one -kilowatt am transmitter, type bta-1s
TRANSCRIPT
RC/1One -Kilowatt AM Transmitter,Type BTA-1S
Excellent frequency response, low distortion
Low operating costs
Circuit breaker overload protection
Positive peak modulation capability: 125%
catalog RA.1011A(Replaces B.6004)
The RCA Type BTA-1S, 1 -kilowattAM Broadcast Transmitter is designedfor reliability, outstanding fidelity, andeconomical operation. It provides a highquality amplitude modulated signal at anyfrequency in the 535 to 1620 kilohertzband and is capable of producing a max-imum of 1100 watts.
Highly perfected audio circuits togetherwith a large, high -quality modulationtransformer and reactor provide 125 -per-cent positive -peak modulation capabilityand unusually high fidelity sound. Stable,long -life tubes and solid-state devices havebeen used throughout the transmitter. Cir-cuit breakers, not fuses, provide completeoverload protection.
Provision for remote control and sim-plified power cutback are reflected inthe BTA-IS design. Front panel or re-mote control selection of any two powerlevels of 1000, 500 or 250 watts is avail-able. No unnecessarily complicated cir-cuitry or superfluous parts have beenincluded and all components are easilyaccessible for maintenance and inspection.
12WB
RA.1011A
Type BTA-1S Transmitterwith outer and inner dooropen to display access-ibility to the tubes. Poweramplifier and modulatortubes are near top whiletie lower chassis carriesthe audio -amplifier andintermediate stages.
in.
Unimpeded rear access tothe transmitter is affordedby the full length door andthe well laid out, verticalconstruction. Power supplycomponents at bottom; r -fcomponents at top.
RA.1011A
Functional DesignImproved functional design includes
RCA's new color combination. Squareconstruction permits locating the trans-mitter against the wall, or it can be in-stalled against other equipment. Thevertical construction makes it accessiblefrom both front and rear for ease ofmaintenance. A single front panel tuningcontrol provides simplified operation. Re-mote control provisions permit unat-tended operation of the transmitter.
Simplified Power CutbackThe BTA-1S easily fits into operations
where power reduction at night is re-quired. For "day -night" operation anoptional Power Cutback Kit may be in-corporated in the transmitter. By pressinga button on the front or at a remotepanel, the transmitter can be cut backin power to either 500 or 250 watts. Ef-ficient operation at the low power levelsis achieved by reducing the high voltageby primary taps on the plate transformer.
Complete AccessibilityThe entire transmitter is housed in a
single steel cabinet that is mounted on asturdy welded steel base. Control com-ponents are conveniently located on thepanel above the front door and all metersare at eye level. Easy access is providedby a hinged front door and two interlockedremovable rear panels. Most BTA-1S com-ponents are mounted on a vertical centerchassis. Tubes and overload relays aremounted on the front and the other com-ponents are mounted on the rear. Largerpower components are mounted on thebase.
Solid State Power SuppliesThree power supplies are used: a low
voltage supply for plate and screen volt-ages of all low voltage tubes, a bias sup-ply for the modulator tubes, and a highvoltage supply for the modulator andpower amplifier tubes. All power suppliesuse silicon diodes which results in lowpower drain, cool operation and reliableperformance. Automatic relays protect thetransmitter against overload. These, inturn, are backed up with automatic circuitbreakers. The design avoids the use offuses anywhere in the unit.
Power RequirementsThe transmitter operates from a 208-
240 -volt, 50/60 -hertz, single-phase powersource for the main power. In addition,the crystal heaters require 115 -volt powersource.
Solid -State Oscillator andBuffer Stages
Adding an extra measure of transmit-ter stability, the BTA-1S combines itsoscillator and buffer amplifier into asingle, solid-state subassembly. The com-bination of transistorized electronics andtemperature -controlled crystals make foran adjustment -free facility which, in turn,reduces routine maintenance. The oscil-lator is equipped with two temperature -controlled crystals arranged through afront -panel selector switch so that a "hot"spare is always at hand, even via remotecontrol.
Simple, Straighforward CircuitryThe buffer feeds a single 6146A driver
tube which in turn feeds the power am-plifier which consists of two 4-400Atubes connected in parallel. Tetrodes havebeen utilized throughout the RF section ofthe transmitter reducing the required stagesand the power consumption. Tetrodes alsoeliminate the need for neutralization.
The modulator comprises two 2E26tubes in push-pull, resistance coupled totwo 4-400A modulator tubes. The modu-lator tubes operate as a class AB, ampli-
fier u.thout grid current which results inan overall distortion of less than 2 per-cent up to 10,000 Hz.
Parallel/Redundant SystemThe BTA-1S is available also as a par-
allel/redundant transmitter system. Thissystem consists of two identical BTA-1Stransmitters and a combiner. In the"parallel" mode, the twin one -kilowattoutputs are combined to provide two kilo-watts of power to the antenna system; inthe "redundant" mode, the system operatesone of the two transmitters as a hotstandby while the other feeds the antennasystem.
In either operational mode, the par-allel/redundant system assures greater on -air dependability. For example, an outagein one transmitter or the other automati-cally switches the troubled transmitter toa dummy load while the operable onefeeds a full kilowatt to the antenna system.This action is the result of a special -designcombiner with essentially zero insertionloss. Further details of the BTA-1S par-allel/redundant transmitter system areavailable from Aural Broadcast EquipmentMarketing, RCA Building 2-5, Camden,N. J. 08102, U.S.A.
L SOLID-STATEOSCILLATOR AND
BUFFER
IPA6146A
POWERAMPLIFIER(2) 4-400A
y
FIRSTAUDIO MODULATOR
(2) 2E26 (21 4-400A
SOLID- SOLID- SOLID-STATE STATE STATE
L. VSUPPLY
B ASSUPPLY
H VSUPPLY Simplified block diagram
of BTA-1S AM Transmitter.
RA.1011A
Specifications
PerformanceAF Input Impedance 150/600 ohmsAF Input Level (100% modulation) +10 ±2 dBmAF Response:
50-7500 Hz ±1 dB30-10,000 Hz ±1.5 dB
AF Distortion (95% modulation):50-10,000 Hz 2%50-12,000 Hz 3%
Noise (below 100% modulation) 60 dBFrequency Range 535-1620 kHzFrequency Stability ±2 HzType of Output Single endedCarrier Shift (0-100% modulation) 3%Output Impedance 40-250 ohms
ElectricalRF Voltage (for frequency monitoring) 6/10 V rms 75 ohmsRF Voltage (for modulation monitoring) 6/10 V rms 75 ohmsPower Output (nominal) 1000 watts
1100 watts208/240 volts
50/60 HzSingle
Power Output CapabilityPower SupplyLine FrequencyPhasePower Consumption (Approx.):
0% modulation 2900 watts100% modulation 3900 wattsAverage program modulation 3200 watts
Power Factor 90%Permissible combined line voltage variation
and regulationCrystal Heater Power Supply 115 volts 50/60 Hz
Tube Complement1 6146A
2 2E26
2 4-400A
2 4-400A
Intermediate Power AmplifierAudio Frequency AmplifierModulatorPower Amplifier
MechanicalHeight 77" (1955 mm)Width 26" (660 mm)Depth 30" (762 mm)Weight (net) 900 pounds (408 kg) (approx.)Altitude Range 0.-5000 ft.* (0-1254 m)Ambient Operating Temperature -20 to 45°C (-4- 113°F)Shipping Data 1200 lbs (544 kg); 79 ft3 (2.23 m3)
AccessoriesOperating Spare Tube Kit ES -560655
Recomended Minimum Spare Tube Kit ES -560656
Frequency and Modulation Monitor,Type BW-50 M I-560767
RF Amplifier (for BW-50) MI -560762
Thirty -Function Remote Control, Type BTR-15 MI -561150
Sixty -Function Remote Control, Type BTR-30 MI -561440
High -Altitude Blower Kit MI -34309-8
Spare Crystal Unit, Type TMV-130(Specify Freq.) MI -27493
RF Ammeters MI -7157-F Series
Remote RF Pickup Unit (less meter) M I -27966-B
Power Cutback Kit (Two Level) MI -560657
Remote Power Adjust Kit MI -560658
Oscillator -Buffer (Solid -State) MI -27592
Ordering InformationOne -Kilowatt AM Transmitter, Type BTA-1S ES -560650
250- or 500 -Watt AM Transmitter,Type BTA-1S (Specify power level) ES -560947
'To 10,000 ft. (3048 m) with optional blower (M1-34309-8).
l'IL A BroadcastFront and Cooper Streets, Camden, New Jersey 08102, U.S.A. Systems
RCA5 kW Ampliphase Transmitter,type b I
High Fidelity Modulation (HFM)
Low -distortion audio
Solid-state exciter/modulator
Extra modulation capability
Designed for remote control
Only two tube types in entire unitNo modulation transformer
catalog RA.1031B(Replaces RA.1031A)
T -e BTA-5L2 is an Ampliphasetransmitter for the AM -broadcast(Tedium -wave) band which delivers5 kW to the antenna transmission line.The system offers superior audioquality, outstanding reliability andexcellent efficiency.
