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Two-way radio with optional encryption
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].
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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.
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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).
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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:
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W Simplex (German: Wechselsprechen) G Half-duplex, repeater operation (German: Gegensprechen)
U Lower band (German: Unterband) O Upper band (German: Oberband)
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In the Dutch variant, this indicator showed that the external crypto unit
was enabled.
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In the Dutch variant, this button is used to turn voice encryption
ON or OFF.
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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]:
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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
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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
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Bundeswehr version
FuG-8b/25
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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'.
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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
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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:
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- 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
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The modifications involved some serious changes 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).
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This resulted in a radio with the following specifications:
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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)
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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.
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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
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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.
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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.
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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.
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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:
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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
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Note that the products from Bosch, Ascom, Teletron and Pfitzner
came from the same factory.
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At the left side of the control unit is a
10-pin U79/U socket,
which accepts a U77/U cable part (plug). Below is the pinout
of the U79/U chassis part, when looking into the receptacle:
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n.c. unused PTT Push-to-Talk PTT Push-to-Talk SPK Speaker SPK Speaker MIC Microphone MIC Microphone GND Ground n.c. unused n.c. unused n.c. unused
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- +12.6V
- +12.6V
- +12.6V
- n.c.
- 0V (battery ground)
- 0V (battery ground)
- 0V (battery ground)
- Ruf 1 (1750 Hz)
- Wandler - Ein
- Wandler - Ein
- NFL
- Ground
- NFLR
- Ein
- Ruf 2 (2135 Hz)
- NF- Ein
- n.c.
- A: Empfangsanzeige RSP
- B: +11.6V (UST)
- C: PTT
- D: Speaker (ground)
- E: Speaker (signal)
- F: Microphone (ground)
- H: Microphone (signal)
- J: Ground
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Document kindly supplied by Klaus Paffenholz [1].
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© Crypto Museum. Created: Friday 07 April 2017. Last changed: Saturday, 11 May 2024 - 06:23 CET.
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