Shortwave Radio Station SE-415; manufactured by Zellweger AG, Uster.
The development period until 1961 fell exactly into the transition period from valve to semiconductor technology. During the development, several parts of the station were redesigned in solid state technology. Problems with the heat dissipation of the valve stages had to be solved, and at the same time, the use of printed circuit board construction was introduced. From 1969 to 1974, more then ninety units were built. The major number of 85 stations did serve in the Swiss army, mostly installed in the off-road radio truck Steyr.
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The radio station is housed in a steel cabinet, which itself has a weight of 89 kg. In it, all the necessary cables and connectors are mounted on swivel arms, which connect the individual units. The rack units mounted on rails make it possible to pull out the individual units like drawers. To do this, loosen the screw knobs on both sides above the handles and push them, to release them.
The complete wireless station with all the modules has a weight of 325 kg, the station is powered from 380 V three-phase alternating current from the mains or from a petrolk generator for field use. To operate only the receiver, the unit uses 250 W, when transmitting 3300 W, but the tranmitter output reaches 1000 W in CW and telephony.
Under the removable bottom cover, the connectors are located: Here the mains connectors, the 10A main fuses, various connectors for teletypewriters and the remote control, 12 and 220 V outputs and of course the transmitting and receiving antenna connectors. The petrol generator can be started and stopped via control lines from the operator.
The next unit is the High Tension Uni, in addition to the high voltage fuses for the 1.8 kV plate voltage, there is also the counter of operating hours.
On the frontplate of the next unit, the so-called Power Supply, the numerous fuses for the various circuits are located. When the unit is pulled out, a switch and an instrument to control the 21 fuses can be accessed at the top of the drawer. Two sockets provide 220V mains voltage, behind a metal grille, the main speaker is located.
A central part of the radio station is the next unit, theso called Signal Unit. Here, the morse key, the headphones and microphone are connected. The transmitter modes switch selects the transmit and receive operation modes on the same or on two independent frequencies, the positions to connect with another SE-415 and also to a SE-222 are marked with corresponding colours.
The speaker switch is set to monitor the AF signal from the receiver or the signal supplied to the transmitter, the middle red knob is the volume control.
The signal control switch is to check the the RF and AF signals of the transmitter and receiver as well as the oscillator and to calibrate the third oscillators of the receiver and transmitter.
The Receiver is designed as a triple conversion superhet, it has two separate antenna inputs and RF / IF amplifier tracks. When antenna diversity is used, the stronger signal is fed to the demodulator.
The switches and indicator lamps of the two receiver tracks are located on both sides of the main oscillator unit. With three rugged tuning knobs, the frequency of the main oscillator and thus the reception frequency is set and displayed on the mechanical digital display, similar to the one found on the Collins R-390A. The sensitivity control at the left serves as RF gain control. A large measuring instrument in the upper left corner of the receiver displays the signal strength, the right instrument a frequency deviation to the other station. In the switch position „Auto.Frequenzregelung“ the station operation frequency is synchronized to the frequency of the remote station. The typical Revue seven day station clock is located between the two measuring instruments (and sometimes missing in stations for sale).
The Transmitter section is located in the top unit. The frequency is also set on a main oscillator unit with the three tuning knobs, the main oscillator units are interchangeable.
The transmitter can deliver upper sideband, lower or independent sideband signals. Typically, the lower sideband was used for A1 and A3A telephony signals, the upper sideband for the radio teletype modes F1a and F1b simultaneously.
The transmitter power can be varied from 10 to 100 W and up to 1 kW Peff; in the transmitter, four air-cooled 4CX250B transmitter tubes are installed. Transmitter tuning is done automatically.
Optionally, the SE-415 came with an external voltage stabilizer, an isolation transformer for mains operation and an automatic antenna tuner for the whip antenna of the radio truck and a Antenna Tuner AG-415 to tune the dipole antenna in the range 2 - 12 MHz.
Zellweger started the development of the SE-415 in 1956. The development took a very long time, as the development time fell into the transition from valve to transistor technology. In 1975, the station was completely reworked and certain assemblies were modified in solid state printed circuit board technology.
In the years 1965/69, 75 mobile stations mounted on radio trucks and 10 stations for fixed operation were acquired.