The R-391/URR Page

by Josh Rovero, KK1D

Updated: July 22, 2008

The R-391 is the autotune version of the famous R-390.  A separate power 28 VDC power supply is required for autotune operation.   Much rarer than the R-390 and R-390A, with only 1440 ever made.

Almost everyone has the provisional Collins manual rather than the official TM11-863.   Dean Davidson managed to find it in the library of the Australian Army Signals Museum in Melbourne, and to obtain a copy of the real thing.     The manual, that is, not the radio. Dean reports that the R-391 and accessories are also on display.

The electronic aspects of the R-391 are very similar to the R-390 (non-A).     Dual 6082 tubes are used as active voltage regulators for all receiver B+ voltage (the R390A uses a split unregulated/regulated B+ scheme).     There has been some recent traffic on the mail lists about a solid-state replacement that would eliminate at least the 30 watts of filament power the 6082s dump into the lower receiver chassis.

Some parts are also the same as the R-390A.   The Carrier Meter adjust pot, power supply rectifiers and ballast tubes are the same, and can be repaired/replaced in the same fashion as one would a R390A.

References:

1. Army TM 11-863, Radio Receiver R-391/URR, 21 March 1955.
2. "Communications Receivers, The Vacuum Tube Era 1932-1981", 3rd Edition, by Raymond S. Moore
3. "Shortwave Receivers Past & Present", 2nd Edition, by Fred Osterman
4. Contributors