Funkgerät SE-103 (RTS); developed and produced by Telefunken AG, Zürich.
Telefunken, Zurich, tried another way to design a successor to the single frequency SE-100: their SE-103 uses plug in frequency modules to select the different frequencies in contrast to the switchable crystals in the rotating „crystal drum“ of the SE-101 / SE-102 developed by Autophon.
One frequency module („Sprechkanal-Einsatz“) with a crystal and tuned antenna coils is in use, a second module can be carried in a compartment at the bottom of the set. There have been several frequency modules available, but the choice is easily made, when you are carrying only two different frequency modules with you…
The SE-103 is powered by one LT / heater battery (LSA Nr. 10001; 1,5 V) and one b+/ HT battery (LSA Nr. 10103; 103,5 V).
The wireless set SE-103 is a portable transceiver, it comes with a metal cabinet with the dimensions of 323 x 148 x 95 mm, a weight of 5,1 kg and is usually carried in front of the soldier's chest. A small canvas bag is used to store headphones and throat mikrophone combination. The transmit - receive switch can be attached to the uniform by use of a metal clamp, so it can be operated will a pressure of the elbow - the SE103 has been ins use with the cavalry, so the soldiers had their hands free to hold the horse's rein.
With it's output power of 0,2 Watts, the standard communication range is 3 km at daytime and around 2 km during the night, it is smaller then the range of a common CB set.
To operate the set, insert the heater and anode / B+ battery in the battery compartment at the bottom of the transceiver.
The frequency module (containing the frequency crystals for the receiver and the transmitter oscillator, the coils for the receiver input circuit and the antenna coil) is inserted in the compartment under the lid with the antenna support. The frequency module's identification letter can be seen through a tiny window.
A second frequency module can be stored in a compartment at the bottom of the SE-103, to change the frequency, You have to open up the compartments and swap the modules.
The set is switched on with a three position switch on a short cable (off - normal - loud), the transmit switch can be attached to the uniform and can be operated by pressing the elbow on it, so the hands are free to ride your horse or bicycle. A hiss in the headphones is audible when the set ist in reception mode, there is no squelch provided to mute the receiver.
The receiver is a single conversion circuit, the R.F. signal from the antenna has to pass one R.F. amplifier stage (1T4) and is mixed with the signal of the crystal oscillator (1R5); the intermediate frequency of 455 kHz is amplified in two stages (1T4, 1T4); after demodulation and the audio frequency preamp (1S5) and final amplifier (3S4) it is fed to the headphones. The set has no squelch function, so an annoying hiss is present all the time, when the set is switched on.
In transmitting mode, the audio signal coming from the microphone has to pass a three stage amplifier (1T4 / V5) used for transmitting only; 1S5 and 3S4 / V6/V7 used in receive and transmit mode), mixed with the oscillator signal (1R5) and is amplified in the R.F. final tube (3S4) to reach an output power of 0,2 Watts.
The heaters of the valves V5, V8 and V9 are active only when the transmit switch is pressed, this arrangement does save battery power but you have to wait 2 seconds before you start talking after you press the transmit switch.
V1 (1T4, RF amplifier); V2 (1R5, oscillator, mixer); V3 (1T4, 1. IF amplifier); V4 (1T4, 2. IF amplifier); V5 (1T4, microphone amplifier); V6 (1S5, AF amplifier); V7 (3S4, AF final amplifier (REC) or modulator (TX)) and V8 (1R5, oscillator); V9 (3S4, RF output stage).
The patrol radio set Ap3053 or RTS has been developed by Telefunken Zürich as a successor to the FOX entwickelt, by making use of a „Sprechkanaleinschubs“ (operation channel unit) with a receiver and transmitter crystal and antenna and receiver circuit coil, changing the frequency while on a mission was possible. In contrast to this, with the „Foxli“ (BC-611), the chassis of the set had to be taken out and after frequency change, the set had to be realigned. In addition, the SE-103 provided hand free push-to-talk operation with an external PTT switch.
In the years 1951/53, a total of 1210 sets for a price of 1'500.- Fr. each had been acquired.
The SE-103 was used by the light infantry, the cavalry and the bicycle troops, for all of them, is was necessary to operate the receive - transmit switch while riding (the horse or the bike).
In the batallions of the light troops, each company used a different frequency channel unit to prevent co channel interference. In the spares compartment, another frequency channel unit was stored with the same frequency for the whole batallion in case of the need to communicate with other units of the same batallion.