Racal RA6790/GM
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| Frequency | RX: 0.5–30 MHz |
| Power | Receiver only |
| Modes | AM, USB, LSB, CW, FM |
| Weight | 22 kg (48.5 lb) |
| Connector | 50-ohm coaxial antenna input |
| Year | 1981 |
| antenna | 50-ohm coaxial antenna input |
Estimated (unverified): Weight ~22 kg (about 48 lb) is approximate and not confirmed on the data sheet. The antenna input is 50 ohm; the exact connector type varies by version. Conceived in the early 1980s (~1981).
Racal's microprocessor-controlled, fully synthesized professional HF receiver. Synthesized tuning to 1 Hz resolution, 100 memories, selectable IF filters and an IF output for external processing. Made by Racal in the USA for a US Navy contract (the military version is the R-2174(P)/URR), it delivered the tuning accuracy and memory that the earlier Wadley-loop receivers could not. Often available as reasonably priced surplus.
It is a heavy 19-inch rack receiver built for fixed installation rather than desktop use, and it is complex to operate and maintain. Documentation is military-style, and the microprocessor board is a known failure point. Some surplus units have restricted or modified frequency coverage.
The RA6790/GM was Racal's solid-state, synthesized HF receiver for professional monitoring, giving operators 1 Hz tuning precision and memory that the Wadley-loop RA17 could not. Built in the USA for the US Navy (as the R-2174(P)/URR) and widely sold to government and commercial users, it remains a high-grade, rugged receiver prized by enthusiasts of military communications gear.
The Racal RA6790 is a professional solid-state HF communications receiver - a microprocessor-controlled, fully synthesized design built to demanding military and government standards. It covers 0.5 to 30 MHz with continuous digital tuning (1 Hz resolution) and receives AM, CW, single sideband and FM, with selectable IF filters and the remote-control capability that professional monitoring and signals work require.
Although Racal was a British firm, the RA6790/GM was designed and built in the United States to fulfil a US Navy contract; the military version carries the designation R-2174(P)/URR, and Racal's UK equivalent was the RA1792. Where the earlier RA17 used the Wadley loop to tame drift, the RA6790 used modern frequency synthesis and digital control for rock-solid stability, precise readout and computer remote operation in a rugged rack package.
The RA6790/GM and related variants saw wide professional service, and it is prized today by enthusiasts of commercial and military communications gear for its performance and build quality. It is a discontinued classic. See the classic tube RA17 and the DSP JRC NRD-545.