SE-018/m / H-Station
Radio Set SCR-287 (BC-375-E / BC-348)
U.S. Signal Corps, different manufacturers

Swiss Army Communication Sets
Synoptic Table
Army Transceivers
Transceivers SE-0xx
(SE-001) / FG I
(SE-002) / FG II
(SE-004) / FG IV
(SE-009) / FG IX
SE-010 / FG X
S-011 / FG XI
SE-013 / SCR-522
SE-015 / STR.9X
SE-016 / Omera
SE-018 / H-Station
SE-020 / Socrat
SE-023 / Collins
SE-051 / Omera
SE-054 / Magnavox
varia / copyright
about / contact

überarbeitet am 1.1.2013

In the years of World War II, the high power shortwave transmitter "Sender Emil" has been commissioned for the central Air Force Command to direct fighter aircraft and control flight operations. Although it's favourable topographic location at Kleine Scheidegg in the Jungfrau massif, it turned out that this transmitter was not capable to reach all aircraft and airfields within Swiss boundaries.
So there was a project taken to erect "mountain wireless stations" which acted as relay stations to optimize wireless signal coverage over Switzerland; the "Mountain stations" Stephan, Neptun, Fortuna and Theodor were the first of it's kind.
There was a lack of suitable high power shortwave transmitters with large frequency coverage. The Swiss Air Force authorities found such wireless equipment in close distance: the aircraft wireless stations SCR-287 of several U.S.A.F. bomber aircraft which had to make an emergency landing in Switzerland and have been interned during the war. This equipment has been taken out of the aircraft and was installed in the mountain stations, Zellweger constructed matching mains power supplies.
After the end of WW II, the Swiss authorities formally paid for the requisitionned wireless equipment and bought further sets of the same type from U.S. surplus.

Transmitter BC-375-E,

1500 - 12500 kHz, 6 tuning units

A1, A2, A3, pout ca. 45 - 75 W

Receiver BC-348 / E-018 / H-Empfänger: superhet, IF 915 kHz

200 - 500 and 1,5 - 18 MHz, analog dial

A1 (telegraphy CW), A2, A3 (telephony)

Mains power supply from Swiss production, BC-221 wave meter for frequency calibration

To ensure reliable shortwave communications over whole Switzerland, there was a great demand of high power shortwave transmitters and receivers in the years of World War II.

As shortwave equipment from Swiss production with sufficient frequency coverage and output power was lacking (the FL 40 station covered shortwaves only up to 4500 kHz, the later KL 43 had a modified transmitter tuneable up to 12 MHz but was available only in small numbers), the Swiss Air Force technicians decided to re-use shortwave wireless equipment from U.S. bomber aircraft which had made an emergency landing or had been forced to land when entering Swiss air space.

The U.S. Signal Corps SCR-287 equipment has been used on a GMC truck for mobile operation (designation SE-018/m) and in fixed installation in "mountain stations" (designation SE-018/f).
These fixed "mountain stations" have been used to link the airfields of Swiss Air Force, they could be operated manned or remote controlled.

The Transmitter BC-375-E is 58 x 51 x 23 cm wide and has a weight of 23,8 kg, there are six tuning units with 6,5 kg each to go with it. The tuning units cover 1,5-3 MHz (TU-5-B), 3-4,5 MHz (TU-6-B), 4,5-6,2 MHz (TU-7-B), 6,2-7,7 MHz (TU-8-B), 7,7-10 MHz (TU-9-B), 10-12,5 MHz (TU-10-B) and longwaves 200-500 kHz /TU-26-B). To select the desired band, the matching tuning unit has to be inserted in the transmitter cabinet.
The transmitter is powered by a dynamotor PE-73-C, it can be powered from 24 (truck battery) or 28 V DC (aircraft power system).

In the transmitter, a valve VT-4-C (corresponding RCA type 211) acts as oscillator, two more VT-4-C valves as modulator and a fourth VT-4-C as transmitter output tube, it's plate modulated; a VT-25 (RCA 10Y) is used as microphone / AF amplifier.

The Receiver BC-348, the Swiss variant carries a "H Empfänger" (receiver of H station) typeplate, comes in a black aluminum cabinet (this to remember, the SCR-287 is an airborne station), it's dimensions are 46 x 23 x 22 cm and it's weight 20 kg.
The receiver is a single superhet with an intermediate frequency of 915 kHz. The RF signal from the antenna has to pass two tuned RF preamplifier stages (two valves 6K7 / VT-86) and is fed to the mixing stage (6J7 / VT-91) to generate the intermediate frequency of 915 kHz with the signal from the main oscillator (6C5 / VT-65). After the IF amplifier stages (1st IF: 6K7 / VT-86, 2nd IF: 6F7/VT-70, 3rd IF: 6B8 / VT-93), the signal is demodulated (diode system of valve 6B8 / VT-93) and fed to the AF output stage (41 resp. VT-48, later 6K6GT). The second triode sytem of the 6F7/VT-70 is used for the beat frequency oscillator for CW reception.

A complete station consists in standard configuration of two receivers BC-348 (with dynamotor inside), two transmitters BC-375-E with their tuning units, dynamotors PE-73-C, a wave meter BC-221 and in some cases a mains power supply made by Zellweger AG, Uster.

I would be very thankful for further information and images.

further information:
Information from the Swiss Air Force Museum Dubendorf, where the equipment is displayed.
e: Manuals of the U.S.Army for the Transmitter BC-375-E and Receiver BC-348

© 3.1.2013 Martin Bösch