Note
QST, Mar 1973, p. 119. (R-4C)
QST, Apr 1975, p. 97.
QST, Apr 1976, p. 103. (extra space for WARC bands)
QST, Dec 1977, p. 152.
The R-4C mirrored the basic appearance of its 4-Line predecessors, but it was a very different receiver. The new triple-conversion model used an 8 kHz wide roofing filter in the first IF at 5645 kHz. The 5695 kHz second IF had a standard 2.4 kHz crystal filter and space for three optional crystal filters ranging in bandwidth from .25-6 kHz. Two L/C circuits in the 50 kHz third IF followed. The pass band tuning had been changed from mechanical to electrical. Additional flexibility was added to the AVC circuit.