A3 a result of the Ampliphase system,th-e BTA-5L2 Transmiter deliversextended audio -frequency responseat distortion levels well below averageperception at enviable operatingeconomy and dependability.
The BTA-5L2 is available also indual -unit systems for parallel oralternate -main operation.
In the "parallel" arrangement, theoutputs of the two transmitters in thesystem are combined for a 10 -kilowattpower output; in the alternate -mainsystem, one transmitter serves theload while the second operates inhot standby mode. In this configura-tion, an outage in one transmitteror the other automatically connectsthe operable unit to the load.A special feature of the parallelsystem is that, in the event of outagein one transmitter, the other trans -m tter delivers a full five -kilowattocput to the load.
SARA
Page 2 RA.10318
Outstanding Audio QualityOf particular interest to broadcasters
who take pride in station "sound", theBTA-5L2 Transmitter offers outstandinglygood audio quality. One reason for thisis that the Ampliphase system eliminatesiron -core high-level modulation compo-nents - and their inherent distortions -without adding the instabilities of separate"carrier" and "peak" power amplifiers.Even on ordinary AM radios, the out-standing audio quality of an Ampliphasetransmitter is immediately apparent.
Extended Frequency ResponseAs evidence of the frequency -response
characteristics the BTA-5L2 offers, it canput 30 kHz on-the-air-at full power-without strain. At the low -frequency end ofthe spectrum, frequencies down to 30 Hzgo on -the -air at full level and low distor-tion. Transformer -equipped transmittersusually cut off below 50 Hz and above15 kHz.
Extra Modulation Capability-"Superphase"
An advantage unique to the Ampli-phase system is its capability for fullmodulation, even for extended periods,without overload. This is particularlyimportant to stations programming musicof high average level and low dynamics.Positive modulation peaks can go as highas 125 percent without transmitter over-load. Another unique feature in Ampli-phase is that it overmodulates withoutthe "splatter" so common to other AMtransmitter forms.
Provision for Spare ExciterFor those who prefer redundant ex-
citers, the BTA-5L2 Transmitter providesrack space for a spare exciter. Offered asan option, the spare exciter includes switch-ing gear for fast exciter substitution. Aspare exciter is particularly valuable tothe full-time station in that exciter main-tenance is independent of transmitteroperation.
Ready for Remote ControlBecause the BTA-5L2 is built for the
modern broadcaster it is engineered withremote control in mind. This manifestsitself in extra components, wiring andconnections fully compatible with remotecontrol equipment carrying the RCAtrademark. As a result, operating a BTA-5L2 via remote control requires investmentonly in control equipment and not intransmitter modification.
Two Tube TypesBeing entirely solid-state at power
levels below the IPA stage, the BTA-5L2Transmitter uses a total of only fourpower tubes: two in each channel. Since
Rear view, panels removed.
Font view, doors open. Note exciter unit.
Page 3 RA.10318
these are of only two types, spares inven-tory need only be two tubes: one of eachtype. This reduces capital investment inspares and periodic rotation.
No Modulation TransformerUsing two identical R -F amplifier
chains, the BTA-5L2 Transmitter usesphase modulation, at a low level, in sucha manner that two phase -modulated car-riers mix at the transmitter output to forman amplitude -modulated carrier. Since thissystem eliminates the modulation trans-former and "carrier -peak" amplifiers, iteliminates the most -troublesome stages.This reflects itself in transmitter depend-ability that virtually eliminates unsched-uled transmitter shutdown.
Faster TroubleshootingA feature unique to Ampliphase makes
routine repair easier. In a sense, a 5 -kWAmpliphase transmitter is two identical2.5 -kW facilities in a single cabinet. Con-sequently, one amplifier chain is an ex-cellent troubleshooting model for theother. Because the operating parametersof the two class -C amplifiers (operatingas CW stages) can be quickly compared,the trouble can be isolated easily. Then,it's a simple matter of component replace-ment.
Ceramic Insulated PA TubesCeramic power tubes have earned an
enviable reputation among broadcasters
POWERCONTROL
CRYSTALOSCILLATOR
Block diagram forBTA-5L2.
EXCITER
PHASEDELAY
PHASEMODULATOR
AUDIOIP.PUT
I
FEEDBACKDETECTOR
Oki fi.)
011.-101.1 MI.1(11:10
IMMINI=:0111MI MI=1:12! 0 0
Ampliphase exciter unit. Completely solid-state, this unit is used in all RCA Am-pliphase transmitters. Available separately for use as a spare. See Accessories.
for dependability and long life. The tubetypes selected for the BTA-5L2 operatewell below ratings to take full advantageof their performance capabilities andbuilt-in expected life. This pays dividendsin low transmitter -operating expenses.
Fully Self -ContainedAs the result of transistorization, the
entire transmitter-including the powersupply-fits within a single cabinet thatoccupies less than 14 square feet (1.3 m2)of floor space (see floor plan). This, ofcourse, frees plant area for other pro-ductive purposes; office, studio or storage.
Parallel/Alternate-MainThe BTA-5L2 transmitter is available
also as a parallel system. This arrangementuses two BTA-5L2 transmitters and a
PULSEGENERATOR
PULSEGENERATOR
DRIVEREGULATOR
SOLID STATEPULSE
AMPLIFIER
SOLID STATEPULSE
AMPLIFIER
combiner. In the "parallel" system, bothtransmitter outputs are combined to pro-vide ten kilowatts to the load. Should onetransmitter or the other have trouble, theoperable transmitter continues to supplythe load while the troubled transmitter isautomatically switched from the antennato a built-in dummy load.
In the alternate -main arrangement, onetransmitter ordinarily feeds the antennasystem while the other operates as ahot standby into a dummy load. Shouldthe "air" unit fail, the system auto-matically connects the standby unit tothe load and the troubled transmitter tothe dummy load.
Further details are available fromAural Broadcast Marketing, RCA Build-ing 2-5, Camden, N. J., 08102, U.S.A.
TRANSMITTER
DRIVER8122
DRIVER812 2
HPA
3CX5000H3
_1 PA3CX5000H3
COMBINING8 OUTPUTNETWORK
TOANTENNA
Page 4 RA.1031B
EXHAUST FAN ( NOT SUPPLIED)
WIRE DUCT TO POWER SOURCE
DOORS REMOVABLE
6" (152)
TRANSMITTER
70" (1778)
22" ( 559) FRONT DOORS
PARENTHETICAL DIMENSIONSARE IN MILLIMETERS
8" ( 203)
OPTIONALPHASING
EQUIPMENT
1
BTA-5L2 Floor Plan.The transmitter isentirely self-contained.
Power Output (Nominal) 5,000 wattsPower Output Capability 5,500 wattsAF Input Impedance 150/600 ohmsAF Input Level +10 ± 2 d B mAF Response ±1.5 dB 30-15,000 HzAF Distortion (95% Mod. 30-10,000 Hz) 2.0% max.Noise (Below 100% Modulation) 60 dBFrequency Range 535-1620 kHzFrequency Stability ±2 HzType of Output UnbalancedOutput Impedance 40 to 250 ohmsCarrier Shift (0-100% Modulation, 400 Hz) 3% max.Power Source 208/240 volts, 3 -phase, +11 volts 50/60 HzCrystal Heater Power 117 volts, 50/60 HzPower Consumption (Approx.):
0% Modulation 10 kWAverage Modulation (30%) 12 kW100% Modulation 17 kW
Power Factor 90%Altitude Range 0-7500 Ft. AMSL (2286 m)Ambient Operating Temperature -20° to +45° C.Tube Complement Two 8122; Two 3CX5000H3Height 77" (1955 mm)Width 70" (1778 mm)Depth 32" (813 mm)
Finish RCA charcoal grey and shadow blue texturedAluminum baked enamel
Weight (Approx.) 2500 lbs. (1134 kg)Shipping Data (Approx.) 3000 lbs.; 180 ft° (1361 kg; 5.1 m')
Accessories and OptionsRecommended Spare Tubes (Set) ES -560682
Complete Spare Tubes (Set) ES -560680
Spare Crystal Unit. Type TMV-130 (Specify freq.) Ml -27493Conversion Kit, 10 kW Power Output ES -560946
Spare Exciter System, Type BTE-20 ES -560752
Manual Exciter Changeover Panel ES -560965
Power Cutback Kit (Two Power Levels) ES -561009APower Cutback Kit (Three Power Levels) .... _____ES -561009BFrequency and Modulation Monitor, Type BW-50 Ml -560767
BW-51 Modulation Meter Ml -561042
BW-52 Modulation Meter MI -563472
RF Amplifier (For BW-50, above), Type BW-60 MI -560762
Transmission Line Protection Kit (VSWR) ES -560961
Suggested Semiconductor Spares (BTE-20B) RO-456
Ordering InformationFive -kW Ampliphase Transmitter, Type BTA-5L2 ES -560676
Dual -Unit Ten -kW AmpliphaseTransmitter System Built to Order
Alternate -Main Five -kW AmpliphaseTransmitter System Built to Order
11111L
iii BroadcastFront and Cooper Streets, Camden, New Jersey 08102, U.S.A. Systems YARDAISI
TRADELAWAR,S1 1t PEGISTEREOREGISTRADAISI
10 kW Ampliphase AM Transmitter,Type BTA-10L2
High Fidelity Modulation (HFM)
Low -distortion audio
Solid-state exciter/modulatorExtra modulation capability
Designed for remote control
Only two tube types in entire unitNo modulation transformer
catalog RA.1041B(Replaces RA. 1041A)
Offering superior audio quality,oJtstanding reliability and excellentefficiency, the BTA-10L2 is anAmpliphase transmitter for theAM -broadcast (medium -wave) band.The BTA-10L2 delivers 10 kW to theaitenna transmission line.As a result of the Ampliphase system,the BTA-10L2 Transmitter offersextended audio -frequency responseat distortion levels well below averageperception at enviable operatingeconomy and dependability.
