The R-390A Frequently Asked Questions Page

R-390A Variations
The R-390A receiver inspired a number of variations and extensions of the basic design by Collins Radio. To see a front photo of an R-389, R-390, R-390A, R-391, or R-392, click here for Luca Fusari's website.


 The R-389 is a Very Low Frequency (VLF) version of the R-390.

The R-390 was the predecessor to the R-390A. It was expensive, complex and difficult to maintain. Its use of LC filters in the IF strip makes it desirable for broadcast band DX enthusiasts because of less passband distortion versus the mechanical filters in the R-390A model. The R-390's innovative design pattern inspired many variations.

The R-390A was produced as a lower cost replacement for the R-390 receiver. It was produced in large quantities and is the most plentiful of the R-390 variants. While it shared the R-390 pattern, most components of the R-390A are not interchangeable with the R-390. The R-390A is distinguished by the location of the antenna trim control located in the upper center of the front panel and by the lack of a squelch control.

The R-391 is an auto-tune version of the R-390. 24 volt motors turned the megacycle and kilocycle knobs to one of xx preset frequencies.

The R-391A is an auto-tune version of the R-390A. 24 volt motors turned the megacycle and kilocycle knobs to one of xx preset frequencies.

The R-392 is a 28 volt watertight radio that used the R-390 pattern to produce a portable/mobile radio that performed quite well. It was teamed up with the T-195 transmitter to create an effective portable HF communications terminal.

The R-648 used the R-390 pattern to create a lightweight airborne HF receiver. Click here to see picture.  Click here for more information on Radio Blvd, then search for R-648. 

The R-725 was a R-390A where the standard IF deck, which contained mechanical filters, was replaced with one containing LC filters. The LC filters had less phase delay across their passband and offered better performance in direction-finding work.  The front panel is the same as an R-390A.  For more information on 'Radio Blvd', click Here and scroll down two pages.

The R-9xx is alleged to have contained a small LED digital readout where the veeder root counter exists in the center of the R-390A. No documentation or photographs of this model have surfaced.

However, an auxiliary digital frequency readout accessory was developed for the Office of Naval Research in 1969. The design report (DSD R-259) is available in the U.S. Navy section of the FAQ references page.


R-1247/GRC-129 receiver was not developed for NASA as is often reported, but for the U.S. Air Force. Developed under contract AF 30(635)30962 by Manson Laboratories, GRC-129 was a frequency synthesized, SSB upgrade to the older AN/GRC-26D mobile, truck mounted HF "RATT" system used by the Army and Air Force.  See the 'AN/GRC-129' entry in the 'Systems and Accessories' page on this website.

NASA did acquire a few R-390As equipped with Manson Labs synthesizers, and these were briefly used at the Bermuda Tracking Station, and perhaps others. But, they were quickly removed from service due to problems with the synthesizers.

Many stock R-390As were used by NASA throughout the ground network, and on the Apollo Tracking Ships as general purpose HF receivers, and especially as tunable IFs for downconverters.


The R-1981 was a R-390A modified to bring out the 17 MHz HFO and the VFO signals to the rear panel and to insert an error correction signal for high-stability operation. It was a part of the TSC-25 communications system. The modifications were done using a kit of parts from The Technical Material Corporation (TMC) under contract number 14385-PC-58.
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Version: 8 - - Last revision: 2022-Sep-09