpful.

I propose to do a little demonstrationwith this set andwill describe it first.(Figs. 1 and 2.) It was intended as acomplete unit primarily for obtainingtime signals from Paris, and it combinesall the apparatus in one case. It is rathera dreadful thing, from a wireless pointof view, to put a lot of metal in themiddle of a receiving coil, and it meansa certain amount of damping; but withthese two valves one can get quite good

signals from Paris. The cover is mademovable, and there is a central pivot sothat the whole set can be rotated to ob-tain the approximate direction of signals.There is a compass fitted in the cover,which enables the latter to be laid downin the right direction, and the desiredstation can be found by turning the boxround. This set will pick up suchspark stations as Paris, Nauen andPoldhu; the C.W. stations come outa good deal better. Fig. 3 is a diagramof the connections, and there is nothingunusual about them. The receiving coilis wound completely round the innerframe, and the valve on the left is thedetector. The main tuning condenseris shown on the left. There is also areaction coil, and a transformerwhich connects to the amplifyingvalve. The filament battery is shownon the right. This set will notpick up spark stations to any extent un-less it is oscillating. In other words,you do not get the true note, you get the"scratch"; but for time signals it is quite

712

M111311111E1

THE WIRELESS SOCIETY OF LONDON

Fig. i. Portable Receiver, showing pivot on detachable cover.

good. There is no difficulty in gettingParis even when there is a fair amountof disturbance. We have also picked upwireless telephone signals with it, and

12'

heard speech. There is a plug for put-ting the filaments in circuit which canbe seen to the right-hand side of thecentre where the socket for the amplifier

Fig. 2. Portable Receiver on pivot.

713


RECEIVING COIL

REACTION COIL

GRID LEAK

AAAAM

11-----.......-..-.

) olo + 1=

-r--... Mr

am

T.p

CONNECTIONS OF PORTABLE RECEIVER

Fig.

is. That plug has a long handle, so thatthe box cannot be closed while the fila-ments are alight. The whole box canbe readily carried.

I will deal first with the action ofwaves on a coil receiver such as is usedin this set. If we consider the wavescoming along to such a coil, we havethe electro-static wave vertically, andthe electro-magnetic wave horizontally.The wave sweeps along from the stationswe are receiving, and cuts first one sideof the coil and then the other, so thatan alternating electro-motive force is induced first in one side of the coil, andthen the other. I have a model here(Fig. 4) which represents the electro-magnetic wave advancing. The lowerpart (white) represents the wave,which can be moved horizontally inguides to represent it passing the receiv-ing loop. The two white vertical arrowswhich rest upon the wave model and are

3.

moved up and down by it as the waveis moved along, represent the e.m.f.'s. in-duced in the two sides of the receivingcoil or loop. These e.m.f.'s are equal andalmost opposed in phase, but not quite,and it is the " not quite " which allowsus to receive signals. In the illustrationthese arrows are shown close together,representing a narrow loop relative to thewavelength. The horizontal lines at thetop form a scale for indicating the magni-tude of the e.m.f.'s. The resultant e.m.f.in the loop is the algebraic difference be-tween the e.m.f.'s. induced in the twosides. Suppose the coil is one foot long,and the wave five thousand feet long, youget a difference of phase of 360 degreesdivided by 5,000, or only 0.072 of onedegree. It is a tribute to the sensitivenessof the valve that you can detect such anexceedingly small difference of phase.Of course, if you make your coil wideryou get a bigger difference of phase

714

THE WIRELESS SOCIETY OF LONDON

Fig. 4. Model showing action of waves on coil aerial.

between the two. This may be shownon the model by moving the right-handarrow into one of the other guides. If youspread out your coil to a half wavelengthyou get as a resultant the full electro-motive force which is induced in oneside of the coil.

An oscillating set like the one shown(Figs. 1 and 2) is exceedingly useful forgetting comparative measurements of in-ductances and capacity, and there is amethod, which we may call the " doubleclick method," which was referred to inthe discussion on Mr. Scott-Taggart'srecent paper, and also in the currentissue of the WIRELESS WORLD. It isan exceedingly good method of compar-ing inductances and capacities. I havea diagram here which I think fairly wellexplains itself. (Fig. 5.) Supposewe are receiving a station, or havean oscillating set which is giving acertain frequency, and also have anotherone which we can mistune to acertain extent and so produce a beatnote as shown on the diagram. I havemarked the diagram in percentages; forinstance a one per cent. increase of L x C

means that your frequency has decreasedroughly by one-half per cent., giving 500vibrations per second; the 1.2 per cent.corresponds to 600 per sec. That dia-gram is approximately right, and nearenough for the small changes marked atthe bottom.

Now if you put a coil, which wewill call A, in the neighbourhood of acircuit B, the effective inductance of B ismodified. I use the term "effective in-ductance " in doing this experiment toshow that B behaves as though its ac-tual inductance were changed. Wehave now one set giving a standard,

715

PITCH OF NOTEVIBRATIONS PER SEC.

700

600

500

400

300

200j. IOS PER SEC.

METRES

1.2 I 0 0.8 0.6 0-4 0-2 0 0-2 0-4 0-6 0$ 1-0 12DECREASE, or (L. % INCREASE or (L. xC)

Fig. 5.


steady frequency. (The valve circuitis really a most convenient thing, be-cause you can start it oscillating, and itwill keep up the same frequency to onepart in ten thousand until you want tochange it.) What I propose to do is totune this second set (coil B) exactlyto the bottom of the curve (Fig. 5.)I am now going to decrease C andbring the note up approximatelyto the top of the line; I will ask you toassume that the note is somewhereup on the left-hand side. In the firstplace, consider the effect of a short-cir-cuited coil in the neighbourhood. Wehave a certain magnetic flux from theoscillating coil B, cutting this other one,A; that produces a current which isa quarter of a period behind the electro-

- motive force. The consequence is thatthe currents in A and B are practicallyopposite in phase, with the result that theeffective inductance of B is diminishedbecause the flux passing through it is re-duced. When this coil is short-circuitedyou hear that the inductance is reducedas the note rises. This showsthat the current in the coil Ais circulating in opposition to the cur-rent in B. Supposing now we con-nect a condenser of not too large a capa-city to coil A, you will notice that thecurrent in that coil is exactly reversedfrom what it was before. The pitch ofthe note comes down. When we havea small capacity connected the currentflows in the same direction as the prim-ary current; when we short-circuit thecoil we have the currents in opposition;there is, therefore, a change of half aperiod between these two conditions.

There is a very good mechanicalanalogy in the reed frequency indicator.In the slide shown on the screen all thereeds are vibrating with the samefrequency. Assume that the one whichis in the middle is tuned to 85 cycles asecond. Reed No. 84, which is next, to

the left, is vibrating also 85 cycles to thesecond, lagging behind about 90 degreesin opposition. On the other hand, thereed to the right of the vibrating one,whose natural period is 86 cycles asecond, is forced to vibrate at 85, and intrying to vibrate faster it advances 90 de-grees and is a quarter of a period in ad-vance. Between 84 and 86 thereforeyou have a displacement of half a period.Suppose you look at the instrumentthrough a stroboscopic disc, you will seethe instantaneous position of all thesereeds. Fig. 6 is a view taken as itappears through a stroboscopic disc andyou will notice that Reed No.85 is in resonance at the moment.You are looking at it as it is movingthrough the centre position. ReedNo. 84 is displaced a quarter of a perioddownwards and 86 a quarter of a periodupwards. You can there see the full dis-placement as you pass through resonance.

FREQUENCY INDICATOR

J 75 80 85 90 95 I

10565

PERIODS PER SECONDN°790

Fig. 6. Frequency Meter, as seen throughstroboscope.

That is a very good analogy of the elec-trical circuit where, when you passthrough resonance, you get a completesweep round of the phase from 90 de-grees lag to 90 degrees in advance.

This coil A has about eleven milli -henries inductance. I start with the con -

716

THE WIRELESS SOCIETY OF LONDONdenser at zero. At present there is nocapacity and no oscillating current in A.As I increase the capacity I begin to get acurrent, which is leading and in phasewith the primary. The result is it isincreasing the inductance of coil B andthe pitch gradually comes down the line(of Fig. 5) to a certain point. As weapproach the tuned position, at a certainpoint we get instability, and then thephase of the current changes right over.The current is now lagging, the note goesup beyond the top of the line, and as youincrease the lagging current it comesdown to where it was at the start. If youdecrease the capacity the jump occurs ata slightly different point. That is whathappens when we tune a separate circuitto an oscillating valve circuit, and it isthat which is the basis of this method ofcomparing inductances and capacities.We can move away the coil A so thatthe points at which these quick changesoccur come very close together, andbetween these points you are in exacttune with your valve circuit. Supposewe want to measure an inductance orcompare it with coil A, we take ourstandard inductance A, connect it witha condenser, and then couple it so looselyto an oscillating valve circuit thatthe two clicks come together. Re-peating this experiment with theunknown inductance we can calcu-late its value by the reading on the con-denser. It is a very convenient method,and gives very accurate results.Fig. 7 shows how the current changes

ti

A

B

4- D

CAPACrTY IN COUPLED CIRCUIT

Fig. 7.

in the circuit. The readings weretaken in a coupled circuit, andthe Fig. shows the current in thecoupled circuit as the condenser is in-creased from zero upwards. Startingwith point A the capacity is very small,and the current is leading by 90 degrees;in other words, it is exactly in phase withthe current in the primary. Startingwith point A we go up the curve alwayswith a leading current; when we get toB the circuit is very nearly in tune. Thisis a point of instability and the currentdrops down to C on another curve. Stillincreasing the capacity it goes on towardsD. When we come back, we come upthe lower curve, which is a curve indi-cating another frequency, on to point Eand back to A. There are thus two fre-quencies present; those frequencies existnot together, but separately, but theirvalues are the same as obtained with twodamped circuits such as in a sparktransmitter. In the spark circuit the twofrequencies occur simultaneously, where-as with the C W. circuit they occur

METALPLATE

P

RELAY

=NB

BATTERY

MILLI -AMMETER

GLOWLAMP

Fig. 8.

separately; but their values are the same,and depend on the inductance, capacityand coupling of the two circuits.

I have one other experiment I thinkperhaps will be of interest; it concernsthe leakage off the grid of a valve. Thearrangement is indicated in Fig. 8, thegrid of the valve being insulated. Theinstrument A shows the plate current ofthe valve. The grid is insulated, but

717


is connected to the variable condenser C,which is joined between the grid and thenegative terminal of the filament. Itis rather interesting to notice that in avalve with the grid insulated the elec-tron discharge from the filament hits thegrid so that it becomes electricallycharged. Supposing the condenser Cis put to its full capacity it thenbecomes charged up by the elec-trons. If we make a sudden reductionin capacity the negative voltage of thegi id is increased, and the plate currentis stopped. I have connected a relay Rand a little lamp which lights up whenthe plate current is flowing. When wedischarge the grid with the finger theplate current starts again. It is curiousto see the effect of radium. Radiumrenders the air conducting in its neigh.bourhood, and will therefore dischargean electrically charged body whenbrought near the latter. It will be notedthat uninfluenced by the radium thecharge on the grid takes about 5 secondsto leak away before the plate currentflows again and the indicating lamp lightsup. On approaching the radium to themetal plate P, the charge takes only onesecond to leak away. I do not knowwhether I have made the experimentquite clear. Assuming that the capacityof the condenser is decreased about 70times from maximum to zero, thenegative potential of the grid will beincreased 70 times. Hence, if the originalvoltage of the grid is minus 1 volt, itwill fall to minus 70 volts. Thatis a very considerable potential so thatthe plate current goes right down tozero, and the charge takes some time toleak off. This forms a good way ofshowing that the grid naturally becomesnegative if it is insulated.

DISCUSSION.The PRESIPENT : I am sure we are very much

indebted to Mr. Clinker for coming and show-ing us these very beautiful experiments andthis very interesting apparatus. I dare say

that some members will like to ask somequestions and also to discuss the results hehas brought before us. The paper is nowopen for discussion.

Professor G. W. 0. Howl: Mr. President,I am sure we are all very much indebted toMr. Clinker for showing us these beautifulexperiments and also for explaining them insuch a clear and lucid manner. I was verypleased when Mr. Clinker, in opening his re-marks, said that he was going to explain themin an elementary manner, and I am sure thatwas a very wise thing on his part. I am afraidit is a common failing with people who readpapers to fancy that their audience knowsnearly as much about the subject as they dothemselves. They usually start too high abovethe heads of their audience, and the resultis that the majority of the audience spendtheir time in wondering what it is all about.

I am very interested in this compact, usefulset. I had the privilege of seeing the originalmodel, which was made, I think, by Mr.Clinker himself, and which he once broughtto my house and with which we picked upvarious Continental stations in my study. Iwas particularly struck then by the sensitive-ness of the apparatus, and the ingenious wayin which it was all fitted together into sucha small compass. We are having illustrationsevery day of the enormous change that hasbeen brought into wireless telegraphy by thethree -electrode valve. All this would have beenimpossible, of course, without that instrument.

I was very much interested in the fact thatMr. Clinker used a mechanical analogy to ex-plain leading and lagging currents in an oscil-latory circuit when its natural frequencychanged from a frequency above that of theforced oscillation to one below the fo-iTd oscil-lation. I was rather amused at th', becauseyou will find a paper of mine read some fouror five years ago before the Institution of Elec-trical Engineers on the amplitude and phaseof higher harmonics in oscillographs ; andthere, where you are dealing with oscillationsof a mechanical system, I think I make itclearer by an electrical analogy. So, while Iexplain the mechanical oscillations of the oscil-lograph by analogy with the electrical circuit,Mr. Clinker follows the other method andseeks to make electrical circuits plainer bymeans of a mechanical analogy.

I was interested in the final remark with re-gard to the method of the double click, whereMr. Clinker drew attention to the fact thatthese two frequencies are the same as you getin ordinary coupled spark circuits. In coupledspark circuits you get them, as he said, simul-taneously, with the result that you get beats ;whereas in the continuous wave case you eitherget the one oscillation or the other. When Iam teaching the subject of the beats in dampedoscillations I usually approach it in a waynot usually found in text books-I publishedthe method four or five years ago in the Ameri-

718

THE WIRELESS SOCIETY OF LONDONway you can prove the ordinary formulae forthe frequency of the oscillation, because themagnetic fluxes are added together in circuit(a) and you have increased the effective induct-ance from L to L M-because you haveequal currents in both circuits-and in thecase of circuit (b) you have decreased the effec-tive inductance of the circuit from L to L - M.That is exactly what is happening in Mr.Clinker's case. He has those two oscillatorycircuits ; in one case the magnetic fluxes areadded, in the other they are opposing, and youget the same two frequencies.

Mr. JOHN SCOTT-TAGGART : I have been verymuch interested in the lecture we have justheard, and especially in the description of anovel method of measuring the length of con-tinuous waves by the double click methodwhich, I believe, Mr. Clinker attributes, to L.W. Austin. Members, no doubt, are alreadyfamiliar with the ordinary type of oscillatingwavemeter, several types of which I devisedearly in 1917, and have described in the Wire-less World (Oct. and Dec., 1917), and theElectrician (Sept. 5, 1919). By combiningtwo such oscillating circuits, I devised shortlyafterwards a very sensitive capacity meterwhich I described in the Wireless Age(U.S.A.) of Dec., /918, and more fully in theElectrician of April /8, 1919. As Mr. Clinkerhas described how the double click arrange-ment may be used to determine capacity andinductance values, my device may also be ofinterest to members.

