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Radio Intercept R&S Operation →
FSK Analyzer
GA-082 is an analyzer for
telegraphy signals (telex),
introduced in 1983 by Rohde & Schwarz in München (Germany).
This microprocessor-controlled device can be used to determine the data
rate (baud) as well as the data format of an intercepted
Frequency-shift Keying (FSK) radio signal,
but is also capable of decoding a range of formats and protocols,
such as ASCII,
Baudot,
ARQ-28 and SITOR.
The range of codes can be expanded with the optional
GA-082/B1 Extension Unit.
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In practice, most telegraphic communications via the HF and VHF radio bands
use some kind of frequency shift keying (FSK), such as F1B or F7B.
Although most radio networks use a standard method for this, such as CCITT,
specific methods were used for diplomatic and military networks.
In radio intercept
stations it is common practice to analyse such signals,
determine the exact data format and speed, and monitor any traffic that is
sent over the air. The R&S GA-082 allows fully automatic analysis of such
FSK radio telegraphy signals (RTTY) with unparalled accuracy.
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The GA-082 can be used for analysis of wireless (modulated) as well as
wired (unmodulated) traffic.
It was officially marketed as an accurate tool for repair
workshops, but in reality it was aimed at the intelligence community.
It can be used for automatic identification of a given
signal, by measuring equipment-specific deviations of all parameters of
the signal data. This technique is known as 'fingerprinting'. In combination
with Radio Direction Finding (RDF),
it can be used to recognise transmitters and detect and profile
entire radio networks.
If the format is known, the GA-082 can directly show the demodulated
text on its LED display or send it to a computer via its
V.24 (RS232) interface. Even when the text is encrypted,
it can be a useful tool for traffic analysis.
The device was initially developed by Dr. Schäfer, who worked at a
research institute close to the German Army (Bundeswehr).
He sold his development to Rohde & Schwarz (R&S) [1].
The GA-082 was released in 1983 and had a mid-life upgrade in 1992.
Main competitor in this era was Wavecom
with its W4010 and later the W4100 and W4100DSP, all of which were
stand-alone solutions.
Between 2000 and 2010 the GA-082 gradually became obsolete when new waveforms
came up and computers had become powerful enough to do the entire
analysis and decoding in software.
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The GA-082 is housed in a 19"-wide 2U-high rackmountable enclosure.
All controls, indicators and displays are at the
front panel, as shown
in the image below. At the bottom right is the mains power switch.
To its left is a keypad with 12 push-buttons, each of which has a
built-in indicator LED. To the left of the keypad are four (red)
display areas with five up/down buttons below them.
The display at the top left holds a LED-bar that shows the
part of the AF spectrum in which the received FSK-tones are active.
The rightmost part of this display holds a synchronisation indicator.
The display at the bottom left shows the session time, the frequency shift
(i.e. the difference between the two FSK-tones) and the measured
baud rate. The display at the top right is used for analysis of the
received bit pattern. The display at the bottom right shows the current
MODE plus additional information like the name and number of the
detected format, or the decoded text.
The diagram above shows the layout of the ANALYSIS display. At the far left
is the mode number (in this case: Mode 0). To its right is a 16-character
alphanumeric display. In Mode 0 and Mode 2, the first 8 characters show the
name of the detected/selected program. The last 4 characters show the program
number, optionally preceeded by a minus sign if the format is inverted.
In between the program name and number are 4 characters with additional
information (when applicable). In the example above, this section
shows the length of the stop bit [ms] of a BAUDOT signal.
In Mode 0
the format is selected automatically. In Mode 2 this is done
manually. In Mode 1, the display shows the decoded text,
if the format is recognised and a suitable decoder is present.
All connections are at the rear panel, as shown in the image above.
The receptacle for the mains power cord is at the top left. At the far
right are the interfaces for control and for output of the
intercepted data. Depending on the requirements, the IEC-625 bus
or the V.24 (RS232) port can be used. At the centre are
various connectors for input of the raw or demodulated signals from
a receiver.
A wide 37-pin socket is present for connection to an
expansion unit or cartridge, such as the GA-082/A1 (A1) or
GA-082/B1 (B1).
The connectors are explained in more detail below.
➤ Operating instructions
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The GA-082 was available in two versions:
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- 19" enclosure
This version is suitable for installation in a 19" standard rack.
It is the most popular version of the device and was intended for use in
fixed and mobile installations, such as monitoring and intercept stations.
The version featured here is of this type.
- Desktop enclosure
This is the same device, but in a regular blue R&S enclosure with an
adjustable carrying handle, suitable for desktop and mobile use. This enclosure
is shown at the front page of the 1983 brochure.
R&S calls it the bench version.
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The diagram below shows how the GA-082 was used in practice. In the simplest
configuration, only a receiver and the GA-082 are needed.
The AF or IF signal from the receiver is connected directly to the
AF/IF input of the GA-082, which shows the decoded text on its
display. If further processing and/or analysis is needed, the data can be
delivered to a computer via the V.24 or IEC ports.
To support non-standard communication protocols, the A1 expansion unit
can be added.
The diagram below shows how the GA-082 was used in a typical intercept or
monitoring station. As the FSK demodulator of the GA-082 is not the best
in its class, a high-end demodulator, such as the
Teletron TG-44E,
was often used to convert the FSK signal to a telex signal.
This signal was then applied to the
demodulated signal input or the
single-current input of the GA-082.
For decoding non-standard communication protocols — today known as waveforms —
the B1 expansion unit was connected to the GA-082.
Many of the additional programs installed in the B1,
were developed especially for the military and
intelligence community
and were classified as SECRET until at least 2005.
In all cases, the decoded output from the GA-082 could be delivered to an
external computer system for further processing, analysis, storage and
fingerprinting.
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There are 10 operating Modes, numbered 0-9. When the device is switched on,
it defaults to Mode 0, which is the auto-acquisition mode. In this mode,
it measures the baudrate, determines the F1/F2 FSK shift and tries to
recognise the code pattern. This is done by first testing it against the
(optionally installed) user programs, and then against the built-in
programs. Modes 0, 1 and 2 are for analysis of the transmission method.
Modes 3 to 9 offer various bit pattern displays.
