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Schwere Funkfernschreibstation /
Zellweger, Uster SE-415

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überarbeitet am 5.1.2008

Receiver, triple conversion

mechanical digital display, 100 Hz


2 - 52 MHz

ZF bandwidths AM 3 kHz, CW/FSK (F1, F1a) 500 Hz and FSK (F1B) 250 Hz.

mechanical digital display, 100 Hz

pout eff
10 / 100 / 1000 W

separate oscillators for transmitter and receiver,

Power supply 380V AC.

The Swiss manufacturer Zellweger, Uster, had a very good reputation for their SE-222 medium power shortwave transceiver, in 1957, they were offered a contract for the construction of a more powerful military shortwave station.
The development of this set coincided with the time changing from hollow state / valve technology to solid state / semiconductor technology. During the construction period, many modules had to be designed completely new using transistors and printed circuit boards, several problems with heat dissipation from valve stages situated close to transistorized modules had to be resolved. From 1969 - 1974, a few more then seventy sets have been constrcuted. 68 of them were used by the Swiss army, mainly vehicle mounted on a Steyr 4WD signal troops truck.

The complete transceivers comes in a heavy duty steel cabinet, the empty cabinet has a weight of 89 kg! In the cabinet, You find supporting rails, oh these all the separate modules can be pulled out like drawers, You have to unscrew the black round knobs and finally press them in to unlock the mechanism. Inside the cabinet, You find flexible supports with attached multipole connectors to connect all the modules together.
The complete wireless set with all the modules will have 325 kg, so it's a good idea to take the different modules out for a transport, all the modules can be carried at least by two men. The transceiver is powered by 380V AC three phase electric power, for military use an engine-generator can be used, it can even be started from the stations's control panel. For reception only, the set will take up 250W, for transmitting with 1000W maximal HF power, You might need 3300 Watts...

Behind the metal plate of the bottom drawer, You have access to the Connectors module: here You have connectors for the mains, the mains 10Amp fuses, several connectors for using teleprinters, the receiving and transmitter antennas, a wired remote control and sockets for 12V DC and 220V AC to connect gear used in the radio shack.

The next "drawer" is the High Voltage, module, You have acess to the fuses for the 1,8 kV plate voltage of the transmitter and a operation hours meter.

Above, You find the so called Power Supply Module, an impressive number of fuses are used for the different voltages used in the set. When the drawer is unlocked and pulled out, You find a circular switch and a meter to perform a quick control, which of the fuses is blown.
Two 220 V sockets allow to operate additional gear, behind a metal grille in the middle, You find the station's monitor speaker.

The following drawer acts as the "central" or "command post" of the transceiver: the Signal Module. You find the connectors for headphones and morse key here, the connector "MIKROTEL" is used for connecting a telephone like handset with a PTT (push to talk) button.
The transmitting mode switch allows to switch to single or split frequency operation, the setting for connections with another SE-415 and for contacting a SE-222 with it's smaller frequency range and reception modes are colour coded.
The speaker switch is used to select the signal com,ing from the receiver or to monitor the transmitted signal, the middle red button is the AF gain / volume button. The signal control switch is also used to calibrate the third oscillator stage of the main receiver and transmitter oscillators.

The Receiver is a triple conversion heterodyne set with two different RF- / IF- amplifier strips used for antenna diversity reception. The three main tuning knobs are used to control the reception frequency, it is displayed by a mechanical digital readout similar to the one found in the Collins R-390A with a dial accuracy of better then 100 Hz.
The SENSIBILITE control is used as RF gain control, the left meter will display the signal strength, the right meter is used to tune the station exactly to the carrier of the communicating set. With the switch "AUTOM.FREQUENZREGELUNG", the signal is synchronised automatically with the communication station in FSK modes. In the middle between the two meters, You usually find the typical Swiss Army seven days movement Revue clock. Because it's finger's have radium colour, You might find it difficult to export the set because of radiation restrictions, but I consider the minimal radiation not as harmful. You might cover the clock with a metal shields like the ones found on american R-390A sets - or You might simply take the clock away and store it in a metal cabinet.

The Transmitter is situated in the top module. You will have to select the transmitting frequency using the three tuning knobs of the transmitter main tuning oscillator, both oscillator modules are interchangeable.
The transmitter can be set up to transmit a upper and a lower or two independant sidebands with reduced carrier. In typical Army use, the transmitter gives A1 / CW or telephony A3A signal in the lower sideband and FSK / radioteletype channels F1a and F1b in the upper sideband.
You can switch the transmitting power from 10, 100 up to 1000 Watts Peff, the transmitting tubes 4CX250B are air-cooled and antenna tuning is automated.

For the SE-415 wireless station, there has been many optional equipment like an external voltage stabiliser and an isolation transformer for mains use, an automatic antenna tuning unit used for the whip antenna of the vehicle on frequencies between 12 and 52 MHZ and a second dipole antenna tuner used for the 2 - 12 MHz range.