The meter utilises the beat phenomenon.(Fig. /o). A circuit B oscillates continuouslyat a frequency which may be altered by meansof a variable condenser C5; the circuit includesa pair of telephones ; another circuit A is ar-ranged which also oscillates continuously ata frequency determined by the capacity of thecondenser it is desired to test. This circuitsets up similar oscillations in the first circuit.There will, therefore, be two superimposed setsof oscillations in the first circuit ; beats will beproduced which when rectified will give a notein the telephones provided its frequency iswithin the audible limits. Now let a stand-ard condenser C, of known capacity be placed

(a)

(f)Fig. g.

can Electrical World. If you have twocoupled circuits (Fig. 9a) one a spark gapcircuit and the other a secondary circuit, then,if instead of assuming that you have a sparkgap in the primary circuit and discharge thecondenser across it, suppose you assume thatyou break both circuits for the time being,charge up both condensers equally and dis-charge them simultaneously. Then, if thesetwo circuits are tuned and have equal decre-ments (most of the treatment in the text -booksassumes they have no decrement at all) theywill oscillate together, and there will beno transfer of energy from one to the other ;each circuit will oscillate almost as if the etherwere not there. In point of fact, because thecurrent in one coil produces a magnetic flux inthe other, that flux will either be added to orsubtracted from the magnetic flux that wouldbe in that coil were the first one not there.Now' if you open the circuits again,charge the condensers in opposite directions(Fig. 9b) and then simultaneously closeboth circuits, the two circuits again willoscillate as before without any trans-fer of energy from one to the other; but herethe two currents are in opposition. In that

719


in the A circuit. The condenser C 2 is nowvaried until the silent point of 'the beat noteis obtained. A graduation is now made onC 2 corresponding to the capacity of C Bysubstituting various known capacities in placeof C the condenser C2 may be graduated insuitable units. To measure the capacity of agiven condenser it is only necessary to connectit in place of C tune C2 until the silent pointis obtained and then read off the capacity fromC2 The device may be used in very manyways which will occur to members of the So-ciety. It may also be used to compare induct-ances by a substitution method. The arrange-ment is exceedingly accurate, and will detectthe difference in the capacity of a condenserproduced by placing the hand within a fewfeet of the condenser whose capacity is beingmeasured.

Admiral Sir Henry B. JACKSON : Mr. Presi-dent and gentlemen, we have had a very use-ful discussion of how the experiments werearranged. Ic brings home very forcibly toone the little troubles that are sometimes ex-perienced through the position of the receiv-ing frames. I have had very similar experi-ences to others in experimenting with rathera big frame ac the Royal Naval College atGreenwich. There is a good deal of metalabout the building-a metal roof and 'a goodmany radiators. On the ground floor, withno radiators and very few pipes, I got verygood results ; but I moved the frame to thetop floor and got nothing. On the interme-diate floor I got certain results. For no par-ticular reason I moved the frame two or threefeet to get a bit of passage round it one day,and found I got very different results. Imoved the frame about in an area not muchbigger than this table, and in one place gotvery good signals and in another nothing what-ever. I traced the cause to the radiators andthe iron in the building. This experimentshows the reason of the failure.

I think the Lecturer explained very clearlythe difference of phase; I never heard it putquite so clearly as that. I should like himto state what wavelengths would suit his ap-paratus best; can he, judging from thephase difference, say if very short waves wouldgive the best results? Most of us, I think,find the long waves rather better on the framesthan the short ones.

Mr. Philip R. COURSEY : Mr. President andgentlemen, Mr. Clinker's demonstrations thisevening have been very interesting. I wasparticularly interested in his demonstration ofthe double click method, as I have used it onceor twice myself, but not very extensively. Thetrouble I found sometimes when trying to getvery accurate results was the space betweenthe two clicks. When the coupling is reducedsufficiently to bring the clicks really close to-gether, they become rather too faint to getsufficiently accurate results. Another methodthat has been used is to insert a measuring

instrument such as a thermal galvanometerinto the oscillating circuit itself-not merelyinto the plate circuit of the valve-and thusto measure the drop in current when the se-cond circuit is brought into resonance. Theeffect can be shown, I think, most convenientlywhen there is an intermediate coupling be-tween the oscillating valve, and what in thiscase is the secondary circuit-but in which inthe method I am now describing would becomethe third circuit. The intermediate couplingcan be made aperiodic, but should preferablybe tuned, and the thermal galvanometer in-serted in the intermediate circuit. When thelast circuit is coupled up there is a very sharpdrop in the intermediate circuit current, andthe coupling can be reduced until the drop ismade quite small, but still noticeable on thegalvanometer. I am rather inclined to thinkthat this method will frequedtly give moreaccurate results, and will eliminate any dis-crepancies that may arise from the two clicksnot being coincident.

Mr. L. A. T. BROADWOOD : Mr. Presidentand gentlemen, there is a method where insteadof using the telephone as an indicator youhave a galvanometer in the plate circuit. Thenyou merely tune until your galvanometer givesthe greatest reading. This gives the absolutetune position with considerable accuracy.When the two circuits are in phase you getthe highest reading. That method was adoptedin the Government heterodyne wavemeters to-wards the close of the war.

The PRESIDENT : If nobody else wishes tospeak I will call upon the author of the paperto reply to the discussion. I would like firstof all to say myself that I think we are verymuch indebted to him. I think it is a greatadvantage, if I may say so, in a society likethis, that we can have actual experiments.After all, this society is mainly an amateurbody, and I think experiments really appealto most amateuts more than the drier chsserta-tions that one has accompanied by nictures onthe blackboard, and lantern slides. Actual ex-periments are the most convincing kind of de-monstration that one can have, and are alsothe type of thing that will draw large audiencessuch as is present this evening. We are in-debted very much to Mr. Clinker for thetrouble he has taken in bringing the appara-tus here and demonstrating it in such a won-derful way. I would like only to emphasisewhat he himself said about the wonderful re-sults that it is possible now to obtain due tothe three -electrode valve which is really oneof the most marvellous discoveries in physicsof modern times, and enables us to take cog-nisance of the almost infinitely small so far aselectrical currents are concerned.

Mr. R. C. CLINKER : With regard to Profes-sor Howe's remarks, I was much interested inthe demonstration he showed on the black-board. (Fig. to.) That, of course, is thesame case as far as inductance and capacity

720

THE WIRELESS SOCIETY OF LONDONf the circuits are concerned, as the continuous

wave, except, as he says, that there the twofrequencies-where there are two-take placesimultaneously ; whereas here one can separatethem and get one or other at will. There arealways carious ways of explaining a thing ; ifyou read a book from a man mathematicallyinclined, he explains things in symbols. Iam interested in Professor Howe's explana-tions because he gives a pictorial representa-tion which I can understand. I was much in-terested in Mr. Scott -Taggares remarks ; I re-member reading his papers on measuring in-ductance and capacity. The fact is that inexperimenting with variable condensers I hap-pened to notice this click occurring, and itseemed to me an accurate way of measuringthose quantities. Very likely there are othermethods which would give, perhaps, as greataccuracy. On the other hand, in view of Mr.Coursey's remarks, I have generally found itpossible to get the clicks so close together thatin some cases the mere twisting of the spindleof the condenser is enough to throw it fromone to the other with a quite sharp click.Some valves gives a sharper click than others.if the click is not sharp enough I have foundthat closing up the coupling of the anode coilis enough to make the click quite sharp. Withregard to the remarks of Admiral Jackson, asto what wavelengths these sets were suitablefor, a coil like this has a great many turns offine wire and it is not possible to get muchbelow two thousand metres. The idea in mak-ing it was primarily to pick up Paris ; conse-

quently two thousand was the minimum wetried for. One of the sets shown goes up to7,7oo metres, whereas the other has a smallercondenser and only goes up to 4,50o metres. Ihave another which goes up to io,000 metres,and with that you can get other long -wave stations. There is just one othervery interesting effect one gets with valvecircuits which reminds me of the running inparallel of two alternators. If you coupletwo alternators to the same bus -bars theywill pull into step. You get very much thesame effect with two valve sets if you bringthem together. I can show you that.(Demonstrating). One of these sets is oscil-lating with a wavelength of about 4,000 metres.If we start the other and gradually bring thetwo circuits closer together, when we get to acertain coupling you will notice that the hetero-dyne note absolutely disappears ; the two cir-cuits pull into synchronism and oscillate to-gether. The action is to raise the frequencyof the one and to lower that of the othei,so that at a certain coupling they pull together.I do not Mink there was any other ques-tion to answer, and I thank you very muchfor your kind attention.

The PRESIDENT : I will ask you to pass avery hearty vote of thanks to Mr. Clinker fora most interesting paper and the beautiful ex-periments he has shown us. (Applause). Ihave to announce that the fourteen gentlemenwhose names have been circulated have allbeen elected members of the society.

WIRELESS CLUB NOTES.THE WIRELESS SOCIETY OF LONDON.

With reference to the affiliation sug-gestion made by this Society the follow-ing are the definite proposals now putforward :-

(1) That an affiliated Club should pay h'fis. od. per annum as subscription and LIIs. od. entrance fee.

(a) That such a Club should adopt as sub-title, "Affiliated with the Wireless Societyof London."

(3) That affiliated clubs should name eachyear, say, in January, one member (probablythe President or Hon. Sec.), who will be duringthe year a member of the Wireless Society ofLondon, and to whom all notices, etc., of theSociety will be sent.

(4) That each affiliated club shall receivetwelve free reprints of the Wireless Society'smonthly lectures and as many more as re-quired at cost price plus postage.

(5) That members of affiliated clubs be in-vited to attend meetings of the W.S. of L.when in London, a letter of introduction

being given from the Hon. Secretary of the'provincial or suburban club.

(6) That an annual conference or conven-tion be held in London, all members of pro-vincial or suburban clubs being invited.

Hon. Sec., Mr. H. L. McMichael,32, Quex Road, West Hampstead,N.W.

THE MANCHESTER WIRELESS CLUB.(Affiliated with the Wireless Society

of London.)A new buzzer circuit has been in-

stalled at the Club Rooms, 335, OxfordRoad, Manchester. There are 5 noteseach of different frequency and bymeans of switches jamming can be intro-duced on any of the 5 circuits. Thearrangement was designed and wired bytwo of the members.

721


The first lecture was given on Wed-nesday, January 21st, by Mr. C. V.Morris. "A talk on Wireless Receivers"was the subject, and great interest wasshown by the members, who tookpart in a discussion after the lecture.

A prize of two guineas and a valvehas been offered for the best paper on" Wireless Telephony." All membersare eligible to compete.

It has been decided to install an ex-perimental receiving set at the Club'sHeadquarters. Members have offeredto supply the necessary instruments.

New members will be welcomed andspecial interest is taken in the beginner.AU communications to be addressed tothe Hon. Secretary, Mr. J. C. A. Reid,16, Hawthorn Avenue, Monton, Eccles.

* * *

THE DERBY WIRELESS CLUB.

(Affiliated with the Wireless Society ofLondon).

The following programme of meet-ings and papers has been arranged. Allmeetings will be held at 7.30 p.m., inRoom 24, Technical College, Derby,unless otherwise notified.

Wednesday,. February 25.-To discuss theClub Station. Members are invited to con-tribute items of Apparatus.

Wednesday, March to.-Electrical Instru.ments and their Calibration. Mr. A. Doanleo.

Wednesday, March 24.-Wireless Telephony,with demonstration. Mr. E. S. Huson.

Wednesday, April 7.-Electrical Apparatusin the Submarine Service. Mr. R. Huson.

Wednesday, April 2h.-Loop Aerials. Mr.J. Lowe. Wavemeters. Mr. S. G. Taylor.

Wednesday, May 5.-Inductance and Capa-city. Mr. A. N. McInnes, B.A.

Wednesday, May t9.-Speech Amplification,with Experiments.

Wednesday, June 2.-Electric Clocks. Capt.W. Bemrose.

NOTICE.

Mr. S. G. Taylor has kindly agreedto act as Hon. Secretary and Treasurerduring the period February 15-April1, and it is requested that all correspond-

ence be addressed to him at St. Mary'sGate, Derby.

W. BEMROSE, Hon. Secretary andTreasurer, Littleover Hill, Derby.

* *

NORTH MIDDLESEX WIRELESS CLUB.(Affiliated with the Wireless Society of

London).The 31st meeting of the Club was

held at Shaftesbury Hall, Bowes Park,on January 28th, the President, Mr.A. G. Arthur, being in the Chair.

After the Secretary had read out aletter received from the Wireless Societyof London regarding affiliation, the Pre-sident said that a few words of apprecia-tion were due to Mr. Gartland for hiswork as head of the Working Commit-tee for erecting the aerial.

An attempt was made to receive sig-nals, but owing to the temporary natureof the wiring, and the instruments beingincomplete, little success resulted.

It is confidently anticipated that bythe time of the next meeting on the 11thFebruary a complete set of receiving in-struments loaned by the Secretary willbe available. Full particulars may beobtained from the Hon. Secretary, E. M.Savage, " Nithsdale " Eversley ParkRoad, Winchmore Hill, N.21.

* * *

THE BURTON WIRELESS CLUB.On Jan. 21st a lecture on " Capacity

and Condensers " was delivered by Mr.A. J. Selby, Mr. A. Chapman presiding.Mr. Smith, in the absence of the Secre-tary, stated that a letter had beenreceived from the Wireless Society ofLondon regarding affiliation. The ques-tion of the provision of buzzers forMorse practice was raised, and Mr.Wright offered to present the Club withone, while Mr. Batt volunteered to lendone. Mr. Chapman said that the arrange-ments for the installation of a horn,for use when time signals were beingreceived from Paris, would not be muchfurther delayed.

722

WIRELESS CLUB NOTES

A meeting of the Club washeld on Wednesday, February 4th,Mr. A. Chapman (Vice -President), pre-siding.

The Hon. Secretary (Mr. R. Rose)read a letter received from the Hon. Sec.of the Wireless Society of London, datedJan. 26th, regarding affiliation. TheClub decided at a previous meeting tobecome affiliated with the LondonSociety, and the Members were unani-mously in agreement with the proposalsset forth in Mr. McMichael's letter.

It was reported that the necessarysanction having been received, a ValveSet had now been installed at the ClubHeadquarters.

Mr. A. J. Selby explained in detailthe construction of an amateur wirelessset, giving a practical demonstration.

The members were instructed in theMorse Code, and concluded a very in-teresting evening with Buzzer practice.

The meeting held on Feb. 4th waswell attended. Six new members wereelected, making a total membership ofthirty-six. It was decided that the fol-lowing programme should be adopted :7.0 p.m. to 7.30 p.m., Buzzer practice;7.30 p.m. to 8.30 p.m. lecture (Techni-cal); 8.30 p.m. to 9.30 p.m., Buzzerpractice and discussion.

Hon. Sec., Mr. R. Rose, 214, Bel-vedere Road, Burton -on -Trent.

THE SOUTHPORT WIRELESS EXPERI-MENTAL SOCIETY.

(Affiliated with the Wireless Society ofLondon.)

The President (Mr. E. R. W. Field)invited the members and their friends toa Social at the Drill Hall, ManchesterRoad, on Jan. 27th. The guests, about60 in number, were received by thePresident and Mr. P. H. Christian.

The President, after welcoming theguests, gave an outline of the methodsin which the Society proposed to work.He pointed out that it had been formed

for the purpose of studying more deeplythe subject of wireless telegraphy. Itwas not an ordinary "tapping club," but,as the title denoted, a wireless experi-mental club. They were out for goodwork, and would assist the Governmentand police authorities in preventingillicit wireless telegraphy. The appara-tus they saw that evening was somewhich had been entirely constructedfrom odds and ends in the possession ofmembers of the club, and they com-pared very favourably with many ofthe manufactured articles.

Messrs. J. Wainwright (Formby),Diggle, Lomas, Henshaw, F. Stansfield,and Christian showed and described thevarious exhibits to the guests. Therewere about 80 exhibits of members'apparatus, including loading coils, loosecouplers, detectors, switches, differentmakes of telephones, a large assortmentof crystals used in the reception ofwireless telegrams and wave meters.

At the close of the exhibition, a con-cert was held, songs being contributedby Mrs. Lomas, Mr. Cooper, Mr.Christian, and Mr. Knock.