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Transmission method analysis
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| Mode | Name | Description |
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| 0 | Search | Enable measurement and search for recognised transmission modes |
| 1 | Decoder | Scrolling display with decoded text.
Press PRINT to deliver text via the V.24 (RS232) port. |
| 2 | Manual | Push-button selection of analysis programs (formats) |
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Bit pattern display
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| 3 | Pattern | Scrolling display of bit pattern |
| 4 | Static | Stationary display of bit pattern. Can be shifted bit-by-bit with ↓↑. |
| 5 | Static (inv) | Inverted display of Mode 4 |
| 6 | Super | Superimposed display of 16 periods of the current bit stream of 8192 bits with a selectable period length of 2-255 bits and bit-by-bit shifting (as in mode 4). |
| 7 | Super (inv) | Inverted display of Mode 6. |
| 8 | Stored | Superimposed display of 16 periods of a stored bit stream of 8192 bits with a selectable period length of 2-255 bits and bit-by-bit shifting (as in mode 4). |
| 9 | Stored (inv) | Inverted display of Mode 8. |
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Development of the GA-082 started around 1980, at a time when the German
Bundeswehr 1 urgently needed equipment for analyzing alien teleprinter
signals from intercepted Short Wave (HF) radio traffic. Main developer was
Dr. Schäfer, who worked for a research insitute with close ties to the
Bundeswehr [1]. He established his own company and developed a prototype
that was well-received by the Bundeswehr.
However, the Bundeswehr was reluctant to rely on a one-man enterprise for large
scale production of the devices, so Schäfer started looking for a large
(inter)national company that would be interested in adding the device
to its product portfolio.
It turned out that Rohde & Schwarz (R&S) in München
was interested. Since R&S is a multinational company, it has marketing
and service divisions in major parts of the world.
Eventually Schäfer sold his entire development to R&S, which then
became responsible for adapting it for large scale production, but also for
marketing it, and for further development of additional applications.
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Development of the device — by now known as GA-082 — at R&S was started
in 1982 and took about one year. When it was released in 1983,
it supported only the most common non-secret communication formats
(protocols)
— R&S calls this code programs —
like Baudot and ASCII,
albeit in a rather limited implementation.
This version was freely available on the market.
For government customers, a special plug-in unit was available, that allowed
the addition of extra code programs and other exotic tools. In addition,
BAUDOT/ASCII support was improved.
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It is currently unknown how many units were made, but it is certain
that the primary customer — the Bundeswehr — ordered several hundreds
of them.
The GA-082 was also sold to The Netherlands, the UK and probably others,
but the quantities are unknown.
The variable part of the serial number is just 3 digits long,
and the numbers of the surviving devices are relatively low. 2
The device was received well and is often praised by its users for its
accuracy, especially after a warming-up period of 1 hour. However, the
fact that there was limited space for additional code programs, was seen
as a severe limitation. Users had to physically swap cartridges with
different code programs for which they had to access the rear of the device.
This would not have been a problem for a desktop user, but was a major
limitation for the radio monitoring services, where the devices were
generally built into 19" racks. Swapping the cartridges was cumbersome
at best.
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It prompted R&S to rethink the design and develop a solution. It was
decided to add an additional 19" 2U enclosure with space for 45
program cartridges. The new unit was named: B1 (in full GA082B1)
and its cartridges: B2 or GA082B2.
Development ran from 1988 to 1992. 3
It was installed above the GA-082 and uses a wide flat cable to
connect to the expansion bus — i.e. the socket that was previously used
for a single A1 program cartridge. In order to support the
use of multiple B2 program cartridges, the firmware of the device had
to be updated to version 3.0.
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This is also the main reason for the
fact that version 3.0 is incompatible with previous versions.
The B1 extension unit was used by monitoring and intelligence services
for intercepting and decoding alien signals in a wide variety of
formats, some of which are classified as SECRET.
For this reason, the B1 was listed in Germany as a classified
device until at least 2005. The enclosure of the B1 is made of
welded stainless steel and the hinged top lid is secured with
a strong cross lock. This was deemed necessary to prevent loss of
the highly secret cartridges. The B1 has space for 45 cartridges,
and the devices that were supplied to the
Bundeswehr were fully populated. 4
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From markings on some surviving
B2 program cartridges it is
known that the GA-082 was used by the Bundeswehr in former
Yugoslavia, as part of the Kosovo peacekeeping Force (KFOR) [6].
At its hight, KFOR troops consisted of 50,000 men and women from
39 different NATO and non-NATO nations, including 269 from Germany.
Within KFOR, the Electronic Warfare unit of the German Signals Corps
(FmKp EK) was responsible for monitoring and intercepting the signals
from the combatting parties. The work was carried out by the
Fm/EloAufklBrig 94 [7].
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Apart from the Bundeswehr, the GA-082 was also used by the
Bundesnachrichtendienst (BND)
— the German Federal Intelligence Service.
It is known that the device was also used in the UK, as
an unknown number of GA-082 units appeared on the British surplus
market in the mid-1990s. It was also used in The Netherlands, but
it is currently unclear by which service(s).
It is unknown how long the GA-082 was used, but it is likely that
they were gradually phased out from 2009/2010 onwards, as the first
devices started appearing on the German surplus market in 2011.
B1 units followed in 2013, but came in most cases without the
secret program cartridges.
It is clear that the device had largely become obsolete by 2010,
when new digital communication modes (waveforms) had entered the scene and
personal computers had become strong enough to do the entire
processing and analysis in software, for a fraction of the price.
It has the added advantage that new waveforms can easily be added
and distributed with a simple software upgrade.
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The German Armed Forces (Bundeswehr) consists of the Army (Heer), Air Force
(Luftwaffe), Navy (Marine), Joint Support Service, Joint Medical Service,
Cyber and Information Domain Service and a civil department [3].
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Most surviving devices seem to stem from Bundeswehr surplus (hence the
BUND label on the front panel), and since they were the first customer,
low serial numbers are to be expected.
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The GA-082/B1 was entered into the NSN database on 15 April 1988 [2].
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By default, the B1 was supplied with 45 empty B2 cartridges.
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Expansion unit A1
GA-082/A1
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For most users, the default 10 programs were not enough.
In such cases, additional (user) programs could be added as a
cartridge that was inserted into the expansion slot at the rear.
