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Radio Intercept R&S GA-082 Programs → ← Back
Operating and control instructions
This page contains detailed operating instructions for the
Rohde & Schwarz
GA-082 FSK Analyzer
and the GA-082/B1 extension unit (B1). It also contains
detailed information about remote controllable features.
Additional information can be found in the original manual,
but please be aware that the original manual is badly structured,
ambiguous and in several cases incorrect.
Unless stated otherwise, it is assumed that firmware version 3.0 is
installed.
After switching the device on, the analysis display first shows
the firmware version number (e.g. 3.0) and then goes blank, with
the number 0 showing in the left corner. This is the current Mode number.
In Mode 0, auto-acquisition is enabled and the unit tries to
recognise the format of the input signal. Once a valid format is found,
switch to Mode 1 to read the decoded text.
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The software (firmware) is held in four EPROMs that are installed
in sockets D19-D22 on the processor board .
Upgrading a device to a higher version, requires only these
four EPROMs to be replaced. No changes are made to the hardware.
The current version number is shown on a removable label at the bottom edge of
the front panel. The following versions are known:
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- 1.0
This was probably the original release version of the firmware.
It was short-lived and was soon replaced by version 2.0.
So far, we have never seen this version.
- 2.0
For a long time this was the defacto standard firmware for the
GA-082. Many of the surviving GA-02 units still have this version fitted
and were never upgraded to a later release. It is believed to backward
compatible with version 1.x. Program packages USER10,
USER13 and
USER20
are compatible with this version of the system firmware.
➤ Download firmware 2.0
- 2.1
This was an update from version 2.0 with only minor fixes.
The reason for the update is currently unknown.
It is fully backward compatible with 1.x and 2.0.
➤ Download firmware 2.1
- 3.0
This was a major new release, introduced in 1992. It offers several improvements,
in particular support for the B1 expansion unit. No changes are made
to the hardware, but the firmware is no longer compatible with previous
user programs such as USER10
and USER20.
Instead is uses USER30 programs.
The programs are numbered from 00 to 99, whilst the extra functions are numbered X00-X99.
➤ See all changes
➤ Download firmware 3.0
- 3.1
This was probably a small update from version 3.0, but we have never seen
it and have no overview of the changes.
- 4.0
There appears to have been a firmware release 4.0. At least one GA-082
with version number 4.0 printed on the front panel has been spotted, but
unfortunately its EPROMs had been removed [2][3].
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Unless specifically stated otherwise, the descriptions below are based on
firmware version 3.0.
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- Program numbers (data formats) are numbered 00-99.
- Extra functions are numbers X00-X99.
- Incompatible with previous user programs (e.g. USER10).
- Requires new program format (USER30).
- In Mode 0, user programs take precedence over standard programs.
- Baudot program now recognises 1, 1.5 and 2 stop-bits.
- SRQ-line of IEC bus can be deactivated.
- Command R0 reads the status of the GA-082.
- Commands R1-R2 can be used to read the analysed data.
- Support for GA-082/B1 expansion unit (B1).
- Command added to set the RTC in the B1.
- Command added to test the B2 modules inside the B1.
- Support for AUDAS computer added.
- When FIX is activated, the frequency is no longer tuned.
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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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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).
➤ Overview of available program packages
➤ List of all known programs
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The keypad consists of 12 push-buttons arranged in a 4×3 matrix,
as shown in the image below. Each button has a specific function.
When a button is pressed, the red LED in the button lights up.
Some functions require multiple buttons to be pressed in a
specific order.
To enter numbers, press the yellow SELECT-button. This works
like the SHIFT-key on a computer keyboard. The red LED
in the SELECT-button lights up to indicate that the alternative
function (printed in yellow) of each key is used. Unfortunately,
the yellow text is barely readable on the grey key tops.
The alternative functions are shown in the right half of the
diagram above.