At the conclusion of the entertain-ment, Councillor Ball said he was highlygratified that such a society had beenformed in Southport. It showed therewas a desire by the younger of thepopulation to study science. He wouldfar rather encourage a number of peo-ple who were so engaged than he woulda multitude of people who were givenover to pursuits not of the same nature,and which were not so interesting andso helpful to the general public. Hementioned that he had been the hon..radiographer at the Infirmary 25 years,and in dealing with the X Rays hewas working at the other end of thespectrum. He wished the Society everysuccess.

Mr. Christian announced that Coun-cillor Ball had promised to give a lec-ture to the Society.

723


Hon. Sec. (pro tern.), Mr. F. J. S.Stansfield, 107, Eastbank Street, South-port.

* * *

THE THREE TOWNS WIRELESSCLUB.

Jan. 7th. The Hon. Secretary in theChair. The Chairman, Mr. J. Jer-ritt, read a paper entitled " The Elemen-tary Principles of Wireless Telephony,"which had been communicated by Mr.E. Blake, A.M.I.E.E. A vote ofthanks was passed by the members.

Jan. 14th. Mr. J. Jerritt in theChair. Mr. Voss (late R.F.C.) lecturedon " Various Wireless Systems and theirefficiency." The Marconi, Poulsen,Lepel systems, and Goldschmidt's alter-nator were considered. It was statedthat the Marconi C.W. system is veryefficient.

Jan. 21st. Mr. J. Jerritt in theChair. Mr. W. Rose (Hon. Sec.) lec-tured on "Telephony and the Use of theSelenium Cell in that connection." Anumber of interesting diagrams wereshown. After the lecture and discussionthe question of affiliation with the Wire-less Society of London was considered.It was decided to hold the matter inabeyance.

Jan. 28th. Mr. J. Jerritt in theChair. Mr. Lock described the con-struction of a condenser from simplematerials.

Visitors or intending members, pleaseapply to Mr. W. Rose, 7, BrandrethRoad, Compton, Plymouth.

THE BIRMINGHAM WIRELESSASSOCIATION.

The first post-war meeting of theBirmingham Wireless Association willbe held on Wednesday, March 10th, at7.30 p.m. in Room 21 at the Birming-ham and Midland Institute. All oldmembers and others interested are in-vited to attend.

Many will no doubt remember thatthis association was incorporated in theScientific Society shortly before the war,but very little was done before all ex-perimenting was prohibited. Now, how-ever, it is proposed to resume activities;the aerial has been erected and the in-struments released from Post Office cus-tody.

Will those intending to be present atthe meeting on March 10th kindly ad-vise the Hon. Secretary, J. C. Watkins,215, Alexander Road, Acocks Green,Birmingham.

THE LEICESTERSHIRE RADIOSOCIETY.

A meeting of this Society was held onFebruary 6th at the Turkey Café, thePresident, E. Masters, Esq., occupy-ing the Chair. There was a recordattendance-upwards of 30 membersbeing present. The speaker, Major A. L.Harris, R.E., was introduced by theChairman, who expressed the pleasurethe members had in welcoming one ofthe oldest of those who were associatedwith the old Wireless Association ofpre-war days. Major Harris, in reply-ing, said that he was delighted to find,on his return from service overseas,that the old Society had been resuscitatedand also to see that it was a real liveSociety. Major Harris then proceededto give an account of the part wirelesshad played during the recent war-inthe Army.

Some interesting specimens of variousapparatus were shown to the membersand proved immensely interesting to all.

Following Major Harris' speech, ananimated discussion took place, thespeaker answering questions put to himby the members.

The next meeting was fixed for Fri-day, March 12th.

Anyone desirous of becoming a mem-ber of the Leicestershire Radio Societyshould communicate with the Hon. Sec.,

724

WIRELESS CLUB NOTES

W. J. Rowlatt, 7, Highfield Street,Leicester.

GLASGOW & DISTRICT RADIO CLUB.(Affiliated with the Wireless Society of

London.)At a meeting of the Club held at 30,

Gordon Street, Glasgow, on Wednesday,4th February, it was decided that thesubscription be fixed at 2s. 6d. per annum,and that the Club become affiliated withthe Wireless Society of London. There-after Mr. Adcock gave a most interest-ing lecture on " Directional Wire-less," and Mr. Dewar, on behalf of theNorth British Wireless Schools, offeredthe entire use of a room at 206, BathStreet, as a Club Room, with occasionaluse of an excellent Lecture Room. Thiskind offer was gratefully accepted, andthe new room will be used at the nextmeeting of the Club, on March 3rd.

At this meeting a lecture on Valveswill be given by Mr. Snodgrass, and itis hoped that members will keep thisnight free.

Meanwhile will any readers who wishto join the Club communicate with Mr.R. A. Law, 7, Queen's Gardens,Glasgow ?

BRIGHTON RADIO SOCIETY.This Society was formed on January

19th, 1920, when 14 members were en-rolled. Mr. J. E. Sheldrick, B.Sc., ofthe Brighton Technical College, haskindly consented to be President andhas promised to conduct a series of lec-tures, some of which will be illustratedby lantern slides.

The second meeting of the Societywas held on January 23rd, 1920, at theY.M.C.A., Old Steine, and was wellattended. Among the subjects underdiscussion was the proposed apparatus forthe Society's station, and it wasannounced that the matter was well inhand. The aerial is a matter for fur-ther consideration.

725

A Committee of eight was electedwhich will meet shortly to discuss im-portant business. At the close of themeeting eleven more applications formembership were handed in.

The third meeting of the Society washeld at the Y.M.C.A., Old Steine, onJanuary 30th.

The Secretary announced that Mr.Chapman, the genial Secretary of theY.M.C.A., Old Steine, who has takensuch a kindly interest in the Society,has allowed the use of a room for meet-ings, and has also offered the use of alantern and screen for lectures.

An interesting exhibition of home-made wireless apparatus was held duringthe evening.

Arrangements were made for meet-ings to be held every Friday evening at7.30 p.m. at the Y.M.C.A., Old Steine(Basement). Full particulars of theSociety can be had upon application tothe Secretary, Mr. W. P. Rogers," Grasmere," Dyke Road Drive,Brighton.

THE WOOLWICH RADIO SOCIETY.The officials of the Society are : -

Secretary, Mr. James M. Ellam, 27,Nightingale Place, Woolwich, S.E.18;President, Col. Cousins, C.M.G., R.E.(o/c. Signals Experimental Establish-ment, Woolwich Common); Vice -Pre-sident, Mr. A. Hogg (Principal of theWoolwich Polytechnic); Lecturer, Mr.W. James.

Mr. Ellam will be pleased to hearfrom other Wireless Clubs with a viewto exchanging ideas, etc., and generally" pulling together."

For the time being meetings will beheld every Friday in the WoolwichPolytechnic, William Street, Woolwich(by kind permission of the Governors ofthe Polytechnic).

On January 16th, Colonel Cousins,C.M.G., R.E., gave an interest-ing lecture on "The History of Wireless


in the Army," bearing on its earlystruggles and rapid advancement.

Other lectures are being arranged,and it is hoped, in due course, to fix upa station, and to carry out some interest-ing and instructive experiments as soonas the G.P.O. licence is obtained.

It has been decided to affiliate theClub with the Wireless Society of Lon-don.

BRISTOL WIRELESS ASSOCIATION.

The opening meeting of the BristolWireless Association was held at 11,Leigh Road, Clifton, on January 24th,at 8 p.m. The business included amotion to affiliate the Association withthe Wireless Society of London, whichwas heartily agreed to.

The Hon. Sec. (pro tem.), Mr. A. W.Fawcett, 11, Leigh Road, Clifton,would be glad to hear from any onewishing to become a member of theAssociation. The subscription is 5s.per annum. Members have the privi-lege of bringing friends to meetings.

THE SHEFFIELD AND DISTRICT WIRE-LESS SOCIETY.

The weekly meetings continue to bewell attended, and the membership isgradually increasing as the work of theSociety becomes more widely known.The difficulty of securing permanentheadquarters is proving a serious handi-cap, but vacant rooms in Sheffield areapparently at a premium at the presenttime.

The following fortnightly papershave been read by Members : -

"Amateur -made Wireless Gear" byMessrs H. O'Neill and C. H. Hand-ford, who described in detail how receiv-ing and transmitting gear could be easilyand simply made.

"The /Ether." This formed the sub-ject of a splendid lecture by Mr. J. G.Jackson.

"The Ionic Valve" was the title of aninstructive paper by Mr. W. ForbesBoyd. The Author, who has carriedout a good deal of experimental work inconnection with the application of ther-mionic valves to aircraft, showed athorough grasp of his subject.

A very interesting discussion followed,and the Secretary announced that apractical demonstration with a 3 -valveamplifier would be given at the nextmeeting, using an indoor aerial.

Hon. Sec., Mr. L. H. Crowther, 156,Meadow Head, Norton, Woodseats.

THE AMATEUR IN BELGIUM.

Le Cercle Belge d'Etudes Radio-teleraphiques, founded in 1914, is

reviving its activities and intends tobecome a wireless society of the first or-der. It wishes friends in allied countriesto know of its existence and desires com-munications from other clubs. TheSecretary is M. Pierre Tollenaere, 209,Bd. Leopold II., Brussels.

WANTED.

To form Wireless Clubs' at Chelms-ford, Croydon, Birmingham, Edinburgh,ralifax, Spalding and Doncaster. Thoseinterested should communicate with :Mr. C. E. Jackson, 3, Seymour Street,Chelmsford; Mr. A. F. Lake, 318,Brighton Road, South Croydon; Mr. A.

-H. Staples, Y.M.C.A., Dale End, Bir-mingham; Mr. W. Winkler, 9, EttrickRoad, Edinburgh; Mr. J. R. Clay," Woodview," Sowerby Bridge, York-shire (for Club in Halifax); Mr. A. H.Wasley, Glenholme, Ravensworth Rd.,Doncaster.

726

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Aviation Notesquilimm11111111111111111111111Immimm11111111111111111111111.101mmitimdr-;

AIRCRAFT WIRELESS ON THELONDON -PARIS AIRWAY.

MA JOR N. B. TOMLIN-SON (late R.A.F.), is atpresent in charge f theCommunications Depart-ment, which comprises

the Wireless Organisation and person-nel of the enterprising Aircraft Trans-port and Travel Company, of whomMr. Holt Thomas (Chairman of Direc-tors), and General Francis Festing,C.B., C.M.G. (Managing Director),are the leading spirits. Major Tomlin-son has been connected with the Air-craft side of wireless engineering since1911, in which year he was engaged onbehalf of the Marconi Company in ex-perimental work at Brooklands andFarnborough. During the war his ex -

Major N. B. Tomlinson.

perience has ranged over the fitting ofW/T. gear to airships, airplanes, sea-planes, armoured trains, motor cars,and motor boats,-a striking illustra-tion of the wide field of wireless workin modern warfare.

The cause of commercial aviation,when it wins through the present preli-minary period of vicissitude to final suc-cess, will owe much to the untiringefforts and financial enterprise of Mr.Holt Thomas and his colleagues, and tothe devoted labours of the flying andtechnical staff associated with them, whotogether have borne the brunt of travailthat is the portion of those who lead theway and clear the path for others tofollow.

The solid achievement represented bymaintaining a practically uninterrupteddaily service of aeroplanes in each direc-tion between London and Paris through-out the severe conditions of last autumnand the present winter has won thegenuine admiration not only of the manin the street, but also of those who havesome inner knowledge of the almost in-supeiable difficulties that have been sosuccessfully met and overcome.

WIRELESS EQUIPMENT.Apropos of the question of wireless

gear, Major Tomlinson explains that thedemands of the moment call for a small,fast type of craft in which it is not fea-sible to provide special accommodationfor a wireless operator. The pilot hastoo much on his hands, as can well beimagined under the present circum-stances, to carry out the additional dutiesof a skilled Morse operator, sothat,. for the time, the undoubted ad-vantages of telegraphy for the longerranges have been outweighed by the cona-

727


parative simplicity of the wireless tele-phone equipment.

The apparatus at present in use is thelatest aircraft telephony set manufacturedby the Marconi Company. It is so ar-ranged that the only parts requiring mani-pulation by the pilot are the windinggear for dropping and winding -in theaerial, and the receiver adjustment bymeans of which signals are strengthenedand weakened as the pilot leaves or ap-proaches the station with which he isworking. The H.T. generator is drivenby a small air screw working in the slipstream of the main propellor.

W/T. COMMUNICATIONS ENROUTE.

A wireless telephone receiver has beeninstalled on the roof of the Company'sOffice in Old Queen Street, Westmin-ster, by means of which it is hoped tomaintain communication with planesfrom the time of leaving the London ter-minus of the London -Paris Service un-til they have crossed the French coast,a distance of some 70 miles. This willenable the London Office to know thewhereabouts of their machines in all wea-thers until they are in France, and on thereturn journey to have all arrangementsmade for their reception and the speedyforwarding of passengers, mails, andgoods to their respective destinations.

The W/T. Stations along the Lon-don -Paris Airway at present are Houns-low, Lympne (near Folkestone) and LeBourget (near Paris). Once a pilot isout of touch with Lympne he must waituntil he is within 60 miles or so fromParis before he can again pick up theCommunication Service. It is hoped inthe near future to erect an additionalstation in France to fill this gap and toenable the pilot to keep in continuoustouch with the ground throughout hisflight. This will be of great advantage,particularly in keeping the pilot advised

of the weather he may expect to meetahead of him. In winter time especially,the weather may change completelywithin the course of an hour or two,and local fogs appear and disappear withgreat suddenness.

FOG TROUBLES AND D. F.Really dense fog is the bugbear of

present-day flying and represents practi-cally the only climatic conditions whichreally trouble the pilot. The aeroplaneas a machine is not prevented from fly-ing by fog, but the pilot is practicallyrendered blind, and therefore helpless inthe matter of navigating his craft or land-ing it.

But with a perfected system of Direc-tional Wireless, this difficulty practicallydisappears. Irrespective of mist or fog, orwhether landmarks are visible or not thecourse will be determined by the constantsignals received from beacon stations atknown points either on or off the lineof flight, but preferably at the destina-tion end. The pilot can detect Instantlyfrom the signals, especially if " homing 'towards a beacon, should he veer in anyway from the set course, and is able tocorrect his line of flight accordingly.

THE VALUE OF WIRELESS.Mr. Holt Thomas explains that when

his present arrangements are completed,as they will be before the ensuing winter,he hopes to be independent of all but ex-ceptionally severe weather conditions." Wireless," he adds, " will help usenormously. We have now theservices of one of the most prac-tical experts in this country, whois concentrating his attention ex-clusively on the question as tohow directional wireless and thewireless telephone may be madeto help us in regular daily flying,and to overcome such difficulties as atpresent cause delay."

728

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Aircraft Wireless SectionEdited by J. J. Honan (late Lieutenant and Instructor, R.A.F.).

These articles are intended primarily to offer, as simply as possible, some= useful information to those to whom wireless sets are but auxiliary

" gadgets " in a wider sphere of activity. It is hoped, however, thatthey may also prove of interest to the wireless worker generally, asillustrating types of instruments that have been specially evolved to meet

the specific needs of the Aviator.

SHORT - WAVE TUNER (MARK IV.).

X1111111111111111111111111111111111111111111! 111111

This set is smaller and even more con-venient from the point of view of porta-bility than the Mark III. It is designedto receive wavelengths between 90 and320 metres.

As will be observed from the skele-ton wiring diagram in Fig. 28, the tele-

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phones are permanently connected in theclosed circuit so that the advantage ofhaving a stand-by position is lost. Again,the buzzer can only be applied to theopen circuit.

The open -circuit inductance is a fixedinductance of two values, the portion L1

Fig. 28.

729


VAPrimary Secondary

Crystal

Fig. 29. Schematic wiring diagram of Tb Receiver.

being permanently in circuit, whilst theportion L2 can be cut in or out by meansof a switch S for long or short wave-lengths. The open and closed in-ductances are of the pancake type andare coupled eccentrically.

Only one detector crystal (perikon)is fitted, so that the potentiometer bat-tery is eliminated.

THE Tb RECEIVER.This was one of the first crystal re-

ceivers actually used for work in the air,mainly by the R.N.A.S. It forms oneof a series ranging from Ta to Tf wnichhave done very useful work.

