Fusprech.f - 1944

(Funksprechgerät f )

A very compact, high-frequency transceiver - MOPA transmitter and heterodyne receiver. The same antenna, the same frequency and certain tubes are used for both transmitting and receiving. A very advanced type believed to be a Lorenz product. In field tests it gives practically the same results as the SCR-195, but the American set is simpler and of a more advanced design*.

The set is contained in a metal case provided with a leather carrying strap. All seven tubes are employed when the set is operating as a receiver and just three are used when it is functioning as a transmitter. It is used with a loudspeaker and is provided with a special push button by means of which a tone modulation is transmitter for calling purposes

Introduced in 1942 by Stassfurt Imperial, the Fusprech. f was mostly installed on armored half-tracks such as the Sd.Kfz. 234, 250, 251.

* This opinion may be biased.

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

22.7 Radio equipment of the armored personnel carriers(Schützenpanzerwagen - SPW)

In the process of motorizing the infantry, armored off-road personnel carriers became necessary to equip protection regiments that accompanied tanks into battle. In 1939, a "team transport vehicle" was created called the Sd.Kfz 251, and was delivered for testing. The Sd.Kfz 251 transported 12 men including the driver and the commander. This vehicle was based on the 1932 Reichswehr half-track tractors (front wheel steering, rear caterpillar drive). After some operational experience, the production of these half-tracked vehicles was accelerated. Two different-length types of these vehicles was manufactured. The shorter version was built to transport a "half-group" of 6 men (including the driver and the commander). This vehicle was termed the "lighter SPW" or "short SPW" - Sd.Kfz. 250. The longer version for 12 men was called the "middle SPW" or "long SPW" - Sd.Kfz. 251. Other than for transporting personnel, these vehicles were modified for many different purposes and configurations, both weapons and other equipment. These modifications reduced the crews to 3 men only. By the end of the war there were 36 different configurations, including 6 communication configurations.

At around 1942-1943, the radio equipment for voice-based communication between armored personnel carriers was the Fusprech.f with a 1.4 meter whip antenna, and later with the 2 meter whip antenna. The range was 2-3 km with the 2 meter antenna when the vehicle was on the move, and 3-5 km when stationary. With the 1.4 meter antenna, the range was one-half of the range of the 2 meter antenna (range also depended on the terrain and the freshness of tubes and other components of the Fusprech.f). Intercom systems were not installed in these vehicles since the spaces were open at the top and confined. The power supply was the SEUa1 (370 V 70 mA) and the 12V vehicle lead-acid battery. The radio operation was done using a throat microphone and headphones (the co-driver was generally also the radio operator). The incoming signal could also be heard over the L.S.Fu.a speaker, which was supported by a round leather-covered bracket.

The Fusprech. devices a, d, f (20.....25 MHz, 1.2 Watt, A3)

Telefunken introduced compact, 1.2 Watt radio communication devices that were easy to use for communication between armored vehicles. These devices were later manufactured by other companies such as Stassfurt Imperial. The Fusprech.a was introduced in 1940, Fusprech.d in 1941 and Fusprech.f in 1942. All three devices have different frequency ranges, virtually the same schematic and have a very similar outside appearance. An exception: the Fusprech.f has an additional fine frequency adjustment knob (required for the interpretation of the 60 channels instead of the 10 for the Fusprech.a and d). Later, The Fusprech.f had the 3-section tuning capacitor replace the 4-section tuning capacitor. The Fusprech devices are contained in a steel case with a carry handle. The measurements are 280 mm width X 200 mm height X 170 mm depth and they weigh around 7.5 kg. All controls and connectors are on the front panel. The devices are equipped with six RV12P2000 tubes and one RL12P10 tube, which is in the final transmitter stage and generates 1.2 Watts of output power, and also for the 4 Watt output of the low frequency amplifier to power the loudspeaker L.S.Fu.a. When the small cover is lifted from the headphone connector, output is automatically switched from the loudspeaker to the headphones. The switching between "Receive" and "Transmit" modes is activated by means of a magnetic switch, which is activated on the microphone cable (Kmf.b). The anode voltage of 275-300 volts is generated from the Umformer SEUa or SEUa(1). Later also with the vibrating power supply (SE)lx and (SE)p.