A cartridge contains two EPROMs (8KB in total).
An example of an external program cartridge is the USER10 package,
which provides 9 additional programs, such as
SITOR and SIFEC.
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Expansion unit B1
GA-082/B1
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In 1992, the B1 external expansion unit (GA-082/B1) was introduced.
It allows 45 additional program cartridges to be installed in a
single tamper-proof enclosure that is connected to the
DC-37 expansion connector at the rear.
The empty bay at the front is for stowing
additional (currently unused) program cartridges.
The case is made of welded stainless steel, with a lock at the front.
Each cartridge holds two EPROMs that can be selected via the
keypad of the GA-082.
Note that this expansion unit requires at least
version 3.0 of the firmware.
➤ Look inside the B1 unit
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The B1 expansion unit was originally supplied with a short round
cable for connection to the GA-082. The cable has DC37 male connectors
at either end, that mate with the female DC37 sockets
on the GA-082 and on the B1. It can be fitted either way around.
The designator of this cable is RuS 709.7627-W60.
In practice, this cable is likely to be missing from surplus GA-082 setups,
in which is it is advised to make a flatcable (see below).
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Alternative interconnection cable
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Some units have been found with a 30 cm long unshielded 40-wire ribbon
cable instead of the round one.
As the interconnection cable was missing from the devices in our collection,
the shielded ribbon cable shown in the image on the right was made at the
Crypto Museum lab.
A similar cable has also been found with some surplus GA-082 and B1 units,
so it seems likely that in practice a flatcable was used as a suitable
alternative to the original round cable.
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GA-082/B2 is a cartridge for additional user programs, that can be
installed into one of the 45 slots of the B1 expansion unit.
Each cartridge contains two 27C64 EPROMs or OTPs, of which
on the upper half is used.
The B2 cartridge is made of aluminium and measures 83 x 53 x 12 mm.
At one side is a 37-pin male DC37 connector that mates with the female
slots of the B1. The other side holds a label with model and serial
number, plus space for additional information.
➤ Look inside the B2 cartridge
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The B4 test cartridge is identical to an empty B2 cartridge. It is supplied
with two empty 27C64 EPROMs or OTP devices, of which only the upper
half is used. The only difference is the
name (B4) and the number (701.1059.02) printed on the label on top of
the cartridge.
The reason for having two identical products with two different numbers
is currently unknown, but it seems likely that it was done to identify
a program-under-development.
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USER10 program package
P1
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The USER13 program package is similar to USER10, but contains fewer
codes. The codes that have been dropped are replaced by the 12:2
protocol. The EPROMs are largely empty.
The package was supplied in two 2732 EPROMs, that
can be installed inside the GA-082 (in sockets D19 and D20),
or in an A1 cartridge that is plugged into the rear of the device.
Note that USER13 can only be used with version 2.x of the system firmware.
It does not run on 3.0 or later.
➤ Contents of USER13 cartridge
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USER30 program cartridges
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The GA-082 has a cross-type lock at the rear side, that can be used to
secure an A1 expansion module that is fitted to the DC37 connector.
A similar lock is present at the front side of the B1 expansion unit.
It locks the hinged top lid that gives access to the installed
B2 cartridges. If this key is missing, it will be hard to access the
interior of the unit, as it is housed in a heavy welded stainless steel
enclosure.
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The GA-082 was supplied with operating instructions and a full technical
description with circuit diagrams. This can be useful when reparing or
restoring the device.
Note that both the manual and the circuit diagram contain several mistakes
that are not always trivial. Check out our restoration notes.
➤ Download the handbook
➤ Other documentation
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The GA-082 can natively decode some well-known data formats,
that are handled by a set of built-in programs.
Confusingly, data formats are also known as modes (not to be
confused with operating modes).
The number of programs can be expanded by adding USER-packages in the
form of an EPROM-set (internal) or a plug-in cartridge (external).
There are four program types:
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- Programs for code analysis (used in Mode 0 and Mode 2)
- Programs for decoding and displaying text (used in Mode 1)
- Programs for processing bitstreams
- Additional functions and special features (directly executed)
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Each USER package may contain any combination of the above program
types. A USER package also determines the order in which the
internal and external programs are used to test an alien signal.
Only one USER package can be installed, and some packages
are restricted to a specific version of the system firmware.
From version 3.0 onwards, the number of additional programs was
greatly extended by adding the external B1 expansion unit.
When applicable, the program number is shown in Mode 2 as Nnn,
in which nn is the program number, e.g.
' N07 ' for
Baudot.
Below is a list of all programs that are currently known.
A detailed description of each program can be found here,
or by clicking the relevant line in the table below.
The tick boxes at the right show what functionality is provided
by the program. The ticks have the following meaning:
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| Analyser | This program does a measurement or checks for a particular condition. |
| Decoder | This program can decode the signal and produces the decoded text on the ANALYSIS display. |
| Function | This program provides a function, which does not necessarily produce any output on the display. It can be activated from the keypad by pressing SELECT followed by two digits. E.g. SELECT-88. Functions are executed immediately. |
| Bitstream | This program does not analyse the input signal, but allows decoding when selected manually. Research into this program type is still ongoing. |
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| Analysis
| Decode
| Function
| Bitstream
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N00
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STOP-MOD
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Permanent start or stop polarity (90% '1' or '0')
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✔
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N01
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IDLE 1.1
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Idle signal, 1 mark and 1 space sent alternately
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✔
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N02
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IDLE 1.6
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Idle signal, 1 mark and 6 spaces sent alternately
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✔
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| N03 | - | Unused | |
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N04
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IDLE 14
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Idle signal with repeating arbitrary pattern of 14 bits
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✔
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N05
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IDLE 28
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Idle signal with repeating arbitrary pattern of 28 bits
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✔
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N06
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IDLE 56
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Idle signal with repeating arbitrary pattern of 56 bits
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✔
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N07
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BAUDOT
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ITA-2, Async. 7.5 bits (1 start, 5 data, 1.5 stop)
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✔
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✔
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N08
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ARQ-28
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ITA-3, Sync. 7 bits (3 mark, 4 space, 4th char inv)
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✔
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✔
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N09
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ARQ-56
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Same as N08, but every 8th character inverted
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✔
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✔
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N10
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ASY-ASCI
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ITA-5, async 10-bit ASCII (8E1, 8O1)
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✔
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✔
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N78
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PERIOD
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Check for repeating patterns of 2-64 bits
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✔
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N79
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M/S L...