As a fairly exhaustive description hasalready been given of a typical crystalreceiver (the S.W.T. Mark III.) it willbe sufficient to point out one or two ofthe characteristic features of the presentset.

AERIAL CIRCUIT.By means of a switch handle P, Fig.

29, the aerial can be used without a con-denser, thereby giving the natural wave-length, or the condensers C1 or C2 canbe inserted in series for shorter wave-lengths.

The primary of the magnetically -coupled tuning inductance is varied bymeans of a switch tapping eleven con-tact points.

CLOSED CIRCUIT.The secondary condenser K1 K2 K2

is so arranged that any one of threevalues can be thrown into the circuit bymeans of a handle Q.

The secondary of the tuning induct-ance has 12 contact studs. Coupling isvaried by means of a slider, and since thewhole of the aerial and secondary in-ductances are involved, any variation in

730

AIRCRAFT WIRELESS SECTION

0 0 N./

Fig.

the degree of coupling will cause a suffi-cient alteration in the mutual inductancevalue of the combination 'to affect thetuning, which must consequently he re-adjusted.

DETAILS.

The carborundum crystal is adjustedby means of the potentiometer M. Ashunt condenser K, is placed across thetelephone terminals. A testing buzzeris provided and is worked from a dry cell,separate from the potentiometer bat-tery.

30.

The plug, BTTBE provides connec-tion with a Brown Relay, or with thethree -valve amplifier shown in Fig. 30,connection being made between the ter-minals designated by the same letters ineach diagram.

A special plug closes the poten-tiometer battery (and the relay batterywhen it is used), and is so arranged thatwhen it is in its operative position itimpossible to close down the front lidof the receiver. The object of this is

to prevent the batteries from being lefton and needlessly exhausted during suchtime as the receiver is out of action.

Aircraft Wireless in the New VolumeNo up-to-date wireless magazine can afford to ignore thedevelopment of wireless in co-operation with Aviation.We have therefore arranged to publish regularly articlesdealing with research, achievement and commercialdevelopments in connection with this subject, written bymen actually engaged in the work.

731

The Library Table,=ITHIIII111,11imilmI11111111111111111111111111111111111111111111111111111111111111111111111m7-:

INDISCRETIONS OF THENAVAL CENSOR.

By REAR -ADMIRAL SIR DOUGLASBROWNRIGG, BT.

London & New York, Cassell & Co.,pp. 280, 12s. 6d. .net.

THIS is one of the mostpleasant of the post-warbooks by men who heldhigh positions during thehostilities which we have

read. it contains no attacks nor is itmeant to justify the author's actions-thereby serving that very end the better-but is simply the story of his work inwhat must have been the most "ticklish"position filled by any man at the homefront. Sir Douglas Brownrigg per-formed an arduous, and to a large degreethankless, task and relinquished his dutieswithout taking with him a single rank-ling thorn. He recalls in charm-ing fashion a number of occasions onwhich he or his department came intosparking contact with higher authorities,but there is no trace of bitterness and thehearty laugh is always near. As he spinshis yarns one can imagine him joviallyslapping his victims on the hack. Hedid his duty to the best of his ability,standing aside for no one save h:ssuperior officers, allowing nothing to puthim out of his stride, and asking nopraise. His hook bears the imprint of a-serene conscience; it is simple andhearty and wholesome.

Sir Douglas deals with many thingswhich once mystified us, such as thefirst British official report of the Battleof Jutland, the loss of the Audacious,and the death of Lord Kitchener, notwithout making one feel guilty of hay-

ing formed hasty and unjust opinions ofcensors. Incidentally he reveals howmultifarious were his duties. Thesewere not confined to muzzling the Pressand deleting the most thrilling portionsof letters, but included the production ofcinematograph films, the organisation ofspecially conducted trips' to the Fleet,the supply of first-class music hall artiststo such units as bade them welcome,and the hunt for authors and artists todepict various scenes and incidents ofthe war. Who would have thoughtthat it was our common enemy, a Cen-sor, who induced Mr. Kipling to writethose wonderful articles about Jutland ?We can forgive him much on that scorealone.

In the chapter on wireless and warnews the general public is enlightenedabout a matter on which it was for thegreater part very hazy. How could wereceive German war news? Why didthe enemy send it to us? Who took itdown ? 'These questions were put tothe writer many times during the war,but the querists never seemed to bewholly satisfied with the replies, partlybecause one was morally bound to beexceedingly sketchy and vague in speak-ing of those things and partly becauseeven at that time the man in the streethad not grasped the fundamentals ofwireless.

In his preface Sir Douglas confesseshimself to be painfully aware that hisbook shows no trace of literary merit.Well, we will not argue that point witha writer who gives us a book which wecould not lay down until we had readit from cover to cover. The chaptersabout authors and publishers and thepressmen of allied countries are littleworks of art.

732

i11111111.11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111

The Construction of AmateurWireless Apparatus

This series of articles, the first of which was published in our Aprilnumber, was originally designed to give practical instruction in the manu-facture of amateur installations and apparatus, and arrangements had beenmade with Marccni's Wireless Telegraph Co., Ltd., to supply completeapparatus to the designs it was intended to detail. The restrictions

cn amateur work, however, remained in force, and the author was com-pelled tc proceed on general lines only. A further series will be pub-lished giving the class of information originally intended.

Article Twelve.-RE-CONDITIONING OF PRE-WAR STATIONS.

;--dili1111111111111111111111111mmull1111mIllimmilmi11111IIIIIIIIIIniiimmillff

IN our last article we consideredcertain simplified circuits for theamateur's use, and made some re-marks concerning interference on aself -heterodyne receiver of the

direct coupled variety. The readermay be somewhat puzzled to realise howthe feeble radiation resulting from sucha receiver can possibly cause any appre-ciable interference. It should perhapsbe mentioned in passing that any aerialsystem which is picking up signals isalways also radiating small amounts ofenergy due to the oscillations which arebuilt up in it by the incoming waves.It is impossible to design a circuit whichis a good absorber of radiation and yetnot also a good radiator. In fact,broadly speaking, the conditions whichhave to be satisfied in designing a goodabsorbing (i.e., receiving) circuit areprecisely those which make the circuita good radiator. As a rule, however,this tendency of a receiving aerial to re -radiate some of the energy it picks updoes not cause trouble at other near -byreceiving stations, because the amount ofenergy so re -radiated is extremely small.If the energy picked up by the aerial is ofthe order of a micro -watt, as is usuallythe case, it is evident that the amountwhich is re -radiated must he even less

than this. Stich amounts could onlygive trouble at other stations if these sta-tions were very near indeed (as for in-stance, in the same building) or wereusing extremely sensitive apparatus.Cases do occur at times however whenlarge receiving aerials, receiving highpower stations on long wavelengths, pickup sufficient energy to re -radiate anappreciable amount, at frequencies whichcorrespond to harmonics of the originalwaves as well as at the fundamentalwavelength. These harmonics havebeen known to give quite readable signalsat short-wave receiving stations distantperhaps a mile or two from the largereceiving aerial.

The amount of radiation from a self -heterodyne set is of quite a differentorder to the above, owing to the fact thatthe oscillations are now being built upin the aerial from a local source which isquite capable of supplying an amount ofenergy some thousands of times as greatas any incoming signals can give. Con-sidering for a moment the simple circuitshown in Fig. 1 in the article in theFebruary number, it is quite easy, by suit-able design of windings, to build uposcillations in the circuit " A " of similarstrength to those which could he ob-tained by exciting the circuit with a

733

THE WIRELESS,WORLD MARCH, 1920

buzzer; and it is well known that it ispossible to communicate over a range ofsome miles using the energy of a buzzer,with ordinary receivers. It is unlikelythat under ordinary conditions of hetero-dyning the oscillations built up wouldbe quite as strong as this, but on theother hand, when the radiation from theaerial caused by these oscillationsarrives at another receiving station usingheterodyning methods, it will be pickedup by a receiver which may be manyhundred times as sensitive as an ordinarycrystal set. This being the case, therange at which it will give annoyinginterference with such receivers willprobably be greater than that at whicha buzzer could be picked up by a goodcrystal receiver.

In view of the fact that amateursare at last able to resume practical work,it does not appear out of placeto conclude this series of construc-tional articles by offering a fewsuggestions of a reconstructional nature,which may be of some use tothose who are now overhauling and re -erecting old sets which have been, dis-mantled since the beginning of the War.A few hours of careful examination ofthe gear before erection may possibly berewarded by subsequent freedom fromas many days of vexatious search for thecause of a complete absence of signalson a receiver which used to give as goodresults as could be desired.

The aerial will in many cases have tobe designed afresh, owing to the presentrestriction of the amount of wire used to100 feet of single, or 70 feet of doubleconductor. The type chosen will, ofcourse, depend on the nature of the site,but in view of the small amount of wirepermitted, it is more than ever necessaryin planning the aerial to arrange it inthe form in which it will be leastscreened from radiation. If the double -wire type is chosen the two wires must

be separated by a distance of severalfeet, the more the better. If they arecloser than this, very little better resultswill be obtained than with a singlewire of the same length. If inany case masts have been erected tosuit aerials which have now to beshortened, the length of span can bemade up with cord separated from thewire itself by good insulators.

The spreaders, if any, should of coursebe located at the mast end of such cords,and not at the wire end.

The earth. It is particularly neces-sary with the new short aerials that thelength of lead to the earth should beas short as possible, and thatthe resistance of this lead and ofthe earth itself should be as small as pos-sible. No reliance should be placed inany earth system which has been buriedwithout attention for some years. Incases where it is not practicable to buryplates close, to the receiver, capacityearths of wire netting of close mesh,laid on the ground near the receiver,will be found to improve the resul tFobtained.

Insulators. It is in the insulation ofthe set that the greatest deterioration islikely to be found. Porcelain and glasswill be little affected, and will probablyonly need cleaning. Rubber will al-most certainly have perished and need re-placement. Ebonite will often lookworse than it really is. All the old sur-face should be removed' by scraping. Ifthe material appears sound underneath itmay be finished with coarse and thenfine emery paper, and used again. Inany case in which the deteriorationappears to have gone much below thesurface, the insulator should be scrapped,as its use will only lead to leakage andconsequent inefficiency of working.

Coils should be carefully dried out bygentle warming. Any damp in the in-sulation of the windings, or in the

734

CONSTRUCTION OF AMATEUR WIRELESSformers on which they are wound, willlead to leakage and inefficiency. Afterdrying out, coils should be treated withshellac varnish, which also should bethoroughly dried before the coils areused. All soldered connections or tap-pings should be examined and remade ifthey appear in any way faulty. Coilsshould be tested for continuity at everypoint by means of a telephone and drycell, used as in Fig. 1. If the wind-ings of the coil are intact, a click willhe heard in the telephones every timethat the circuit is made or broken.If, however, there is any fault in thewindings nothing will he heard.

Fig. 1.

Condensers, if with a dielectric ofebonite, should be opened up and ex-amined. If the dielectric is of air, glass-,mica 'or similar material, they are notlikely to have deteriorated much, andshould not be interfered with unless thereis any particular reason to suppose themfaulty.

Switches should be carefully cleanedand tested for continuity in the same wayas coil;.

In connecting up the set, aerial leadsinside the receiving room should be wellinsulated. Best results will be obtainedif they are run in small fibre or porcelaincleats. Connections in the receiver it-sel f >hould not be longer than necessary,and should be run neatly and fastened in

place permanently. Wires left hangingabout will be found to have an uncannyknack of fouling and causing a shortcircuit of some part of the apparatus justat a most inconvenient moment. Also, ifall leads are fastened down neatly insuch position that their exact course canbe, seen at a glance, not only will the:appearance of the set be improved, butmuch time will be saved in tracing anyfaults such as disconnections which mayarise in working. In deciding the posi-tion of the various pieces of apparatus,care should be taken to keep thedifferent circuits apart. Coils should be sodisposed that the coupling between themis as small as possible, except in the casewhen they are intended to be coupledtogether.

When the set is erected, all partsshould be tested for continuity in the.manner described above. If a testing`galvanometer is available the earthshould be tested by running a lead fromsome part of the aerial circuit througha dry cell and the galvanometer to an-.other earth, such as a water pipe. Forthe purpose of this test it does not mat-ter if this lead is quite long, providedit is not of too fine wire. If the earthof the set is good, a quite good deflectionshould be obtained on the galvanometer.The insulation of the aerial can then betested by disconnecting the earth fromthe aerial at some point below that atwhich the lead is taken off. No deflectionshould then be obtained. This test willshow up any definite short to earthon the aerial, but is not delicateenough to detect a small leak over an in-sulator. In the above tests, if an aerialtuning condenser is fitted it should heshorted.

in the new series of these articles which starts in the next volume informationwill be given 6 n the details of practical design and construction of apparatus describedin general terms in this series. As previously explained, it was originally intended

dc this in the present series, but the plan was of necessity postponed owing to thenos: -removal for so many months ref the restrictions on amateur working.

735

11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111ILL

Questions and Answers

NOTE.-This section of the magazine isplaced at the disposal of all readers who wishto receive advice and information on matterspertaining to both the technical and non -'technical sides of wireless telegraphy. Readers. should comply with the following rules:(s) Questions should be numbered and writtenon one side of the paper only, and should notexceed four in number. (2) Queries shouldbe clear and concise. (3) Before sending intheir questions readers are advised to searchrecent numbers to see whether the samequeries have not been dealt with before.(4) The Editor cannot undertake to reply toqueries by post. (5) All queries must beaccompanied by the full name and address ofthe sender, which is for reference, not for pub-lication. Queries will be answered underthe initials and town of the correspondent, orif so desired, under a " nom -de -plume."(6) Readers desirous of knowing the con-ditions of service, etc., for wireless operatorswill save time by writing direct to thevarious firms employing operators.

G.H.S. (Hull).-A 220 -volt supply will bequite satisfactory for a " Q " valve, providedthat it is direct and not alternating. Thevalue of 200 volts given as a maximum is arough approximation only, and it is oftenpossible to use a good deal more than thisquite satisfactorily.

J.A.W. (S.S. Pearlmoor).-(1) We areafraid that the exact losses due to a jumperstay of only partly defined dimensions,situated near to an aerial of unstatedlength, carrying an unknown current, arequite incalculable,-without the additionalcomplications of sparking between the stayand the mast, and other intermittent contacts.We are sorry, but the problem is rather be-yond us ! (2) The rough note you mentionis sometimes due to too low a supply voltage.You can check this of course by noting whatvolts you get on the A.C. side. Incidentally,we may mention that it is very risky to put thetransformer in series on the condenser inparallel unless the voltage is very low. Theresult of this experiment is often a pleasanthalf day spent in replacing broken plates inthe condenser. Another possible cause of theroughness of the note may be unevenness ofthe disc studs. (3) We can recommend Ban -gay's Oscillation Valve, and Goldsmith'sRadiotelephony. We do not know of a bookdealing exclusively with direction -finding, anddo not think that you would require one.You will get some account of this part of thesubject in most of the better books on WirelessTelegraphy. (4) It will be more satisfactory

if you apply direct to The Secretary, G.P.O.,London.

A.F.L. (South Croydon).-There is nothingvery remarkable in your hearing a wireless'phone on your ordinary receiving set. Ordin-ary detectors though quite incapable of re-ceiving C.W. are able to make audible theaudio -frequency variations of the C.W. bywhich the speech is transmitted. You wouldof course not get the range that you wouldwith a set designed for the purpose, but thestation you heard was probably Hounslow,which is only a few miles from you, anduses a good deal of power. You will verylikely hear him state who he is when you hearhim again.