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 | The START-button is used to start a new measurement (acquisition). The LED lights up until the first baud rate has been determined. Note however that measurement continues until the FIX button is pressed. |
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When this button is active (LED is on), the ANALYSIS display shows the control loop constants. The value of the constants can be altered manually between 0 and 15 by means of the STEP buttons. In this state, automatic stepping of the constants is disabled. |
 | When this button is active (LED is on), the SHIFT/FREQ display shows the current centre frequency, whilst the DEMOD display shows the momentary frequency with a resolution of 64 Hz. |
 | When this button is active (LED is on), the internal demodulator is enabled. In this state, the DEMOD and FREQ/SHIFT displays are active. Note that by default, DEMOD is off, so in most cases, this will be the first button that must be pressed after switching the device on. When the device is used in combination with an HF receiver with built-in FSK demodulator, this button should stay off. |
 | This is the yellow prefix button. It enables the functions that are printed in yellow on the grey key tops (barely visible). It should be followed by two digits (nn) or by 'X' and two digits (Xnn). A two-digit number (nn) selects the corresponding code (protocol). Xnn selects an extra function. Note: On version 2.x a single digit is used: Xn. |
 | When active (LED is on), output from the device is sent to the configured data port (IEC or V.24). The output depends on the selected mode. In Mode 1, the decoded clear text is sent (when a decoder is implemented in the selected program). Note that when the LED is off, no data will be sent to the V.24 port. ➤ More information |
 | This button can be used to switch to the second input signal at the 7-pin Tuchel socket at the rear. In F6 mode, the demodulator switches over to the 2nd channel. The 2nd channel is active as long as the LED in this button is lit. |
 | This button enables the built-in self test. It allows all displays at the front panel to be checked. When pressing the 'A', 'B' or 'C' button before the TEST-button, a specific self-test is activated. Pressing C-TEST, activates the internal 75 baud loop test. In this state, 1200 and 2400 Hz are used as F1/F2 frequencies. |
 | This button can be used for switching off the automatic restart of a measurement. After pressing START, the first baudrate evaluation is skipped and the control loop is directly started with the previously adjusted baudrate. The control loop is adjusted for Baudot signals by activating button 'B'. By additionally activating 'C', it is adjusted for inverted Baudot signals. |
 | Auxiliary function for suppressing the sync test for the first baudrate evaluation. With baudot signals, each individual character is synchronised. Each (active) program may assign an alternative function to this button. |
 | Auxiliary function for PRINT and FIX. Each (active) program may assign an alternative function to this button. |
 | Auxilary function key for PRINT, TEST and FIX. With Baudot signals, the case shift is made in Mode 1. In Mode 2, inverted code is selected. Each (active) program may assign an alternative function to this button. |
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The following functions were available from the keyboard in version 2.x of
the firmware. Note that the SELECT button must be pressed before entering
the function number. The function consists of two digits (nn) or X
followed by a single digit. The functions were changed in version 3.0.
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| CMD | Description |
| nn | Code program number |
| X0 | Front panel off |
| X1 | F6 on |
| X2 | Phase control loop off |
| X3 | Phase control loop on |
| X4 | Baudrate control loop off |
| X5 | Baudrate control loop on |
| X6 | User EPROM off |
| X7 | User EPROM on |
| X8 | Bit clock and regenerated signal off |
| X9 | Bit clock and regenerated signal on |
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In version 3.0 of the system firmware, the special functions were
reassigned and reordered. They now consists of X followed by two digits
(nn) and behave exactly like remote control command 'X' (e.g. SELECT-X-0-3).
The selection of a code program (SELECT-nn) is unchanged.
➤ More
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Here is an example of how to get the device going if you are in a hurry:
- Configure the internal DIP-switches for AF-input.
- Connect an AF source (audio) of sufficient strength to the
BNC socket marked 'AF/IF input'.
This can be the speaker output of a receiver tuned to a known RTTY frequency,
or a computer playing back a previously recorded FSK session.
A line output may be too weak.
- Turn the device on. It should first display the version number, and then Mode 0.
- Apply a known-good FSK signal to the AF input (Baudot or ASCII).
- Press DEMOD-START.
- After a short while the frequency shift and later the baudrate should appear.
- Switch to Mode 1 by pressing the ↑ button under the Mode display.
- The ANALYSIS-display should now show the decoded text.
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| | Demodulator on.
Start measurement. |
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When no external AF signal is available, most of the device can be checked
quickly by starting the internal self test. The test feature can be combined
with the auxilary functions 'A', 'B' and 'C'.
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Apart from the keyboard, the GA-082 can also be controlled via the
IEC-625 bus, or via the V.24 interface (RS232).
Basically, all functions that are available on the keypad
are also available remotely via the RS232 port.