The BTA-10L2 is available also indual -unit systems for parallel oralternate -main operation.
In the "parallel" arrangement, theoutputs of the two transmitters in thesystem are combined for a 20 -kilowattpower output; in the alternate -mainsystem, one transmitter serves theload while the second operates inhot standby mode. In this configura-tion, an outage in one transmittercr the other automatically connectstie operable unit to the load.A specia' feature of the parallelsystem is that, in the event of outagein one transmitter, the other trans-mitter delivers a full ten -kilowattcutput to the load.
SARA
Page 2 RA.1041B
Outstanding Audio QualityOf particular interest to broadcasters
who take pride in station "sound", theBTA-10L2 Transmitter offers outstanding-ly good audio quality. One reason for thisis that the Ampliphase system eliminatesiron -core high-level modulation compo-nents - and their inherent distortions -without adding the instabilities of separate"carrier" and "peak" power amplifiers.Even on ordinary AM radios, the out-standing audio quality of an Ampliphasetransmitter is immediately apparent.
Extended Frequency ResponseAs evidence of the frequency -response
characteristics the BTA-10L2 offers, it canput 30 kHz "on-the-air"-at full power-without strain. At the low -frequency end ofthe spectrum, frequencies down to 30 Hzgo on -the -air at full level and low distor-tion. Transformer -equipped transmittersusually cut off below 50 Hz and above15 kHz.
Extra Modulation Capability-"Superphase"
An advantage unique to the Ampli-phase system is its capability for fullmodulation, even for extended periods,without overload. This is particularlyimportant to stations programming musicof high average level and low dynamics.Positive modulation peaks can go as highas 125 percent without transmitter over-load. Another unique feature in Ampli-phase is that it overmodulates withoutthe "splatter" so common to other AMtransmitter forms.
Provision for Spare ExciterFor those who prefer redundant ex-
citers, the BTA-10L2 Transmitter pro-vides rack space for a spare exciter.Offered as an option, the spare exciterincludes switching gear for fast excitersubstitution. A spare exciter is particu-larly valuable to the full-time station inthat exciter maintenance is independentof transmitter operation.
Ready for Remote ControlBecause the BTA-10L2 is built for the
modern broadcaster it is engineered withremote control in mind. This manifestsitself in extra components, wiring andconnections fully compatible with remotecontrol equipment carrying the RCAtrademark. As a result, operating a BTA-10L2 via remote control requires invest-ment only in control equipment and notin transmitter modification.
Two Tube TypesBeing entirely solid-state at power
levels below the IPA stage, the BTA-10L2Transmitter uses a total of only six power
ram 11111111111111111 EN INIMI MINI11_,
Rear view, panels remcved.
SIM1
Front view, doors open. Note exciter unit.
Page 3 RA.1041B
tubes: three in each channel. Since theseare of only two types, spares inventoryneed only be two tubes: one of each type.This reduces capital investment in sparesand periodic spares rotation.
No Modulation TransformerUsing two identical R -F amplifier
chains, the BTA-10L2 Transmitter usesphase modulation, at a low level, in sucha manner that two phase -modulated car-riers mix at the transmitter output to forman amplitude -modulated carrier. Since thissystem eliminates the modulation trans-former and "carrier -peak" amplifiers, iteliminates the most -troublesome stages.This reflects itself in transmitter depend-ability that virtually eliminates unsched-uled transmitter shutdown.
Faster TroubleshootingA feature unique to Ampliphase makes
routine repair easier. In a sense, a 10 -kWAmpliphase transmitter is two identical5 -kW facilities in a single cabinet. Con-sequently, one amplifier chain is an ex-cellent troubleshooting model for theother. Because the operating parametersof the two class -C amplifiers (operatingas CW stages) can be quickly compared,the trouble can be easily isolated. Then,it's a simple matter of component replace-ment.
Ceramic Insulated PA TubesCeramic power tubes have earned an
enviable reputation among broadcasters
POWERCONTROL
CRYSTALOSCILI ATOP
EXCITER
PHASEDELAY
PHASEMODULATOR
Block diagram forBTA-10L2.
AUD 0IA PUT
a )
111=1=11111=111111==1 M1321== 1=11=11111
*
Ampliphase exciter unit. Completely solid-state, this unit is used in all RCA Am-pliphase transmitters. Available separately for use as a spare. See Accessories.
for dependability and long life. The tubetypes selected for the BTA-10L2 operatewell below ratings to take full advantageof their performance capabilities andbuilt-in expected life. This pays dividendsin low transmitter -operating expenses.
Fully Self -ContainedAs the result of transistorization, the
entire transmitter-including the powersupply-fits within a single cabinet thatoccupies less than 14 square feet (1.3 m2)of floor space (see floor plan). This, ofcourse, frees plant area for other pro-ductive purposes; office, studio or storage.
Parallel SystemsThe BTA-10L2 transmitter is available
also as a parallel system. This arrangementuses two BTA-10L2 transmitters and a
PULSEGENERATOR
PUL SEGENERATOR
SOLID STATEPULSE
AMPLIFIER
FEEDBACKDETECTOR
4
DRIVEREGULATOR
SOLID STATEPULSE
AMPLIFIER
combiner. In the "parallel" system, bothtransmitter outputs are combined to pro-vide 20 kilowatts to the load. Should onetransmitter or the other have trouble, theoperable transmitter continues to supplythe load while the troubled transmitter isautomatically switched from the antennato a built-in dummy load.
In the alternate -main arrangement, onetransmitter ordinarily feeds the antennasystem while the other operates as ahot standby into a dummy load. Shouldthe "air" unit fail, the system auto-matically connects the standby unit tothe load and the troubled transmitter tothe dummy load.
Further details are available fromAural Broadcast Marketing, RCA Build-ing 2-5, Camden, N. J., 08102, U.S.A.
TRANSMITTER
DRIVER812 2
( TWO I
DRIVER812 2
( TWO )
PA3C X10,000113
C X107000113
COMBININGB OUTPUTNETWORK
TOANTENNA
Page 4 RA.1041B
/// , DO riff EXHAUST FAN ( NOT SUPPLIED )
WIRE DUCT TO POWER SOURCE
DOORS REMOVABLE
6"(152)
TRANSMITTER
70" (1778)
22" ( 559) FRONT DOORS
PARENTHETICAL DIMENSIONSARE IN MILLIMETERS
8" ( 203)
OPTIONALPHASING
EQUIPMENT
BTA-10L2 Floor Plan.The transmitter is en-tirely self-contained.