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Code statistics MARK/SPACE ratio etc.
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✔
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Xn
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Extra functions X0-X9
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✔
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➤ Codes 11-77 and 80-99 reserved for user programs (see below)
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| Analysis
| Decode
| Function
| Bitstream
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N00
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STOP-MOD
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Permanent start or stop polarity (90% '1' or '0')
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✔
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N01
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IDLE 1.1
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Idle signal, 1 mark and 1 space sent alternately
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✔
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N02
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IDLE 1.6
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Idle signal, 1 mark and 6 spaces sent alternately
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✔
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| N03 | - | Unused | |
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N04
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IDLE 14
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Idle signal with repeating arbitrary pattern of 14 bits
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✔
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N05
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IDLE 28
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Idle signal with repeating arbitrary pattern of 28 bits
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✔
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N06
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IDLE 56
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Idle signal with repeating arbitrary pattern of 56 bits
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✔
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N07
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BAUDOT
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ITA-2, Async. 7.5 bits (1 start, 5 data, 1.5 stop) 1
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✔
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✔
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N08
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ARQ-28
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ITA-3, Sync. 7 bits (3 mark, 4 space, 4th char inv)
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✔
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✔
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N09
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ARQ-56
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Same as N08, but every 8th character inverted
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✔
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✔
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N10
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ASY-ASCI
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ITA-5, Async. 10 bits (1 start, 7 data, 1 parity, 1 stop)
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✔
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✔
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N78
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PERIOD
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Check for repeating patterns of 2-64 bits
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✔
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N79
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M/S L...
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Code statistics MARK/SPACE ratio etc.
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✔
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Xnn
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Extra functions X00-X15
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✔
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| X97 | | Checksum test for user cartridge A1 | | | ✔ | |
| X98 | | Checksum test for user cartridge in B1 | | | ✔ | |
| X99 | | Set clock | | | ✔ | |
➤ Codes 11-77 and 80-96 reserved for user programs (see below)
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Improved BAUDOT program with measures the stop-bit length
and adjusts itself accordingly. The BAUDOT program can also
handle Cyrillic (Russian) characters.
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In addition to the standard programs provided by the system firmware,
additional USER programs can be added in the form of two EPROMs.
These EPROMs can be placed in the two empty sockets on the processor
board, or in an A1 expansion unit that is fitted at the rear
of the device. When switching the GA-082 on, the USER number
package will be shown briefly on the display, e.g.:
SYSTEM2.0 USER10
If the USER package is not recognised, the display shows
-- instead of the version number, e.g.:
SYSTEM2.0 USER--
In that case the package is not compatible with the version of the system
firmware, or the ROMs have been installed in the wrong order or the
wrong way around. USER10 contains the following:
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Improved BAUDOT program with measures the stop-bit length
and adjusts itself accordingly. The BAUDOT program can also
handle Cyrillic (Russian) characters.
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This package was probably released as a gap-fill solution.
It adds program 12:2, but several other programs have been dropped.
Furthermore, it uses program numbers that have been reserved for
other programs.
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USER30 is an arbitrary collection of external
B2 program cartridges,
that can be installed in the B1 expansion unit. They are compatible
with system v3.x. Any single B2 cartridge developed for the
B1, can also be
installed directly to the DC37 connector
at the rear of the GA-082. On startup,
all single B2 cartridges report themselves as
USER30 .
The table below shows the currently known USER30 programs.
Items marked with ★ are in the Crypto Museum collection.
There are many more USER30 programs. If you come across any that are not
listed here, please contact us.
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This video shows both GA-082 in our collection, just after they had been
repaired. One runs on firmware version 2.0. The other one has 3.0.
You will also see the internals and our newly developed PSU.
The upper one successfully decodes a live signal from our portable SDR
receiver. The other one runs the built-in self test.
Source
Crypto Museum
Date
19 January 2025
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Demonstration of desktop version
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This video clip was published on YouTube in 2022, and shows the
desktop model of the GA-082, with firmware version 3.0.
In the video, the Baudot signal from a weather station on
short wave radio is decoded and displayed.
Source
BoscoLab on YouTube
Date
5 August 2022
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Baudot signal at 14.465 MHz
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In this video clip, Roland Haas demonstrates the reception of a
50 baud Baudot telegraphy signal, received at 14,465 MHz.
Source
Roland Haas
Date
10 December 2024
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The GA-082 is housed in a 2U 19" rackmount enclosure. The interior can be
accessed by removing the upper panel, which is held in place by
17 screws.
After removing this panel, the interior becomes visible as shown in the
image above. At its right is a narrow compartment with the PSU.
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The largest compartment holds two large PCBs:
(1) the processor board at the right and
(2) the interface board at the left.
At the front of the device is the user interface, which comprises several
LED displays and push buttons.
Behind the front panel are two further PCBs
that hold the LED displays, the buttons and control logic.
Both the front panel and the interface board are connected to the processor
board by means of ribbon cables. At the rear panel is a small PCB
that hold the connectors of the IEC 1 and V.24
interfaces, plus configuration DIP-switches.
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Although the GA-082 was a high-end analysis tool — sold for a high-end price —
the design of the PCBs is horrible: both the processor board and the
interface board are 2-layer auto-routed PCBs. There is a complete lack of
ground plane, and there are insufficient decoupling capacitors.
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The voltage rails are far from clean and the few tantalium capacitors on
the board aren't anough to fix this. Although this might have been
sufficient when the device was new,
it will definitely become a point of faillure when the device ages.
The image on the right shows our desktop light shining through the processor
board; something one wouldn't expect from a high-end manufacturer
like R&S. The design of the power supply unit (PSU) is minimalistic
and inefficient. In particular the 5V rail, which is regulated down
from 10V, dissipates unnecessarily into a heatsink.
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With all this in mind, it's a miracle that the device actually works.
That being said, hats-off for the software developers who managed to
create a stable and reliable piece of firmware — entirely written in
assembler — on one of the first 16-bit microprocessors of the era:
the Intel 8086.
