SE-402: SM46

Motorized Radio Station 46, SM46 („Schwere motorisierte Funkstation“) or SE-402; manufactured by various U.S. manufacturers.

In the post-war period, the Swiss military short-wave radio network needed renewal and much more equipment was needed, than the domestic industry was able to deliver. From American surplus stocks, sixty shortwave stations SCR-399 were purchased, the Hallicrafters HT-4 transmitter was initially developed for the amateur radio market, the receivers BC-342 and BC-312 for the Signal Corps.

In the Swiss Army, the station got the designation SM 46 and later SE-402. One of these stations was restored and was put back to service at the occcasion of „Ustertag 2006“ of the Swiss signals interest group (IgUem).

SE-402 / SM46 ready to move

Technical Specifications

Power Supply

  • Mains: 120 V
  • Generator: the station can be fed independent of the mains in the field by a PE-95 unit. A Willys 35 hp four-stroke gasoline engine is installed on the generator trailer, it drives a 120 V, 10 kW single-phase alternator, on the same axis a DC exciter is installed, which provides 28 V CD and can charge the starter battery of the truck and accumulators. The generator can be started from the radio operation site via remote control.


  • The dimensions of the GMC truck with the shelter are 6.3 x 2.3 m, with the antenna, the total height is 3.6 m. Together with the generator trailer, the total length is 10 m and the total weight 8.5 t.


SE-402 / SM46: Antenna Erected

  • The standard antenna is a rod antenna consisting of five to seven elements mounted on the roof of the shelter.
  • For fixed operation, the construction of a long-wire antenna or a powerful half-wave dipole was intended.
  • The subsidiary operation site can be operated from accumulator power supply. In this case, the secondary receiver BC-312 at the remote site is used for reception and the transmitter is remotely operated.
  • Wave meter BC-221 for frequency calibration

SE-402 / SM46: in the Shelter

Station Material

The entire 400 watt AM / CW ​​radio station is housed in a shelter mounted on a GMC all-terrain truck; a trailer with the generator is used for power supply, if there is no mains connection.

In the interior of the shelter, there is a bench for the operator in the middle, the compartments underneath contain spare parts.
In the front, the transmitter with the US designation BC-610-E, technically based on the Hallicrafters HT-4 and the antenna tuner BC-939-A - or Hallicrafters AT-3, is located.
The cabinets to the right contain not only spare parts but also the tuning and antenna coupling coil units for the transmitter.

To the left, next to the transmitter, the chest CH-120-A, containing the receiver BC-342, the amplifier BC-614-E, the speaker LS-3, the morse key and the switch box JB-70-A is located.
To the left of it resp. in the back of the vehicle, the chest CH-121-A containing the receiver BC-312, another loudspeaker LS-3 and a morse key J-37. This secondary receiving equipment can be operated from a 12V accumulator pack CH-109-A, the entire radio station can be remotely operated.

Three antennas are mounted on the roof of the shelter, the front is the five-segment transmitting antenna, the two rear antennas are the receiving antennas.

Technical Principle

SE-402: Transmitter Transmitter BC-610-E : the transmitter is a four stage tranmitter, all four stages must be tuned separately: oscillator stage (the oscillator can be crystal controlled or tunable), doubler stage, intermediate stage and output stage. Of all eight Tuning Units TU-47 / TU-54 with three pre-tuned channels each and eight output stage coil units „Tank Coils“ C-387 / C-449 two sets are stored in the accessories chests.
For crystal controlled fixed frequency operation, the station has two sets of 36 crystals, it can be tuned depending on switching of the doubling / quadrupler stage to the second or fourth harmonic, so that 72 operation frequencies are possible.

SE-402: Receiver
Receiver BC-342 / BC-312 : the receivers of the main and secondary operation sites are largely identical, they are only differentially powered from 120 V AC or 12 V DC. The single conversion set with an IF of 470 kHz covers the frequency range from 1.5 - 18 MHz in six segments.

Valve Layout

Transmitter BC-610-E : oscillator (V8, 6V6), buffer (2 - 4 MHz) / frequency doubler (4 - 12 MHz) / frequency quadruple stage (12 - 18 MHz) (V9, 6L6); transmitter driver stage (V10, V11, each 807 in parallel); transmitter output stage (V16, 250TH).
In the AF circuit, two AF stages (V1, V2, each 2A3 in push-pull arrangement), modulator stage (V3, V4, two 100TH); in the power supply unit a rectifier for the RF stages (V12, 5Z3), plate voltage rectifier for the AF stages (V5, 5Z3), plate voltage rectifier for the RF stages (V6, V7, two mercury rectifiers 866A).


Transmitter SM46: BC-610A The transmitter BC-610-E is a very performing Amateur radio transmitter HT-4 developed by Hallicrafters. Due to the US entry into war and the increased need, the Hallicrafters station was produced in large numbers.

During wartime, an „austerity“ version of the BC-610 was made, all expendable elements were omitted and the transmitter was structurally simplified, the technical specifications were kept unchanged. This militarized version of the BC-610 was named BC-499. From the Swiss side, it was used only in the context of the Koreafunk, the equipment of the station HBM-46 in Panmunjom and also the transit station in the Swiss embassy in Tokyo were provided from the U.S.

The receivers BC-342 / BC-312 were used as receivers in both operation sites, the local operation site near the transmitter and the remote operation site.

Field use

After the end of the Second World War in the years 1946/48, 60 stations were purchased at a price of 103,000 Swiss francs from U.S. surplus to be used in command communications.

The stations were used in addition to the high power wireless stations for command communications and links between the field corps commands. Furthermore, the SM46 station was used to broadcast alarm messages, the corresponding receivers E45 or E-627 then were crystal controlled.

The last stations were used until they were replaced by the alarm messaging station S-510 in 1979; the stations were liquidated in 1980 and some were purchased by radio amateurs.

Technical Documentation

Additional Informations

en/se-402.txt · Zuletzt geändert: 2019/12/13 21:02 von mb