Channel Description and Frequency Ranges

Fusprech Frequenzber. (MHz Kanäle Abstand
a 24,11-25,01 101-110(10) 100 kHz
d 23,10-24,01 141-150(10) 100 kHz
f 1) 19,9975-21,4725 314-400(60) 25 kHz

1) Because of the austerity measures enacted during the war, there were several version of the Fusprech.f transceiver. Some modifications were the removal of the frame around the scale, integrated labels on the front panel, replacement of ceramics by Pertinax, etc., and specifically from about 1943 - the omission of the fine-tuning control from the Fusprech.f.

A button on the front panel generates a tone of 1000-Hz to call another Fusprech transceiver. This tone is sent before and at the end of the conversation.

The required current to operate the set is quite high. It takes 0.9 A to heat all of the vacuum tubes. The magnetic switch takes 0.4 A. The Umformer SEUa1 (an improved version of the SEUa, which introduced much interference) uses approximately 4.1 A from the 12 Volt battery of the vehicle - consuming a total of 66 Watts of direct current. The total efficiency of this transceiver (ratio of RF output power to the consumed DC power) with Umformer operation is between 2..3%. With the vibrating power supply with the (SE)Ix or from Herbst 43 with the (SE)p resulted in a lower current draw, so the total efficiency becomes 3..4%. (To compare: 10W.S.c by itself was 10%. Together with the filament current of the Ukw.E.e in an Fu5 configuration it was 7%. More modern tube devices such as the SEM 25 (1980) have an 18% efficiency).

MANUFACTURER: Stassfurt Imperial
(KHz) 19998 - 21473 divided into 60 x 25 KHz channels (German frequency numbers 341 - 400) for both transmitter and receiver. Tuning dial has 60 channels numbered 341-400, each representing 25 kHz)
Rod - 2 meter
(MO OR CRYSTAL) MO. The tuning dial has a graduated scale calibrated to kilocycles whose color codes agree with those of the band switch.

Dynamotor unit SEUa or SEUa1 which operates from a 12 volt storage battery at 5.2 amperes. Power requirements:
Filaments: 12 volts, 1 A
Anode: 130 volts, 25 A to 180 volts 85 mA
Current drain from 12-volt battery is approx. 5.5 A.

SCR-195, SCR-536a, SCR-610, Fusprech.a, Fusprech.d
8 Watts

7 total ( 6x RV 12 P 2000 (pentodes) and one RL 12 P 10) in the receive position, one Rl 12 P10 is used as AF output and six RV 12 P 2000 tubes are used as mixer, HF oscillator, 1st and 2nd IF amplifiers, detector and 1st AF amplifier; In transmit position, one of the RV 12 P 2000 tubes performs the function of MO and the RL 12 P10 that of power amplifier. A second RV 12 P 2000 serves to modulate the power amplifier.

Radiotelephone communication between reconnaissance armored cars and tanks. It is used only for voice communication. It can be used in nets with American AM radio sets within the frequency and distance range.
Voice only.
3.5 approximately
Fusprech.f, Torn. Fu. d3 (yes d3)

Vehicular - mounted in reconnaissance cars and tanks.

Fusprech.f mounted in Sd.Kfz.251



The pristine face plate. Note the integrated control descriptions. Note the absence of the fine-tuning knob.



1944 manufacture - as always "The enemy is listening!"



Power connector.



Antenna current indicator for tuning the transmitter.



Cover off - this is the reverse of the Fusprech.f.



Top of the Fusprech.f. Accessible controls allow you to tune the device after the MO tube has been replaced.



Right side.



Left side.



Inside the lid...this is original paint. The connection instructions for the vehicle.



Built-in instruction booklet.




The antenna connection system canned "Ant-Zuleitung r". This is the correct system to use with the Fusprech. f, a and d systems when used on the Sd.Kfz 251, and Stug IIIg (for the single Ukw.E.e or Ukw.E.h on the right side of the vehicle).



The "2k" box, closest to the antenna, and featuring the smoothing inductor.



The "2b" box, which is a part of several other types of matching systems. This box provides a disconnected female port to plug the Fusprech antenna output connector if another antenna is being used.



Close up of the intricate antenna connector.



The "2k" box opened.



Close up of the "2k" box interior.



The "2b" box interior.