Trunked Radio Station SE-225
Arbeitsgemeinschaft ABZ / Autophon - Brown Boveri - Zellweger

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Swiss Army Communication Sets
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Army Transceivers
Transceivers SE-1xx
Transceivers SE-2xx
Transceivers SE-3xx
Transceivers SE-4xx
SE-200 / LUX
SE-201 / REX
SE-202 / SEF
SE-210 / TL
SE-211 / TLA
SE-212 / TL BBC
SE-213 / TLD
SE-214 / TS 25
SE-215 / TS 40
SE-216 / SM
SE-217 / KL Tfk
SE-218 / KL 43
varia / copyright
about / contact

überarbeitet am 10.1.2013

For a project to replace the very commonly used Swiss Army wireless stations SE-206/9 and the vehicle stations SE-407/11, a call for projects was made in the sixties. United as a consortium, the three major Swiss manufacturers Autophon - Brown Boveri and Zellweger started the devlopment of a new station in 1966. As the requirements made by the Signal's Command in Bern were very high, the whole project got to a stop and had to be relaunched in 1972, only after several years, the first sets reached the prototype stage.
In the meantime, the Swiss Army had purchased the American M113 armoured personnal carrier which came already equipped with the American VHF radio VRC-12. These frequency modulated radios turned out to be very useful, they were tuneable within the complete military VHF frequency band in 50 kHz channels without the use of any crystals - but there was no speech scrambling, so codelists had to be used to scramble the content of voice messages.
For the infantry and the mechanized troops, large numbers of VRC-12 (SE-412) VHF radios and of the matching manpack VHF radio PRC-77 (SE-227) have been acquired, these made the backbone of tactical military communications in the Swiss Army until the end of the 20th century.
So only the Air Force / Anti Aircraft Troops had the pantience to wait for the new SE-225 from Swiss production: the development of this had taken years until 1986 and it was introduced with the troops in 1992/94. But what they finally got was a trunked VHF radio system with integrated voice scrambling.


Trunked radio, adaptive automatic frequency selection
30 - 86,975 MHz (4 x 19 frequency trunks)

FM (F3)

pout 2 (un to nominal 4) Watts

Sensitivity: < 0,4 uV


Trunked VHF radio with adaptive frequency selection, a free frequency is selected from a bunch of available frequencies automatically,
automatic selective call;
automatic internal voice scrambling
powered from NiCd accumulator (AKF-225) or Li battery (BAF-225), from vehicle accumulator 12/24 V (Einbauausrüstung EA-225), power buffer unit PE-225 to run the set from accumulators during a mains breakdown; mains power supply NG-225;
Antenna MA-225 for portable use, vehicle antenna FZA-225 or long distance aerial FA-225.

The SE-225 is a trunked VHF radio system with frequency modulation which is intended to be used as manpack radio, on vehicles or in fixed buildings or shelters.
A suitable unused frequency is selected automatically from the 30 - 87 MHz frequency range every time, the push-to-talk button is depressed, when it's released, the channel will be free for other communication and the next time, the PTT button is depressed, a new free frequency will be selected.

The VHf radio operates in the 30 - 87 MHz range, 76 (19 x 4) channel bundles with a bandwidth of 3 MHz kan be used, each with 30 channels with 100 kHz channel spacing. Using the selective call capability, 1 up to 9 members of a network can be called selectively.

SE-225 Prot. Front
The front panel is structured very straightforward: At the left, you find the connectors for the rod antenna and a 50 Ohms antenna jack, at the right the frequency selector, the operation switch, the volume control and at the right the connectors for the "microtel" (combined military handset) / BG-225 (control unit) and the remote control unit FBG-225.
The modes switch has the following settings: FF (fixed frequency operation, to be used for communications with older equipment like SE-125, SE-227 or SE-412), AUS (stands for OFF), wireless operation with call buzzer on/off, radio silence and relay operation (RE); the switch has to be pulled out slightly to active the first and the last positions.
If you turn the volume switch to the left, the frequency bundle windows will be illuminated and a self-test will be done, if turned to the right, volume can be set in four positions.

