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Spy radio set
The RS-1 is a robust valve-based spy radio set that was developed in the USA
by the CIA and Radio Development and Research Corporation
at the start of the Cold War, probably around 1948. The first units
appeared in the field around 1950. They were intended for use by CIA field
agents and for stay-behind organisations. The US Army adopted it in 1961
and designated it GRC-109.
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The RS-1 consists of separate modules that are each housed in a
water-tight container, allowing the radio to be stored under
harsh conditions for an extended period of time.
Each box has a lid with 4 screws at the corners and
a rubber gasket to protect it against water. The set is heavy and
can withstand air droppings and being buried in the ground;
ideal for stay-behind organisations.
An example of a complete radio station is shown in the image on
the right. It consists of a T-784 transmitter,
a R-1004A receiver and a PP-2684 (or the small PP-2685) power
supply unit (PSU).
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The CIA used the RS-1 spy set in many countries around the world,
such as South-East Asia, some countries behind the former Iron
Curtain (East-Europe), Vietnam, Tibet and Cuba.
With the CIA it lasted for nearly 15 years because of its proven
track record and reliability.
The Army used it even longer,
despite the fact that newer and lighter spy sets had become available
in the meantime.
The RS-1 went out of production in 1964 and was used well into the 1970s.
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The RR-2 is a single-conversion super heterodyne receiver with 6 valves:
RF pre-amplifier (1T4), local oscillator/mixer (1L6), 2 x IF amplifiers (1T4),
AF amplifier (1U5) and a BFO (1T4).
The intermediate frequency (IF) is at 455 kHz.
The receiver can be crystal or VFO operated.
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The image on the right shows an RR-3B receiver.
It covers 3 to 24 MHz over 3 ranges:
- 3 - 6 MHz
- 6 - 12 MHz
- 12 - 24 MHz
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The transmitter was suitable for CW only and covers 3 to 22 MHz in 4 ranges.
It contains just 2 valves: an 6AC7 for the crystal oscillator and a 2E26 for
the RF power amplifier.
The output power is 12-15W (at 3-15MHz) and 10-12W (at 15-22MHz).
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Two different types of power supply are available for this set:
a small one (RP-2) at the same size as the transmitter and receiver,
and a large one (RP-1) that has a built-in power inverter.
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Power Supply Unit RP-1 (PP-2684)
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The RP-1 is the larger of the two power supply units. It can
be used to power the RS-1 radio station from virtually any mains
voltage in the world.
In addition it contains a built-in power invertor, allowing the
radio to be powered by a 6V DC source such as a car battery.
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The RP-1 could also be used to recharge the 6V battery from
the mains.
The RS-1 could also be used in combination with the SSP-11
hand-crank generator, which was a modified version of the GB-58.
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Power Supply Unit RP-2 (PP-2685)
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The smaller RP-2 PSU has the same size as the RX and TX units.
It is suitable for connection to the mains only and does not
have a DC or battery input.
Note that the mains plug is made
of rubber, so that the two contact pins can be pressed together
in order to fit a variety of mains sockets.
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In order to avoid detection by enemy eavesdroppers, it was necessary
to be on the air as short as possible. The Army version of the RS-1
was therefore modified to allow an AN/GRA-71
burst encoder to be connected.
A limited number of CIA sets was also modified for use with this
burst encoder and the RT-3 transmitter was then renamed RT/D-3.
 More information
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Connecting the Burst Encoder
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When using the RS-1 in combination with the
AN/GRA-71 burst encoder described above,
the encoder has to be connected to the special socket, marked
KEYER, just above the internal morse key of the T-784 transmitter.
This socket is only available on modified T-784 transmitters.
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Keyer socket (M10S)
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The actual burst encoder of the GRA-71, the so-called KE-8B Keyer,
can be connected to the T-784 transmitter, using the
KA-3 Keyer Adapter as an interface. It converts the low-voltage
signals of the transistor-based GRA-71 into the high-voltage levels
of the valve-based T-784.
The transmitter is modulated by
switching the Anode of the Power Amplifier (PA) valve in the rithm
of the morse data. During transmission, the transmitter's oscillator
is kept running by an R/C timing circuit inside the Keyer Adapter.
The oscillator is turned off automatically approx. one second
after the last (morse) character has been sent by the burst encoder.
The Keyer Adapter also contains a stabilizer for the PA screen grid
voltage. Please refer to the circuit diagram of the Keyer Adapter
in the GRA-71 Depot Maintenance Manual for further information [2].
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Originally, the set was called RS-1 by the CIA.
Around 1961 the US Army adopted the set for their special forces (DF)
and designated it AN/GRC-109.
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| Description
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CIA
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Army designation
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| Complete radio set
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RS-1
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AN/GRC-109
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| Transmitter
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RT-3
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T784/GRC-109
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| Receiver
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RR-2
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R1004A/GRC-109
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| Large PSU
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RP-1
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PP-2684/GRC-109
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| Small PSU
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RP-2
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PP-2685/GRC-109
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| Burst Encoder (optional)
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GRA-71
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AN/GRA71
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| Hand-crank generator
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SSP-11
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GN-58 (mod)
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| Maintenance kit
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(unmarked)
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CY-1321/GRC-109
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Supersedes TM 11-5835-224-45, 15 February 1967,
and TM 11-5835-224-45P, 24 June 1966.
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Saturday, 29 December 2012 - 13:12 CET
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