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It allows connection of the (optional) GA-082/A1 or GA-082/B1
expansion units. The latter is basically a big ROM expansion board that
is mapped directly into the memory map of the Intel 8086.
It offers space for up to 45 additional decoder programs, many of which were secret.
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The leftmost PCB is the interface board. It has the same size as the
processor board and holds the reference oscillator, the analogue and
digital interfaces and the IEC controller (GPIB).
The serial V.24 port
is provided by the processor board, but is routed via the interface board.
The image on the right shows the interface board. The ribbon cable
at the top right is connected to the corresponding header on the
processor board. At the far left is the connector to the IEC and V.24
receptacles. The big can in the upper corner is the reference oscillator.
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It is a Temperature Compensated Crystal Oscillator (TCXO) that runs
at 5 MHz. It provides the timing for the analysis circuits and a
variety of frequencies in the range 360 Hz to 737 kHz for the IF mixer.
When feeding AF signals to the GA-082 (instead of IF-signals),
the latter isn't used.
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The microprocessor's address and data busses are also connected
to the front panel electronics, via a 26-wire ribbon cable.
All 7-segment displays, the alpha-numeric displays and the LED bars
are controlled by the Intel 8086 processor, via this cable.
Likewise, the push-buttons at the front panel are scanned and
passed to the 8086.
The front panel electronics consist of two PCBs: one with the
push-buttons, the LEDs and the displays, and one with the control
logic, interconnected by 6 soldered orange flex wiring strips.
They are visible in the image on the right.
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Although the base unit can be expanded with additional user programs,
this option is rather limited as there are only
two free EPROM slots
on the processor board.
Optional program packages like USER10 have the same
2-EPROM limitation.
For this reason, R&S introduced the large B1 expansion unit
in 1992. It offers space for 45 additional program cartridges, each
of which can hold additional codes, programs or protocols.
A fully populated B1 unit is shown in the image on the right.
It is housed in a welded stainless steel enclosure that is secured
with a physical lock.
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The B1 unit can only be accessed from the top, after
releasing the security lock
and raising the top lid. Inside it is a large PCB with
sockets for a total of 45 cartridges, divided over two banks of
24 and 21 cartridges respectively. Towards the front is storage
space for additional cartridges.
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The circuit is layed out in such a way, that each cartridge can
be mapped into the memory space of a single (2-EPROM) cartridge that
is installed directly at the back
of the GA-082. This is the same memory space as is assigned to the
two empty EPROM sockets
inside the GA-082 itself.
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Each cartridge is housed in a small aluminium enclosure that measures
83 x 53 x 12 mm. At the bottom is a 37-pin DC37 connector that
mates with the DC37 socket inside the B1 unit.
Inside the cartridge are two 8KB 27C64 EPROMs: one for the lower
eight bits and one for the upper eight bits of the 16-bit data bus.
There are no labels over the EPROM windows, but that should not be a
problem as the case is normally closed. There is no indication of the
contents of the EPROMs, neither inside the enclosure nor on the
case label, apart from its serial number. 2
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Note that only one cartridge is active at any given time, under
control of the GA-082. For this to work, the data format of the
cartridge was changed and the firmware of the GA-082
was upgraded to version 3.0 and is no longer compatible with
earlier version of the firmware such as 2.1.
Also note that only the upper half of each EPROM is used, as address
line A12 is tied to +5V.
➤ Memory map
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IEC-625 is also known as IEEE-488, HPIB and GPIB.
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This is how the bare B2 cartridges were supplied: with blank EPROMs.
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Crypto Museum has two GA-082 devices in its collection, that were acquired
in 2013. At the time, one of the units appeared to work, whilst the other
one was dead; intended as a parts donor. In December 2024, we retrieved
both devices from storage in the hope to put one of them to work.
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Unfortunately, this time neither device worked. Although the
device had been on a shelf for the past 12 years, some components – in
particular capacitors – may degrade, sometimes even to the point were a
device is no longer operational.
A quick inspection of the interior was enough to come to the conclusion that
the PSU had died. The large capacitors had starting leaking out and had
already caused irreparable damage to the mains power switch. In addition,
the three largest capacitors showed significant burn marks; evidence
that the device had been used heavily.
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Rather than replacing the capacitors, it was decided to
redesign the PSU completely.
The original design was rather minimalistic, and the 5V was
regulated down from 10V, which caused significant dissipation.
For this reason, the original PSU has a fairly large heatsink at the
rear panel.
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A new PCB was designed with the same foot print, so that it would be
a drop-in replacement. As before, the new PSU
delivers +12V and -12V,
but the +5V supply for the logic is now created with a switched-mode
drop-down converter with a much higher efficiency than the original one.
As a result, the transistors on the heatsink at the rear are no longer
used. They are left in place however as otherwise a hole would be left
in the rear panel, but they are no longer wired.
The image on the right shows the new
Crypto Museum-designed PSU
at the original location.
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At the same time, the mains power switch – which had been damaged by
leaking capacitors from the old PSU – was replaced by a functionally
equivalent one. Furthermore, a new voltage selector
— one was missing — was made from a piece of ABS plastic.
After turning the device on, it came to life instantly,
but produced only garbage on its displays, whilst none of the buttons worked.
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As the effect was random — the display was different each time we
tried — it was decided to replace the tantalium capacitors on both boards, and
add some additional 10µF ceramic ones
to the +5V rail at various places
on the PCB. We also added 100nF capacitors close to certain
chips, in places where they had been omitted.
This improved the situation dramatically. After switching the device on,
it showed the firmware version number on the display, but then it stopped
completely. Apparently, something caused the device to 'hang' after
successful initialisation.
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In order to find the root cause of the problem, we measured the signals
on the data and address busses. Luckily, we have the full service documentation
of the GA-082, but unfortunately there are quite a few mistakes in the
original circuit diagrams. The measurements were futher hindered by the
bad design of the PCBs, as a result of which many signals look 'dirty'
on the oscilloscope.
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Eventually we noticed that one of the bits on the main databus was held
in mid-state, indicating that one IC was pulling the line
high, whilst another was simultaneously pulling it low.
After a long search, we found that the issue was caused
by U25, an 74LS365 that reads the state of
the 8 DIP switches at the edge of the processor board.