The following commands are currently known:
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| CMD | Description | Reply |
| An | Auxiliary function A off (0) on (1) |
| Bn | Auxiliary function B off (0) on (1) |
| Cn | Auxiliary function C off (0) on (1) |
| Dn | Demodulator off (0) on (1) |
| En | User EPROM off (0) on (1) |
| Fn | FIX function off (0) on (1) |
| Gnnnnnn | Set baudrate nnnn.nn |
| Hnnnn | Set FSK shift nnnn in Hz |
| Innn | Set frequency n.nn in kHz |
| Jn | Autofeed off (0) on (1) |
| Kn | CONST function off (0) on (1) |
| Lnnn | Set line length nnn |
| Mn | Set Mode [0-2] |
| Nnn | Select user program (code) nn [00-99] |
| Onn | Same as Nnn 1 |
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O
| Set clock (RTC) (same as 'X99')
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| Pn | PRINT function off (0) on (1) |
| Qn | Bit clock off (0) on (1) |
| R | Print status 1 |
| R0 | Read GA-082 status | 7 Byte Hex |
| R1 | Read Freq/Shift/Q | 11 Bytes |
| R2 | Read Baud/Min/S | ?5 Bytes |
| R3 | Read analysis displays | 16 Bytes |
| S | START function on |
| Tn | TEST function off (0) on (1) |
| Un | Select channel 1 (0) or 2 (1) |
| Vn | Step - (0) or + (1) for CONST and code number in Mode 2 |
| Wn | SHIFT indication (0) or FREQ indication (1) |
| Xn | Front panel off (0) on (1) |
| Yn | Rate loop on (0) off (1) |
| Zn | Phase loop on (0) off (1) |
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Special functions
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| Xnn | Select extra function nn [00-99] |
| X00 | User programs off |
| X01 | User programs on |
| X02 | Bit clock off |
| X03 | Bit clock on |
| X04 | Phase control loop off |
| X05 | Phase control loop on |
| X06 | Baudrate control loop off |
| X07 | Bautrate control loop on |
| X08 | IEC SRQ off |
| X09 | IEC SRQ on |
| X10 | AUDAS off |
| X11 | AUDAS on |
| X12 | Front panel off |
| X13 | Front panel on |
| X14 | F6 off |
| X15 | F6 on |
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| X97 | Checksum test for user cartridge A1 |
| X98 | Checksum test for user cartridge in B1 |
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X99
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Set clock (same as 'O')
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Items shown in red are version 2.x only. Removed in version 3.0.
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Commands with 2-digit suffix are introduced in version 3.0.
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The expansion unit B1 (GA-082/B1)
has a built-in real-time clock (RTC) that can be set with command 'O' or
command 'X99'. In the description below, it is assumed that command 'O' is used.
The command has the following format:
OhhmmssMMDDYY
Example: to set the time to 23:58.20 and the date to 31 December 1994,
one of these commands should be used:
O235820123194
X99235820123194
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Whenever the GA-082 has captured 1024 new bits of data, the
available analysis programs are called one-by-one in a predetermined
order to see if any of them recognises the characteristics of
the signal. The first code that has sufficient correlation between the
input signal and the code structure, is displayed along with its name,
its program number and up to four extra characters of additional
information. The format of the 16-character alphanumeric display is
as follows:
The first eight characters are used for the program name (e.g. BAUDOT).
The last four characters show the program number (e.g. N07). It will be
preceeded by a minus sign when the code is inverted (e.g. -N07).
In between the program name and number are four characters that are
reserved for additional information — here shown as XXXX —
such as a measurement (e.g.: 29.7).
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When a Mode 1 decoder is implemented in the program that has been selected
automatically in Mode 0 (or manually in Mode 2), and a positive
correlation has been found, any received text will be decoded instantly and
will be shown on the ANALYSIS display at 8-bit intervals:
Note that non-printable characters like Carriage Return (CR) and
Line Feed (LF) cannot be displayed. Instead they are shown as plain text
control codes, such as M (carriage return) and J (line feed).
The text can be printed (or delivered to a computer) by turning on the
PRINT button. This is always done in ASCII format
(i.e. text in BAUDOT code will automatically be
converted to ASCII).
