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FuG-8
4m police radio with optional encryption - under construction

FuG-8 was an analogue two-way mobile radio set for the 4 metre radio band, with optional voice encryption, developed and manufactured in the late 1970s by AEG Telefunken in Ulm (Germany) for police and other government services in Germany and the Netherlands. The radio uses FM/PM modulation and is suitable for simplex, half-duplex (repeater) and full-duplex operation [1].
 
The image on the right shows a typical FuG-8b as it was supplied to the Dutch police. The radio consists of two parts: the actual radio set which has a standard size, and a remote control unit (RCU) that is somewhat smaller, so that it can be fitted in the space of a standard civil car radio.

The RCU can be fitted directly to the body of the radio, as shown in the pictures, or detached by means of a multi-cable. It has a built-in speaker, hidden behind the logo at the left, and a socket for connection of a microphone or handset. The channel is set by means of small push-buttons.
  
Telefunken FuG-8b

The FuG-8 does not have standard provisions for voice encryption but in practice, they were commonly equipped with an external voice security unit, such as the BBC Cryptophon 1100 or the BBC Vericrypt. In the Netherlands, the FuG-8 was modified in such a way that the external voice encryption unit could be enabled/disabled with the second tone call button (Ruf II) at the front.

The FuG-8 was used by the police, fire brigrade, paramedic services and even the German Army. The designator FuG was assigned by the German Government to any radio that was built to their specifications, regardless the manufacturer. The AEG Telefunken FuG-8 was introduced around 1978, alongside FuG-8 designs from other manufacturers, like Bosch and Teletron. The radio was in use for nearly two decades, and in some places even well into the 2000s, after which they were replaced by digital alternatives like TETRA (in the Netherlands known as the C-2000 network).
 
Telefunken GuG-8b Telefunken GuG-8b Telefunken FuG-8b Microphone socket Rear panel Front Front panel detail Selectors for channel and mode of operation

 
Controls
The diagram below shows the front panel of the remote control unit (RCU) of the Telefunken FuG-8. The RCU is somewhat smaller than the body of the radio. This was done to allow the RCU to be fitted (in detached configuration) in the dashboard of a car in the space that was normally reserved for the car radio. It also allows a protective rubber brace or bumper to be fitted.


The front panel is pretty straightforward. The unit is turned ON and OFF with the red switch at the bottom. Audio volume can be adjusted in 5 levels with the rotary switch at the center. Above the volume knob are three indicator lights: a green one that lights when when transmitting, a red one that is lit when a call is being received, and a yellow one 1 to indicate that the unit is switched on.

The the right of the indicator lights is the switch for opening the squelch (German: Rauschsperre). To the left of the volume knob are two push-buttons (I and II) for transmitting a tone call (Ruf). The upper one transmits a 1750 Hz tone, whilst the lower one 2 transmits a 2135 Hz tone.

At the right are the CHANNEL, MODE and BAND selectors, which are normally protected by a transparent door (missing here). The three leftmost digits show the currently selected channel number. Depending on the variant, the first digit may be disabled. In the example it is fixed at '8'. The rightmost two selectors are for selecting the MODE and the BAND, as follows:
 
  • W
    Simplex (German: Wechselsprechen)
  • G
    Half-duplex, repeater operation (German: Gegensprechen)

  • U
    Lower band (German: Unterband)
  • O
    Upper band (German: Oberband)
  1. In the Dutch variant, this indicator showed that the external crypto unit was enabled.
  2. In the Dutch variant, this button is used to turn voice encryption ON or OFF.

Front Front panel detail Selectors for channel and mode of operation Microphone socket Microphone socket Lid-release push-button RCU detached Connector between RCU and radio body

 
Versions
Standard version
The standard version of the FuG-8 allowed the use of several hundred channels, with a spacing of 20 kHz. The exact number of channels depended on the selected band (upper or lower band) and the model variant, which was often customer-specific [A]:
 
FuG-8a/8b
  • Lower band
    Channel 400 - 510 (74.125 - 77.475 MHz)
  • Upper band
    Channel 400 - 509 (84.015 - 87.255 MHz)
  • Channels
    221 channels (lower band: 111, upper band: 110)
  • Spacing
    20 kHz
  • Shift
    9.8 MHz (mode G)
  • Output
    10W, 3W
FuG-8a-1/8b-1
  • Lower band
    Channel 347 - 510 (75.275 - 77.475 MHz)
  • Upper band
    Channel 347 - 509 (85.075 - 87.255 MHz)
  • Channels
    306 channels (lower band: 143, upper band: 163)
  • Blocked
    Channels 376 - 396 (in lower band)
  • Spacing
    20 kHz
  • Shift
    9.8 MHz (mode G)
  • Output
    10W, 3W
Bundeswehr version   FuG-8b/25
A special variant of the FuG-8 was made for the German Army (Bundeswehr). It had a different channel spacing (25 kHz instead of 20 kHz) and only the channels 100 to 199 were used. This means that the first digit of the frequency selector was fixed at '1'.
 
  • Lower band
    Channel 100 - 199 (72.750 - 77.475 MHz)
  • Upper band
    Channel 100 - 199 (75.225 - 85.025 MHz)
  • Channels
    100
  • Spacing
    20 kHz
  • Shift
    9.8 MHz (mode G)
  • Output
    10W, 3W
Dutch version
The FuG-8 radio shown here was used by the Dutch Police force from 1980 onwards, and was modified for this purpose by the Dutch Radar Laboratory (NRP) in Noordwijk (Netherlands) [A], in order to meet the specification of the Dutch Police Signals Corps. The following was modified:
 
  • Different frequency range (channels 800-899)
  • Different channel spacing (12.5 kHz instead of 20 kHz)
  • Different Duplex-shift (8.4 MHz instead of 9.8 MHz)
  • Control of optional crypto equipment (via Ruf II button)
  • Output power adjustable to below 1W
The modifications involved some serious changed to the radio's circuits. The first digit of the channel selector is no longer used and is externally fixed at '8'. In order to meet the frequency schedule of the Dutch Police and the required channel spacing of 12.5 kHz, several internal dividers were changed, along with four christals; two in the transmitter and two in the receiver.

