Note
Ham Radio, Jan 1971 p. 70.
The Collins 651S-1 is versatile general purpose receiver providing reception from 0.4 to 30 MHz, with tuning phase-locked in 100-Hz steps.
Because of the unique tuning system, the convenience and "feel" of traditional receiver tuning is not sacrificed as a result of using discrete 100-Hz frequency steps. Large changes in frequency are aided by the 0.1-MHz and 1-MHz selector knobs.
Capabilities of the radio include computer programming, independent sideband, narrow band FM, operation from a remote control head, comparability with secure voice modems, phase-locked or manually adjusted VBFO, and syllabic squelch providing better reception of a weak voice signal in the presence of background noise.
Frequency readout on the front panel is provided by six, seven-segment vacuum fluorescent tubes.
The receiver construction techniques include Collins multilayer circuit boards mounted in plug-in card installations with blue-line connections. Microelectonics logic and linear circuits are utilized. The plug-in card technique, along with convenient arrangement of other parts of the radio, provides easy accessibility. The receiver has no mechanical linkages - all tuning and band switching is performed electronically.
References
Brief description. Ham Radio, Jan 1971 p. 70.