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Radio Intercept Teletron
Telegraphy demodulator
- this page is a stub
TG-44E is a demodulator (German: Tast-Gerät) for wireless
Frequency Shift Keying (FSK) telegraphy
(telex), introduced in 1965 by H. Pfitzner
in Frankfurt (Germany) and sold under the Teletron brand.
The device was typically used in civil and military
radio monitoring and intercept stations.
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The device is suitable for demodulating virtually all types of telegraphy
signals (CW, RTTY, Multi-tone and Data),
with accurately adjustable tone filters and indicators for
monitoring the signals.
It can be connected to the IF output of virtually any type of
HF/VHF/UHF receiver, and offers automatic antenna
or receiver diversity control.
It comprises a heavy 3U 19" rackmountable chassis, with an
optional metal enclosure for desktop use. All controls are at
the front panel, whilst all connections are located at the rear.
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The TG-44E was first introduced in 1965 and was initially used
with monitoring receivers like the
Teletron TE-704
and TE-712.
Main customers for the unit were the German Army (Bundeswehr) and
Navy (Marine),
but also the Radio Monitoring Services and
Intelligence Agencies
of a number of European countries.
In later years, the Teletron receivers were gradually replaced by modern
alternatives, like the Telefunken
E-1800
and E-1800/A,
but the TG-44E often remained in use.
The device was in production until at least the early 1980s, but was
used in practice until well after 2011. This gives it a unique lifespan
of no less than 45 years! Today, the TG-44E can be found on auction sites
like eBay and in military surplus stores, for prices around EUR 200-250.
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Below is the front panel of the TG-44E. At the center is a recessed
oscilloscope on which the FSK tones are displayed as vertical lines.
It can be used as an aid when adjusting the desired centre frequency
and deviation with the two adjustment knobs to its right. Below these
knobs are the selectors for the FSK mode (F1, F4, F6I, F6II and F9)
and the baudrate (50-3200 baud and higher).
To the left of the oscilloscope are the controls for diversity reception
and two meters: one for checking various settings and voltages, and one
that shows the deviation of the selected centre frequency. Below the
meters are knobs for selecting the meter function, the oscilloscope function
and the diversity settings. A toggle switch allows selection between the
two diversity modes.
The image above shows the rear side of the TG-44E. At the left are four
6-pin military connectors. The bottom one (the only male receptacle) is
used for connection of the power supply. It can be wired for the 117/220V AC
mains as well as for a 21-30V DC source. The other three receptacles are
for connection of various types of telegraphy equipment:
tone or single/double current.
At the right are BNC sockets for connection of the antennas and the
receiver(s). At the center is the IF-selector that should be set to the
IF-frequency of the receiver(s). Two IF-frequencies are readily available
(30 and 525 kHz). For other IF-frequencies,
additional crystals must be installed.
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The TG-44E has two modes for diversity reception: (1) antenna diversity and
(2) receiver diversity. The desired mode is selected with the toggle switch at
the lower edge of the left half of the front panel.
The indicator lights at the top left shows the currently selected antenna
or receiver.
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- Antenna diversity
In this configuration, only one receiver is used (EI) and up to three
antennas. The antennas are connected to the TG-44E, and the socket Funkempfänger is
connected to the antenna input of the receiver. The IF-output of the receiver is
connected to the EI input of the TG-44E.
When idle, the TG-44E continuously switches between the antennas
with a configurable interval (Verweilzeit). When is measures an IF-signal of
sufficient strength, it stops switching.
This is the cheapest form of diversity reception.
- Receiver diversity
In this configuration, two receivers are used, each with their own antenna.
The IF-outputs of the receivers are connected to the EI and EII inputs
at the rear. The TG-44E continuously monitors the signal strength at each of
these inputs, and automatically selects the stronger of the two. This is the best,
but also the most expensive form of diversity reception, as it requires two
(expensive) receivers that somehow have to run in tandem.
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The TG-44E must be connected to the IF output of an HF
communications receiver. As there are many different IF frequencies,
the selector at the centre of the rear side must be set accordingly.
The leftmost setting is always 30 kHz, which matches the internal IF
frequency of the TG-44E.
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For each additional IF frequency, a suitable crystal must be installed
behind the grey panel at the centre. The crystal must always be chosen
30 kHz higher than the desired IF frequency, so that after mixing it
with the input signal, the result is 30 kHz (the internal IF of the TG-44E).
Popular intermediate frequencies are 200 kHz, 300 kHz, 455 kHz and 525 kHz.
30 kHz and 525 kHz are installed by default. The table below shows the frequencies
that are available in the TG-44E in our collection:
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| IF | Crystal | Description | Default |
| 30 kHz | - | Default internal frequency (no crystal required) | ✔ |
| 200 kHz | 230 kHz | |
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| 300 kHz | 330 kHz | |
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| 455 kHz | 485 kHz | Used in regular AM broadcast receivers | |
| 525 kHz | 555 kHz | Popular IF used in communications and monitoring receivers | ✔ |
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Telegraphy decoder
TG-44E
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The image on the right shows the actual TG-44E telegraphy decoder.
The device is housed in a 19" enclosure that is open at the top
and at the bottom. It can be placed in a 19" rack, but one has to
ensure that the bottom and top are free of connectors and other
metal parts, as they could easily cause a short circuit in the
interior.
For desktop use, a separate metal enclosure
was available, with carrying handles at the sides.