U25 is only accessed during startup. It reads the state
of DIP-switches S1, which determine the state of the
microprocessor and the baudrate of the V.24 port. It is also used as
a buffer for one of the timing signals from the interface board.
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After replacing U25, the GA-082 survived a fresh start and seemed
to work as expected. However, when comparing it to our other GA-082
(which had meanwhile become fully operational) it was noticed that
there was a severe jitter on the SYNC display and that the V.24 port was dead.
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Swapping parts from our known-good GA-082, revealed that the problems
were caused by one of the
P8253-5 programmable interval timers
[c] and the
P8251A programmable communication interface (UART)
[b]. As there were so many simultaneous faults in this single
unit, it seems likely that the device had suffered an ESD or a
lightning stroke at some point in its life.
New Old Stock (NOS) replacement parts were ordered from a Chinese
vendor on eBay. Upon arrival, the parts were placed in the defective GA-082
and the unit was tested once again.
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This time the device worked as expected. It captures and decodes an
input signal relatively fast, and the serial port works again.
During our tests, we noticed that the serial port (V.24) of one of our
GA-082 units didn't work correctly at 9600 baud. We had to reduce the
speed to 4800 baud to get a readable signal on our terminal.
On the other GA-082 device, the highest speed of 9600 baud works fine,
so the problem might be limited to that particular device.
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Both units not working One unit mains voltage selector missing One unit PSU in bad state (leaking capacitors) One unit mains power switch broken - Badly designed PCBs
Insufficient decoupling capacitors High dissipation by the PSU Excess jitter on SYNC display of one device Broken V.24 port on one device - V.24 port does not work at 9600 baud on one device
- Various incompatible firmware versions
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To improve the overall stability and reliability of the GA-082,
we've carried out the following modifications. Check out the
photographs at the end of this section for further details.
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- Power supply replaced
Some units have a faulty power supply unit (PSU). Although it might be
sufficient to replace the electrolytic capacitors, it is advised
to replace the PSU altogether,
as the exiting one has a rather bad
efficiency. This is described above under ➤ Restoration.
- All electrolytic capacitors swapped
It is advised to replace all electrolytic capacitors,
as the existing
ones have lost most of their capacity and might eventually start leaking.
It is also advised to add some 100nF in parallel
to the 5V power rail, close to the ICs.
This is particularly important in places where
such a capacitor is not present. This will improve the overall stability
of the unit.
- Resistor R10 on interface board swapped for 2k2
The AF/IF input at the rear is internally terminated at 50Ω
by means of resistor R10 on the interface board. Although this is correct
for connection to the IF-output of a receiver, the load is too heavy
for the AF-output of most receivers. This can be solved
by using an external amplifier, but it is easier to
replace R10 by a 2k2 resistor.
In case 50Ω is needed again in the future, one can always use a
T-connector with an external 50Ω terminator.
- IC D11 on interface board swapped for HCT-version
If DEMOD and SYNC displays show an unstable cursor when running
a self test (DEMOD-C-TEST-START), IC D11 on the interface board
(74LS393) must be
replaced by a HCT-version (74HCT393).
This improves decoding and results in an absolutely stable display.
- Reset button added
In some areas, the firmware of the GA-082 is a bit flaky. In particular
when returning from manual program selection (in MODE 2) to
auto-acquisition mode by pressing the START button, the firmware sometimes
does not recognize the data format. This can be fixed by turning the device
OFF and ON again, but this causes unnecessary wear of the ON/OFF button.
This problem can be solved by
adding a reset button to the front panel.
The button can be placed above the power switch.
One side of the switch should be connected to ground, whilst the other side
is connected to the reset circuit.
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As the GA-082 does not have a battery-backed configuration memory,
it can only be configured with DIP-switches that are mounted at
various places inside and outside the device. Unfortunately,
R&S selected a rather ambiguous type of DIP-switch of which it is unclear
when it is on or off. This is further complicated by ambiguous terms like
'open' and 'close', or '1' and '0', and by mistakes in the original manual
when describing the state of the switches, such as 'open = 1'.
It is best to ignore the descriptions in the original manual.
Each switch has a rocker with a flat and a sloped side. At the centre of
each side is a small dent that can be depressed with a sharp object,
such as a ballpoint. When doing this, the state of the switch changes.
In the example above, the rightmost switch is set to the upper position.
This corresponds to a closed contact, also known as on or a logic 1.
The state of the above set of 4 switches can be described as 0001.
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Frequency standard
INT S1
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| | S1.1 | | Frequency selection |
| | S1.2 | | Frequency selection |
| | S1.3 | | unused |
| | S1.4 | | unused |
Frequency selection:
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| | S1.1 | S1.2 | |
| | 0 | 0 | Internal |
| | 1 | 0 | External 1 MHz |
| | 0 | 1 | External 5 MHz |
| | 1 | 1 | External 10 MHz |
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IF mixer frequency
INT S2+S3
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The GA-082 accepts an input signal from the IF or AF output of an HF
receiver. When using IF signals, the internal mixer of the GA-082 must
be 2 to 3 kHz above the IF frequency of the receiver. It is adjustable
between 0 and 1,474.2 kHz in 360 Hz steps, by means of
DIP-switches S2 and S3 at the front edge the of interface board
(INT). Multiple switches can be active
simultaneously. Alternatively, an IF frequency of 0 (zero) can be used
when operating directly on AF signals.
The diagram below shows the switch settings for use with AF signals
(i.e. all switches set to 'off').
As an example, the lower diagram shows the required setting for an IF frequency
of 455 kHz.
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| | S2.1 | | 360 Hz |
| | S2.2 | | 720 Hz |
| | S2.3 | | 1.44 kHz |
| | S2.4 | | 2.88 kHz |
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| | S3.1 | | 5,76 kHz |
| | S3.2 | | 11,52 kHz |
| | S3.3 | | 23.04 kHz |
| | S3.4 | | 46.08 kHz |
| | S3.5 | | 92.16 kHz |
| | S3.6 | | 184.32 kHz |
| | S3.7 | | 368.64 kHz |
| | S3.8 | | 737.28 kHz |
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Processor configuration
CPU S1
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The processor board (CPU) has only one array of DIP-switches (S1),
located at the front edge of the board.
