SE-100 / FOX

Kleinfunkgerät SE-100 / FOX; developed as BC-611 by the U.S. Signal Corps and produced by Autophon AG, Solothurn under U.S. Licence.

Shortly after the end of WWII, the Swiss Army acquired a quantity of the first U.S. made „walkie talkie“ transceivers BC-611 from military surplus, in Switzerland this was referred to as „Modell 44“. Due to increasing demands, the Swiss company Autophon has been licensed to produce a production run at their own plant in Solothurn („Modell 48“).

In Switzerland this set got the military designation FOX, after 1951 this has been changed to SE-100 according to the new naming scheme.

Technical Data

Principle: Transceiver, receiver single conversion, IF 455 kHz
Modes: AM (A3)
Frequency range: 3500 - 6000 kHz, one crystal controlled channel pre-tuned; 50 possible channels with a channel spacing of 50 kHz
Output Power: 0,027 Watt
Sensitivity: AM (A3) / Selectivity:

Power Supply

Accumulator / Batteries: Heizbatterie 1,5 V (BA37, rund), Anodenbatterie 103,5 V (BA38, eckig)

The set is powered from a 1,5 V heaters batterie and a 103,5 V B+ / anode batterie; batteries will keep 10 up to 20 hours depending from the intensity of transmitter use.

Dimensions

80 x 320 x 90 mm; 2.5 kg (with batteries inserted)

Accessories

Standard antenna is the built in Telescopic antenna, the set is switched on, when the bottom segment has been bulled completely out.
Prüfausrüstung FOX, testing unit and set with an alignment cabinet in which the set's chassis has to be inserted to pre-tune the operation channel.

Operation

The U.S. made personal portable transceiver BC-611 got a very good reputation in World War II, it was the earliest really portable „walkie talkie“.

Like in a huge telephone handset the microphone and speaker are integrated in the cabinet of the set. The set is switched on by unscrewing the cover of the antenna and by pulling out the telescopic antenna. To talk, just push the „push-to-talk“ button. There are no other controls or knobs to operate the set.

The single transmission / reception frequency is controlled by crystals in the 3,5 - 6 MHz shortwave range, the frequency is written on a small tag on the cabinet and cannot be changed in case of co-channel interference. Later, the frequency channels have been coded by different label colours, to you just had to use two sets with the same frequency label colour.

The standard range is only 150 - 200 m under standard conditions, unter optimal conditions, the set might reach up to 1,5 km - malicious gossip has it that a powerful megaphone might be at least as useful…

Alignment

To operate on a certain channel, before use, a transmitter and receiver crystal, a tank coil and an antenna coil have to be installed on the chassis (these sets of components, four for each channel, are stored in the box BX-49), and after each change of operation frequency, a complete realignment has to be made.

So the Uem Ger Mech (signal troops mechanic) has to take out the chassis and has to install the four frequency dependent components on it (two crystals (TRANS (exactly on operation frequency) / REC (operation frequency + 455 kHz), two coils (the antenna and the tank coil)). For the realignment, which is necessary after each frequency change, the chassis has to be inserted in a realignment cabinet. It has the same capacity like the original cabinet and has colour marked holes, through these, the alignment points can be reached. If you would go through the aligment procedure without the alignment cabinet, the frequency will be shifted, after the chassis is inserted into the original cabinet.

The Prüfgerät SE-100 test set with a meter can be used for the alignment procedure and to control all necessary voltages and battery voltages, in the technical manual „Regl für UemGeräte Mech 65.5“ you will find all the details (for english language, you might refer to the original TM).

Technical Principle

To reduce the number of valves to five, some valves have double use, which is altered with the receive - transmit switch.

In Transmitter mode, the RF signal is generated in a crystal controlled oscillator (1R5), in the RF outpus stage (3S4) the RF signal is amplified, the modulation type is anode modulation. The audio signal coming from the microphone is amplified (1S5) and fed to the audio final stage (3S4) and from there to the RF output stage and to the headphone capsule, so that the transmitted audio can be heard for control.

In Reception mode, the RF signal coming from the antenna is amplified in a RF amplifier stage (3S4) and then fed to a 1R5 valve, which acts as oscillator (controlled by the receiver crystal REC) and mixer stage. After an IF amplifier stage valve (1T4), the intermediate frequency of 455 kHz is fed to the 1S5 valve, there signal is demodulated and amplified in an AF preamplifier stage. A 3S4 valve acts as AF final amplifier.

Valve layout

V1 (3S4, REC: RF amplifier, TX: RF output stage); V2 (1R5, REC: Mixer and oscillator, TX: oscillator); V3 (1T4, REC: IF amplifier); V4 (1S5, REC: demodulator, AF preamplifier, TX: microphone amplifier); V5 (3S4, REC: AF final stage, TX: Modulator).

Development

The portable transceiver BC-611 respectively the wireless equipment SCR-536 (consisting of the BC-611, the box BX-49 with two crystals and two coils for twelfe different frequencies and the test set IE-17 with the alignment cabinet) had been developed in around 1940 by a team working under Don Mitchell from Galvin Manufacturing, a predecessor of the U.S. american company Motorola, and was used as first personal radio or „Walkie talkie“ on World War II.

The Swiss Army could acquire after the end of the war 5777 units with corresponding accessories and spares from U.S. surplus (called „Modell 44“ in Switzerland). An even bigger number of sets, around 12'000 units, habe been produced by Autophon under U.S. licence (called „Modell 48“).

Field use

The SE-100 „FOX“ soon was the most often used means of wireless communications in Swiss infantry units, the colour of the frequency labels does indicate the purpose of use:

Colour	Use
white	Sets used for tactic communications
red, orange	Sets used by observers of the anti aircraft units
green, blue	Sets used for shooting exercises
yellow	Sets used for supervisors and referees (in infantry schools)