" SPARKS " (Exeter).-(1) We think theaerial with the horizontal top 40 feet longwill be the better of the two arrangements yousuggest. At any rate it will be a good dealthe cheaper, as you will need much less wire,and this appears to be a consideration in yourcase. It should give the better signals too.(2) Two parallel wires are better than asingle wire provided that the distance betweenthem is some feet at least. If you put themcloser together than that the results are prac-tically no better than with a single wire. (3)The gauge of wire is not very important, pro-vided that it is heavy enough to withstandthe mechanical stresses to which it is exposed.The thicker you make it the less will be itsresistance, and therefore the less the loss ofenergy due to that resistance. (4) There isno simple way of satisfactorily receiving longwaves on a very short aerial. It can only bedone with special apparatus and methodswhich are beyond the range of a beginner.You would be much better advised to com-mence with a set for short and medium wavesonly. You will find the information you re-quire for this in the instructional articlespublished in the WIRELESS WORLD, or in anyhandbook for amateurs.

C.S. (Penrith).-The probable reason ,ofyour not getting sharp tuning is that the capa-city of the receiving condenser is too small,if the dielectric is 4 inch thick. With a con-denser such as this, unless the plates were verylarge, the capacity of the coil itself wouldprobably be important. The sound you gDt

with the condenser disconnected would prob-ably not be due to direct induction from thebuzzer, but to forced oscillations set up in t. -ereceiving coil by the oscillations in the tran;-mitting circuit, owing to the coupling betweenthe circuits being too great.

F. J. K. (Co. Kerry).-It is quite possibleto test the main condenser of a k.w. set bythe method you suggest. A better method,

736

QUESTIONS AND ANSWERShowever, is to test each bank separately. Re-duce the gap between the spark rods of theinduction coil to about r or 2 millimetres andif a spark is obtained on pressing the keythe condenser is in working condition. If nospark is obtained open up the condenser andrepeat the test when the broken plate can belocated.

(2) A 4.3o-tnetre wave can be obtained ona xt k.w. set by using one-half of the maintransmitting condenser, and with the transfor-mer secondaries in parallel.

A better method perhaps would be to take atapping off the jigger primary, using the con-denser banks in parallel.

(3) A condenser placed in a circuit inwhich direct current is flowing would act asa very high resistance, in fact as an insulator,and, therefore, no current would flow in thecircuit.

When a condenser is placed in an alternat-ing current circuit the condenser sets up aback electromotive force which is equal andopposite to the applied E.M.F.

Imagine a simple circuit containing a con-denser and an alternating pressure appliedto its terminals. Let the pressure be in apositive direction increasing from a minimumto a maximum. As soon as a pressure isexerted on a condenser a B.E.M.F. is set upwhich opposes the charging pressure. Whenthe charging pressure becomes a maximum,the condenser has its maximum charge. Assoon as the charging pressure is reduced thecondenser starts to discharge in a negativedirection, and will continue to discharge untilthe applied E.M.F. is zero.

Now the applied voltage will increase to anegative maximum during which time thecondenser current will decrease to zero.

Thus during the first and third quarterperiods the current is flowing with the pres-sure, while during the second and fourth quar-ter periods the current is flowing against thepressure.

C.T.A. (Leicester).-Without actually tryingout your telephone transformer it is impossibleto give a definite opinion as to whether it issuitable or not, but we think it would be wellworth your while to make it up and try itout. Use a condenser across the primary ofabout .0002 mfd. A condenser across thesecondary is not required, but if you do decideto use one make it about .os mfd.

It would be advisable to immerse the trans-formers in hot paraffin wax in order to ensuregood insulation between the turns.

C.E.B. Mech. W/T.-Asks why, unlike acrystal receiver, better results are obtainedwith a valve receiver'when the detector circuitis coupled directly to the aerial instead ofbeing inductively coupled?

We cannot agree with C.E.B. that betterresults are obtained with a valve if coupleddirectly to the aerial.

A crystal detector needs a certain oscillatoryE.M.F. in order that it shall detect incomingsignals. Now if the aerial be small and thereceived wavelength long the amount of in-ductance required would be sufficient to -.pplythe required E.M.F. to the crystal. In thiscase a crystal directly connected to the aerialwould be sensitive. On the other hand, if theaerial is large and the received wavelengths'on.... little inductance would be required inthe aerial, and the voltage across this induct-ance would be too small to affect the crystal.Hence a secondary circuit with small capa-city and large inductance would be necessary.

The same remarks apply to valve receivers,the only difference being that valves lo notrequire stch a high oscillatory E.M.F. as acrystal, and can, therefore, be tapped offsmaller inductances thari can a crystal.

E.K. (Newport, Mon.).-Has been trying ex-periments with the rj,t k.w. rotary converterand finds that if the slip rings are short-cir-cuited and the starter handle is moved to thefirst stop, the armature gives little jerks, con-tinually starting and stopping. Why is this?

When the starter handle is moved to thefirst stop a current will flow in the D.C. arma-ture winding causing the armature to revolve.Now the slip rings are tapped off the D.C.armature winding at opposite points. Whenthese two points come under two oppo-site brushes, the D.C. supply is momentarilyshort-circuited, causing the armature to pullup. This short-circuit will be only momentaryowing to the ineritia of the armature.

We should like to point out that this experi-ment is not conducive to the well-being ofthe rotary, owing to the heavy current thatwill flow in the D.C. windings, besides thebad effect of short-circuiting the D.C. supply.

ENQUIRER (Leek) (t) (2) and (3).-Theselestions can be answered only by the firms

themselves. We advise you to apply rlirect.

J. G. (Cork).-Yes, the wearing of uniformis compulsory for wireless operators on boardship.

F. J. K. (Cahirciveen) (O.-The method fortesting the condenser bank is quite sound. Inpractice it is more convenient to isolate thetwo halves of the bank before applying thetest, as by this means the broken down halfcan be at once traced. (2) The arrangementwould give about 425 m., which might bebrought up somewhat by the sliding induct-ance. This is the nearest that the set willgive to 450 m. The fixed gap would not benecessary. (3) A condenser entirely preventsthe passage of D.C. It will, however, allowthe passage of A.C., but not without alteringthe phase relation between the current and theapplied E.M.F.

J.G.R. (Enniskillen).-(1) In order to useyour low resistance 'phones you will need atelephone transformer, which consists of two

737


separate windings on a core of soft ironwires. One winding is of comparatively fewturns of not too fine wire, say, No. 30, woundto have a resistance equal to that of the'phones. The other winding consists of manyturns of very fine wire, say, No. 36-40, havinga resistance of at least 5,000 ohms. Thehigh resistance winding is connected in theposition shown for the high resistance 'phones.Your low resistance 'phones should then beconnected across the low resistance winding.See article in this issue for further de-tails of the practical construction. (2)

D.W.S.22 " means wire of gauge No. 22,insulated with a double winding of silk.(3) Any other Popper wire will do forthe aerial, provided, that it is sufficiently heavyfor mechanical strength. The dimensions neednot be altered. (4) This receiver was de-signed especially for the benefit of beginnerssuch as yourself, in order that you should beable with very little experience to make afairly efficient set. It could not be altered forgreater range and selectivity without en-tirely re -designing it,-which, of course, wecannot undertake in these columns. We re-Lorttmend you to confine your attention to thetype shown until you possess greater experi-,ence. You will then find many other suitabletypes described in this magazine.

A.G.B. (Corsham).-(i) The circuit yourefer to is quite obsolete, and we do not thinkit was ever used in practice. We have t-',clin vain to get further information as to theconstants of the circuits employed. Your ex-planation of the action of the balanced crystalsis quite correct. We think that there is anerror in Bucher's statements with regard tothe pitch of the note. With the values of theincident frequency and buzzer group frequencyhe gives, the pitch should be either too or4,900, or a mixture of the two, dependingchiefly on the damping in the circuit B. (Itmay, of course, be a mixture of these twovalues.) If the damping in B is excessive, asignal will only be obtained when the maximadue to the incoming radiation and the buzzerradiation exactly coincide, and the pitch shouldtherefore be too. If, however, the dampingis negligible, there will always be a coin-cidence of maxima, and the pitch shouldtherefore be that of the buzzer trains. (2)The apparent reason for the tuning of circuitB to a very high frequency is that by thismeans it is ensured that in each train of oscil-lations set up by the buzzer, at least one maxi-mum should come near a maximum of the in-coming radiation. This would not necessarilybe true if the frequencies were nearly equal.(3) The oscillation transformer BJ willprobably be about right with a similar amountof turns on each coil. (4) We are afraid wecannot suggest the best values for these con-densers, which are probably used to diminishthe shunting effect of the circuit J, across thecrystals for the incident radiation.

STRATHMERE (Bayswater). - (a) The

usual causes of false bearings are the presenceof mountain masses in the region, the presenceof deposits of mineral ores in the neighbour-hood, and possibly the variation in conduc-tivity of the earth in different directions fromthe receiving station-as for instance with astation on a rocky coast. (2) The aerial andits associated coils must of course be tunedto the incoming radiation. We do not thinkthat any other relation between the Induct-ance and Capacity, subject to this condition,has been worked out. In considering themechanical dimensions, the rough principle isto make the area of the loop as large as pos-sible without the natural wavelength exceedingthe desired value.

H.H. (Ely).-(1) There does not seen muchwrong with your arrangements. However,the potentiometer connections in your diagramare quite incorrect. Consult any receiver dia-gram about this. This should not be enoughto stop your getting any signals. Your earthis rather small. Try burying a lot more wire,and spread it more. If this is not convenienttry wire netting laid on the ground. Youshould also insulate the lead-in more care-fully,-the insulation at this point hasprobably chafed, and if the wooden wall isat all damp, you may be getting seriousleakage there. Examine all your connectionsand insulation carefully. (2) No. (3) es,but get the set working without this addi-tional complication first.

(We regret we are compelled to hold overmany answers. In the next volume morespace will be devoted to this Section, and wehope speedily to wipe out our arrears.)

PATENTS, Trade Marks.-Advice and handbook free.-B. T. KING, A.i.m 5. Registered Patent Agent, 165, Queen

Victoria Street, London, E.C.4.

FOR SALE, WIRELESS WORLD Volume 4 ( Bound), and Volumes5 and 7 in clean condition. Suitable offer accepted. -22 Sprot -

borough Terrace, Nottingham.

YOUNG MAN (E3oo capital) would like to meet ocher ex-perienced operators (with capital), view-starting school.

-Write Box 3o Bertram Day's Advertising Offices, ito Strand,London.

WANTED "September" WIRELESS WORLD 1918. VOL VI.No. 66.-H. LOTT, r62 Elms Road, Clapham.

WIRELESS WORLD Parts 1-12. and Parts 49-60 wanted.Write stating price to Captain M. cjo Nt.o, Dept., Wireless

Press, Ltd.. 12-13 Henrietta Street, London, W.C.

COMPITE as a wood substitute which is cheaper than woodfor making electrical and other small accessories. It is harder

than wood, cheaper to produce, non-flammable and has good in-sulator properties. Write for full particulars and samples toA.P.S. LTD., W. Department, Publicity House, Bucknall Street,W.C.z.

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738

THE WIRELESS WORLD Odzertisenrem,;

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THE BENNETT COLLEGEDept. 129 SHEFFIELD. Estab. 1900

'11-e=1'Accessible to YOU on Palmers:No.5-Packhorse Briage at Chanuaton,

dating front the liars of the Roses.

The Palmer Cycle Tyre Fabric minimisesloss of power, ensures easy propulsion, and its resiliencegives perfect smoothness of motion. Hence Palmer Tyresgive cycling an added pleasure and make possible a widerfield in which to explore.Send now for FREE Palmer Map Book (D. 12)and make sure of a Copy. Con, ains Sectional Maos of theBritisn Isles, with Cycling Roads, Dangerom. Hills, Distances,

and Hints on Repairs.THE PALMER TYRE. Ltd.. .9-m, Shaftesbury Avenue,W.C.,a. Cycle Tyre Depot. 103, St. John Stre.t, Clerkenwel ,

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ACYCLE TYRESAnd MOTOR

March, 1920.

CYCLE TYRES

ELECTRIC COILWINDING MACHINES

Made by the Universal Winding Co..Trade Mark

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with less labourThey DETECT ALL FAULTSas soon as they occur instead of afterthe coil is finished.

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MARK

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Telephone : North 580 (2 lines/.Telegrams: Conductivity. London."

xii Please mention the Wireless World


Pelmanists v. Non Pelmanists." HAVE altered a good deal under the grip-

ping influence of your Course, and continueto do so-I have gained tremendously on thespiritual or intellectual side-and, as far asmoney is concerned, I am now possessed of

a life-long (I am sure it will be life-long) impetuswhich will make it impossible for me ever to needmoney. I have earned and gained more cashsince I took the Course than during any previousperiod of the same time.

" We most of us have competitors and rivals-and woe to the non-Pelmanist who tries to runthe race and win against a Pelmanist." (F13131.)

The above letter has recently been receivedby the Pelman Institute. Some may consider ita remarkable letter. It is not a remarkableletter, however, from the Pelman point of view,as hundreds of equally striking letters are re-ceived by the Institute almost every day. Butit contains certain points which will interestevery reader.

MAKING BRIGHT MINDS.In the first place, it emphasizes the intellectual

benefits of Pelmanism. " I have gained tremen-dously on the spiritual or intellectual side," saysthe writer. The practical, business, and financialbenefits which follow from a course of Pelmanismare so striking that sometimes this particularfeature of the Pelman Course is apt to be over-shadowed. But it is always present all. the same.The atmosphere of optimism, the bright keenness.of spirit, developed by Pelmanism is testified toby thousands. Men and women of all ages andprofessions write continually to say how Pelman-ism has benefited them intellectually, how it hasgiven them a new outlook on life, how it hasopened to them rich stores of knowledge andenjoyment unknown to them before, how it hasrolled away the clouds of depression and unrestfrom their minds and enabled them to live fuller,richer, and happier lives. The records of thePelman Institute are full of such cases. Thegood that Pelmanism is doing in this directioncan never be over -estimated or too highly praised.

INCOMES QUADRUPLED.But then turning to the more practical side of

Pelmanism, " I am now possessed of a life-longimpetus" says the writer, "which will make itimpossible for me ever to need money. Ihave earned and gained more cash since Itook the Course than during any previousperiod of the same time." This same experi-ence has been that of thousands. Space isinadequate to give the slightest idea of the workPelmanism is doing in

doubling, trebling, and quadruplingthe income -earning power

of those who take the Course. In every pro-fession that could be mentioned, in every formof business or industrial work in which people

Hardt, 1920.

are engaged, there are literally hundreds of menand women who are earning bigger money, hold-ing higher positions, and rising rapidly to thesummit of their ambitions entirely through theincreased efficiency brought about by a shortcourse of Pelmanism.

165 PELMANISTS IN THE FIRM.So greatly is the value of Pelmanism appreciated

by business men that batches of enrolment formsare constantly applied for by business firms inorder that the whole of their staffs may beenrolled simultaneously. Well-known firms haveenrolled as many as

165, 145, 100, and 70members of their staffs in this way

at one time.A well-known business man writes :-" I do not see how anyone can study the

Pelman lessons seriously and not gain thereby,reaping a reward which-besides its definite and,in my case, tangible advantage-also brings withit developmentswhich have no parallel in moneyvalues.

" To those of my acquaintances who have beensufficiently interested to ask my opinion of thePelman training, I have said-and shall continueto say :-

" ' Take it-follow instructions carefully-andif at the end of the Course you do not admithaving gained something good, right out of pro-portion to its cost, I will personally refund youroutlay.' "

TO -DAY'S GREAT OPPORTUNITY.No one who wishes to get on-and who does

not ?-can afford to do without Pelmanism. Ifyou are efficient already, Pelmanism will makeyou more efficient still. If you are handicappedby faults which keep you down-mental faultssuch as indecision, forgetfulness, pessimism,timidity, lethargy, and so on-Pelmanism willbanish these faults and make you alert, resource-ful, keen, and efficient.