SpecificationsAF Input Impedance 150/600 ohmsAF Input Level +10 ±2 dBmAF Response ±1.5 dB 30-15,000 HzAF Distortion
(95% Modulation 30-10,000 Hz) Less than 2.0%Noise (Below 100% Modulation) 60 dBFrequency Range 535-1620 kHzFrequency Stability ±2 HzType of Output UnbalancedOutput Impedance 40 to 250 ohmsCarrier Shift (0-100% Modulation, 400 Hz) 3% max.Power Source 208/240 volts, 3 -phase, +11 volts 50/60 HzCrystal Heater Power 117 volts, 50/60 HzPower Consumption (Approx.):
0% Modulation 17 kWAverage Modulation (30%) 21 kW100% Modulation 29 kW
Power Factor 90%Altitude Range 0-7500 Ft. AMSL (2286 m)Ambient Operating Temperature -20° to +45° C.Power Output (Nominal) 10,000 wattsPower Output Capability 11,000 wattsTube Complement Four 8122; Two 3CX10,000H3Height 77" (1955 mm)Width 70" (1778 mm)
Depth 32" (813 mm)Finish RCA charcoal grey and shadow blue textured
Aluminum baked enamelWeight (Approx.) 2700 lbs. (1224 kg)Shipping Data (Approx.) 3200 lbs.; 180 ft' (1452 kg; 5.1 m')
Accessories and OptionsRecommended Spare Tubes (Set) ES -560681
Complete Spare Tubes (Set) ES -560679
Spare Crystal Unit, Type TMV-130 (Specify freq.) M1-27493Spare Exciter System, Type BTE-20 ES -560752
Manual Exciter Changeover Panel ES -560965
Power Cutback Kit (Two Power Levels) ES -561009APower Cutback Kit (Three Power Levels) ES -561009BFrequency and Modulation Monitor, Type BW-50 MI -560767BW-51 Modulation only Meter M1-561042BW-52 Modulation only Meter M1-563472RF Amplifier (For BW-50, above), Type BW-60 M1-560762Transmission Line protection Kit (VSWR) ES -560961
Suggested Semiconductor Spares (BTE-20B) RO-456
Ordering InformationTen -kW Ampliphase Transmitter, Type BTA-10L2 ES -560677Dual -Unit Twenty -kW Ampliphase
Transmitter System Built to OrderAlternate -Main Ten -kW Ampliphase
Transmitter System Built to Order
ni A BroadcastFront and Cooper Streets, Camden, New Jersey 08102, U.S.A.Systems .
TRADEDARKISI Et REGISTEREDILSEICAISI REGISTRAPAISI
50 kW "Ampliphase" AMTransmitter, Type BTA-50J
Excellent audio quality
All solid-state exciter
Only six tubes, three types
High modulation capability
catalog RA.1061A(Replaces B.6050)
Ar AM transmitter with FM quality,the Type BTA-50J uses phasemodulation in a way that results inhigh quality AM. The transmitterincludes a fully solid-state exciter andmodulator. "Ampliphase" appliesmodulation at a low level and usesClass C power amplifiers to providethe 50 -kW output.
a
CZ.
0 H
'
00
a
a 0 0a 0 0a 0 0
lOWB
RA.1061A
O
LJ
Compact in -line construction of BTA-50J showing left to right, left hand poweramplifier, exciter, right hand power amplifier, and rectifier -control cubicle.
The RCA Type BTA-50J AMBroadcast Transmitter is a completelyair-cooled, 50 -kW phase - to - amplitudemodulated transmitter designed for highfidelity transmission in the standardbroadcast band (535 kHz to 1620 kHz).It provides a signal of exceptionally lowdistortion and extended frequency re-sponse. Measured response is flat within±3 dB from 35 Hz to 25,000 Hz. Theequipment is capable of being modulatedover the frequency range of 10 Hz to30,000 Hz. Frequency response has beenextended largely through the eliminationof unnecessary transformers in the audiosystem as well as improved circuitry.
Low harmonic distortion with negli-gible carrier shift at maximum signaloutput has been achieved in the BTA-50J by selection of adequate power tubetypes and advanced solid state circuits inthe exciter -modulator -drive regulator de-
sign throughout the entire equipment.The design features an inherently linearsystem capable of continuous high modu-lation levels impervious to inadvertentovermodulation. For example, the trans-mitter may be modulated 100 percent atany frequency between 30 and 15,000 Hzcontinuously for many hours without det-rimental effects to any of the componentparts. A small amount of overall feed-back is incorporated to provide the ex-ceptional performance. With the feedbackcircuit removed, the BTA-50J still meetsFCC specifications for audio frequencyresponse, harmonic distortion and noise.
Lowest Operating Cost in50 -kW Transmitters
A number of new refinements as wellas time tested features which have proventheir worth are incorporated in thismodern 50 -kW transmitter. Power require-ments are moderate for the equipment.
Power amplifier plate efficiency of theorder of 75 to 80 percent is obtained.
Fewer major components, as comparedto those required by many 50 -kW trans-mitters, are used in the BTA-50J. In ad-dition to the low cost of operation of thetransmitter a power -cutback kit can beadded which permits operation at 10 kW.(Other power levels available on specialorder.)
Dual RF ChainsIwo identical RF chains, each develop-
ing 25 kW, are incorporated in this equip-ment. Since they are identical, servicingis made easy by comparison of the twochains. Components are directly inter-changeable, which allows substitution forcomparison purposes. All components areeasily accessible which results in a mini-mum schedule for maintenance. In addi-tion, fewer replacement parts arc requiredfor adequate protection against lost air
RA.1061A
time should a failure occur. Low powerconsumption, fewer major components anda reduced maintenance schedule make theBTA-50J operation cost the lowest.
Ready for Remote ControlDesigned with unattended remote con-
trol in mind, the BTA-50J includes thecomponents, wiring and connections tomake it completely compatible with eitherof two RCA remote control systems (seeAccessories). Such components as metershunts, motorized controls and switchingdevices make remote control more efficientand dependable.
Lightweight Type 6697Tubes in Final PA
One Type 6697 power amplifier tubeis used in each of the two RF chains.Each amplifier tube is capable of deliver-ing in excess of the normal 25 kW ofmodulated power to the common load.The Type 6697 is rated at 35 kW dissipa-tion and under average modulation con-ditions it is only required to dissipateapproximately 14 kW. Operation of thePA tubes so far below their maximumratings assures long tube life. In addition,the 6697 is physically small in size andweighs only 43 pounds. One person, with-out the aid of mechanical assistance, canquickly and easily replace any tube in thetransmitter.
One Type 4CX5000A tube is used ineach of the driver stages in the two RFchains. The 4CX5000A is also operatedwell below its maximum ratings and giveslong trouble free service. The only othertubes used in the transmitter arc thetwo Type 4-250A intermediate power -am-plifier tubes. Solid-state design extendsinto the monitor circuitry as well. Tubecomplement is such that inventory costfor required spares is kept at a minimumwhile adequate outage protection is main-tained.
Solid State RectifiersUsed Throughout
All power supplies utilize solid staterectifiers. The plate supplies, bias supplyand low -voltage supply use silicon units,very conservatively rated to assure longlife. The current rating of the units is
such that any conceivable load fault is
cleared without jeopardizing the diodeunits. The use of solid state rectifiers per-mit the transmitter to operate in ambienttemperatures as low as -20 degrees centi-grade.
FCC and CCIR HarmonicSuppression
A completely shielded two section lowpass filter is incorporated in the BTA-
50J. It consists of one pi (,r) section andone T section and each inductive seriesclement is completely shielded. Twoseries -tuned, shunt -connected traps areused to provide added attenuation of thesecond harmonic.
Transmitter EquipmentType BTA-50J AM Broadcast Trans-
mitter consists of four equipment cabi-nets, two of which house the power am-plifiers, one the exciter unit and the fourthcabinet the rectifier and control unit. Thehigh -voltage reactor is housed in thelower rear compartment of the excitercabinet, with the IHV plate transformerin the lower rear compartment of therectifier and control cabinet.
Each of the four transmitter cabinetsmeasure 44 inches wide by 60 inchesdeep by 84 inches high, and consists of anall aluminum cubicle erected on a weldedsteel base. This cubicle consists of a seriesof panels fabricated and assembled to
form a rigid structure. The use of alumi-num eliminates unnecessary weight andprovides excellent shielding to assure ef-fective confinement of spurious energy.Maximum accessibility to all transmittercomponents are afforded by 28 -inch wide,six-foot front doors, while rear access
is through two covers attached withquick -disconnect fasteners for easy re-
moval.A center vertical panel separates the
cabinet into a front compartment andrear compartment which is further di-vided by a rear horizontal shelf into up-per and lower compartments, giving each
cabinet three basic totally shielded com-partments in which to mount the electri-cal components. The eye -level meters,pilot lights and interlocks, mounted oneight -inch wide panels flanking each ofthe front doors, are also shielded.
In the rear at the top of each cabinetis a built-in wire duct. It joins similarducts of adjacent cabinets to form a con-tinuous duct on the four cabinets. Thisduct has a divider down the center onwhich the interconnection terminal boardsare mounted. The rear half of the duct is
used for interconnection wiring while thefront half is used for internal cabinet wir-ing from the terminal boards. The internalwiring is carried through conduits to itsdestination in the cabinet thus shieldingall power and control wiring from RFfields. Provision is also made at the topof the cabinets for the addition of anexhaust air duct.
