Funkgerät SREX, SE-201; U.S. Signal Corps SCR-610, erworben aus amerikanischen Surplus-Beständen.
To be used by artillery units as a mobile transceiver on the jeep, a series of 1510 units of U.S. Signal Corps BC-659 sets has been bought as war surplus after the end of WWII. In Switzerland, these sets got the designation REX, after the new naming scheme in 1951, they carried the designation SE-201/m (the m stands for mobile use).
The wireless station SE-201 consists of the transceiver itself in a metal cabinet (14 kg) attached to either a battery case CS-79 (for portable use, HT / anode battery BA-39 and LT / heaters battery BA-40) or a vibrator voltage converter case PE-117 (for mobile use onboard a vehicle from a 6 or 12 V car battery).
The transceiver can be operated with a 4 m rod antenna or for onboard use on a vehicle with a 3 m whip antenna; a remote control set allows the transceiver to be controlled over fiel telephone line from a maximum distance of 200 m.
As standard communications range, a distance of 3 - 15 km is stated, that's a bit more then with a standard citizens band radio.
For proper operation of the transceiver, presetting of the two crystal controlled channels is necessary. This procedure had to be done by a signals mechanic according to the procedure in the rear part of the technical manual TM-11-615 (Presetting, from page 91) by a trained signals mechanic. First channel A is pretuned for the lower frequency, after that channel B for the higher frequency. On the chassis top face, you find seven controls for each channel (A1-A7 and B1-B7), two switches and a socket to connect a service meter, in Switzerland the T-101 has been used to measure the voltages.
To operate the set, the microtel and the headphones normally stored in the battery case fpor transportation, are plugged in and the power cable is used to connect to the battery case or vibrator case.
The switch on the right side is the volume contorl, the switch in the middle lets you select channels A or B (the crystals have to be plugged in the sockets on the chassis and the presetting prpceure has to be done before). The left switch controls the meter function, PLATE lets you control the plate voltage of battery BA-39), in position FIL(ament) the heaters voltage (Battery BA-40), the meter needle must reach at least the 2. In position OPER(ation) the meter does display the antenny current. While transmitting, the meter must 1.5 to 3 in the OPERation position.
Transmit / receive switchin is done with the PTT button on the mikrotel; when the headphones are not plugged in, the set is wired for speaker operation.
Technically, the receiver part is single conversion, the antenna signal is amplified in two stages (1LN5, 1LN5) and mixed with the fourth harmonic of the crystal controlled oscillator (3D6, crystal frequency = (operation frequency - 4,3 MHz)/4) in the mixer stage valve V7 (1LC6), the IF of 4,3 MHz is amplified in two IF stages (1LN5, 1LN5) and after a limiter stage (1LN5) it is demodulated in the discriminator stage (Diodes 1R4 and one of the double diodes 1LH4 in a push-pull - arrangement). The AF signal is amplifed in the AF stage (3D6) and fed to the headphones or the speaker.
When transmitting, the audio from the microphone is fed through a microphone transformator to the modulator tube (3D6), this acts a reacting modulator, the frequency of the transmitter oscillator (3D6) is altered with the audio information coming from the microphone and thus frequency modulation is generated. The first harmonic or the double frequency of the transmitter oscillator is filtered out and it's frequency is doubled in the frequency doubler / buffer stage (3B7) to generate the final transmitter frequency. The signal is amplified one more time in the double triode 3B7 of the transmitter output stage in a push-pull arrangement.
V1 (3B7 (VT-182, 1291), transmitter output stage); V2 (3B7 (VT-182, 1291), RF double / buffer); V3 (3D6 (VT-185, 1299), RF oscillator); V4 (3D6 (VT-185, 1299), transmitter modulator); V5 (1LN5 (VT-179), 1. RF amplifier); V6 (1LN5 (VT-179), 2. RF amplifier); V7 (1LC6 (VT-178), receiver mixer); V8 (3D6 (VT-185, 1299), receiver oscillator); V9 (1LN5 (VT-179), 1. IF amplifier); V10 (1LN5 (VT-179), 2. IF amplifier); V11 (1LN5 (VT-179), limiter); V12 (1R4 (1294), receiver diode); V13 (1LH4, receiver diode / amplifier); V14 (3D6 (VT-185, 1299), AF output stage).
In the vibrator case PE-117 valve Pos. 4 (VT-195, rectifier), Pos. 9 stabiliser 0B3 (VT-184) or VR-90/30.
The wireless station SCR-610 has been developed by engineers of the U.S.Signal Corps in around 1940 and was produced by different contractors in the USA.
The complete station SCR-610 consists of the transceiver BC-659, the battery case CS-79, the vibrator poweer supply PE-117, mounting frame FT-250 anmd remote control RM-29 intended to be used onboard vehicles.
The portable version SCR-609 consists of the transceiver BC-659, the battery case CS-79 and the remote control RM-29 as an option.
In the Swiss Army, the SE-201 / REX has been used as manpack or jeep vehicle station by the artillery. The 1510 units habe been faded out in 1974, many sets have been sold to vehicle enthousiasts, that's why only few of the sets can be found second hand nowadays. If you encounter a BC-659 set carrying a label as REX in the USA, you can be sure, that that's a set that has seen use in Switzerland.