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110 Watt base station transmitter
- this page is a stub
- wanted item
URT-11 1 was a valve-based HF/CW base station transmitter for diplomatic
and spy radio traffic, introduced in late 1953 by the US
Central Intelligene Agency (CIA) as the successor
to the similar RT-1-B. It is suitable for frequencies
between 3 and 30 MHz and produces 75-100 W output [1].
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The URT-11 was developed as successor to the RT-1-B, which had
some issues, especially when sending messagesin CW
(morse code). The exteriors is of the two devices are
nearly identical, but there are some intrnal changes.
In early September 1953 it was reported that the first URT-11 units would
be delivered later than month [2]. During its lifetime, the accompanying
power supply unit (PSU) was modified at least once, in 1957, when it
exhibited transiet problems [3][4][5].
The URT-11, whch was also known as an Emergency Transmitter,
was in use until at least 1969 [9].
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In CIA nomenclature, 'URT' is the abbreviation of Universal Radio Transmitter.
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Differences with the RT-1-B
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- XTAL/VFO selector on side panel (rather than front)
- Single crystal socket (no socket for 3/4" spacing)
- Improved crystal oscillator (with 6AG7 rathr than 6AC7)
- 6AU5 P.A. screen clamper valve (rather than 6Y6)
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Device HF Base station transmitter Purpose Long-distance diplomatic and spy radio traffic Model URT-11 Manufacturer ? User CIA Year 1953 Predecessor RT-1-B (1950) Frequency 3-30 MHz Bands 5 (see below) Output 100 W (3-21 MHz), 75 W (21-30 MHz) Valves (see below) Power 115V AC 1 Dimensions 243 × 264 × 356 mm (HWD) Weight 16.33 kg Quantity 87 ~
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The device was made for the US mains voltage of 115V AC.
For other mains voltages, use the 2000 W VARIAC.
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- 3-5 MHz
- 5-8 MHz
- 8-13 MHz
- 13-21 MHz
- 21-30 MHz
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6AG7 Oscillator/VFO, doubler 2E26 Driver 4-65A Final 0D3/VR-150 Regulator 6AU5-GT Clamper
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Device Mains power supply unit Purpose Providing DC voltages for URT-11 transmitter Input 115 V/AC 50-400 Hz Output 1350 V/DC 200mA, 500 V/DC 100 mA Dimensions 243 × 264 × 362 mm Weight 28.8 kg
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Device 2000 W VARIAC Purpose Connecting URT-11 (PSU) to different mains AC voltages. Dimensions 245 × 264 × 356 mm (HWD) Weight 18.2 kg
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Surviving serial numbers [1]
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40 URT-11 Pete McCollum, USA 70 URT-11 Unknown 70 PSU Unknown 86 URT-11 Unknown 328 URT-11 Found in Greece 354 PSU Found in Greece
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- Pete McCollum, The RT-1-B and URT-11 Transmitters
Spy Radio (website), 1999-2024.
- Security Information - News letter
About delivery of 2ST (Class 'C') Mobile Units and delay of the URT-11.
CIA, 9 September 1953. SECRET.
Declassified by CIA on 30 March 2001.
- Memorandum - Information about Modification Work Orders 10, 19 and 20
About modifying the URT-11 and URT-1B transmitters in use or in stock.
CIA, 12 August 1957. SECRET.
Declassified by CIA on 13 November 2002.
- Material Support Branch, Monthly Report 1 August - 31 August 1957
About the modification of 10 URT-11 units.
CIA, 31 August 1957. SECRET.
Declassified by CIA on 13 November 2002.
- Trip Report,
- 18 August 1957
About power supply issues with URT-11.
CIA, 19 September 1957. SECRET.
Declassified by CIA on 14 February 2012.
- Monthly Report, 1 February - 28 February 1958
About modifying URT-11 for use inside a van.
CIA, 28 February 1958. SECRET.
Declassified by CIA on 12 July 2001.
- Installation & Maintenance Staff, Monthly Report, 1 December - 31 December 1958
About repair needed for URT-11 installed in a transmitting van.
CIA, 31 December 1958. Page 5. Confidential.
Declassified by CIA on 1 May 2002.
- R&D Lab, Monthly Report, 1 December - 31 December 1958
About transient problems with URT-11 power supply unit.
CIA, 31 December 1958. Page 3. SECRET. Confidential.
Declassified by CIA on 2 May 2002.
- Staff Emergency Transceiver Specification
About replacement of existing RT-1-B and URT-11 Transmitters.
CIA, 31 January 1969. SECRET.
Declassified by CIA on 15 August 2000.
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© Crypto Museum. Created: Monday 17 November 2025. Last changed: Monday, 17 November 2025 - 15:27 CET.
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