Power AmplifiersThe first cabinet and the third cabi-
net from the left end are identical and
contain the final power amplifier stages.The 6697 tube and its grid circuits andpart of the plate circuits are contained inthe front portion of the cabinet. The up-per rear section contains the plate tankcoil, filament transformer and grid leakresistors. The lower rear section containsa low -noise blower which cools the 6697tube and its cabinet and the adjacent halfof the exciter cabinet. The two 6697power amplifiers are designed to supplyequal amounts of power to the outputnetwork. Because of the balanced dissipa-tion in the two 6697 PA tubes, less airpressure with resultant lower air flow isrequired for adequate cooling of thepower amplifier cubicles. The lower rearpanel contains an impingement type airfilter for the blower. The PA cabinets areconstructed so that the blowers and filterscan be mounted externally to the cabi-nets, if so desired.
The PA output circuit is a conventionalpi -network type of tank circuit. Eachtube has its own tank circuit, with a com-mon output shunt element. Each networkis adjusted to provide the proper load tothe power amplifiers.
Solid -State Exciter -Modulator,Drive Regulator
Packaged in a series of four plug-inmodules, the Ampliphase exciter -modula-tor uses a crystal -controlled, field -effect -transistor oscillator, a solid-state driveregulator, modulator and power supply.The entire assembly occupies only 51/4inches (133 mm) of rack space in theleft -of -center cabinet (see photo, facingpage). As a result of untuned, digital -integrated circuits, the exciter -modulatoris set up with but three trimmer adjust-ments. The RF chains in the exciter oper-ate without tuned circuits.
The drive regulator circuitry uses en-tirely solid-state electronic devices; theregulator samples the audio, amplifies thesample and applies it to the grid circuitsof the twin driver stages so as to adjustfinal amplifier drive in step with the levelof the modulating audio. This system con-tributes significantly to the exceptionallinearity of the Ampliphase system.
Solid -State ReflectometerThe far -right module in the exciter -
modulator unit is a solid-state reflectom-eter that protects the transmitter fromtransmission line and/or antenna irregu-larities. The reflectometer senses changesin the voltage/current ratio on the load.
A large change in load characteristicscauses the reflectometer system to momen-tarily interrupt the drive (to let the faultclear, if transient). If the fault persists
RA.1061A
11111
,,,,,,,,, t
Close-up view of one of the dual final power amplifier stages. The newtype 6697 tube together with grid circuits and part of the platecircuits are readily accessible from the front of the transmitter.
after several cycles, the reflectometer shutsdown the transmitter thereby reducing thepossibility of chain -reaction damage to anypart of the system.
Above the exciter -modulator are twovertical sub -compartments, behind inter-locked doors, which contain the 4CX5000Adriver stages. A meter panel for these stagesis located beneath the sub -compartments.
The common output capacitors of thetwo PA tanks and the harmonic filter arelocated in the upper rear of the cabinet.Sub -partitions are so arranged in thissection that complete isolation and shield-ing is effected between the various sec-tions of the filter and the outputcapacitor. The lower rear section of thiscabinet contains high voltage filter re-actor and driver dc filament supplies.
Provisions for Standby OperationSpace is provided in the exciter cabinet
for the mounting of a second exciter -modulator unit. Each of the modulator -exciter units are complete and arrangedso that either may be selected instantlyby means of cutover switches. Thus, whileone modulator is in operation, the othermodulator is in standby condition. Theseprovisions, with the extreme reliabilitydesigned into the high -power stages, essen-tially provide a second 50 -kW transmitterfor standby service.
Rectifier and Control UnitThe far right cabinet contains the high
power rectifiers, low power distributioncomponents, and the majority of the controlcomponents. The front portion of the cab-
inet contains the solid state 15 -kV, 5 -kVplate supplies and the low -voltage biassupplies. Also included here are the high -voltage grounding switches and the 15 -kVfilter capacitors. The top rear section ofthe cabinet contains control relays, over-load relays, distribution contactors, andlow -power distribution circuit breakers.The distribution breakers and overloadrelays are readily accessible, recessed sothat they will not be damaged or im-properly operated. The bottom rear of thecabinet contains the 5 -kV rectifier com-ponents including plate transformer.
Solid -State Power SuppliesDuring periods of 100 percent modu-
lation, the 6697 power amplifier tubes re-quire 15 -kV dc at 7.5 amperes, which isobtained from a three-phase, full -waverectifier circuit. Two other plate voltages,5 -kV and 1 -kV, are provided by separatesupplies. Bias voltages for all tubes aresupplied by an additional supply. Thehigh -power distribution equipment for thetransmitter consists of an electrically op-erated air circuit breaker, and a manuallyoperated delta-wye switch for the 15 -kVrectifier. The remaining transmitter pow-er is distributed through a manuallyoperated distribution circuit breaker to a460- to 230 -volt distribution transformerto voltage regulators and thence to thevarious low power distribution circuitbreakers.
Transmitter ControlControl circuits in the BTA-50J con-
tain a number of features which are de-signed to provide maximum flexibility incontrol, protection and operation. Amongthese are choice of single -button or step-by-step starting, automatic timing andsequencing of starting operations, and lo-cation of transmitter faults by a system ofindicators. Protection of the operator isachieved by a system of interlockinggrounding devices; protection of theequipment by conventional relays andcircuit breakers.
Control of the transmitter is accom-plished from the front of the rectifier andcontrol cabinet. All necessary wiring toallow control from a remote location orconsole has been provided. Lamps, whichshow the status of the transmitter controlcircuits, are also mounted on the frontof this cabinet. The control ladder is ar-ranged and interlocked so that the BTA-50J can either be turned on by operatingthe control switches in sequence or byleaving all control switches in the "on"position with the exception of the startswitch which, when operated to the "on"
RA.1061A
position, allows the transmitter to comeon automatically.
The two types of overload circuits usedin this transmitter are the current type,instantaneous or time delay, that are con-nected directly in the tube circuit andrectifier ground leads, and the thermalmagnetic circuit breakers connected in thea -c power leads used as back up protec-tion and disconnect switches. The trans-mitter circuitry is arranged so that anoverload either locks out the plate circuitor allows a single reclosure that resets ifthere are no further overloads. In eithercase, when a lockout position is reached,the transmitter resets by means of an Over -
toad Reset control. The principal overloadriays have indicating flags so that, evenafter the overload has cleared, there is arecord of which overload relay operated.Another feature of the control circuit isthe indicator lamps on each cabinet thatindicate the interlock status in that par-ticular cabinet.
Installation and LayoutOutstanding features of the BTA-50J
are the small floor space requirements
Upper rear of exciter cabinet showingthe combining and output networks.
POWERCONTROL
CRYSTALOSCILLATOR
EXCITER
PHASEDELAY
PHASEMODULATOR
AUDIOINPUT
FEEDBACKDETECTOR
PULSE.
PULSEGENERATOR
DRIVEREGULATOR
SCLID STATEPULSE
AMPLIFIER
TRANSMITTER
IPAU- 250
DRIVER4E65000
SOLID STATEPULSE
AMPLIFIER
PA
4 270DR1 ER
AC 65C 00
PA6697
COMBININGS OUTPUTNETWORK
PA
6697
TOANTENNA
Simp ified block diagram of the BTA-50J.
MONITOR &PROTECTIVE
UNIT
RA.1061A
and ease of installation. In general, thetransmitter layout consists of three basicunits: the four, in -line cabinets which con-tain the major part of the transmitter;the wall -mounted switchgear componentsand the main plate transformers. The Hootplan illustrates a typical layout of the'complete equipment. Elimination of theneed for under -floor cable trenches andconsiderable reduction in external airducts, simplifies installation and reducescosts.
As shown in the layout, it is desirableto leave a passageway at the right end ofthe frontline cabinets since the circuitbreakers and overload relays are mostaccessible from this end of the transmit-ter. The layout of the front line cabinetsis such that a common exhaust duct canbe used to carry off heated air from thetransmitter.
Wall mounting of the switchgear asshown on the overall floor plan is sug-gested to make the BTA-50J most adapt-able to existing transmitter buildings. Themounting of these components, however,is not critical as to location. They can bemounted in existing power distributionareas if desired. These components includethe main plate circuit breaker, a delta-wyeswitch, a distribution circuit breaker, a460- to 230 -volt bank of distributiontransformers, and two single-phase opendelta connected regulators with their con-trol panels. These components are wiredthrough conduit and overhead ductworkto the main plate transformers and thetransmitter cabinets.
