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Radio Crypto Key Gun →
Military HF radio station
- this page is a stub
CHX-200 was a high-end military HF radio station,
developed in the late 1970s
by Siemens AG
in München (Germany) and several other parties,
for use by the German Army, the Bundeswehr. The system went into
production around 1981 [2].
The system has a modular design and can be used
in many different configurations, making it suitable for
morse code (CW), voice (phone) and data.
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At the heart of the system is the CHX-200 RX/TX unit, which consists of
a receiver with a built-in exiter. By adding an external HF power amplifier (PA),
the station can be configured for short-range,
mid-range or long-range applications.
It could (optionally) be expanded with features to reduce the risk
of interception and location,
and to improve data integrety,
such as SITOR, ARQ, FEC, Frequency Hopping,
Burst Transmission
and Data Encryption. The image on the right shows a mobile setup
with a CHX-200 RX/TX (bottom left), a CHP-200 Processor (top left)
and a PA [1].
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Due to the highly modular design of the system, it was suitable for a
wide variety of military HF applications, including Reconaissance and Special Forces
— using the manpack configuration
— battalion level communication — using a mobile
setup — and full base station communication.
Within the Bundeswehr, the 400 Watt version of the CHX-200 was used
in fixed C2 2 bunkers, as well as in mobile communications shelters —
commonly fitted on the back of a military truck —
with the CHO-902 magnetic loop antenna at the roof.
Apart from the Bundeswehr, the CHX-200 was used by the
German Meteorological Services, and by the armies of
other NATO countries.
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The CHX-200 is sometimes classed as an Emergency Communications set (ECCOM),
but this is not the full story. Whilst it was used as an ECCOM by the
German Government, it found a much wider application.
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C2 = Command and Control.
➤ Wikipedia
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During the Cold War,
the CHX-200 was also used for the
Secret Emergency Radio Network 1 of the West-German Government.
They were installed in secret underground bunkers — for the Chancellor
and the Prime Ministers of the 10 German Counties 2 — that had to
survive a possible war with the Warsaw Pact.
Each bunker had everything that was needed to survive a
nuclear war for several weeks, such as food, electricity generators, fresh-air
systems, fallout filters, etc.
Each nuclear bunker also had a fully equipped radio station, with a 1kW transmitter
and separate receivers — all connected to camouflaged antennas — using
Siemens T-1000 teleprinters
for the exchange of messages. The messages were encrypted with the
software-based CHP-200.
In addition, there were many trucks that could be used as a mobile
Command and Control (C2) centre, equipped with 100W or 400W CHX-200
configurations.
It is known that mobile tests were carried out in various countries
around the world, including in Indonesia and in Thailand [1].
After the fall of the
Iron Curtain
from 1989 onwards, the reunification of East and West Germany in 1990,
and the subsequent collapse of the
Soviet Union
in 1992, the Cold War
was over and the
secret emergency network was no longer needed. The nuclear bunkers and
the mobile stations were dismantled, and most of the high-end radio
equipment was scrapped.
Only a small number of Siemens CHX-200 radio stations are now
in the hands of collectors and radio amateurs.
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German: Notfunknetz der Bundesregierung und der Landesregierungen.
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German: Bundesländer.
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- CHX-202 · low power
This is the manpack version of the CHX-200, which consists of the CHX-200/RX/TX,
and the AM-921/GY 20W RF amplifier (the latter made by TELEMIT in München, Germany).
- CHX-210 · medium power
This is the CHX-200/RX/TX combined with the 100 Watt PA-100 Amplifier,
the ATU-100 automatic antenna tuner and a PS-100 mains power supply unit.
- CHX-240 · high power
In this setup, the CHX-200/RX/TX is combined with the 400 Watt PA-400 Amplifier
and a 400 Watt ATU-400 automatic antenna tuner — both made by
Rohde & Schwarz 1 —
and a PS-400 mains power supply unit.
- CHX-250 · very high power
This is the very high power version of the CHX-200, in which the exiter is
combined with the 1 kW fully transistorised PA-1000 power amplifier,
the CHP-200 processor (or the F1 Modem) and the PS-1000 mains power supply.
The PA-1000 was designed for use with wideband antennas, and did not have
an antenna tuner.
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The PA-400 Power Amplifier and the ATU-400 Antenna Tuner are the same
as the ones used with the Rohde & Schwarz XK-405/XK-245 radio station.
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This is the basic transceiver, which consists of a receiver and a built-in
exiter. It could be combined with a selection of Power Amplifiers (PAs).
Two versions of the CHX-200/RX/TX are known, with the later one having a
modernised circuit and SQUELCH.
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This is an HF modem that allows transmission and reception of digital
information in F1B mode (F1), with a speed of up to 200 baud,
using an FSK frequency shift of ±85Hz or ±425Hz. This modem is not used
when the CHP-200 Processor is part of the setup.
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This is a (digital) processor that replaces the CHX-200/F1 modem. It makes
the CHX-200 radio station suitable for a number of additional ECCM
features and communications protocols, such as SITOR, ARQ, FEC,
Frequency Hopping,
Burst Transmissions and
Crypto.
For some of the ECCM features, suitable cryptographic keys had to be
loaded into the CHP-200 by means of a Key Gun.
The CHP-200 was fully under software control, and it is known that
different versions of the software were available, to accomodate the
needs and requirements of the various customers.
