This is a page devoted to the R-390 and R-390A state of the art receivers.
The R-390 is a double / triple conversion superheterodine receiver, designed by Collins and manufactured from 1950 to 1954. It uses a mechanical digital dial, has a PTO and supports AM and CW modes. It has 32 bands of 1MHz bandwidth each, covering from 0.5 to 32MHz. Its IFs are 9 to 18Mhz (only for 0.5 to 8MHz), 3 to 2Mhz and 455KHz. It has 32 tubes plus one semi-diode. Filtering is made with crystal and cascaded L/C filters at 455KHz.
The R-390A was developed in 1951 by Collins as a reduced cost R-390 and was by far more popular than its predecessor. It is also a double / triple conversion superheterodine receiver and covers the same frequencies (from 0.5 to 32MHz). It also uses a mechanical digital dial, has a PTO and supports AM and CW modes.The IFs are 17.5 to 25MHz (only for 0.5 to 8MHz), 2.5 to 2MHz (0.5 to 1MHz band only), 3 to 2MHz and 455KHz. It has one crystal (for 0.1 and 1KHz bandwidths) and four mechanical (for 2, 4, 8 and 16KHz bandwidths) filters at 455KHz IF. It has 26 tubes.