Parallel/Redundant SystemThe BTA-50J is available also as a
parallel/redundant transmitter system. Thissystem consists of two identical BTA-50Jtransmitters and a combiner. In the "par-allel" mode, the twin fifty -kilowatt outputsare combined to provide 100 kilowatts ofpower to the antenna system; in the "re-dundant" mode, the system operates oneof the two transmitters as a hot standbywhile the other feeds the antenna system.
In either operational mode, the parallel/redundant system assures greater on -air de-pendability. For example, an outage in onetransmitter or the other automaticallyswitches the troubled transmitter to adummy load while the operable one feedsa full fifty kilowatts to the antenna system.This action is the result of a special -designcombiner with essentially zero insertionloss. Further details of the BTA-50J par-allel/redundant transmitter system areavailable from Aural Broadcast EquipmentMarketing, RCA Building 2-2, Camden,N. J. 08102, U.S.A.
V
a
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-
Front view of the awiter-rrodulatc- cab net coitain-ing all sections from oscilla:or through driver stages.
RA.1061A
DISCONNECTSWITCH
AT SWITCH
BREAKERP -ATE
\ \DISTRIBUTIONTRANSFORMER
AIR INLET LOUVRES TRANSMISSION LINEI.4--
APPROX. 10 SO.FT. ( I In2 ) I I
FREE OPENINGI I
WIRE DUCT INTOP OF CABINETS
AIR FILTERINLET
POWER AMPLIFIER CH 1 EXCITER
)VOLT METER
6' 0" (1.8m)
P_ATE PLATETRANSFORMER TRANSFORMER
PLATETRANSFORMER
VOLT N.ETER
I I
I
I I
I AIR FILTER- AIR FILTER --INLET / INLET
I
rl
II 'POWER AMPLIFIER CH 2
I I
b
RECTI- FIER & CCNTROL
1
[I
- EXHAUST AIR DUCT42 W. X 24 H.(1067 X 610 men ION TOP OF TRANSMITTER87 CUSTOMER
'-BUILDING HEATINGOUTLET LOCATEDTO SUIT CUSTOMER
1
15'- 11/2" 14.6 m1
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Typical flcor plan for the BTA-50J Transmitter.
EIn
0
4 X 4 (10. X 101 mm)SQUARE DUCTSUPPLIED BY CUSTCMERIF REQUIRED
0
RA.1061A
SpecificationsGeneral
Power Line Requirements:Line 460 V, 50/60 Hz, 3 phasesCombined Regulation and Variation . Not more than ±5%
Power Consumption 96 kW (approx.) at zero modulation;100 kW (approx.) at average modulation
Power Factor ... 90% min.Crystal Heater Power 110 V
Type of Emission A3
Power Output (at transmitter terminals) 56 kW (max.)'Frequency Any specified between 535 and 1620 kHzFrequency Stability ±2 HzType Modulation (High Level) Phase to amplitudeAF Input Impedance 150/600 ohmsAudio Input Level +10 ±2 dBmAudio Response ±1.5 dB 30-10,000 HzAF Distortion Less than 3% RMS 50-7500 HzNoise Level (Below 100% modulation) 60 dBCarrier Shift (Neg. 100% modulation) 5% max.Type Output UnbalancedOutput Impedance 50 ohmsSpurious Emission (2nd Harmonic and above) 83 dB
Mechanical
Cabinet Size 44" W, 84" H, 63" D (1118, 2134, 1600 mm)Overall Weight (approx.) 11,500 lbs. (5216 kg),,Maximum Altitude 7500 ft. (2286 m)Ambient Temperature -20°C +45°CPA Cabinet Weights (each) (approx.) . 953 lbs. (432 kg)Plate Transformer Weight (each) (approx.) 820 lbs. (372 kg)Rectifier Cabinet Weight (approx.) 3,093 lbs. (1403 kg)Exciter Cabinet Weight (approx.) 1,041 lbs. (472 kg)Filter Reactor Weight (approx.) 570 lbs. (259 kg)
'Other line voltages available on request.=Other output impedances available on request."Operation at higher altitude available on request.'Cutback to other power levels available on request.Available in 100- and 200 -kW systems as Types BTA-100J and BTA-200J.
Shipping DataWeight, Domestic Packing (approx.) 13,500 lbs. (6124 kg)
Weight, Export Packing (approx.) 14,000 lbs. (6350 kg)
Tube Complement
Intermediate Power Amplifier: Type 4-250A
Driver Amplifier: Type 4CX5000A
Power Amplifier: Type 6697
AccessoriesSpare Solid -State Exciter -Modulator ES -560752
Complete Set of Operating Tubes ES -27222E
Recommended Spare Set of Tubes ES -27223D
Spare Crystal Unit, Type TMV-130B(Specify Frequency) MI -27493
Type BTR-30 Remote Control(30 Functions) MI -561446
Type BTR-15 Remote Control(15 Functions) MI -561157/58
50 10 -kW Cutback Kit MI -27688C4
Dummy Load ES -34234
BPA-50 Antenna Tuner (230 ohms) ES -28903
BPA-50 Antenna Tuner (70/51.5 ohms) ES -28903
Remote RF Pickup Unit MI -28027
Type BW-50 Frequency and ModulationMonitor M I-560767
Type BW-60 RF Amplifier MI -560762
Ordering Information50 -kW AM Broadcast Transmitter, Type BTA-50J, with two
crystals, remote meter, one set of operating tubes, siliconrectifiers, and one exciter. Antenna tuning unit not included.(Specify operating frequency) ES -272221D
l'ILell Broadcast
Front and Cooper Streets, Camden, New Jersey 08102, U.S.A. Systems
100 kW "Ampliphase"Medium -Wave, AM Transmitter,iype BTA-iuus.;
Excellent audio quality
All solid-state exciter
Only eight tubes, three types
High modulation capability
catalog RA.1071(Preliminary)
An AM transmitter with FM quality,the Type BTA-100J uses phasemodulation in a way that results inhigh fidelity AM. The transmitterincludes a fully solid-state exciter andmodulator. "Ampliphase" appliesmodulation at a low level and usesClass C. continuous -wave poweramplifiers to provide the 100 -kWoutput.
rn
6:03
RA.1071
The RCA Type BTA-100J AMBroadcast Transmitter is a completelyair-cooled, 100 -kW phase -to -amplitudemodulated transmitter designed for highfidelity transmission in the standardbroadcast band (535 kHz to 1620 kHz).It provides a signal of exceptionally lowdistortion and extended frequency re-sponse. Measured response is flat within±3 dB from 35 Hz to 25,000 Hz. Theequipment is capable of being modulatedover the frequency range of 10 Hz to30,000 Hz. Frequency response has beenextended largely through the eliminationof unnecessary transformers in the audiosystem as well as improved circuitry.
Low harmonic distortion with negli-gible carrier shift at maximum signaloutput has been achieved in the BTA-100J by selection of adequate power tubetypes and advanced solid state circuits inthe exciter -modulator -drive regulator de-sign throughout the entire equipment.The design features an inherently linearsystem capable of continuous high modu-lation levels impervious to inadvertentovermodulation. For example, the trans-mitter may be modulated 100 percent atany frequency between 30 and 15,000 Hzcontinuously for many hours without det-rimental effects to any of the componentparts. A small amount of overall feed-back is incorporated to provide the ex-ceptional performance.
Lowest Operating Cost in100 -kW Transmitters
A number of new refinements as wellas time tested features which have proventheir worth are incorporated in thismodern 100 -kW transmitter. Power re-quirements are moderate for the equip-ment. Power amplifier plate efficiencyin the order of 75 to 80 percent isobtained.
Fewer major components, as comparedto those required by many 100 -kW trans-mitters, are used in the BTA-100J. In ad-dition to the low cost of operation of thetransmitter a power -cutback kit can beadded which permits operation at 50 kW.(Other power levels available on specialorder).
Dual RF ChainsTwo identical RF chains, each develop-
ing 50 kW, are incorporated in this equip-ment. Since they arc identical, servicingis made easy by comparison of the twochains. Components are directly inter-changeable, which allows substitution forcomparison purposes. All components areeasily accessible which results in a mini-mum schedule for maintenance. In addi-
tion, fewer replacement parts are requiredfor adequate protection against lost airtime should a failure occur. Low powerconsumption, fewer major componentsand a reduced maintenancec schedulemake the BTA-100J operation cost thelowest.
Ready for Remote ControlDesigned with unattended remote con-
trol in mind, the BTA-100J includes thecomponents, wiring and connections tomake it completely compatible with eitherof .two RCA remote control systems (seeAccessories). Such components as metershunts, motorized controls and switchingdevices make remote control more efficientand dependable.
Lightweight Type 6697Tubes in Final PA
Two Type 6697 power amplifier tubesare used in each of the two RF chains.