Yet Pelmanism takes up little time. Its costis small,and it is perfectly easy to practise. Nohard study is Pelmanism, but a pleasant, delight-ful, and exhilarating recreation for your mind.Learn all about it to -day. A postcard or letterwill bring you full particulars post free by return.A copy of " Mind and Memory," a copy ofTruth's Report on Pelmanism, and particularsenabling you to enrol for the complete Courseon special terms will be posted you directlyyour application is received. Or call personallyif you can. Address the Pelman Institute,145, Pelman House, Bloomsbury Street, London,W.C. i. You will never regret it.

xiii Please mention the Wireless World

THE WIRELESS T VORLD (Advertisements)

New 6dition in 'Ciro Volumes

Text -Book on Wireless TelegraphyBy RUPERT STANLEY, B.A., Tp. Maj., R.E., and Chief Wireless Instructor in the B.E.F., France

8uo. With IllustrationsVolume I.-General Theory and Practice. 15s. net.Volume II.-Valves and Valve Apparatus. 15s. net.

" Some of the results of the rapid developments of the hard vacuum valve, and of valve circuits, are dealtwith in the second volume, which is the most up-to-date book on the subject published. Major Stanley'sfirst volume has been recognised as a standard work."-Vhe Scotsman.LONGMANS, GREEN & CO., 39, PATERNOSTER ROW, LONDON, E.C. 4.

THE NORTH WALES

Wireless SchoolsCARNARVON

The Home of WirelessSchools ideally situated. Pupilsaccepted for board -residence.

Special Postal Course for Amateurs.Write for Free Book "Selecting a Career."

CONDENSER

PLATESMICA&IIICANITE SUPPLIES

LIMITED.GMICA HOUSE OFFORD

LONDON. N.I.PRone. Dortk 805.

VARI AB L ECONDENSERS

These condensers are moving vane typefitted in lacquered brass case and engravedin degrees from 0 to 90. They are continu-ously variable with an even scale and madein the following maximum capacities :

0.00050.00100.00150.00200.0025

m.f.

It

£2 15s. Od,£2 17s. 6d.£3 Os. Od.£3 2s. 6d.£3 5s. Od.

Calibration Chart in direct readings ... ... 2/6 extraWith divided scale engraved in micro-microfarads 51- extra

The MARCONI SCIENTIFIC INSTRUMENT LTD21-25, ST. ANNE'S COURT, DEAN ST., SOHO, LONDON, W.1Telephone : 7745 Gerrard. Telegrams: THEMASINCO OX LONDON

March, 1920. xiv Please mention the Wireless World

-u.s.:=2:gi

.larch, f}-20.


GREYS'dominate

/

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THESE fam-iliar "Greys"

advertisementsreflect thechar-acterof "Greys"cigarettes. Big,wholesome" Greys " add azest to life.Healthy, active,joyous mensmoke them.

helpatekrfientar'

RE SBig CIGARETTE with the Choice Flavour

SILK CUT VIRGINIA

20br14 NOI:r361'71Of High Class Tobacconistsand Stores everywhereManufactured byMAJOR DRAPKIN&DKingdomf the Unxte4Tobacco COL..r

X V Please mention the Wireless World


WIRELESS ENTHUSIASTSWE have now ready our Receiving Set No. 140, for C.W. Reception. This Set is

quite unique and will give you extraordinary results. Price £6 es. Od.Complete including Valve.

Our Set W.R. 139, for Spark and C.W. Reception, with a Wave Length from 400 to 20,000metres. Price £18 188. Od. The demand has been so great for these Machinesthat orders are being dealt with strictly in rotation. We are the actual Designersand Manufacturers of these Sets. Prov. Patent No. 347/20

WE HAVE ALSO IN STOCK '-Valve Amplifiers. Telephone Transformers from 35) -Grid Condensers 816 Intervalve Transformers £3 3s.Grid Condensers with Leak 12/6 AERIAL WIRETuning Coils from £4 Variable Condensers 35/ -Valve Holders 12/6 Potentiometers 18/6Selected Crystals Loading Coils from 30/ -

We also have a splendid stock of Valves specially designed for Amateur use, workingfrom 24 volts at 22/- to 35/.. These are not WAR STOCK.We have a Staff of Experts at the disposal of our customers to advise and help inerecting and choosing suitable Apparatus to get the, best results on the Aerial permittedby the P.M.G. of the G.P.O.

F. 0. READ & CO., LTD., Wireless Experts,Telephone : Gerrard 442. 13-14, GREAT QUEEN STREET, KINGSWAY, W.0 2

McGRUER SPARSThe ACME of STRFNGTH

and LIGHTNESS.This Hollow Wooden Structure is ideal forWIRELESS MASTS (telescopic or in onelength), AERIAL SPREADERS, IN-DUCTANCE FORMERS, etc.Combination Flag Pole and Mast in three sectionsextending to 25 feet, weight 9 lbs., completewith guys, halyards and pickets : Price £6 6s.The efficiency of these Spars has been proved bytheir use in Aircraft Construction. The fuselagesof the VICKERS VIMY ROLLS which flewthe Atlantic and from England to Australia, areconstructed with McGruer Longerons and Struts.The successful HANDLEY PAGE V.15oo hasMcGruer Spars in the fuselage, wings, and tail unit

These facts speak for themselves.

WRITE FOR BOOKLET.

ALL INQUIRIES WILL RECEIVEPROMPT ATTENTION.

COMMERCIAL ROAD,LAMBETH, LONDON, S.E.I

Telephone : Hop 718.Teleg. : "011osparsh, Watloo, 1,011d017.

March, xvi Please mention the Irin;


MARCONIWIRELESS TELEGRAPH

INSTALLATIONSEnquiries invited for WirelessTelegraphInstallations for communication overany distance, in any part of the WorldPORTABLE APPARATUSFOR ARMY PURPOSESIn addition to Installations, Special Apparatus has been

designed for many purposes, amongst others :-AP PA RATUS FOR ACTUATING FOGSIGNALS BY WIRELESS TELEGRAPHY

SELF - CONTAINED RECEIVERS FORTHE RECEPTION OF TIME SIGNALSWIRELESS COMPASSES TO ASSIST

NAVIGATIONPRACTICE BUZZERS FOR INSTRUCTIONIN TELEPHONE MORSE SIGNALLING

PORTABLE WAVEMETERS,DECREMETERS, INDUCTION COILS,

etc., etc.

Marconi's Wireless Telegraph Company, Limited,MARCONI HOUSE, STRAND, LONDON, W.C.2.

Telex one 8710 CITY. Telegram EXPANSE, ESTRAND, LONDON

March, 1920. xvii Please mention the Wireless World


THEMARCONI INTERNATIONALMARINE COMMUNICATION

CO., LTD.

Wireless Operatorsrequired for ships ofMercantile Marine.Applicants must bephysically fit, aged 18to 25 years, and inpossession of 1st ClassP. M. G. Certificates.

Appiy to The Traffic Manager,THE MARCONI INTERNATIONALMARINE COMMUNICATION

COMPAN't , LIMITED,MARCONI HOUSE, STRAND, W. C. 2.

1837 1919

EMUABLES

give to the userthe fullest satis-faction and tothe contractorthe greatestcredit - always

W. T. HENLEY'STELEGRAPH WORKS CO., Ltd.

Blomfield Street, LONDON, E.C.2

iht reit , 1920.

On Learning aLanguage.

By A. L.Ir I inquired of the intelligent reader," Can a sound knowledge of languages beacquired through the post ? " I think he

ould answer, I don't see why not, but "-and it is this possible ` but " that I hope todeal with in the course of this article-" thequestion arises whether it will be acquiredsoquickly or so thoroughly as by the vivavoce method."

I have before me the Courses issued bythe School of Simplified Study. In someprefatory notes its scholarly authors i e -

mark, " We would ask students to rememberthat these Courses are not books, no par-ticular attempt has been made at literarystyle. Our object has been to give in thesimplest possible language the explanationsof the teacher:"

Let the would-be student subscribe to oneof the " Simplified " Courses. They areunlike any others that I have inspected.They are inspired with the gift of teaching,a very rare gift. You are carried alongstep by step in a way which you will findalmost irresistible. You have merely togive the matter twenty minutes of your timeand attention every day. and your progressis sure and certain. The system is theoutcome of fifteen years' teaching; and tothose of us who have to spend most of ourtime earning our livelihood, it is more con-venient to carry a slip in the pocket thanto keep appointments. We can spare afew minutes during the day and in theevening. It is because the instruction is soflawlessly clear that we can attain ourambition at the smallest expenditure of timeand energy, In order to demonstrate thethoroughness and efficiency of the SIMPLI-FIED method of teaching languages by post.the Governors of the School have arrangedto send FREE OF ALL CHARGE fourlessons papers taken from any of theCourses enumerated below, to readers, to-gether with brochure giving full particularsof these Courses. Write to the Secretary,The School of Simplified Study, 65, St. Paul'sChambers, 19.21, Ludgate Hill, London,E.C.4.

S.S.S. Courses inFRENCH SPANISH ENGLISHLATIN GREEK HEBREWARABIC LOGIC PSYCHOLOGY

Viii I'Irrtsr Mr)? I loll ike


ATLANTICCOLLEGE

OF

Wireless andSubmarine Telegraphy,DUBLIN : 45, 46, 47, HENN STREET.

and CA HIRCIVEEN.

Send your boy to the centre ofthe Telegraphic World to learnWireless or Submarine Telegraphy.

Most Successful Tuitionby fully qualified Staff.

Students can qualify for shoreappointments, as the Colleges areequipped with the most completeand up-to-date Wireless Plant inIreland - an exact facsimile ofShore and Ship installations.

Illustrated Prospectus on application to

M. M. FITZGERALD, A.M.I.E.E.Principal.

ESTABLISHED 1809.

NORTH BRITISH& MERCANTILEINSURANCE COMPANY

FIRE LIFEACCIDENT ANNUITIESBURGLARY MARINE

FUNDS

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LONDON : 61, Threadneedle Street, E.C. 2.EDINBURGH : 64, Princes Street.

" You cannot charge me with not preparing betimes to assistyou to secure your due share of World Trade after the War."

-J. C. H. Macbeth.

HAVE YOU HEARD ABOUT THE WONDERFUL

Marconi InternationalCODE ?

THE CODE THAT IS MORE THAN A CODE.It halves the cost of Cabling, and is an Interpreting Agent andPhraseological Dictionary in Nine Languages. It places in cp:',/,your hands the Master Key to the Trade of the Globe !

4,bn 9'0?We shall be pleased to send you, free of charge, our Linguistic Map of the World :,>9

and Handsome Illustrated Booklet if you will cut off this corner, pin it to onecs,4, c,

of your letter headings and post it to us.

THE MARCONI INTERNATIONAL CODE CO., LTD. ,,cese:0,4F'\st4S' ('Marconi House, STRAND, LONDON. (co4% "

March, 1920. xix Please mention the Wireless llorld

THE WIRELESS WORLD (ildvertisements)

The Specialists in RheostatsFOR

GENERATING PLANT

AND

RECEIVING SETS

ISENTHAL & CO., LTD. (4;(i.,ac:',',nt,"V,.cdemiir,a/s1;;;Ialsizteatcrea,iindr.a.

DENZIL WORKS, WILLESDEN, LONDON, N.W. 10

POSH SLACKSPERFECT CREASE-LONGER WEAR

-Bought by Thousands or Officers.A Necessity for Camp or Civil Lire.

' ALPHA ' PORTABLEHandiest Trouser Press ever madeWeighs cc ozs. Packs into z' in. by2in. by 3 tn. Hangs in Wardrobe whenin se.

No. 1 post freeNo. 2 Press and Suit

7/-

11/1qP:sit"Ferreectrtned 8/6(France 6d. Extra.)

Cross Cheque., P.O." LondonCity and Midland Bank."

MAY & CO. (i)riP,t) 3, TUDORDON,

S

E.C. 4TREET,LON

Designing Girls'-CH A14.. E. DAWSON.Creator of the Dawson Girland Founder of Great Brilant'sFIRST and Greatest Corres-pondenee ART College, doesnot teach so-called "comic'sketching, but dignified designsthat appeal to people of culturelid refinement. He has t iught

more beginners to earn moneyby 'trt than any other artist.lie will send gratis a letter ofcriticism, advice and particularsto any read r nnerested zndeeming who s lids to him atthe Y. L. C., n td., 69, ThanetHouse, Strand, W.C. a, withstamp for return, a small specimen "Girls' Head" sketch.

Heads for Posters,Covers. Advt.. &c.

...000essman..,

7"11756

P. ORMISTON a SONS(P. H. ORMISTON) :: ESTABLISHED 1793

79 Clerkenwell Rd., London, E.C."Ormiston, London." :: 13259 Central

Silk and Cotton Covered H.C. Copper Wire,Resistance Wires, Fuse Wire, Binding Wires,Charcoal Iron Core Wire, Asbestos CoveredWire, Braided and Twisted Wires, Bare CopperStrand and Flexibles of any Construction, WireRopes and Cords (tine sizes) in Galvanized Steel,

Phosphor Bronze, &c.

COMMERCIAL UNIONASSURANCE CO., LTD.

FIRE, LIFE. MARINE. ACCIDENT.Capital sully Subscribed ... L2,950000Capital Paid UpTotal Assets (including Life Funds,

/lead ()Ike: ;1st December, 1913 £24002,25224, 25 & 26. I.ORNHILL LONDON. E.C. Total Annual Income exceeds 8,5oo,000

The following classes of Insurance efteCied FIRE, LIFE AND ANNUITIES, M A EINE, LEASEHOLD REDEMPTION AND SINKINGFUND, ACCIDENT, inChUIN Personal Accident, Third Party, Burglary, Plate Glass, Fidelity Guaramee, Employers Liability andWorkmen's Compen,,lon. inducible Domestic Servants' In:tiran4 e. The Company also act as TittbSTEES AND EXECUTORS.

Worth, 1920. XX Please mention the Wireless World

=NW


Easy Lessons in WirelessA PRACTICAL COURSE OF INSTRUCTION ON THE PRINCIPLES- CONSTRUCTION AND THE WORKINGS OF WIRELESS APPARATUS :-

MP ;1311! STUDENTS, EXPERIMENTERS & OPERATORSFULLY ILLUSTRATED AND IN THE NEAT FORM OF A POCKET BOOK

By A. F. COLLINS 44/. COMPLETE Gilt EdgedPOST FREE.

From

H. L. WOOD & SON, "THE ELECTRIC SHOP"115, HIGH STREET, CLAPHAM, S.W. 4

SEND US YOUR ENQUIRIES FOR EVERYTHING ELECTRICAL.

'Tapper and Buzzer Sets, complete with bulb and battery in polished box, from 15/6,19/6 and 21/6 post free; Morse Keys from 4/-; Induction Coils from 15/6 ; Buzzersfrom 4/. ; Buzzer Sets from 12/6, 15/6, 18/6, 22/- E9' 25/6 ; Volt. and Amp. Meters6/6, 8/6, 10/6,15/6 up to 35/.. ; best quality Bells 5/., 7/. and 10/6 post free ; smallMotors 7/-, 9/6, 11/-, 16/- and 21/6 ; small Dynamos 7/_, 15/6 and 21/6 post free.

ALL TYPES OF ACCUMULATORS IN STOCK FROM 516 POST FREE.

NOTE-As an Advertisement, we will send per return one of our beautifulPenlite Torches complete with bulb and battery. Each one guaranteed the finestmake and finish, for PIO for 3/9 post tree. As sold in our shop and elsezvherefor 5/6. Money returned in full if not satisfied.

ACCUMULATORSFOR WIRELESS & EXPERIMENTAL WORK

ELECTRICALeSTORAGE V

LIMITED

CLIFTON JUNCTIONMANCHESTER

LONDON OFFICES -39 VICTORIA ST S.W.1

March, 1920.

Wireless OperatorsIN THE

Royal Indian MarineThe Secretary of State for India is preparedto receive applications for eleven appoint-ments as Wireless Operator in the RoyalIndian Marine. These appointments arepensionable on the completion of therequired period of service. Pay at thefollowing rates is admissable.

On appointment ... Rs. 200 a monthAfter 3 years ... Rs. 215 a monthAfter 6 years ... Rs. 230 a monthAfter 9 years ... Rs. 250 a month

together with food and accommodation orallowance in lieu.