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This is an integral part of the CHP-200 Processor, that controls its mode
of operation, checks the security features and raises an alarm if they are
not functioning properly. The CHO-200 can be detached from the CHP-200
and mounted in a convenient place.
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This was a magnetic loop antenna that was suitable for mobile applications.
As such, it could be mounted on the roof of a truck or a communications
shelter. The antenna came with the CHO-902 Antenna Control Unit.
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This is a 400W power amplifier that can be connected directly to the
exiter (CHX-200 RX/TX). It should always be used in combination with
the ATU-400 antenna tuner. Both the PA-400 and the ATU-400 were made
by Rohde & Schwarz,
and were taken from their XK-405/XK-245 radio station.
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This is a fully transistorized power amplifier, with an output power of
1 kW. It is indended for use in combination with wideband antennas, and
does not have or need an antenna tuner. The PA-1000 consists of four
individual 50V wideband amplifiers, each of which is built around four
MRF-150 transistors — two in parallel in a push-pull configuration —
delivering approx. 300W per module. Each module has a MRF-148 in the
driver stage.
In the output of the PA-1000 are 7 low-pass filters, each of which can
be selected by means of PIN diodes.
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When using the CHX-200 in combination with the CHP-200 Processor,
it was possible to use data encryption
and frequency hopping
as two techniques to improve security, also known as
Electronic Counter Counter Measures (ECCM).
The Siemens Key Gun – shown in the image on the right – was used
to load the cryptographic KEYS into the
CHP-200. It was common practice to change the KEYS at least
every 24 hours.
➤ More information
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ARQ
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Automatic repeat request
Error-control method for data transmission that uses acknowledgements and timeouts
to achieve a reliable data transmission over an unreliable medium.
Also known as Automatic Repeat Query.
➤ Wikipedia
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ECCM
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Electronic Counter Counter Measures
Equipment used in secure communications (COMSEC) to protect against
counter measures, such as eavesdropping, interception, direction finding,
etc. Frequency Hopping (FH) is an example of ECCM.
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FEC
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Forward error correction
A technique for controlling (and correcting) errors in data transmission
over an unreliable or noisy medium, such as an HF radio channel.
➤ Wikipedia
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FH
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Frequency Hopping
Method for quicky changing the frequency (channel) during a transmission
in a seemingly random order. This is done as an electronic counter counter
measure (ECCM), to protect the conversation against eavesdropping and
interception by the enemy.
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Frequency 1.5 — 29.999 MHz in 100 Hz steps Modulation A1, A3H, A3J (LSB/USB), DATA
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High power 400W +1/-2dB 1 Low power 70W +1/-2dB 1 With load > 100W, < 500W (s=2)
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Continuous in A1 and F1, Peak power in A3J, A3H and DATA.
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Document kindly supplied by [1].
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Note that the information on this web page contains many factual errors.
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© Crypto Museum. Created: Thursday 28 December 2017. Last changed: Sunday, 11 February 2018 - 21:30 CET.
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![CHX-200 RX/TX (bottom left), CHP-200 Processor (top left) and Power Amplifier. Photograph kindly supplied by Jim Meyer [1].](img/chx200_chp200.jpg)
![Complete mobile CHX-200 setup. Photograph kindly supplied by Jim Meyer [1]](img/chx200_chp200_thumb.jpg "image # chx200_chp200.jpg")
![CHX-200 manpack setup. Photograph kindly supplied by Jim Meyer [1]](img/chx200_manpack_thumb.jpg "image # chx200_manpack.jpg"){kind=small}
![Setup with CHO-902 magnetic loop antenna and antenna control unit. Photograph kindly supplied by Jim Meyer [1]](img/cho902_thumb.jpg "image # cho902_large.jpg")
![CHX-200 with DSP modem. Photograph kindly supplied by Jim Meyer [1]](img/chx200_dsp_thumb.jpg "image # chx200_dsp_large.jpg")
![CHX-200/F1 modem. Photograph kindly supplied by Jim Meyer [1]](img/chx200f1_thumb.jpg "image # chx200f1_large.jpg")
![CHO-200 controller. Photograph kindly supplied by Jim Meyer [1]](img/cho200_front_thumb.jpg "image # cho200_front.jpg")
![CHO-200 controller (connections). Photograph kindly supplied by Jim Meyer [1]](img/cho200_conn_thumb.jpg "image # cho200_conn.jpg")
![CHX-200 RX/TX with CHP-200 Processor. Photograph kindly supplied by Jim Meyer [1]](img/RXTX_CHP_thumb.jpg "image # RXTX_CHP.jpg")
![CHX-200 manpack setup. Photograph kindly supplied by Jim Meyer [1]](img/chx200_manpack.jpg)
![Setup with CHO-902 magnetic loop antenna and antenna control unit. Photograph kindly supplied by Jim Meyer [1]](img/cho902_large.jpg)
![CHX-200 with DSP modem. Photograph kindly supplied by Jim Meyer [1]](img/chx200_dsp_large.jpg)
![CHX-200/F1 modem. Photograph kindly supplied by Jim Meyer [1]](img/chx200f1_large.jpg)
![CHO-200 controller. Photograph kindly supplied by Jim Meyer [1]](img/cho200_front.jpg)
![CHO-200 controller (connections). Photograph kindly supplied by Jim Meyer [1]](img/cho200_conn.jpg)
![CHX-200 RX/TX with CHP-200 Processor. Photograph kindly supplied by Jim Meyer [1]](img/RXTX_CHP.jpg)
