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CIA Bugs ← ST-2A
Solid state surveillance transmitter · 1959
- this page is a stub
RT-3R was a solid-state 1 covert listening device,
also known as a surveillance transmitter
or a bug, developed around 1959 by the
Technical Services Division (TSD, later OTS) of the US
Central Intelligence Agency (CIA).
It was an improved version of the RT-3 transmitter [A],
which in turn was the successor to the ST-2A.
The device operates in the VHF-L band (56 to 84 MHz) and uses
Frequency Modulation (WBFM).
Confusingly, the device is also known as ST-3 and as SRT-3.
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The bare transmitter measures just 97 x 45 x 19 mm and weight no more
than 170 grams.
It is housed in an aluminium enclosure with black wrinkle paint finish.
Power is provided by an external battery pack or by the purpose-built
ST-3PS mains PSU. The transmitter was supplied with a
Shure MC-30 dynamic microphone,
attached to the end of a long shielded cable.
The circuit is nearly identical to that of the ST-2(A),
except that the 1AD4 valves in the RF-stages have been replaced by 2N500
transistors.
The image on the right shows a complete kit.
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The ST-3PS power supply unit is now shown in this image, but is fully described
in the manual [A]. A switch receiver, or Latching Radio System — LRS-1 —
was later tested with the RT-3. It allowed the transmitter to be remote controlled, making it more difficult to discover.
There seems to be some confusion in the nomenclature of this device. Initially,
it was assigned the designator ST-3, in line with earlier surveillance
transmitters like the ST-1 and ST-2A.
At that point, the unit still had a built-in AC mains PSU.
The name BT-2 was used for a battery powered variant.
Along the project, it was renamed RT-3, (Radio Transmitter).
It is likely that the prefixes 'ST' and 'RT'
were later merged into 'SRT', which stands for Surveillance Radio Transmitter.
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In this context, solid-state means that it was built with transistors
rather than valves (tubes).
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Device Covert listening device (bug) Purpose Room overhearing Developer Technical Services Division (TSD) of the CIA Model RT-3R, ST-3, SRT-3 User CIA Frequency 55 to 81 MHz (see below) Modulation FM Sensitivity 1 to 3 kHz/100µV Response 500 - 5000 Hz ±1dB Hum/noise 500 Hz max. Microphone Shure MC-30 Output ≥ 7 mW into 50Ω load Power ≤ 65 mW Voltage 6.5V ±0.5V Current ≤ 10 mA Antenna ¼λ whip Dimensions 97 x 45 x 19 mm Weight 170 g Finish Black wrinkle paint Quantity 305 (est.)
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Green 55 - 63 MHz Blue 64 - 72 MHz White 73 - 81 MHz
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Batteries 5 × Mallory RM-12R cells connection in series Exterior Carboard case. Lifetime ≥ 360 hours Wiring Cable for connecting further battery packs in parallel
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Input 105/210V AC ±20%, 50-60 Hz Output 6.5V DC ±0.5V Current 0 - 15 mA Ripple ≤ 0.5% Dimensions 132 x 22 x 24 mm Weight 285 g Finish Black wrinkle paint
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Green 55 - 63 MHz Blue 64 - 72 MHz White 73 - 81 MHz
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Declassified in part and approved for release by CIA on 29 May 2012.
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© Crypto Museum. Created: Tuesday 22 September 2020. Last changed: Monday, 28 August 2023 - 14:36 CET.
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![Complete RT-3 kit as shown in the manual [A]](img/CIA_RT3_set.jpg)