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SE-125

Kleinfunkgerät SE-125; developed and produced by Autophon AG, Solothurn.

In 1969, a new „Walkie Talkie“ has been introduced as standard handheld personal radio in the Swiss Army: the SE-125 developed by Autophon AG, Solothurn.
The solid state set exists in six variants: they all have three channels 6, 7, 8 in common, the channels 1 - 5 operate on different frequencies according to the set variant; they can be recognized by the color of the typeplate.

The SE-125 has been replaced by the SE-135, it has still been used by Swiss Civil Protection after 2000.

Technical Data

SE-125

Power Supply

  • Accumulator / Batteries: Battery 7,5 V (alternatively, a NiCd Accumulator 6 V or a battery adaptor filled with UM-3 batteries can be used)

Usually, the SE-125 is powered by a special cylindrical 7,5V battery, as an alternative special 6V NiCd accumulators could be used - the batteries are inserted in a compartment covered by a lid at the bottom face of the set.

Dimensions

  • 287 x 142 x 57 mm, 2.4 kg

Accessories

  • standard antenna is a rod antenna of 1,2 m plugged in to the antenna connector on the top face of the set.
  • as an alternative, the long distance antenna „Fernantenne FA-125“ or „Grabenantenne“ GA-125 (trench antenna) can be used.

SE-125 Mikrotel

  • as a standard, the „Monophon“, a combinated microphone / speaker mounted on the top face of the set is used, there is also a Lärmgarnitur LG-125 throat microphone and headphones and a Mikrotelephon MT-125 (like a telephone handset) available.
  • only for training purposes, there was an external speakter to be used with the SE-125.

Variants

The different variants of the SE-125 which come with different frequency coverage can be distinguished by their channel numbers and the colour of the typeplate. The channels 6, 7 and 8 are common channels, on which SE-125 sets from different variants or colours can communicate.

Colour code Channels Common
grün12345678
weiss1112131415678
gelb2122232425678
blau3132333435678
rot4142434445678
schwarz5152535455678

Operation

The set has a typical rounded metal case, the combined microphone / speaker (the so-called „monophone“) is mounted in an inclined position at the front of the top face of the set, at the rear the push-to-talk button and the few other controls in between.

The dimensions of the SE-125 are 287 x 142 x 57 mm, it's weight with the battery 2,4 kg; it can be carried with a canves strap and has a flexible (often bended) wire antenna screwed plugged in the socket on the top face of the set.

SE-125 At the front and of the top face of the SE-125, You find the „monophone“, it's a combination of a mikrophone and a small speaker and looks like the microphone part of an old fashioned telephone handset. Just behind it, there is the three position power switch: = stands for „Off“, big dot stands for „On“, small dot stands for „On with squelch activated“. The BNC antenna socket is located next to it. The rotary control is the channel selector, channels 6, 7 and 8 eight are the common channels found on all SE-125 variants, the frequencies of channels x1 - x5 are different according to the colour of the type plate - on these channels, only the SE-125 with the same colour type plate can communicate.
At the rear end, You find the push-to-talk button and underneath the connector for an external handset (called „microtel“) or a headset / throat microphone combination to be used in noisy surroundings.

A simple antenna that is made of a kind of stiff wire can be connected to the BNC antenna socket, it's top part can be pulled out to give a total length of 1,2 m. After some time of use, these antennas have been bent many times and do not look like new anymore. The same antenna can be connected via a coaxial antenna cable, this arrangement is called „Grabenantenne“ (trench antenna), there has also been an external „Fernantenne“ (long distance antenna).

The SE-125 is extremely easy to operate: insert the battery and mount the antenna, select the desired channel, main switch to „big dot“, You should hear a noise. After having made contact with the second set, switch to „little dot“, the squelch should be active and should be opened, when the other station is on the air.

The „Antenna lamp“ is a very useful accessory to control the function of the set: it is screwed instad of the antenna on the antenna socket - the lamp should be lit when You press the „Transmit“ button; if it goes out after a few seconds, the batteries are exhausted.

The SE-125 is a short distance personal transceiver, under standard conditions, it's operation range is 3 - 5 km, from an optimum hilltop location, You can reach longer distances, as the VHF signal travels in the distance of sight. As I remember, there have been moments when we used the cellular phone to communicate when our SE-125 transceiver's range was too short - the so called SE-079 (SE stands for „transmitter - receiver“ and 079 is the prefix of the Swiss nationwide mobile telephone network…).

It is illegal to operate your SE-125, as it's operation frequencies are just below the FM broadcast band, but it's a nice set to have in the collection.

Technical principle

In reception mode, the SE-125 acts as a double conversion set: in a first step, the signal from the antenna ist converted to an IF of 10,7 MHz. This is mixed with an oscillator signal of 10,245 MHz, so in the second mixer stage, the second IF of 455 kHz is generated. The frequency modulated signal is demodulated in the discriminator stage, in in the intervalls without communication, the receiver module is muted in operation switch position „Squelch On“.

Semiconductors

The SE-125 is a solid state set.

Development

In the early sixties, Autophon had developed a compact VHF transceiver which was widely used in public services communications and by swiss railways. It turned out to be so successful, so that Autophon got an order to develop a compact squad radio. After the development phase 1960/5, a total of 28'200 sets have been acquired for the army and 9410 sets for Swiss Civil protection in the years 1967/76.

Field Use

SE-125 The SE-125 is intended for short range communications, depending on the topography, the typical operation distance is around 3 - 5 km, from hilltops, the range is double or three times as much.

In the seventies until 2002, so for over thirty years, the SE-125 was the most commonly used wireless set in the Swiss Army and it was used in virtually every company and squad. The SE-125 was used for squad exercises, for guard patrols and shootings exercise guard. It was the only military radio that was used not only by signalmen, but also by untrained soldiers. Caporals (sergeants) and officers got a quick instruction without technical beackground, how to communicate with the set.

The major drawbacks was the demand for special 7,5 Volt batteries (which had the tendency to be exhausted when really needed), the short transmission range and the fact that the frequency modulated speech signals werde not encrypted or scrambled.

So all message content hat to be „blurred“, it was not allowed to communicate even over short distances with open speech messages. So codelists had to be used, which coded station names and sender / receiver (like „Alfa“, „Beta“, „Capo“, „Luna“), and even the contents in a way like „Capo from Luna, please respond…“ „Luna from Capo, understood, please respond“ „Capo from Luna, meeting hour delta at point ypsilon, then move together with Falco to point zeta, respond“ „Capo from Luna, understood, correct, end“.

Technical Documents

Additional Information

en/se-125.txt · Zuletzt geändert: 2018/12/25 17:12 von 127.0.0.1