Every candidate must be a British subjectof European descent, of good moral characterand of sound physique. He must be notless than 21 years of age and not more than30 years of age on his next birthday.

A free passage to India will be provided, andan outfit allowance of 1.20 granted on selection.

Full particulars and application forms may be obtainedfrom the Secretary. Military Department (Room 102)India Office, Whitehall. London, S.W.!, and appli-cation forms duly completed must be received notlater than 29th February. 1920.

xx* Please mention the Wireless World

M

THE WIRELESS WORLD (A.dvertisements)

VALVE PANELS.The finest of its kindwhich will appeal toexperimenters desiringan instrument of high-class finish at a mini-mum cost. Resistanceis wound on a threadedformer, which, whenset, is fitted liana flush -turned groove, ensuringperfect rigidity. Size7 ins. x 4.11 ins. x a ins.high. Each 37/6 postfree. No. O. A smallerpattern preferred bymany on account of itscompactness. Each30i- post Lees _

"PESCO" RECEIVING TRANSFORMER.A new design which will appeal to the experi-menter, and be found efficieni on crys to I or valvereceivers. Primary winding 51 ins. long x 4 ins. dia..wound with 22 enamelled wire.secondary Sins. x 3ins.dia.. wound with 28 enamelled wire. Wark manship and finish all that can be desired."A improved type slider. " B " im-proved type secondary tuning slide,giving access to every turn. irrespectiveof secondary position. "C' lockingscrew for secondary. " D " double barmounting to keep secondary rigid. " F"triangular slider bar (note flat face forslider contact ). No. W. 88A.Each 70i- post free.TUNING COILS MADE TOYOUR OWN SPECIFICATION

APPARATUS MADE TO YOUR OWNSPECIFICATION WITH PROMPTITUDE

WE STOCK EVERYTHING FOR THE WIRE-LESS EXPERIMENTER, FROM A CONTACT

STUD TO A COMPLETE PLANT.

C

11111111111111

VARIO METER. New efficient pattern with shortwave switch. giving all ontrol from 125 to 8,000metres. (- hart of approxi nate wave lengths sent withthese. Well made and fi.t cd in mahogany case approx.3 ins. x 5 ins. x 6 ins. Insulation guarantee. Price I 10/.

11111111111111111111111111

" PESCO " HYTONEBUZZER. A special neat Buzzerwith steel reed emitting a range ofnotes over an octave according toadjustment. The finest instrument ofits kind for setting crystals. Each 6/6

VALVE HOLDER. Standardtype of moulded ebonite with four

extended pinsa s illustrated.Each 3/6. post-age 4d. extra.Ditto of solidturned ebonite,mounted onsquare ebonitebase with four

to minals. Each 8`.

Mitchells

VALVE

The Unitwhich every

wirelessexperimenter

is talkingabout.

A

,))1111

p,07,1110,1111111400:011111111, la .4,

111111 IIIlilll I11111IIIIIIIIIIIIIIIIlill111111111111111111111111111111IIIIIIC1if11V11111

DETECTORS.Being a completeUnit, for adaptingyour pre-war outfit.Necessary con-densers and leaks,being fitted, the fol-lowing companentsare needed to makea complete station,

viz : - Tuner.'Phones, H.T.Battery, Fila-

mentBattery.Variable

Con-denser

11,111'111111 I1111111111'::11111111111111111,111111111;111,,,1111111111111111

Sketcb of cannections for G.P.O. Requirementssupplied with all order?.

No, I-Without Filament Resistance ... each 67/6No. 2-Fitted with Resistance as illustrated. each 851.

11

VARIABLE CON-DENSER No. I, Thestandard experimenters con-denser. I I fixed and 10 movingvanes. Adjustment for regu.lating tension of adjusting knobfitted. Ebonite ton and bottom.5 ins. diameter. Each 35/- postfree No. 10 as No. I but fittedin mahogany case, price 301-.

188, RYE LANE,PECKHAM, S.E. 15

lfarclt, 1920. xxi Please mention the Wireless World


To be Published this Month

THE YEAR BOOK OF WIRELESSTELEGRAPHY & TELEPHONY 1920DI Over 1,2008vo.Coth PRICE 10/6 NET pages.

POSTAGE 6d. I \ LAND ABROAD Is.

CONTENTSCALENDARS: Wireless Summary for 1919 : Record of Development:National and International laws and regulations, revised to dateand reset in handy form with map indicating Wireless Stations ofeach country ; Call Letters of Land and Ship Stations. Definitions.Directory of Technical Terms, &c. Also a large number of exclusivecontributions by eminent scientists on the following subjects :Direction Finding, Wireless Telephony, Continuous Waves, AircraftControl, Valves, &c. &c.

ALL PREVIOUS ISSUES ARE OUT OF PRINT-ORDER EARLY

THE WIRELESS PRESS LTD., 12-13 Henrietta Street, London, W.C.2

2J11111111111111111111111111111111111111111111111111111111111

SCIENCE & EST IN PICTURE

INVENTION TE: & TORY

A MAGAZINE OF MODERN ENDEAVOUR.

CONQUEST records, describes, and explains all the great achieve-ments of modern Science, Invention, and Industry. It takesits readers "behind the scenes" and shows them "how it is done."

CONTENTS FOR MARCH.The Puke of the Globe. The Problem of our Water Supply.Vegetable Ivory. Conquests of Medicine.A New Wireless Calling Device. The Story of Anthracite.The World of Sound. The Aeroplane's Debt to the Car Rer,rdPatents and New Ideas. Experiments.Popular Astronomy. Animals of Interest.The Vacuum Flask. Questions and Answers.

PJ11111111111111111V

E ORDERIT

NOW

Subscription Rate 15s. per annum,post free.

12-13, HENRIETTA ST., LONDON, W.C.2

March, 192o. psi' Please mention the Wireless World

THE W IRELESS WORLD (Advertisements)

Alternating and Direct CurrentGENERATORS and MOTORS

D.C. MOTOR -DRIVENAIR COMPRESSOR.

GENERATORS SELF - CONTAINEDOIL AND STEAM GENERATINGPLANTS FOR WIRELESS AND SHIPLIGHTING BATTERY CHARGING, @c.

Also manufacturers of: :

HIGH FREQUENCY MACHINESBOOSTERS SWITCHGEAR ARC LAMPSCONVERTERS INSTRUMENTS PROJECTORS

CFt01%/IF'IT'CITV & CO. LTDTelegrams:-Crompton. Chelmsford

CHELMSFORDTelephones :-161 Chelmsford

linesi

THE ZODIACTHE SUBMARINE

CABLE -SERVICE PAPER.News from the Cable Stations and Ships,illustrated with many interesting photo-

graphs and drawings.

Monthly, 6d.; or 6s. per annum,post free to any part of the world.

THE ZODIAC PUBLISHING COMPANY. LtdElectra House, Finsbury Pavement. London. E.C.

LIVERPOOL VICTORIAFRIENDLY SOCIETY.

Chief Office-ST. ANDREW STREET, LONDON, B.C. 4.

Claims Paid - - £14,750,000Invested Funds - £7,500,000Annual Income - £3,000,000

LIFE AND ENDOWMENT ASSUR-ANCES AT POPULAR RATES

Liverpool Victoria Approved Society.- Ournumerous Branch Offices and Agents throughout theKingdom transact National Health Insurance.

ARTHUR HENRI, Secretary.

MINERAL CRYSTALSFOR DETECTORS

Pure Zincite...7/6 oz. Galena ...6d. & 2/6 ozFused Silicon 2/- Iron Pyrites 6d. & 5/6 Copper Pyrites 6d. Bornite 9d. Molybdenite... 116 Carborundum 1/- Tellurium 2/6 dram " Radiocite,- mtd.5/-Wood's Metal for fixing Crystals ... ...2/ -Set of 9 Crystals and Wood's Metal, 5/- & 7/6Write Secretary. G.P.O. London. for permit to purchase.

RUSSELL & SHAW38, GREAT JAMES STREET,

BEDFORD ROW, LONDON, W.C. 1.

ALL ENQUIRIESrespecting Advertisementsin the "Wireless World"should be addressed

To the

ADVERTISEMENT OFFICES,BERTRAM DAY & CO. LTD.110 -11 1, STRAND, LONDON, W.C.2

Telephone-.8166 Gerrard.

March, 1920. xxii Please mention the ll'ireless World


WestonSTUDENT'S

GALVANOMETER

Model 375 Galv.anometer isa moving coil instrument witha uniformly divided scale 2.35inches long.Its resistance is approximately29 ohms and the currentrequired for a millimeter(i scale division) deflectionis 20-2 5 micro -amperes.

WESTON ELECTRICAL INSTRUMENT CO., LTD.Audrey House, Ely Place, Holborn, E.C.

PATTERNS, PRICES, andMEASUREMENT FORMS

POST FREE

Telephone - 139 CENTRAL

forWIRELESSUNIFORMSUP TO Dc.17'8, -write

SELF & SONUniform Specialists

RAILWAY PLACE (oppositeFenchurch St. Railway Station)

9, LONDON STREET, AND79, FENCHURCH STREET

LONDON, E.C. 3.11-areh, x. PleaRe mention the Wireless World

THE TVIRELESS WORLD (.1dyertisenicnis)

WIRELESS TRAINING COLLEGE LTD.ST. MARY ST., CARDIFF, and CASTLE ST., SWANSEA

The above Colleges are amongst the most successful in Great Britain forquickly qualifying Students for the Wireless Service. We have, since theoutbreak of War, passed over 1,000 Students to Wireless Appointments.Two Systems are taught, the Marconi and Siemens Quench Spark System.We make a speciality in training ex -service men who have some know-ledge of Wireless. Ex -service men can have a free test to ascertainthe time it would take to qualify them if they will call at the College.

For Terms apply to-LIEUT - COMDR. J. R. SCHO FIELD, M.B.E., R.N.V.R. (C), Principal

P.S. Every student who qualified at our Colleges was placed in a permanent situation.

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BRITISH &

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Established 1818.

SAILORSSOCIETY

A GREAT RECORDOVER 100 YEARSIN SERVICE FOR THE SAILOR

MORE THAN 100 HOMES & RESTSestablished in well knownPorts the world.

DURING THE WAR: -40,000 men, women and children fromtorpedoed ships received in our Homes.1,000 Sailor Prisoners of War savedfrom starvation.

WILL YOU HELP US TO CARRY ONby sending a contribution to:-Sir FrederickGreen. K B.E.. Hon. Treas. 32, Cheapside, E.0 .2

Bank,rs : General Sec.Bank of England. Rev. T. Eynon Davies

The Telegraph andTelephone JournalPublished Monthly in the interestsof the Telegraph and Telephone Service,

under the patronage of thePostmaster -General

PRINCIPAL CONTENTSOF FEBRUARY ISSUE

Telephone Development StudyBy Geo. E. NICHOLLS.

The Farewell to Sir Andrew Ogilvieand Mr. Leonard Horne.

Paris TelegraphsBy H. BOOKER.

Telegraphic Memorabilia.The Baudot (V) By J. J TYRRELL,

The " Crystal " Telephone.EDITORIAL-Reconstruction.

PUBLISHED ATGeneral Post Office North, London, E.C. IPrice 4d. per copy, or 5/6 annually

OFFICIAL ORGAN OF THE ROYAL AERO CLUB PREMIER &FIRST AEROWEEKLY INTHE WORLD

The ADVERTISER'SMEDIUM

soVe.41/R,CRA Fr

ENGINEER,.

6d. WEEKLYPublishing Offices:

36, GT. QUEEN ST.,KINGSWAY. W.C. 2Telephone : Gerrard 1828

Telegrams:Truditur, Westcent.

London"

I.: ii, 1920. xxiv i'tease mention the Wireless World

7'HE WIRELESS WORLD (Advertisements)

NEW PUBLICATIONS OF

THE WIRELESS PRESS LTD.12-13, Henrietta Street, Strand, London, W.C. 2

Just Published.SELECTED STUDIES INELEMENTARY PHYSICS

A Handbook for Wireless Students & Amateurs.By E. BLAKE A.M.I.F .1.

17Er6owpnag

try o PRICE 5/- NET 84t111Dusitargaortime:Cloth POST FREE 5,. 4d.

Just Published.WIRELESS TRANSMISSION OFPHOTOGRAPHS By MARcus J. MARTIN

Second Edition, Revised and Enlarged

Demy143 pa ges PRICE 5/- NET Diagrams &

8vo.Cloth POST FREE 5s. 6d.

USEFUL NOTES ONWIRELESS TELEGRAPHY

By H. E. PENROSE.

Crown 8vo. 1 /4 EACH Post Free Is. 6d.

Book I. Direct Current. Book 2. Alternating Current.Book 3 High Frequency Current & Wave Production.Book 4. The I K.W. Ship Set.Book 5. The Oscillation Valve,

TELEPHONY WITHOUT WIRESB' PHILIP R. COURSEY, B.Sc. (Engg.) A.M.I.E.E.

grAY 8'. PRICE 249 Diagrams1 5/- NET & IllustrationsPOST FREE 15s. 6d.

THE OSCILLATION VALVEThe Elementary Principles of its application toWireless Telegraphy. By R. D. BANGAYCrown 8vo. 110 Diagrams215 pages 5/- NET & Illustrations

POST FREE 5s. 6d.

THE THERMIONIC VALVEand its Developments in Radio -Telegraphy andTelephony. By J.A.ELEMING, NI.A.,D

1 5/- NET 144 Diagrams279 pages.Demy 8vo,

POST FREE 15, 6d.

ALTERNATING CURRENT WORKAn Outline for Students of Wireless Telegraphy.

By A. SHORE, A.M.1.1.E.163 pagesCrown 8vo. PRICE 3/6 NET 86 Diagrams& IllustrationsCloth POST FREE 3s. 10d.

NOTICE OF INCREASED PRICES.While we regret the necessity of making these increases, the bigadvances in cost of paper, printing and binding oblige us toincrease the prices of the following publications.

Practical Wireless Telegraphy by E. BUCHER ...Vacuum Tunes in Wireless Communication by E. BUCHERPractical Aviation by J. ANDREW WHITE ... .Electrical Experimenter's Manual by E. BUCHER ... ..Signal Corps Manual by J. ANDREW WHITE ... .Radio Telephony by A. N. GOLDSMITHRadio Instruments and Measurements ...How to Pass U.S. Government Wireless Examinations

by E. BUCHER ... 5s. Od.How to Conduct a Radio Club by E. BUCHER ... 5s. Od.Handbook of Technical Instruction for Wireless Telegraphists

by HAWKHEAD and DOWSETT 7s. Od.Bangay's Elementary Principles of Wireless Telegraphy,

2 Vols. in one 7s. Od.Elementary Principles of Wireless Telegraphy, Parts I and

II, sold separately... ... 3s. 6d.

12s. 6d.12s. 6d.12s. 6d.12s. 6d.12s. 6d.15s. Od.9s. Od.

FULL CATALOGUE POST FREE UPON APPLICATION

March, ipso. xxv Please mention the Wireless World

THE WIRELESS WORLD (A dvertisem cuts)

USEFUL PUBLICATIONSfor a WIRELESS BEGINNERMorse Code Card

Contains full alphabet, with punctuationmarks, figures, abbreviations, and contractions.Price 2d., post free.

Dictionary of Technical Termsused in Wireless Telegraphy.

By HAROLD WARD. Second Edition.Revised and Enlarged. Vest Pocket size.Contains over 1,500 definitions. Price 2s. 6d.net. (Postage 2d.)

The Elementary Principles ofWireless Telegraphy.

By R. D. BANGAY. In two parts. Price 3s.each. (Postage 4d.) Or in one volume,price 6s. net. (Postage 6d.) Invaluable forinstructional purposes. Used by H.M.Government.

The Maintenance of WirelessTelegraph Apparatus.

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Magnetism and Electricity forHome Study.

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Answers to above. 2s. net per series.(Postage 3d. each.)

The Handbook of Technical In-struction for Wireless Telegraphists.

