(c) 2004,2024 Peter McCollum

ELINT and SIGINT - Electronic and Signals Intelligence, and Surveillance

ELINT and SIGINT, or Electronic Intelligence and Signals Intelligence, involve monitoring the transmissions of the opposition, and studying the received signals to learn not only their message content, but also to learn the capabilities and limitations of the technology. For example, a major ELINT activity during the Cold War was to monitor Soviet missile tests, and try to determine the capabilities of the missiles, their payloads, and the radar systems used to track them. Some very important data is acquired by intercepting various radio signals related to a missile launch. These signals include rocket telemetry, radar pulses, and also the 'human' communications that may be discussing the launch.

Several companies made VHF and UHF surveillance and telemetry equipment for various government agencies during the 1950’s and 1960’s. CIA documents include references to the following receiver models: Communications Electronics Inc. (CEI) models 901 and 904; and Nems-Clarke models 167-J2, 1302A, 1306, 1501, 1702A, and 2801.

See Terry O'Laughlin's site for much more info on these types of equipment.


Surveillance Receivers

These receivers were used by CIA to monitor listening devices (‘bugs’), and in the R&D Lab to support the development of various surveillance devices.

The Nems-Clarke model 1306, as shown in the manual. Released in 1961, it tunes 30-260 MC in two bands, with separate front-end tuners for each band, and four separate IF strips providing bandwidths of 10 KC, 300 KC, 500 KC, and 1 MC. Click HERE for the 1306 manual.


An example of the Nems-Clarke 1500 series Surveillance Receivers. Models include the 1501, 1502, 1503, 1509, 1510, 1511, and 1512. Most models cover 55-260 MC, but some are 40-180 MC. The first I.F. is 21.4 MC, which makes them compatible with panoramic adapters used by other brands, such as CEI and Watkins-Johnson. Most models use a 6J4 as the RF front-end; but in some models the 6J4 is preceded by a 416B planar triode for better sensitivity and/or noise figure.


Telemetry Receivers

Many VHF telemetry receivers in the 1960’s tuned only the IRIG telemetry band from 216-260 MC, but some more flexible models supported plug-ins for wider coverage. Specializations for telemetry use included wide bandwidths, frequency deviation meters, and ‘video’ output connectors.

The Nems-Clarke model 1400 Telemetry Receiver tunes 216-245 MC, and was used extensively in the Atlantic Missile Test Range. It is the second major receiver model following the 167, and was made in the 1950’s, after the Nems-Clarke name was incorporated in 1951. [The preceding name was NEMS, an abbreviation for National Electrical Machine Shop. Note that NEMS was the manufacturing contractor for the RS-1 agent radio set, after initial production done by RDR.] A 1961 catalog includes various 1400-series models, but no longer this particular model. Click HERE for the 1400 manual. Related 1400-series models include the 1401, 1403, 1412, 1432, 1433, and 1455.

Nems-Clarke model 1400 Telemetry Receiver, serial # 238. Controls are, from left to right: audio gain, I.F. selector (100 KC or 500 KC), deviation range select (25, 75, or 150 KC), 2nd L.O. frequency adjustment, and front-end tuning. The meters indicate frequency deviation, tuning, and signal strength. The power supply filter caps, and many of the tubes, are dated 1957. This particular unit is believed to have been used by Martin-Marietta in Colorado Springs in 1965-66, to monitor the LES-3 satellite beacon, which broadcast on 232.9 MC. Inside view of the model 1400 . Author's collection.


Nems-Clarke model 1401A. This model seems to represent a transition between the 1400 and the 1412, and Nems-Clarke is now owned by Vitro Corp since 1957. The internal circuitry is almost identical to the 1400, except that the upper limit of the tuning range has expanded from 245 MC, up to 260 MC. The front panel is the same as the 1412, but the knobs are the style used on the 1400. A model VF-1400A transistorized VFO option is installed in the crystal socket. Author’s collection.


Two other models from the 1400 series - a model 1412 (left, nearly identical to the 1401A shown above), and a model 1433. These models are seen in a 1961 catalog. Click HERE for the 1412/1432 manual.



Nems-Clarke model 1037F-39 Multi-Range Telemetry Receiver. The model 1037 represents one of the last models from Nems-Clarke before the Vitro Electronics telemetry receiver line was sold to DEI in the mid-1960’s. It was developed for the Mercury and Gemini space programs. The example shown here was made in 1965. The 1037 series (with letter suffixes from ‘A’ to ‘G’) supports plug-in modules for the front-end tuner and the discriminator. With various tuners, the frequency range is 55 to 2300 MC. The technology is a mix of tubes (in the RF tuner only) and transistors. Click HERE for a block diagram, and notes on the functionality of the rear-panel connectors. The blank panel in the upper-right is for an optional spectrum display unit. Author’s collection.


Defense Electronics Inc. (DEI) model TMR-5A. This example was made in 1963. DEI was formed by former employees of Nems-Clarke. Nine RF plug-ins were available to cover the range from 55-2300 MC. The “Video Unit” plug-in (on the left) supports at least 11 different IF amplifier modules, and 4 demodulator modules. Author’s collection.