The rightmost 4 switches are used for setting
the baudrate of the V.24 serial port (RS232). Note that settings 0000 and 1111
are forbidden. Switch S1.4 can be used to insert a linefeed (LF) after each
received carriage return (CR). Switches S1.1, S1.2 and S1.3 must be off. 1
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| | S1.1 | | CPU on |
| | S1.2 | | ALE on |
| | S1.3 | | NMI off |
| | S1.4 | | Autofeed (LF) |
| | S1.5 | | Baudrate |
| | S1.6 | | Baudrate |
| | S1.7 | | Baudrate |
| | S1.8 | | Baudrate |
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| | S1.5 | S1.6 | S1.7 | S1.8 | |
| | 0 | 0 | 0 | 0 | ← forbidden |
| | 1 | 0 | 0 | 0 | 50 |
| | 0 | 1 | 0 | 0 | 75 |
| | 1 | 1 | 0 | 0 | 100 |
| | 0 | 0 | 1 | 0 | 110 |
| | 1 | 0 | 1 | 0 | 134.5 |
| | 0 | 1 | 1 | 0 | 150 |
| | 1 | 1 | 1 | 0 | 200 |
| | 0 | 0 | 0 | 1 | 300 |
| | 1 | 0 | 0 | 1 | 600 |
| | 0 | 1 | 0 | 1 | 1200 |
| | 1 | 1 | 0 | 1 | 1800 |
| | 0 | 0 | 1 | 1 | 2400 |
| | 1 | 0 | 1 | 1 | 4800 ← recommended |
| | 0 | 1 | 1 | 1 | 9600 ← unreliable on some devices |
| | 1 | 1 | 1 | 1 | ← forbidden |
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Switches S1.1, S1.2 and S1.3 are for use by service engineers,
and must be off for normal operation.
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| | IEC.1 | | IEC/V.24 |
| | IEC.2 | | unused |
| | IEC.3 | | TON |
| | IEC.4 | | IEC Address A5 |
| | IEC.5 | | IEC Address A4 |
| | IEC.6 | | IEC Address A3 |
| | IEC.7 | | IEC Address A2 |
| | IEC.8 | | IEC Address A1 |
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All connections to and from the GA-082 are located at the rear panel
of the device; shown in the image below. In the following section, each
individual connection is described in more detail. Additional information
can be found in the manual, but bear in mind that it contains mistakes.
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At the rear panel
is a female DB25 receptical with a RS232 interface
(V.24) for connection of a printer, computer or VT100 terminal. Note
that this interface will only work when the IEC DIP-switch (IEC/V24)
is in the rightmost position and the PRINT-button on the keypad is
activated (the LED in the button must be on).
Note that the wiring table in the original manual is unclear.
➤ More about V.24 (RS232)
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| 1. | GND | Shield (case) |
| 2. | TX | Data out (from GA-082) |
| 3. | RX | Data in (into GA-082) |
| 4. | RTS x | Request to Send |
| 5. | CTS x | Clear to Send |
| 6. | DSR | Data Set Ready |
| 7. | GND | 0V (data ground) |
| 20. | DTR | Data Terminal Ready |
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The pins marked 'x' (4 and 5) must be interconnected in the plug.
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Note that the connector is wired as Data Terminal Equipment (DTE) — like a
computer — but with the wrong gender connector (female instead of male).
For this reason, standard cables will not work. If you want to connect the
GA-082 to a computer (PC), a special cable must be made.
Pin 4 is internally connection to pin 20, and pin 5 is internally connected to
pin 6. As in most cases handshaking is not required, a shorting bridge (x)
between pins 4 and 5 in the plug is required.
When this port is enabled, the GC-082 will transmit the decoded data in
ASCII format, at a baud rate between 300 and 9600 baud 8N1,
adjustable with internal DIP-switches. Note that the
9600 baud setting does not work reliably.
It is recommended use 4800 baud 8N1. The V.24 port can
also be used for sending commands from a Personal Computer
(PC) to the GA-082.
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The GA-082 can also be controlled via an IEC-625 bus, which is available
on a 24-way Amphenol connector at the rear panel. This bus is also known
as IEEE-488, HPIB and GPIB. Note that the IEC bus and the V.24 interface
are mutually exclusive. When using the IEC bus, the DIP-switch IEC/V24
at the rear panel should be set to the leftmost position.
In this state, the V.24 port is disabled.
A description of the wiring of the IEC bus is beyond the scope of
this web page.
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At the rear is a circular
7-pin C091-series Tuchel connector
with two independent fully isolated input channels that are connected
to internal opto-couplers. This can be useful when receiving F6 mode
signals. Switching between the two channels can be done with the
CHAN 1/2 button on the keypad.
This connector also outputs the regenerated signal and the bit clock
at TTL levels.
The part number of the Amphenol-Tuchel
7-pin plug (i.e. the cable part) is T 3475 002 U.
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REG Out Regenerated signal BCLK Out Bit clock CH2+ In Channel 2 + CH1+ In Channel 1 + CH2- In Channel 2 - CH1- In Channel 1 - GND - Ground
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The GA-082 works on signals from the IF-output of an HF receiver
of the era, or directly on the AF-output of the receiver.
Note that in both cases, the correct
mixer frequency must be configured.
The signal should be between 30 mV and 1 V and is internally
terminated at 50Ω. Note that at Crypto Museum we've
modified the terminator to make
the input suitable for AF signals.
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AF/IF In Audio or IF signal GND - Ground
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At the rear is a BNC input marked FSK. It can be used to apply an already
demodulated signal directly to the GA-082. The line is terminated at 2kΩ
and is suitable for V.28, RS232C and TTL level signals, as well as single
current 10-60mA. When using a receiver with a built-in high-end FSK
demodulator, such as the AEG/Telefunken E-1800, it is best to use
this input.
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Signal In Demodulated signal GND - Ground
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The GA-082 has an internal reference oscillator from which all internal
timing signals are derived. When necessary, it can be sychronised with
an external reference signal of 1, 5 or 10 MHz applied to the BNC socket at
the rear panel (30-500 mV). Note that, whichever of the possible three
input frequencies is used, DIP-switches S1 on the interface board
must be set accordingly.
In most cases, this input remains unused, in which case DIP-switch
S1 must be set to all 0.