Each final amplifier is capable of deliver-ing in excess of the normal 50 kW ofmodulated power to the common load.The Type 6697 is rated at 35 kW dissipa-tion and, under average modulation con-ditions, is only required to dissipateapproximately 14 kW. Operation of thePA tubes so far below their maximumratings assures long tube life. In addition,the 6697 is physically small in size andweighs only 43 pounds (20 kg). One per-son, without the aid of mechanical assist-ance, can quickly and easily replace anytube in the transmitter.
One Type 4CX5000A tube is used ineach of the driver stages in the two RFchains. The 4CX5000A is also operatedwell below its maximum rating and giveslong trouble free service. The only othertubes used in the transmitter are thetwo Type 4-250A intermediate power -am-plifier tubes. Solid-state design extendsinto the monitor circuitry as well. Tube
Close-up view of one of the dual final power amplifier stages. The newtype 6697 tube together witl- grid circuits and part of the platecircuits are readily accessibc from the front of the transmitter.
---- - - - - -
oe:T.101111,1.1:11M,I,Z1,111110
tiiimopolbouipoliomiu
11111ttie'0
RA.1071
complement is such that inventory costfor spares is kept at a minimum whileadequate outage protection is maintained.
Solid State RectifiersUsed Throughout
All power supplies utilize solid staterectifiers. The plate supplies, bias supplyand low -voltage supply use silicon units,very conservatively rated to assure longlife. The current rating of the units issuch that any conceivable load fault iscleared without jeopardizing the diodeunits. The use of solid state rectifiers per-mit the transmitter to operate in ambienttemperatures as low as -20 degress centi-grade.
FCC and CCIR HarmonicSuppression
A completely shielded two section lowpass filter is incorporated in the BTA-100J. It consists of one pi (w) section andone T section and each inductive serieselement is completely shielded. Twoseries -tuned, shunt -connected traps areused to provide added attenuation of thesecond harmonic.
Operated in ParallelType BTA-100J Medium -Wave Trans-
mitter consists of six equipment cabi-nets, four of which house the power am-plifiers, one the exciter unit and the sixthcabinet, the rectifier and control unit.
Each of the six transmitter cabinetsmeasure 44 inches wide by 60 inchesdeep by 84 inches high, (1118, 1524,2133 mm) and consists of an all alumi-num cubicle erected on a welded steelbase. This cubicle consists of a seriesof panels fabricated and assembled toform a rigid structure. The use of alumi-num eliminates unnecessary weight andprovides excellent shelding to assure ef-fective confinement of spurious energy.Accessibility to all transmitter componentsis through 28 -inch (711 mm) wide, six-foot (1.8 m) front doors, while rear accessis through two covers attached withquick -disconnect fasteners for easy re-moval.
A center vertical panel separates thecabinet into a front compartment andrear compartment which is further di-vided by a rear horizontal shelf into up-per and lower compartments, giving eachcabinet three basic totally shielded com-partments in which to mount the electri-cal components. The eye -level meters,pilot lights and interlocks, mounted oneight -inch wide panels flanking each ofthe front doors, are also shielded.
111
.4 I
Front iew of the exciter-mods,ator cab,net contaiing 211 sections from oscillator through driver stages.
RA.1071
POWER SUPPLY
1111141.1.
OuTT I r PM".New
DRIVE REGULATOR OSC ILL ATOt
v171;44.,,,A1111
tAtt '41
MODULATOR
nleuo Cl .. ma
COW 11114.COOP, ORM r MMus I JEARAIM
10A1.
SP- -CAL
SY 10 UM,131tIO SENS
METER MIME
LINE PROTECTOR
CRIAT .1111, HAD Cs, .11 1/4P
Exciter/modulator unit. Completely solid-state, this unit is Lsed in all RCA Am-pliphase transmitters. Available separately for use as a spare. See Accessories.
POWERCONTROL
CRYSTALOSCILLATOR
EXCITER TRANSMITTER
PHASEDELAY
PHASEMODULATOR
AUDIOINPUT
FEEDBACKDETECTOR
PULSEGENERATOR
GENERATORPUSEL
DRIVEREGULATOR
SOLID STATEPULSE
AMPLIFIER^-10. 4-250P4
DRIVER40.05000
SOLID STATEPULSE
AMPLIFIER
IPA4-250
DRIVER4CX5000
PA6697
PA6697
PA6697
PA
6697
COMBININGB OUTPUTNETWORK
Simplified block diagram of the BTA-100J.
TOANTENNA
MONITOR BPROTECTIVE
UNIT
RA.1071
In the rear at the top of each cabinetis a built-in wire duct. It joins similarducts of adjacent cabinets to form a con-tinuous duct on the four cabinets. Thisduct has a divider down the center onwhich the interconnection terminal boardsare mounted. The rear half of the duct isused for interconnection wiring while thefront half is used for internal cabinet wir-ing from the terminal boards. The internalwiring is carried through conduits to itsdestination in the cabinet thus shieldingall power and control wiring from RFfields. Provision is also made at the topof the cabinets for the addition of anexhaust air duct.
Power AmplifiersThe first and second cabinets and the
fourth and fifth cabinets from the leftend are identical and contain the finalpower amplifier stages. The 6697 tubeand its grid circuits and part of the platecircuits are contained in the front portionof the cabinet. The upper rear sectioncontains the plate tank coil, filamenttransformer and grid leak resistors. Thelower rear section contains a low -noiseblower which cools the 6697 tube andits cabinet. The blowers in cabinets twoand four are arranged to cool the excitercabinet. The two power amplifiers aredesigned to supply equal amounts ofpower to the output network. Becauseof the balanced dissipation in the PAtubes, less air pressure with resultant lowerair flow is required for adequate coolingof the power amplifier cubicles. Thelower rear panel contains an impingementtype air filter for the blower. The PAcabinets are constructed so that theblowers and filters can be mounted ex-ternally to the cabinets, if so desired.
The PA output circuit is a conventionalpi -network type of tank circuit. Eachtube has its own tank circuit, with a com-mon output shunt element Each networkis adjusted to provide the proper loadto the power amplifiers.
Solid -State Exciter -Modulator,Drive Regulator
Packaged in a series of four plug-inmodules, the Ampliphase exciter -modula-tor uses a crystal -controlled, field -effect -transistor oscillator, a solid-state driveregulator, modulator and power supply.The entire assembly occupies only 51/4inches (133 mm) of rack space in theleft -of -center cabinet (see photo). As aresult of untuned, digital -integrated cir-cuits, the exciter -modulator is set upwith but three trimmer adjustments. TheRF chains in the exciter operate with-out tuned circuits.
The drive regulator circuity uses en-tirely solid-state electronic devices; theregulator samples the audio, amplifies thesample and applies it to the grid circuitsof the twin driver stages so as to adjustfinal amplifier drive in step with thelevel of the modulating audio. This sys-tem contributes significantly to the ex-ceptional linearity of the Ampliphasesystem.
Solid -State ReflectometerThe far -right module in the exciter -
modulator unit is a solid-state reflectom-eter that protects the transmitter fromtransmission line and/or antenna irregu-larities. The reflectometer senses changesin the voltage/current ratio on the load.
A large change in load characteristicscauses the reflectometer system to momen-tarily interrupt the drive (to let the faultclear, if transient). If the fault persistsafter several cycles, the reflectometer shutsdown the transmitter thereby reducing thepossibility of chain -reaction damage to anypart of the system.
Above the exciter -modulator are twovertical sub -compartments, behind inter-locked doors, which contain the 4CX-5000A driver stages. A meter panel forthese stages is located beneath the sub -compartments.
The common output capacitors of thetwo PA tanks and the harmonic filter arelocated in the upper rear of the cabinet.Sub -partitions are so arranged in thissection that complete isolation and shield-ing is effected between the various sec-tions of the filter and the outputcapacitor. The lower rear section of thiscabinet contains high voltage filter re-actor and driver dc filament supplies.
Provisions for Standby OperationSpace is provided in the exciter cabinet
for the mounting of a second exciter -modulator unit. Each of the exciter -mod-ulator units are complete and arrangedso that either may be selected instantlyby means of an accessory cutover panel.Thus, while one modulator is in operation,the other modulator is in standby condi-
0
ft
OP
0
A look inside the rectifier cabinet.
RA.1071
tion. These provisions, with the extremereliability designed into the high -powerstages, essentially provide a second 100 -kWtransmitter for standby service.
Rectifier and Control UnitThe far right cabinet contains the high
power rectifiers, low power distributioncomponents, and the majority of the con-trol components. The high -voltage andlow -voltage transformers, filter capacitorsand reactors are mounted externally tothe transmitter cabinetry (see floor lay-out).
