SE-404: G1.2K

High Power 1.2 kW shortwave station, G1.2K, „C-station“ of the air force resp. SE-404; manufactured by Lorenz / Standard Telephon und Radio AG, Zürich.

The G1.2K was developed for the Air Force. The high power shortwave station, which got the designation C-station is technically quite similar to the G1.5K / B station. According to the needs of the Air Force, the frequency range of the transmitter was adjusted to a higher frequency range of 2 - 12 MHz and covered the needs of Switzerland well. The need for improved mobility was taken into account, the station was installed it in a truck with better off-road performance.

The shortwave transmitter with it's 1.2 kW output and plate modulation was developed around 1935/37 by C. Lorenz AG in Berlin - Tempelhof and constructed in 1940 - 1941 by the Standard Telephon & Radio AG in Zurich. The G1.2K station was used for Air Force command communications and later for broadcasting air alert messages.

SE-404 / G1,2K

Technical Specifications

Power Supply

  • Generator: single axle trailer with three-phase generator (380 V, 50 Hz, 15 kVA) powered by a gasoline engine 22 HP.


SE-404: station vehicle

  • Saurer 6×6 off-road truck as station vehicle


  • A self-radiating 25 m telescopic mast from Magirus is used as standard antenna.

Station Equipment

As an alternative to the High power shortwave station G1.5K, the transmitters of the G1.2K was adapted to the needs of the air force to operate in a higher frequency range, which caused a certain reduction in the output power.
To improve mobility, the station was mounted on a Saurer 6×6 off-road truck (10,000 kg); the generator was mounted on a single-axle trailer (2,200 kg).

SE-404, transmitter Transmitter: The three stage Lorenz transmitter can be tuned by means of variable capacitors in four frequency ranges, all circuits run in synchronism; the antenna is tuned by means of a sliding wire variometer.
One tube RS337 is used in the driver stage, two RS337 in the intermediate stage, two RS329g in the final output stage, two RS382 and three rectifier tubes RGN2504 in the modulator and keying stage. In the (microphone) amplifier, two RS282 and three RE084k are used.
The station has a maximal output power of 1200 W in CW telegraphy (A1) and 400 watts in modulated telegraphy and telephony.

SE-404: Empfänger Receiver: The all-wave receiver „Uster“ / E41 was used as main receiver.
Operation modes are CW (A1) and modulated (A2) telegraphy, telephony (A3) and also Hell teleprinting. The Hell-Schreiber developed by Siemens is a 7×7 dot matrix teleprinter which prints directly readable plain text on paper tape. The technical requirements for Hell teleprinting over short-wave connections were very high and communication suffered from poor propagation conditions, so that in 1944 the Hell mode was suspended.
Later, the Autophon E44 all-wave receiver was used as main receiver; apparently after 1948. Then, also high speed telegraphy was introduced.

The G1.2K / C station is powered by a four-stroke petrol engine „Phaenomen“ which drives a 15 kVA three-phase generator mounted on the generator trailer (2200 kg).

A self-radiating 25 m Magirus telescopic mast was used as standard antenna, is was erected on the roof of the station truck.
The vehicle antenna or a long-wire antenna was used as receiving antenna. For duplex operation, the receiving site had to be remote operated.

Technical principle

Valve Layout

Transmitter: V1 (RS337, driver stage), V1, V2 (two RS337, intermediate stage), V3, V4 (two RS329g, final stage)
V5, V6 (two RS382, modulator and keying circuit), two RS282 and three RE084k in the (microphone) amplifier, three rectifier tubes RGN2504.


The high power shortwave radio station G1.2K was developed by C. Lorenz AG, Berlin in around 1935/37 and manufactured by Standard Telephon & Radio AG in Zurich in 1940/41.

A total of 16 stations (according to Ritter 20, 8 of them on chassis M6 and 12 on chassis 2CM) were purchased and handed over as G1.2K or „C Station“ to the Air Force signal units.

Field use

The G1.2K / SE-404 was used by the Air Force signal units for command communication; after TO 1961, the SE-404 were transferred to the signal troops as alert message broadcasting stations and faded out in 1967.

Technical Documentation

Additional Informations

en/se-404.txt · Zuletzt geändert: 2019/12/14 22:29 von mboesch