A control unit, the Bediengerät BG-225, is an important part of the system: it's a telephone like handset with an integrated numbered keybord which is used to control and to program the radio and to enter the key used for voice scrambling. The important keys are the "Talk" key to start a transmission which acts as PTT (push to talk key), the key "F" (FREE) which will and a transmission, the key with the key symbol to enter the transmission key for scrambling/unscrambling and the key with the triangle, which indicates unscrambled / unsecure operation.
The first four windows will show the channel bundle and the frequency when in fixed frequency mode. The complete frequency range of the SE-225 is divided in 19 channel bundles with a frequency range of 3 MHz each. The lowest frequency is calculated 27 + X * 3 MHz, so channel bundle 9 starts at 54 MHz.
The next place in the frequency desgination indicated the channel bundle A to D, (A stands for frequencies ending on 000 MHz, B for frequencies ending on x25 MHz, C for frequencies ending on x50 MHz, D for frequencies ending on x75 MHz.
The following two digits between 00 to 29 indicate the 100 kHz segment within the corresponding 3 MHz range, so for e.g. a frequency of 56,425 MHz you have to set the channel selector to 9 (range starting with 54 MHz), B 24.
One channel bundle is allocated to every network, it consits of a bundle number from 1 - 19 and the bungle group letter A - D.
For selective call functions, every set carries an adress number, under which this individual set can be reached. This address number consists of two digits for a group number (01 - 99) and the last digit als single user number (1-9). On each SE-225 trasceiver, three adress numbers can be programmed, so every set can take part of three different networks. To make a selective call to another station, you have to type in the group number (01-99) and the user number (1-9), sometimes you have to add other criteria (broadcast "to all", "relay service", and so on. Up to ten adress numbers can be stored in the control unit / handset of each SE-225 radio.

The Se-225 has an internal voice scrambling function. The key consists of 12 digits, four of them are already stored in the set and the other 8 digits have to be keyed in using the control unit. The key saved on memory channel one is the main key in use, when no other key has been entered.

In the "manpack" variant, the transceiver is mounted on a carrying rack TR-225 together with a lithium battery or an accumulator. With the batteries, the complete set has a weight of 13,0 kg.

As said before, the set can be powered from a lithium battery in the battery compartment BAF-225 or a NiCad-accumulator in the accumulator compartment AKF-225, as an alternative, the set can be run from a 12 or 24 Volts vehicle battery of for fixed use from a NG-225 mains power supply.

The SE-225 can use different antennas: the 1,6 m rod antenna MA-225 for use as manpack, a 1,9 m vehicle antenna FZA-225, or the long distance antenna FA-225, mounted on a eight segment glass fibre mast with a height of 10,8 m.

A high power RF amp LV-225 will increase the set's output, it can be regulated from 400 uW / 0,4 W / 4 W and 40 Watts.
Se-225 complett

A remote control unit (Fernbetriebsausrüstung FBA-225) gives the opportunity to control the SE-225 radio over field telephone lines over 3 km, there is a provision for a service telephone communication from the remote to the transmitter location. A RS232 interface allows data transfer of up to 1200 Baud.

There were prototypes of an on-board intercom BVA-225, with an onboard switchboard BZ-225, junction boxes and a noise garnish LG-225, but all of this equipment has not been introduced with the troops as the mechanized troops had already introduced the SE-412 / VRC-12 radio and there was no need for on onboard-use with the Air Force troops.

The equipment shown makes part of a Swiss private collection

further informations:
d: Reglement: VHF - Funkstation SE-225 Benützerhandbuch (prov.)
d: Reglement 56.514 d/f Funksystem SE-225

d: SE-225 at www.hamfu.ch of the IgUem

© 10.1.2013 Martin Bösch