In Finland arrested in WW-2 about 700 Soviet agents. They represented quite many nationalities. Usually they jumped with a parachute and they had weapons, explosives and radio sets with them. One of those sets was Sever. It was very small insize, battery powered and packed to the two shoulder bags of cotton stuff inside surfaces of material covered with a rubber film. The radio bag (abt 4 kg) contained except the radio chassis in a wooden cover, also a little telegraph key, 3 crystals, headphones, two antennas, reserve tubes and the necessary tools. The battery bag (5,9 kg) contained 4 pcs 60V/0,45Ah anode batteries and 2 pcs 1,5V/29Ah heater batteries. In this bag there was also a 75 cm long 6-core battery cable terminated with a 7-pin connector. At the other end point there was a bakelite box (50 x 100 mm). From six screws of the box divided six well marked cables to the batteries.
The frequency range for the 2-stage transmitter was abt 3,4 - 6,3 MHz and output the RF-power was maybe 1,5 W. The frequency range for the 3-stage straight receiver mode was stated in range one 3,5 - 6,8 MHz and in range two 6,5 - 12 MHz. The radio tubes were 2 pc 2K2M and one C-244 or type 24 or 2 - 4M. The require heater voltage of 2 V is reduced from the 3 V batteries by "Filament" potentiometer. There was a danger that the tubes could easily burn. The mechanical construction of Sever was rather firm. The tuning dial of the receiver behind an arched, narrow window was not easily readable. The tuning gear with ratio 60:1 is good. During reception Sever was very microphonic. According to experience, it has been told, that the original batteries became empty at most one month and the tubes lasted abt two months. This can be true, the current consumption is high and the short life of tubes depends on the user.
The mains powered Sever might have been the latest type of that radio which was designed at the end of the war. I have not seen it, only an old copy of the circuit diagram is available. The circuit of this model is basically similar but the tubes are 6,3V AC-steel tubes. The RF-output power of transmitter might be abt 10W. The Soviet radio factories began to use the USA-type radio tubes in the beginning of the early thirties, when Sylvania sold a radio- and radiotube factory to the USSR, located in Moscow. They used small 2V battery tubes in their field-radios and the steel tubes were used in their aircraft and tank radios . The power supply could be called "The spy killer". The anode voltages are rectified by a voltage doupling circuit directly from the mains voltage.
Sever is very rare. In Finland we know only about ten sets.