The RA.1772 is a fully synthesized, solid state, communications receiver providing reception facilities for I.s.b./u.s.b. (A3A,A3H,A3J), i.s.b. (A3B), a.m. (A3) and c.w.(Al).

The built-in synthesizer is phase-locked to the output of a 5 MHz frequency standard and covers the frequency range 15 kHz to 30 MHz. The MHz selection is in switched 1 MHz increments; a single-knob tuning control tunes the synthesizer continuously over each 1 MHz band, with switched selection of FAST or SLOW tuning rates, or LOCK. In the LOCK position the synthesizer is disconnected from the kHz tuning control. At the ends of each 1 MHz band, the tuning provides a 20 kHz overspill to eliminate the need for reverse tuning of the kHz control. Overspill is indicated by an illuminated lamp behind the appropriate MHz dial setting, above or below the setting initially selected. An electronic digital display indicates the kHz setting to 10 Hz.

A built-in meter may be switched to indicate r.f. and a.f. signal levels as well as supply-voltage levels. A slow-motion BFO control is provided for c.w. operation.

A switched monitor loudspeaker is provided and two front panel mounted jacks permit headphone monitoring of the output selected by the MODE switch. When the right-hand phones jack is in use the internal loudspeaker is muted.

A rigid, die-cast, full-width chassis provides the basis for the main frame of the receiver. Mounted within compartments on the underside of this chassis are the first and second mixer boards together with three boards of the frequency generation system (hf loop board, transfer loop board and the 74 MHz generator board).

Mounted on the top of the cast chassis is an aluminum box structure which houses six printed-circuit boards, each individually screened. These printed-circuit boards may be hinged out and then fixed in position for servicing. Also mounted on the top of the chassis is the frequency standard module and the power supply transformer. The power supply regulator board is mounted on the inside of the rear panel and adjacent to this board are mounted the power supply smoothing capacitors. The power supply regulator output transistors are mounted on a heat-sink attached to the rear panel of the receiver, A further power supply board, the af and memory regulator board, is mounted adjacent to the power supply transformer, The display board (including the digital display) is mounted on the inside of the front panel, the logic board is attached to the front panel MHz switch, and the meter switching board is attached to the front panel METER switch.

A 12-volt battery module can be mounted on the rear panel of the receiver to preserve the frequency determining information applied to the synthesizer should a brief interruption of the main power supply occur.

The receiver may be safely operated (for servicing) with both the front and rear panel assemblies lowered in order to gain access to preset controls and other components.

Something to watch out for when purchasing these receivers is the condition of the wiring looms. Like the looms in the Ra17 PSU compartment, heat causes them to become very brittle and the first indication of problems is when lifting out the pcb's or lowering the front or rear panels to work on the receiver. As the looms flex, the insulation on the wiring cracks and small pieces break off leaving the wires bare. This is a very common problem with the Ra1772 and a major job to rectify. Luckily, this one appears to be OK is this respect.