To allow the addition of an internal or external voice encryption unit, the 2135 Hz tone call button (Ruf II) was replaced by an on/off switch that is wired to two free lines 1 of the 36-way D-type connector between the RCU and the radio body. The new switch also controls the yellow indicator light at the front panel so that it is ON when crypto is enabled (was on/off indicator).
 
This resulted in a radio with the following specifications:
 
  • Lower band
    Channel 804 - 886 (77.675 - 78.700 MHz)
  • Upper band
    Channel 804 - 886 (86.075 - 87.100 MHz)
  • Channels
    77
  • Blocked
    Channels 800-803, 805-809 and 887-899
  • Spacing
    12.5 kHz
  • Shift
    8.4 MHz (mode G)
  1. The Ruf II switch (crypto on/off) delivers an isolated contact on pins 12 and 27 of the 37-way connector between the RCU and the radio body.

Encryption
In order to provide some level of confidentiality, a speech security was often added externally. In most cases this was limited to a time domain voice scrambler, such as the BBC Vericrypt 1100, as its signal had to stay within the bandwidth of the existing voice channel.

The image on the right shows a typical Vericrypt 1100 unit as it was used by the German and Dutch police. An external loader or fill unit was used to enter the cryptographic keys.

 More about the BBC Vericrypt 1100
  
Vericript 1100 with key loader connected

 
Interior
The main radio body is housed in a green painted die-cast aluminium enclosure that is accessible from both sides, via a large lid that is held in place by four large bolts in the corners. After removing the large bolts, the top and bottom lids can be removed and the interior is exposed.
 
The interior consists of a top and a bottom section, that are separated by a metal frame that is part of the die-cast enclosure. The various modules from which the service-friendly radio is built, are mounted to both sides of the frame.

The image on the right shows the bottom side of the interior, as seen from the front. At the left are the transmitter's PLL and driver stages. At the right are the receiver's PLL and the antenna switcher. The empty space towards the rear was reserved for expansions like a full duplex filter or an (unknown) internal voice encryption unit.
  
Interior - bottom view

The remote control unit (RCU) holds the speaker and is connected to the main radio body via a 37-way D-type connector that carries all power, control and audio signals. The RCU also holds a common socket for connection of a microphone or handset, with a NATO 7-pin U-77 plug.
 
Interior - top view Interior - bottom view Top view Bottom view RCU interior RCU interior Channel selectors Speaker

 

 
Competition
In order to guarantee a fair competition, the German Government used to write out a tender for an FuG designated radio, in which they specified the exact features and in some cases even the layout of the front panel. In practice, the orders were often divided over the various suppliers. Similar (but not identical) FuG-8 radios were developed and built by the following manufacturers:
 
  • Telefunken
    Telecar 100
  • Bosch
    KF-802 1
  • Teletron
    FuG-8 1
  • Pfitzner
    FuG-8 1
  • Ascom
    FuG-8 1
  • SEL
    FuG-8
  • Storno
    FuG-8
  1. Note that the products from Bosch, Ascom, Teletron and Pfitzner came from the same factory.

Connections
Handset
At the left side of the control unit is a 7-pin U-79U socket, that accepts a standard NATO 7-pin U-77 plug with the following pinout:
 
  1. n.c.
  2. PTT
  3. PTT
  4. Speaker
  5. Speaker
  6. Microphone
  7. Microphone
  
Rear connector
  1. +12.6V
  2. +12.6V
  3. +12.6V
  4. n.c.
  5. 0V (battery ground)
  6. 0V (battery ground)
  7. 0V (battery ground)
  8. Ruf 1 (1750 Hz)
  9. Wandler - Ein
  10. Wandler - Ein
  11. NFL
  12. Ground
  13. NFLR

  14. Ein
  15. Ruf 2 (2135 Hz)
  16. NF- Ein
  17. n.c.
  18. A: Empfangsanzeige RSP
  19. B: +11.6V (UST)
  20. C: PTT
  21. D: Speaker (ground)
  22. E: Speaker (signal)
  23. F: Microphone (ground)
  24. H: Microphone (signal)
  25. J: Ground
  
Documentation
  1. FuG-8a/8b und FuG-8a-1/8b-1 leaflet
    1-7285/5 (German). Date unknown. 1

  2. FuG-8 instruction card (German)
    AEG Telefunken. N 13/V 3888 - 2303 Str (Mo).

  3. Beschrijving Modificatie AEG-Telefunken FuG-8 Mobilofoon
    CM302613. 28 November 1980. Description of modifications (Dutch).
     Uncensored version

  1. Document kindly supplied by Klaus Paffenholz [1].

References
  1. Klaus Paffenholz, Verschlüsselte Sprach-/Datenübertragung
    Website: Geschichliche Entwicklung des BOS-Funks (German).
    Retrieved April 2017.

  2. Klaus Paffenholz, Telefunken FuG 8a/8b/8b-1
    Website: Geschichliche Entwicklung des BOS-Funks (German).
    Retrieved April 2017.

  3. Oppermann Telekom, Vielkanal Sprechfunkgerät FuG 8a/8b
    Retrieved April 2017.

Further information

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Crypto Museum. Created: Friday 07 April 2017. Last changed: Saturday, 08 April 2017 - 11:37 CET.
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