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)
Collins product catalog, 16M-CR-12-74
QST, Apr 1975, p. 2. (75S-3C - first reference in QST advertising)
QST, Feb 1977, p. 117. (75S-3C)
The successor to the 75S-1 added rejection tuning, a choice of crystal or variable BFO, and a 200 Hz CW filter. Other changes included concentric knobs for the RF and AF gain controls and selectable AVC.
The later 75S-3A version added extended frequency coverage with the addition of another 14-position crystal deck.
References
A switch for cross band with the 32S-3. 73, Jul 1967, p. 82.
Frequency synthesizer for. Ham Radio, Dec 1975, p. 8.
Improved selectivity. Ham Radio, Jun 1976, p. 36.
Improved frequency readout. Ham Radio, Jun 1976, p. 53.
Better CW performance. 73, Nov 1971, p. 93.
