30 W. S. a

(30 Watt Sender a - Telefunken)

The 30 W.S.a is a vehicular-type, medium-frequency, radio transmitter. Interconnections between the transmitter and receiver permit the transmitting antenna to be use for reception in the "off" and "standby" positions of the main switch. Both voice and telegraph transmissions are monitored by the receiver (Mw.E.c, Torn.E.b and Lw.E.a).

The transmitter is enclosed in a metal casing. A brass strip, approximately 2 cm wide and 24 cm long runs from front to back on each side of the top of the metal casing and insures good ground contact with the metal frame into which the casing is fitted in the vehicle.

Eight controls on the front panel are:

  • 3-position band switch
  • Main tuning knob
  • 5-position antenna coupling knob
  • 5-position antenna tuning knob (coarse tuning)
  • Continuously-variable antenna tuning knob (fine tuning)
  • Frequency check switch (thrown by raising the lid over the headset jack which is used during frequency calibration)
  • 4-position main switch

The telegraph key is inserted in the two-contact jack at the extreme lower left corner of the front panel and the microphone plug is inserted in the three-contact jack beside it. The frequency dial is calibrated in kHz and is numbered every twenty kHz. The dial is illuminated by a blue pilot light which is removable through a spring-hinged lid in back of the dial.

For telegraphy operation, the key completes the circuit to a 12 volt relay which in turn by-passes to ground the excessive grid bias applied to the grids of the RF oscillator and the RF amplifier tubes. In telephony operation, the suppressor grids of the RF amplifier tubes are modulated. A pair of RV12P2000 tubes in parallel acts as a single speech amplifier with transformer input and transformer output.


1.12-3.01 MHz in 3 bands as follows:

  • 1.11-1.55
  • 1.53-2.15
  • 2.13-3.01

One removable used for frequency calibration purposes.

Two with click-stop settings

Stationary, 8-meter vertical mast with star capacitance hat; mobile, vehicular rod or roof antenna.

Master Oscillator = ganged tuning of RF oscillator and RF amplifier. Calibration obtained by crystal resonator cut to resonate at 771 KHz.




Dynamotor U-30a with output of 400 Volts, 175 milliamperes and 70 Watts;

Motor, input 12 Volts , 12 Amperes and 144 Watts

80 W.S.a, These two sets are similar in design and identical in operation. The American sets SCR-177, SCR-188, SCR-193, SCR-197, SCR-299 cover the greater portion of the frequency range of the 30W.S.a and have comparable transmission ranges.

30 Watts


6. Three RL12P35 (35 Watt pentodes) and three RV12P2000 (knob-type pentodes). One of the RL12P35 pentodes is in a tuned grid oscillation circuit which is capacitively coupled to a pair of the same type tubes in parallel as an RF amplifier. This RF amplifier has a tuned grid circuit. Two of the RV12P2000 tubes are used as speech amplifiers and the third as frequency check oscillator which can be put into operation only when the main switch is in telephony position. The filaments of all tubes are connected in parallel. The cathodes of the RV12P35 tubes are connected internally to the metal bases of the tubes.


In tank division and tank brigade radio sets especially in liaison operations with reconnaissance cars and tanks. It is being replaced by the 80W.S.a in the German Army. German receivers appropriate for use with this transmitter are types Torn.E.b, and Mw.E.c.

CW and Voice


With 30-foot antenna:
100 for CW
31 for voice

With roof antenna (fixed station):
31 for CW
10 for voice

With roof antenna (on the move):
25 for CW
6 for voice

80 W.S.a, 100W.S., American SCR-177, SCR-188, SCR-193, SCR-197, SCR-299 cover the greater portion of the frequency range of the 30W.S.a and have comparable transmission ranges.

TO REPLACE IN PART: 30 W.S./24a-120 - which became obsolete at the start of the war.
Armored command car or reconnaissance car. Command tank.

30W.S. Prototype


This version of the 30W.S.a has a mechanical memory pre-set mechanism on the control panel. The two lugs move around and are secured at the desired frequencies.



Outside the data plate, there is a notice about where to install the frequency test crystal.



Close up of the mechanical memory system. The external arm is connected to the internal tuning mechanism. Therefore, if the frequency is being tuned by the "Frequenzeinstellung" knob, the arm rotates synchronously.



From left to right, top to bottom: antenna ammeter, ground lug and antenna connector, antenna coupling control, fine antenna tuning, frequency adjustment control (under small lid), coarse antenna tuning, device power and mode selector switch, power socket.


Selective voltmeter for both 12 and 400 volts.



Close up of the ammeter.



Photo of the interior. The chassis is made from early war "Electrum" alloy, and all shields are in place.



The transmitter as seen from above.



Another photo from the reverse.



Right side of the transmitter. Note the antenna tuning variometer, fuse, and heat-compensation capacitors.



Left side of the transmitter.


Close up photo of the "Nüral" trademark. Along with Mähle, this company produced many of the radio chassis seen on this site.



This is the frequency calibration crystal.



A very convenient feature of this transmitter (and the 80W.S.a) is this testing panel. The table below is a reference to each port:






Material-sparing lightweight design.



Antenna-tuning variometer.



Inside the variometer.


Spare fuses sign.



Spare fuses.



Cable connection diagram which includes the 80W.S.a