Although some programs contain support for other alphabets, such as
Cyrillic (Russian), the output from the serial V.24 port will always be
in plain ASCII. Any conversion to a different alphabet is up to the settings
of the printer or any further software running on the connected computer.
Note that even with the correct settings, text will be unreadable if it
is encrypted or scrambled.
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Mode 2 is very similar to Mode 0, which the exception that the device
does not search for the most likely format, but that the format (i.e. the
program) can be selected manually. If a correlation is found
between the signal and the selected format,
the ANALYSIS display shows the same information as in Mode 0.
If there is no correlation, the 'extra'-field of
the display shows 'NO':
A program can be selected in two ways: (1) by pressing the
SELECT button on the keypad followed by the 2-digit program number, or (2)
by using the STEP ↓↑ buttons below the ANALYSIS display.
Note that this only works after a program has successfully been selected
automatically in Mode 0.
A dedicated analysis of the manually selected format (program) is carried
out every 1024 bits. When the PRINT function is on,
the results of the analysis are printed (or shown on a terminal).
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In Mode 3, the current bitstream is shown on the CODE display
as a scrolling display.
The display is 48 bits wide and shows the last 48 bits of the 768-bit
buffer. A burning LED is equivalent to a logic '1' in the code.
The diagram below shows a simple 10101010 idle signal.
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Mode 4 is the static variant of Mode 3. When the 768-bit buffer is full,
no further bits are captured and the last 48 bits are shown on the display.
The STEP buttons ↓↑ can now be used to step through the buffer.
When doing this, the ANALYSIS display shows the current position (STEP):
Hold down the STEP button to step faster. Press STEP ↓ and ↑
simultaneously to reset the position. Use the LENGTH ↓↑ buttons
to alter the line length (LEN). This setting in only relevant when sending the
output to a printer or terminal.
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Mode 5 is the inverted version of Mode 4.
A burning LED is equivalent to a logic '0' in the code.
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In this mode, code bits are constantly entered into 16 lines of refresh memory,
and the rapidly changing lines are superimposed on the CODE display.
This way, periodically recurring bits can easily be recognised.
The example below shows a Baudot signal with 1 start- and 2 stop-bits.
When selecting this mode, the display initially shows rapidly flashing
LEDs on the CODE-display, until the entire buffer is filled. From then on,
only the bits that are different will flash rapidly.
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Mode 7 is the inverted version of Mode 6.
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Mode 8 is very similar to Mode 6. The difference is that the code memory
accepts 8192 bits and that the display remains dark until 1024 have been
captured. Once the buffer is filled, the LED-bar in the CODE display is
updated instantly.
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Mode 9 is the inverted version of Mode 8.
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Printing is enabled with the PRINT-button (LED is on).
The output of the GA-082 can then be printed directly on an EPSON
MX-80 (or compatible) printer that is connected to the V.24 (RS232) port.
This function should also be activated when a computer is connected to the
V.24 port. Note that each time the device is switched on, this setting is lost.
Furthermore, the V.24 interface and its baudrate must be selected with the
DIP-switches prior to attempting to use the serial port.
The output depends on the currently selected Operating Mode:
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- Mode 0
Measured data is reported each time 1024 bits have been captured.
Output of the code bits (provided that auxilary function B and/or C is on).
→ C = bits, B = nibbles, B+C = bytes.
- Mode 1
Clear text (same as in the scrolling ANALYSIS-display).
- Mode 2
Measured data is reported each time 1024 bits have been captured.
Output of the code bits (provided that auxilary function B and/or C is on).
→ C = bits, B = nibbles, B+C = bytes.
- Mode 3
Output of the code bits (provided that auxilary function B and/or C is on).
→ C = bits, B = nibbles, B+C = bytes.
- Mode 4
Output of the code bits (provided that auxilary function B and/or C is on).
→ C = bits, B = nibbles, B+C = bytes.
- Mode 5
Output of the code bits (provided that auxilary function B and/or C is on).
→ C = bits, B = nibbles, B+C = bytes.
- Mode 6
Output of 16-line contents of the refresh memory.
- Mode 7
Output of 16-line contents of the refresh memory.
- Mode 8
Output of 16-line contents of the refresh memory.
- Mode 9
Output of 16-line contents of the refresh memory.
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© Crypto Museum. Created: Wednesday 15 January 2025. Last changed: Tuesday, 18 February 2025 - 10:21 CET.
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