Solid -State Power SuppliesDuring periods of 100 percent modu-
lation, each 6697 power amplifier tuberequires 15kVdc at 7.5A, which is ob-tained from a three-phase, full -waverectifier circuit. Two other plate voltages,5kV and 1 kV, are provided by separatesupplies. Bias voltages for all tubes aresupplied by an additional supply. Thehigh -power distribution equipment for thetransmitter consists of an electrically op-erated air circuit breaker, and a manuallyoperated delta-wye switch for the 15 -kVrectifier. The remaining transmitter pow-er is distributed through a manuallyoperated distribution circuit breaker to a460- to 230 -volt distribution transformerto voltage regulators and thence to thevarious low power distribution circuitbreakers.
Transmitter ControlControl circuits in the BTA-100J con-
tain a number of features which are de-signed to provide maximum flexibility incontrol, protection and operation. Amongthese are choice of single -button or step-by-step starting, automatic timing andsequencing of starting operations, and lo-cation of transmitter faults by a system ofindicators. Protection of the operator isachieved by a system of interlockinggrounding device, protection of theequipment by conventional relays andcircuit breakers.
Control of the transmitter is accom-plished from the front of the rectifier andcontrol cabinet. All necessary wiring toallow control from a remote location orconsole has been provided. Lamps, whichshow the status of the transmitter controlcircuits, are also mounted on the frontof this cabinet. The control ladder is ar-ranged and interlocked so that the BTA-100J can either be turned on by operatingthe control switches in sequence or byleaving all control switches in the "on"position with the exception of the startswitch which, when operated to the "on"position, allows the transmitter to comeon automatically.
Upper rear of exciter cabinet showing the combining and output networks.
The two types of overload circuits usedin this transmitter are the current type,instantaneous or time delay, that are con-nected directly in the tube circuit andrectifier ground leads, and the thermalmagnetic circuit breakers connected in thea -c power leads used as back up protec-tion and disconnect switches. The trans-mitter circuitry is arranged so that anoverload either locks out the plate circuitor allows a single reclosure that resets ifthere are no further overloads. In eithercase, when a lockout position is reached,the transmitter resets by means of an Over-load Reset control. The principal overloadrelays have indicating flags so that, evenafter the overload has cleared, there is arecord of which overload relay operated.Another feature of the control circuit isthe indicator lamps on each cabinet thatindicate the interlock status in that par-ticular cabinet.
Installation and LayoutOutstanding features of the BTA-100J
are the small floor space requirements
and ease of installation. In general, thetransmitter layout consists of three basicunits: the six, in -line cabinets which con-tain the major part of the transmitter;the wall -mounted switchgear components,the main plate transformers, the HV filtercapacitors and reactors and the LV powertransformers. The floor plan illustrates atypical layout of the complete equipment.Elimination of the need for under -floorcable trenches and considerable reductionin external air ducts, simplifies installationand reduces costs.
As shown in the layout, it is desirableto leave a passageway at the right endof the frontline cabinets since the circuitbreakers and overload relays are mostaccessible from this end of the transmit-ter. The layout of the front line cabinetsis such that a common exhaust duct canbe used to carry off heated air from thetransmitter.
Wall mounting of the switchgear asshown on the overall floor plan is sug-gested to make the BTA-100J most adapt-
RA.1071
able to existing transmitter buildings. Themounting of these components, however,is not critical as to location. They canbe mounted in existing power distributionareas if desired. These components includethe main plate circuit breaker, a delta-wyeswitch, a distribution circuit breaker, a460- to 230 -volt bank of distributiontransformers, and two single-phase opendelta connected regulators with their con-trol panels. These components are wiredthrough conduit and overhead ductworkto the main plate transformers and thetransmitter cabinets.
Parallel/Redundant SystemThe BTA-100J is available also as a
parallel/redundant transmitter system.This system consists of two identical BTA-100J transmitters and a combiner. In the"parallel" mode, the twin 100 -kilowattoutputs are combined to provide 200 kilo-watts of power to the antenna system; inthe "redundant" mode, the system oper-ates one of the- two transmitters as a hotstandby while the other feeds the antennasystem.
In either operational mode, the parallel/
redundant system assures greater on -air de-pendability. For example, an outage in onetransmitter or the other automaticallyswitches the troubled transmitter to adummy load while the operable one feedsa full hundred kilowatts to the antennasystem. This action is the result of aspecial -design combiner with essentiallyzero insertion loss. Further details of theBTA-100J parallel/redundant transmittersystem are available from Aural BroadcastEquipment Marketing, RCA Building 2-7,Camden, N. J. 08102, U.S.A.
Typical floor plan for the BTA-100J Transmitter.
WIRE
DUCT
(162 mm)
6- (162 mm).7..
H. V. H. V. fi5 f- -4 TRANS. TRA1S.
FLIERCAPACITORS -
E
DISCONNECT Y PLATE DISTPIB. VOL. .
SWITCH SWITCH BREAKER BREAKER REG. zo
AIR1
PA #1
AIR
VOL.
REG.'
AIR
2'6"(0.760 m)
4,
FILTER
REACT.
FILTER
REACT. 2'6"(C.760m
6' (162 mm)12'6" (3.8 m)
AIR
TRANSV.
L. V.TRANS
I_ I I 1
PA k2 EXCITER PA -zr-3 PA .±..-4
RECTIFIER
& CONTRJL
22'2" (6.7 m)
25'8" (7.8 m)
(All measurements in metric system are approximations...measurements in feet and inches are accurate)
mL11
)I( 3'0"(0.91 m)
I
m-
RA.1071
Specifications
GeneralPower Line Requirements:
Line 460/380 V, 50/60 Hz, 3 phasesCombined Regulation and Variation Not more than ±5%
Power Consumption 180 kW (approx.) at zero modulation;200 kW (approx.) at average modulation
Power Factor 90% min.Crystal Heater Power 110 VType of Emission A3
Power Output (at transmitter terminals) 110 kW (max.)*Frequency Any specified between 535 and 1620 kHzFrequency Stability ±2 HzType Modulation (High Level) Phase to amplitudeAF Input Impedance 150/600 ohmsAudio Input Level +10 ±2 dBmAudio Response 30-10,000 Hz ±1.5 dB; 30-15,000 Hz ±3 dBAF Distortion Less than 3% RMS 50-7500 HzNoise Level (Below 100% modulation) 60 dBCarrier Shift (Neg. 100% modulation) 5% max.Type Output UnbalancedOutput Impedance 50 or 230 ohms2Spurious Emission (2nd Harmonic and above) -83 dB
MechanicalCabinet Size (each) 44" W, 84" H, 63" D
(1118, 2134, 1600 mm)Overall Weight (approx.) 17000 lbs. (7700 kg)Maximum Altitude 7500 ft. (2286 m)3Ambient Temperature -20°C -4-45°CPA Cabinet Weights (each) (approx.) 1000 lbs. (454 kg)Plate Transformer Weight (each) (approx.) 1500 lbs. (680 kg)Rectifier Cabinet Weight (approx.) 2000 lbs. (907 kg)Exciter Cabinet Weight (approx.) 1200 lbs. (544 kg)Filter Reactor Weight (approx.) 1500 lbs. (680 kg)
Shipping DataWeight, Domestic Packing (approx). 19,000 lbs. (8618 kg)Weight, Export Packing (approx.) 20,000 lbs. (9072 kg)
Tube ComplementIntermediate Power Amplifier: Type 4-250A (Two used)Driver Amplifier: Type 4CX5000A (Two used)Power Amplifier: Type 6697 (Four used)
AccessoriesSpare Solid -State Exciter -Modulator ES -560752
Complete Set of Operating Tubes ES-27222FXRecommended Spare Set of Tubes ES-27223EX
Spare Crystal Unit, Type TMV-130B(Specify Frequency) MI -27493
Type BTR-30 Remote Control(30 Functions) ES -561446
Type BTR-15 Remote Control(15 Functions) ES -561157/58
100/50 -kW Cutback Kit MI-27688CX4
Remote RF Pickup Unit MI -28027
Type BW-50 Frequency and ModulationMonitor MI -560767
Type BW-60 RF Amplifier MI -560762
Ordering Information100 -kW AM Broadcast Transmitter, Type BTA-100J, with two
crystals, remote meter, one set of operating tubes, siliconrectifiers, and one exciter.
(Specify operating frequency) ES-34100CX
200 -kW AM Broadcast Transmitter, Type BTA-200J (Custombuilt from two BTA-100J Transmitters) (Please specify oper-ating frequency) ES-34100DX
'Other line voltages available on request.'Other output impedances available on request.'Operation at higher altitude available on request.'Cutback to other power levels available on request.'Available in 200 -kW systems as Type BTA-200J.
nil BroadcastFront and Cooper Streets, Camden, New Jersey 08102, U.S.A. MEM Systems 011 NT