By J. C. HAWKHEAD and H. M.DOWSETT. Second Edition. ThoroughlyRevised. Provides a complete theoreticalcourse for the Postmaster -General's certificateof proficiency. 344 pages. 240 diagramsand illustrations. Price 6s.net. (Postage 6d.)

THE MARCONI OFFICIAL GRAMOPHONE RECORDS

For Self -Tuition in Receiving Morse SignalsPrice 4s. each, double -sided. (Postage 9d.)

COMPLETE DETAILS UPON APPLICATION.

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THE W. P. BUZZER SETConsisting of KEY BUZZER, BATTERY, AND CONNECTIONS

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Brass Key on Ebonite Base, mounted on PolishedWood Box, containing Buzzer and Standard Bittery Price 1

Pottage (earn) British Isles 6d., Abroad is. 6,1.

1 0

The Wireless Press Ltd., 12-13 Henrietta Street, London, W.C.2March, 192o. Please mention the Wireless World


A,avAL, miLiTaxr and E

SHIPPIA9 OUTFITTE70== == REGULATION UNIFORM= == -for MARCONI OFFICERS.==M ii

= 'Her, Rayner & HaysomLIMITED.

110, FENCHURCH STREET, LONDON, E.C.3

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ESTABLISHED 1818.

CONTRACTORS TO H.M. GOVERNMENT AND= THE PRINCIPAL STEAMSHIP LINES, ETC.

=_ =

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MAKERS OF

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CONTRACTORS TO ADMIRALTY, WAR OFFICE,INDIA OFFICE, AND COLONIAL GOVERNMENTS

ilarch, 792o. xxvii Please mention the IVireless World

THE WIRELESS

You are invited to read

THE

"Merchant Shipping Reviewand Empire Trade Gazette "

THE MONTHLY JOURNAL

For those interested in

Transport,Ship Construction,EngineeringandAviation.

To be obtained of all bookstalls, Newsagents,etc., at the principal ports at home and abroad,

or direct from the Publishers -

5, Richmond Street., Liverpool,and

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T T-ORLD (At17'crtisc,;/ /its')

"HOW TO BUILD

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Although this course o, lessons is worth pounds uponpounds to anyone who uses it rightly, the price has been fixedvery low-al- net. "How to Build Mental Power," a wellbound volume of boo pages; with many diagrams in black andcolours, will be sent on three days' approval upon receipt ofthe special order form below.

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Please Note New Registered Address

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Telegrams-NORNODESTE

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701-802, Tower Building, Liverpool66, Scottish Temperance Buildings, Belfast

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.11q1 , / fi Please mention the Wireless World

THE WIRELESS TVORLD (Advertisements)

Pitman's Technical BooksNew Edition

WIRELESSTELEGRAPHY

BY

W. H. MARCHANTA Practical Handbook for theuse of Operators and StudentsThis book is intended primarily for the useof those engaged in the practical operationof Radio -Telegraph installations, and forstudents who already possess some knowledgeof electrical science. It has been thorough yrevised and now includes all the latestdevelopments.

Second Edition, Revised and Enlarged.With 201 Illustrations, 7s. 6d. net.

GUIDE TO THE STUDY OF THE IONICVALVE. By W. D. OWEN, A.M.I.E.E. This is not a text -bookbut a carefully prepared résumé of the whole valve situation. which willenable operators to bring themselves abreast of the enormous developmentsin Wireless transmission and reception. Students will find this little book anexceedingly useful companion volume to text -books on the subject.Illustrated 2s. 6d. net.

WIRELESS TELEGRAPHY AND HERTZIANWAVES. By S. R. BOTTONE. Filth Edition. thoroughly revised byC. SYLVESTER, A .M.I.E.E An elementary text -book. Contentsinclude -Preliminary Motions - Historical Considerations on the HertzianWaves-Construction fl Details. With 39 Illustrations. 3s. net.

THE RADIO TELEGRAPHISTS' GUIDE ANDLOG -BOOK. By W. H. MARCHANT This book should be foundbeside every operator of wireless telegraphy apparatus. It describes theapparatus, gives regulations and instructions for the working of installations,log sheets for keeping records. etc. etc. With 90 Illustrations Ss. &I. net.

LIGHTNING CONDUCTORS & LIGHTNINGGUARDS. By Sir OLIVER J. LODGE, F.R. S., LL.D., D.Sc.,M.1.E.E. A Treatise on the protection of buildings, telegraph instruments,and of electrical installations generally, from damage by atmospheredischarges, With numerous Illustrations, 15s. net.

Write for Complete List of Technical Handbooks post free from:-SIR ISAAC PITMAN & SONS, LTD., I AMEN CORNER, LONDON, E.C.4

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Catalogue nd expert adv.ce where necemo, to*.PINCH1N, JOHNSON & Co., Ltd.,GENERAL BUILDINGS ALDWYCH. LONDON W C.2

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THE WIRELESS T VORLD (Advertisements)ii11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111ii

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March.. 1920. x xx Please mention the Wireless World


The London Telegraph Training College Ltd.Telephone

WESTERN 2696. Morse House, Earl's Court, S.W. ES21.5A[31X/TD

OFFICIALLY RECOGNISED BY THE WAR OFFICE AND POST OFFICE AUTHORITIES

CABLE AND WIRELESS TELEGRAPHY.PARENTS desirous of placing their sons in either of the above Services and of affording them the

best training facilities should apply for particulars of Courses and the methods of instruction whichplace this Institution ii the first rank. Cable Telegraphy offers at the present time excellent

prospects to youths from 15 years of age and upwards, and the College has exclusive facilitiesfor obtaining posts for qualified students in the leading Cable Companies at commencing salaries of£140 to £200 per annum, with yearly increments of £12 to £25, and ultimate possibilities ofobtaining positions as Supervisors, Assistant Superintendents, Managers, etc.

In the Wireless Telegraph Service the commencing remuneration at the present time isapproximately £150 per annum, and Operators, when qualified by obtaining the Postmaster -General'sCertificate of Proficiency, are nominated by the College for appointments.

ACo Correspondence Classes or Branches.

DAY AND EVENING CLASSES.

An Illustrated Prospectus containing all information will be forwarded on application to

THE SECRETARY (Dept. H), 262, Earl's Court Road, Earl's Court, London,S.W.5Sole Proprietors of the Scott Training Disc which contains useful formul& and other informationfor Wireless Telegraph Operators and is invaluable to Army Signalling Officers for range finding, etc.

Price, complete with instructions for use, 1/... Postage 2d.

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Young men wishing to enter a remunerative and pro-gressive profession should commence training asWirelessOfficers in the Mercantile Marine or the CommercialService. Fully qualified Operators are in demand,and first-class training is given at our Schools.A new field is opened up for ambitious young men inthe construction of Aircraft and Wireless EquipmentWe give special facilities to those wishing to studyin this branch Day and Evening Classes

THESE ARE THE ONLY SCHOOLS INGREAT BRITAIN FITTED WITH COM-PLETE STANDARD MARCONI. POULSENAND TELEFUNKEN INSTALLATIONSThese 'chcol are now fitt-d with a standardMarconi Valve Transmitter and Amplifying Receiver.

Write now for Illustrated Prospectus

North-Eastern Schools of Wireless Te!egraphy6. BLENHEIM TERRACE, LEEDSCENTRAL CHAMBERS, HIGH ST., SHEFFIELD18, ELDSON SQUARE. NEWCASTLE - ON -TYNEHarsh, 1920.

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xxxi Please mention the Wireless World

THE WIRELESS WORLD (A dvertisetnents)

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41 arch, 7920. xxxii Please mention. the Wireless World

THE WIRELESS WORLD (i..1dvcrliseincnts)

1920 DIARIES NOW READYTHE WIRELESS AMATEUR'S THE WIRELESS OPERATOR'S

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CONTENTS.Principal Wireless Stations on Ocean Routes.Table for Calculating Tolls on Messages.Some Typical Valve Circuits. Freak andLong Distance Communications. Best Adjust-ments of Receiver for Various Wavelength.

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The Wireless Press, Ltd., 12-13, Henrietta Street,London, W.C.2.

ROBISON'S MANUAL ofRADIO -TELEGRAPHYAND TELEPHONY

(Fifth Edition, revised and enlarged)By Capt. S. S. ROBISON, U.S.N.,

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A NEW BOOKBY THE AUTHOR OF THE FAMOUScc THEORETICAL PRINCIPLES OFWIRELESS TELEGRAPHY"

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March, 1920. xxxiii Please mention the Wireless 1V orld

THE 'WIRELESS WORLD (Advertisements

Tel. Address- Telephone-' Gardlocket. Fen. London.- 1o50 Avenue (3 lines).

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THE 100 PER CENT.Wireless MagazineThe Magic of Wireless iscalling. You can now hearwireless 'phone talk and re-ceive messages from the U.S.All about these and hundredsof other important things ofinterest to the Amateur are inthe Radio Amateur News.The greatest and biggestwireless magazine in U.S.Over 10) illustrations. 48 bigpages,

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Radio Amateur News254. Fulton St.. New York.

A New Instrumentfor Rapid LearningScribo-Morse No. S. 167Scribo-Morse, No. S. 167, consists of arectangular polished mahogany box con-taining inside a buzzer and battery, andaffixed to the outside a metal plate havingthe Morse characters in relief, as shownwhite in the illustration, the remainder ofthe plate being heavily coated with anon -conducting material.

One end of the buzzer circuit is connected to the plate and the otherto a metal Pen by means of a flexible lead. By passing the Pen firmlyover the metal signs, each in turn will emit through the buzzer itscharacteristic sound, and thus the learner's ear will rapidly becomeaccustomed to the peculiar rhythm of each letter as he hears it.

GRAHAM & LATHAM, LTD., Military Engineers(Dept. W. 2), 27, LOTS ROAD, CHELSEA, LONDON. S.W. 10

March, 1920. xxx Please mention the Wireless World

/ / f .1(17'cr/iscii/

A WIRELESSTRAINING

A T A CITY SCHOOL is a guarantee of the best possible Wireless' training. Efficient staff and thoroughly up-to-date methods. TheSchools at MANCHESTER, NOTTINGHAM and BIRMINGHAM are eachequipped with a standard 11 K.W. Ship Set, etc. Day E.4 Evening Classes,also Postal Course. Students may join at any time. Fees moderate.

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Full particulars and Prospectus on application to the Principal : Mr. J. R. HALLIWELL

CITY SCHOOL of WIRELESS TELEGRAPHY61, HIGH ST., MANCHESTER (Tel. CITY 5210).County Chambers, 66i, Corporation St., Birmingham.Guardian Chambers, 4, Bridlesmith Gate, Nottingham.

"The Model Engineer"A splendid paper for young Engineers, Apprentices.Students and Amateurs interested in Mechanics,Electricity and Model Making. It contains practicalarticles by experienced writers on Electrical andMechanical subjects. Locomotives, Motor Cycling.

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XX XV

REGARDING MARINE UNIFORMSA CUSTOMER WRITES:-

" The uniform arrived in quick time.fits well, and is very satisfactory. -

IF you are requiring a complete Sea OutfitPaterson's have made a special study of the

requirements of Mercantile Marine officers,and guarantee correct regulation style. Youshould call and see their splendid range ofsuperior cloth, the smart high-class make, theperfect fit and finish, and exceptional value.

UNIFORM Made to your orderSUITS Complete in every detail

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D EGULATION Naval Trench CoatsINAINCOATS Oilskins & WaterproofsSPECI .1 L. ATTENTION TO POST ORDERSWrite to -day Joy scientzn: self-nteasurement form

PJ. & M. PATERSON LIMI1 ED

NAVAL AND MARINE TAILORS301 ARGYLE ST., GLASGOW

ATERSON

Specially Recommended /or Good Honest raz,,,,

IMMINNI NMI Please mention the Wireless World


HARVEYS'17, London Street, London, E.C. 3Telephone :Avenue 2200.

FACING FENCHURCH STREET STATION.I Book to Mark Lane or \kFencharch St. Station/

Eusiness hours 9-6.Saturdays 1.30.

HOSIERY DEPARTMENT :: 15 LONDON STREET.OUTFITTING :: 16

WE HOLD

SPECIAL PRICESFor OPERATORS

Uniform Serge Suit complete,lace and buttons £6 6 0Superfine Cloth Coat andTrousers, lace and buttons

L8 8 0Bridge Coat or Naval Warmwith shoulder straps andbuttons, complete £4 15 0R.N. Cloth Cap, standardbadge and band ... 24/ -

Badges, standard .. 15/ -

Standard Buttons : Coat,Mess, Vest, per dozen 3/-,

2/6, 1/6White Suits,Naval Belted Coats, andeverything for NAVAL wear.

THE LARGEST STOCK OF WHITE

9,1

SUITS IN LONDON, ALL SIZES TO BE HAD HERE.

TAILORS, OUTFITTERS, BOOTS, HOSIERY,OILSKINS, WATERPROOFS. Noted for First-class Cut.

HARVEYS'Our Name is Your Guarantee. Send for Our -List.

(OPPOSITE FENCHURCH STREET STATION)

March, 192c. xxxvi Please mention the Wireless World

V he OHMER INSULATIONTESTING SET (COX'S PATENT)This is the lightest, cheapest and best instrument of itskind on the market. It consists of an Ohmeter and Generatormounted in one case. The Ohmeter is of the Electrostatictype, giving extreme lightness. Absolutely unaffected byexternal fields. It reads directly in Megohms and isindependent of the voltage or speed of the generator.

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TWO GOOD WALLETSSolid Leather, size 6i X 4 when folded

"THE LONDON "-With space for photograph.Two roomy pockets. Two pockets for Treasury Notes.Space for cards and postage stamps.

"THE YORK"-With pull-out photograph holder.One tight pocket for Treasury Notes. One gussetpocket for letters. Card and stamp pockets.Price, either pattern, by registered post, 17/6 each.

EDEN FISHER & CO., LTD.95, 96 & 97, FENCHURCH ST., LONDON, E.C.3

UNDERTAKE SUPPLY OF ALLREQUISITES FOR ENGINE ROOMS,POWER PLANT, MACHINE SHOPS, &c.

WRITE FOR ILLUSTRATED LISTS

W. H. Willcox & Co., Ltd.32 to 38 SOUTHWARK ST.. LONDON, S.E. I

Our Specially RefinedLubricants are in use onevery class of Machinery.

Registered NIPHAN " Trade Mark

WATER - TIGHT PLUGS& CABLE COUPLINGSTO MEET HOME OFFICE REQUIREMENTS

5 to 250 Amps500 Volt Circuit

1,11P14AN

As used by H.M.War Office, Electric Supply Cm..Railway Cos., Marconi's Wireless Telegraph Co.

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Patented in Englandand Abroad.

COUPLING CONNECTING CABLES 3 -WAY TEE

March, 1920. Please mention the Wireless World

THE

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BUILDERS OF STEEL BRIDGES,PIERS, ROOFS, GIRDERS, & ALLKINDS OF CONSTRUCTIONALSTEEL AND IRON WORK

Electrical Transmission Masts

CHEMICAL PLANT MANUFACTURERSSEGMENT AND PIPE FOUNDERSCASTINGS OF EVERY DESCRIPTION

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Works :

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Telegrams : " Foundry, Widnes."

Telephone : No. 225 Widnes.

London A gents :GEORGE F. WEST & CO.,

13, VICTORIA STREET,LONDON, S.W.

Telegrams : " Westeelite, London."Telephone : 4340 Victoria.

Printed by Sanders Phillips Co., Ltd., 6 P 8 Upper Thames Street, E.C. 4, for the Proprietorsand Publishers. The Wireless Press Ltd., 12-13 Henrietta Street, London W.C. 2 ; Sydney, N.S.W97 Clarence Street; Melbourne, 433/4 Little Collins Street ; New York, 25 Elm Street; Rome. via.Gregoriana. 36 ; South Africa, Exchange Buildings, Cape Town, and Central Nevis Agency, Ltd.

Xxx v t

price 9d. net. march, 1920. · 2019. 10. 6. · registered at the g.p.o. for transmission by...

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