Note
QST, Aug 1961, p. 2.
QST, Jun 1963, p. 161. (75S-3A)
QST, Mar 1964, p. 2. (75S-3B - "what's new?")
QST, Jan 1965, p. 140. (75S-3B)
QST, Feb 1966, p. 2. (75S-3B)
QST, Apr 1967, p. 2. (75S-3B)
QST, Feb 1968, p. 2. (75S-3B)
QST, Oct 1970, p. 2. (75S-3B)
QST, Sep 1971, p. 2. (75S-3B)
QST, Nov 1972, p. 2. (75S-3B)
QST, Apr 1975, p. 2. (75S-3C - first reference in QST advertising)
Collins product catalog, 16M-CR-12-74
QST, May 1976, p. 2. (75S-3C)
QST, Feb 1977, p. 117. (75S-3C)
The 75S-3B and C continued the evolution of the Collins S/Line receiver. The B model added flexible selectivity choices to those found in the 75S-3. It was supplied with a 2.1 kHz mechanical filter and had plug-in sockets for three others. These were selected by the front-panel Mode switch. Zener-diode regulation was added to improve oscillator stability.
The 75S-3C was the expanded crystal-deck version of the 75S-3B.
References
Improved selectivity. Ham Radio, Jun 1976, p. 36.
Improved frequency readout. Ham Radio, Jun 1976, p. 53.