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Most PCBs are installed in a socket, or slot, so that
they can be removed for servicing and aligment. At the top of
each plug-in card are two holes that allow easy removal by means
of the extraction tool shown in the image on the right.
When unused, the extraction tool is
stowed in the hollow compartment
at the left side of the unit. It can be removed by
pressing the two legs together.
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Once a PCB has been extracted, it can be installed on top
of the so-called extender board, shown in the image on the right.
It is installed in place of the removed board, whilst the removed
board is installed on top of the extender.
When unused, the extender board is
stowed in the hollow compartment
at the left side of the unit. It is held in place by two thumb screws.
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The device can be powered from the 127 or 220V AC mains, or
from a 21-35V DC source, such as the battery of a car.
In both cases, the voltage should be applied via the 6-pin
male military connector at the rear.
The image on the right shows the mains AC cable that was
recreated at Crypto Museum.
➤ Connector wiring
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The TG-44E in the Crypto Museum collection was found in 2019 on eBay.
It was in unknown condition and when we received it, it was established
that the mains power cable was missing and that the device was probably broken.
Someone had clearly been too rough when fitting the device inside the optional
metal enclosure, and had broken some of the wire contects of the Cathode Ray Tube (CRT).
Due to time restrictions and other priorities, it landed on a shelf until
early 2025, when we decided to restore it and try it out with the
GA-082 FSK analyzer and several receivers.
The broken wire contacts on the CRT board were restored and a suitable
mains power cable was made. The unit was powered up
and, although the light at the front panel were lit, the device did not appear to
work. It turned out that most of the multi-turn potentiometers at the upper edge
of some of the PCBs were completely gone, probably as a result of storage in
a damp place.
Aparently, someone had already attempted to repair the unit in a previous life,
and had replaced a resistor by one with an incorrect value. After correcting this,
and replacing several other suspicious parts, the device gradually came to life.
Next the device was completely tested and readjusted, as per manual.
Note that the circuit diagram is complex and difficult to understand, and that
the descriptions in the manual are unclear and at times even ambiguous.
Nevertheless the device is now fully operational again and has meanwhile been
tested with several HF receivers.
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Power cable missing Unknown condition (probably defective) Connector on CRT unit broken (internal) - Mains transformer saturates with 240V/AC
Entire unit misaligned
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At the rear of the device are four 6-pin military connectors, of which the lowest one
is the power connector. It can be used for 117/220V AC as well as for 21-35V DC.
Below is the pinout when looking into the male receptacle. When connecting the device
to the AC mains, pins (E) and (F) must be shorted in the cable part. When connecting
the device to a 21-35V DC source, the (+) terminal should be connected to pin (E)
and the (-) terminal to pin (F), whilst the rest is unused.
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- not connected
- 220/117V AC (1)
- 220/117V AC (2)
- GND
- (+) 21-35 V 1
- (-) 21-35 V 1
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When connecting the device to the AC mains, pins (E) and (F) must be shorted
in the connector (cable part). Without this wire bridge, the unit will not work.
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The drawing below shows the wiring of the mains AC power cable. The pinout is
when looking into the receptacle at the rear of the TG-44E. This is the same as
the solder side of the 6-pin female cable part. Note the wire bridge between
contacts (E) and (F), which must be present.
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Below is the wiring of the power connector when the device must be powered by
a DC voltage between 21 and 35V. The pinout is
when looking into the receptacle at the rear of the TG-44E. This is the same as
the solder side of the 6-pin female cable part.
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Double-current telex output
20-30 mA
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Grey Ch. A (+) 20-30 mA Black Ch. A (-) 20-30 mA Green Ch. B (+) 20-30 mA Yellow Ch. B (-) 20-30 mA Blue Data (+) 10 V Red Data (-) 10 V
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Single-current telex output
40-60 mA
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Grey Ch. A (+) 40-60 mA Black Ch. A (-) 40-60 mA Green Ch. B (+) 40-60 mA Yellow Ch. B (-) 40-60 mA Blue GND Red GND
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Grey Tone (A) F1 1500 Hz (1) Black Tone (A) F1 1500 Hz (2) Green Tone (B) F6 1500 Hz (1) Yellow Tone (B) F6 1500 Hz (2) Blue F4/F9 4500 Hz (1) Red F4/F9 4500 Hz (2)
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Device Telegraphy demodulator Purpose Diversity reception and demodulation of RTTY signals Name Tastgerät TG44E Model TG-44E Brand Teletron Manufacturer H. Pfitzner Year 1965~1982 Users Bundeswehr, Heer, Marine HF input Automatic/manual antenna diversity system Waveforms F1, F4, F6, F9 AFSK Multi-tone, freely adjustable Meters HF level, Line current level IF 30 kHz, 200 kHz, 300 kHz, 525 kHz, ... (selector at rear) 1 CRT D7-16GJ Mains 117 or 220V AC Battery External 21-30V DC Dimensions 500 x 350 x 150 mm Weight 13.5 kg Quantity 200 (Bundewswehr, Heer)
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Depending on installed crystals at the rear.
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| | Old | New | Name | Description |
| • | F1 | F1A | CW | Telegraphy with frequency shift keying (RTTY) |
| • | F4 | F1C | FAX | Facsimile |
| • | F6 | F7B | 4FSK | Multi-Frequency Shift Keying (also known as MFSK-4) |
| • | F9 | F1D, F2D | Data | All other data transfer modes |
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© Crypto Museum. Created: Saturday 24 August 2019. Last changed: Thursday, 27 March 2025 - 15:36 CET.
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