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WWII German 20 W. S. c (20 Watt Sender c - Lorenz) 20 W.S.b1 VHF transmitter

WWII German 20 W. S. c (20 Watt Sender c - Lorenz) 20 W.S.b1 VHF transmitter - 743a2 - - Original, very nice, RARE 20 W.S.b  1 VHF transmitter. It was used by Artillery troops as a sound ranging transmitter. Three such transmitters with special micropho

Code : 743a2
Availability : Available


Original, very nice, RARE 20 W.S.b  1 VHF transmitter. It was used by Artillery troops as a sound ranging transmitter. Three such transmitters with special microphones would be placed some distance apart parallel to the front line with a fourth further forwards as a warning transmitter. As the warning transmitter picked up the sound of enemy artillery firing, a recorder in the receiving vehicle would be started and the sound traces of the three other transmitters would be recorded. The recorded time differences could then be used to triangulate the enemy battery.

20 W. S. d

(20 Watt Sender d - Lorenz)

This is an amplitude-modulated transmitter, well designed both electrically and mechanically, with excellent frequency stability and affording dependable voice and tone communications. Side tone is present on both voice and tone.

The quality of voice modulation is excellent; tone is remarkably free from chirps and clicks.

Tis set is identical to the 20.W.S.c transmitter with the only difference being the range.

Translation from Die deutschen Funknachrichtenanlagen bis 1945 - Band 3 "Funk- und Bordsprechanlagen in Panzerfahrzeugen" by Hans-Joachin Ellissen

The Lorenz 20 W.S.d was a 3-stage transmitter, was introduced in 1936 with five Wehrmacht triodes RL 12 T 15 for telephony (A3) and tone-based telegraphy (A2). The simplified schematic dictates the basic design: oscillator stage, frequency doubling stage, push-pull power amplifier stage, modulation pre-amplification stage (low frequency amplifier), in setting "Tg tönend" it operates as tone frequency generator (approx. 1000 Hz). The anode voltage of all tubes can be tested. Filament and microphone voltages are both 12 volts and come directly from the vehicle's battery through the anode voltage generating Umformer U20a2. The anode voltage is approximately 375 Volts with an approximate current of 130 mA. The range with the 2 meter rod antenna detailed in D 982/1 is 3-6 km for voice and 4-8 km for telegraphy. The three locally separated variable capacitors of the oscillating, doubling and power stages are mounted on a common long shaft for synchronized operation. In the frequency range of the transmitter of 42.1 to 47.8 MHz, two pre-set frequencies can be configured. The transmitter can be tested by removing a cover from the front panel which reveals a three-pronged plug where the frequency tester b (Frequenzprüfer b) can be inserted. If, for example, the oscillator tube is replaced, one can use a screwdriver to tune the oscillator for the proper frequency (tuning correction to be done for the lower frequency range, using the red mark at 42.45 MHz).

As far as the schematic design is concerned, the 20W.S.d does not have any particular complexities. The use of triodes is required because of low amplification coefficient of a three-stage transmitter, the desired output power in the antenna circuit of 20 Watt is accomplished by two tubes in the output stage. This is because the push-pull configuration of the final stage accomplished light neutralization. Without this neutralization, the entering self-adjustment over the screen-grid/anode capacitance (4-5 pF) will be compensated for through the neutralizing trimmer (3-7 pF). At the intermediate stage, the neutralization is omitted, since the frequency doubler is working, and the control grid plus anode circuits operate at different frequencies. When using higher amplification Pentodes two stages would be sufficient, could also because of the small grid-anode capacitance (e.g. in the RL12P35 less than 0,05 pF)) account for the neutralization. Examples of transmitters with pentodes are the 10 W.S.c (2 x RL12P35) and the 30W.S.a (1 RL12P35 in the oscillator stage, and 2x RL12P35 tubes connected in parallel in the power amplification stage).

The mechanical construction of the 20W.S.d is based on the injected 3-dimensional aluminum-elektrum chassis design as shown in the photos below. The detachable lower module contains the modulator amplification tube, the low-frequency components for voice and tone-based telegraphy communications (e.g. the four-section modulation transformer for the control grid modulation voltage of the push-pull final stage), the operation mode switch 'Aus - Telefonie - Empfang - Telegr. tönend', the power supply components and the connection sockets for the microphone, key and also for the side-tone of receiver I and II. (In the tank installation, only one receiver was used)




42.1 - 47.8 MHz


Two with click-stop settings

Variable - 1.5 to 2 meter whip or umbrella

Master Oscillator




Dynamotor U-20a, U-20a2 or U-20a3 connected to 12 volt battery. Power requirements for filament 12 volts (2.75 A) approx.; for anode 370 volts (130 mA) approx.

20 W.S.b, 20 W.S.c, and American BC-307 and BC-684

20 Watts


5-All RL 12 T15, used as master oscillator, doubler, power amplifier (2 tubes) modulator and tone oscillator (1 tube)


20W.S.c is used in a Panzer regiment net, tank-to-tank and tank-to-rear.

The 20W.S.d is used as tank regiment command set for tank-to-tank and tank to AIR.

Tone (800 to 1000 cycles) and voice (AM)


20W.S.c - tone 5, voice 3.

20W.S.d - tone 50, voice 30

20W.S.c communicates with 10W.S.c used in tank battalion, the receiver used being the Ukw.E.c. 20W.S.d provides two-way connection with airborne set FuG16, and also with the Ukw.E.d1 receiver.


20W.S.d is mounted in tanks and armored cars of battalions. 20.W.S.d is mounted in regiment staff armored cars.