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REF In External 1. 5 or 10 MHz refrence GND - Ground
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Expansion connector
Program unit
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At the rear panel is a 37-way DC37 socket
for connection of additional programs (formats) in the form of a
single-program unit (A1)
or a multi-program unit (B1).
The latter is a 19" 2U expansion unit in which
up to 45 additional program cartridges can be installed. A1 units are fitted
directly to this socket. Connector X1 of a B1 unit can be connected with a 1:1 cable.
Below is the pinout of the expansion connector when looking into the
37-pin socket. The numbers in red are the corresponding pins of the
40-pin header (X16) inside the GA-082 (to the left of the EPROMs).
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- +5V
- +5V
- D14
- D13
- D12
- D11
- +5V
- A9
- A10
- A12
/RD /OE - A11
/ML1 /CE(L) - D7
- D6
- D5
- D4
- D3
- GND
/MH1 /CE(H) - D15
- D8
- D9
- D10
- GND
- GND
- A8
- A7
- A6
- A5
- A4
- A3
- A2
- A1
- D0
- D1
- D2
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The rear half of the processor board has
eight 24-pin sockets for
memory devices, numbered D17-D24. As the memory bus is 16 bits wide
and the memory devices are only 8 bits wide, they are used in pairs.
The pairs are mapped into four address ranges.
Both the manual and the brochure specify the memory size at 24KB,
but this appears to be incorrect. There are four EPROMs of 4KB each,
plus two RAMs of 2KB each. This gives a total memory size of 20KB.
The diagram above shows the positions of the memory devices. The
two RAM chips are at the far right (D23-D24). To their left
are the four EPROMs that hold the firmware (D19-D22). Left of
the firmware are two empty sockets for optional user programs (D17-D18).
These spaces are also known as A (lower 8 bits or ML) and B
(upper 8 bits or MH). By default they are not populated.
At the far left is connector X16 which makes the two empty sockets
also available at the rear panel.
➤ More about memory arrangement
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Device Telegraphy FSK analyzer Purpose Radio monitoring, intercept and 'fingerprinting' Model GA-082 Developer Dr. Schäfer Manufacturer Rohde & Schwarz Year 1983 Designator 624.0512.02 (see below) NSN 5865-12-190-1946 Country Germany Users Germany (Bundeswehr, BND), Netherlands, UK, ? Demodulator F1 (F1B, 2-FSK), F6 (F7B, 4-FSK) Range 30-2000 Hz (AF) Target 2-600 bps Resolution 10 µbps (< 1000 bps)
100 µbps (≥ 1000 bps, < 2450 bps)
1 bps (2450-9600 bps) TCXO 5 MHz ±1·10-6 (0-40°C) Baudrate 50, 75, 100, 110, 134.5, 150, 200, 300, 600, 1200, 2400, 4800, 9600 Interface RS232, IEC-625 1 Processor 8086 (16-bit) Memory 20KB (16KB ROM, 4KB RAM) Power 110, 120, 220, 240V AC Consumption 50 W Temperature 0 to 40°C Storage -40°C to +70°C Dimensions HWD 88 × 483 × 391 mm (10" version)
HWD 110 × 471 × 346 mm (desktop version) Weight 5 kg Quantity 700 (est.) Price ?
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Device Expansion unit for GA-082 Purpose Modular expansion of user programs Model GA-082/B1 Manufacturer Rohde & Schwarz Year 1992 Designator 709.7504.02 Country Germany Cartridges 45 Dimensions ? Weight ? Quantity 300 (est.) Price EUR 11,500 2
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IEC-625 is also known as IEEE-488, HPIB and GPIB.
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Price indication found on a VEBEG slip when the units were sold as surplus.
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The serial number of the device is printed on a label in the top right
corner of the front panel.
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- FSK Analyzer GA-082 - Brochure (English)
Rohde & Schwarz, 8-page full-colour brochure.
Data sheet N 6-331 E-1. December 1983.
- FSK Analyzer GA-082 - Brochure (German)
Rohde & Schwarz, 8-page full-colour brochure.
Data sheet N 6-331 D-1. October 1983.
- FSK Analyzer GA-082 - Technical description (German)
Rohde & Schwarz, September 1982.
- FSK Analyzer GA-082 - Manual (English)
624.0512 (617.2436.42) (42101). Rohde & Schwarz.
Undated, but probably 1983. 86 pages.
- USER10 code package, manual (English)
Program for Additional Codes for FSK-Analyzer GA-082.
GA-082/P1. 4PVF. Rohde & Schwarz, April 1986.
- Firmware EPROM swapping instructions (German)
Austauschanleitung EPROM-Satz GA-082.
640.4619 V. Rohde & Schwarz, October 1992.
- Changes in firmware version 3.0 (German)
Änderungen des GA-082 fur System - Version 3.0.
Rohde & Schwarz. Undated.
- GA-082/B1 fitting instructions (German)
Einbauanleitung BA-082 mit GA-082/B1.
701.1171. Rohde & Schwarz, March 1988 (updated December 1989.
- GA-082/B1 Zubehörliste / List of Accessories
709.7504.02/05. Rohde & Schwarz, October 1992.
- GA-082 circuit diagrams
Rohde & Schwarz, October 1983.
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- Technik der Fernschreib-Erfassung in der Fernmeldeaufklärung der Bundeswehr
Rudolf Grabau, Funkgeschichte 27 (2004), Nr. 153, pp. 35-36.
- NSN 5865-12-313-5643 - Amplifier Subassembly
Created 15 April 1988. Visited 19 January 2025.
- Wikipedia, Bundeswehr
Visited 19 January 2025.
➤ German version
- Bertrand Velle, GA82: First tests
Radio Communications Blog, 8 January 2023.
- Rudolf Schuba, Rohde & Schwarz Telegrafieanalysator FSK Analyzer GA 082
BoscoLab blog. Personal correspondence, 16 December 2024.
- Wikipedia, Kosovo Force
Visited 18 February 2025.
- Wikipedia (Germany), Fernmelde- und Elektronische Aufklärungsbrigade 94
Visited 18 February 2025.
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© Crypto Museum. Created: Wednesday 01 January 2025. Last changed: Friday, 14 March 2025 - 10:09 CET.
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