Note
Osterman, fourth edition, p. 107.
Many consider the Collins R-390 to be the ultimate receiver from the vacuum-tube era. In some ways it still surpasses anything made since. The 32-tube, 65 lb. set tuned from 0.5 to 32 MHz in 32 bands. The receiver's PTO was linked to a mechanical counter, providing a digital readout in an era when that was uncommon. It employed a crystal filter and L/C circuits in the IF to provide a range of selectivity from 0.1 to 16 kHz. The R-390 was triple conversion below 8 MHz and double conversion above that.
The R-390A shared design similarities with its predecessor, the R-390. The 26-tube set offered a selection of crystal and mechanical filters in its 455 kHz IF. It was introduced in 1954 as a lower cost alternative to the R-390 and remained in production for 30 years. A dozen other companies joined Collins in manufacturing the R-390A under contract.
References
Modifications. Ham Radio, Nov 1975, p. 66.
