Surveillance and Monitoring Receivers Over the Years


Some HF receivers

(Click on the small photos to enlarge)

The SPARC Museum in Vancouver has a receiver on display that is similar to the one apparently built by the Canadian Government Radio Service.

HRO, 9 tubes, from 1934 - this receiver model was very common in interception centres during the 1939-1945 war. At frequencies above 28 megahertz, use of the Hallicrafter S27 was nevertheless required.

Hallicrafter S27, much more sensitive in the 30 megahertz range.

National NC100, 12 tubes, covered 540 kHz to 30 MHz.

CSR5, made in Montreal by Marconi, from 1942, covers 80 kHz to 30 MHz - frequently used on Royal Navy vessels.

AR88LF made by RCA, a very sensitive, stable receiver.

National's HRO60, less effective than the RCA above. In addition, it required several plug-in coil sets to change bands, which was not very convenient. Covered 50 kHz to 54 MHz, double conversion above 7 MHz, AM and CW.

The Hammarlund HQ129X, from 1945. It was used by the district offices in particular. A bandspread was provided for amateur radio bands. Some offices had the SP600 and others had the GPR90 from Technical Material Corporation.

Racal RA17 circa 1960, the arrival of this receiver in Beaumont made many people happy. Calibrated to the kilohertz, very sensitive and stable, it was relatively easy to modify and adapt for measuring frequencies.

Racal 1217, a transistorized version of the former, with a few changes with respect to conversion. An unstable receiver that was subject to overloading.

Racal 1772, frequency synthesized and enabling easy frequency measurement. A very effective receiver.

Some VHF/UHF receivers

The Eddystone 770R receiver, covering 19 to 165 megahertz and the 770U, with a similar chassis, covering 150 to 500 megahertz. Broadband filter that allowed for some frequency drift on the local oscillator.

Made by Vitro Electronics, apparently the model used by NASA. Relatively sensitive and tolerant to overload through use of the Nuvistor.

Astro SR208.

CEI and Watkins-Johnson, 906A covering 30 to 300 MHz with a 300-1,000 MHz down converter and 60 MHz output. A simple conversion that made it easy to measure frequencies by coupling into a mixer for the local oscillator and the 21.4 MHz IF output.

The modern day receiver, controlled by computer, making it possible to scan thousands of frequencies per minute.


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