The R-390A Frequently Asked Questions Page

Welcome to the R-390A Frequently Asked Questions (FAQ) Page. The R-390A/URR radio receiver is arguably the best performing high-frequency (HF) receiver of the tube era. Its sensitivity, selectivity, resistance to adjacent strong signal overload and resettability set it far apart from its contemporaries.

It was designed in the early 1950's by Collins Radio Company under government contract and manufactured by a number of companies.

The receiver was used in may different roles in the U.S. military,other government agencies, and civilian operations ranging from point-to-point radio communications to Signals Intelligence (SIGINT) gathering to communications for the Apollo space program.

This compendium of knowledge is assembled to provide those with an interest in restoring, operating, or just reading about the history of the R-390A/URR with a set of reference material to assist in their endeavours.

This page would not have been possible without the generous efforts of many contributors who have provided documentation, recollections, experience, and opinions in abundance. Their contributions are attributed on the pages where they appear.


Provides introductory information about designs, physical characteristics, operational characteristics, intended uses, current uses, construction and features.


Records and recollections about the adventures (and mis-adventures) of the R-390A.


Provides information about each manufacturer of R-390A receivers.


Provides information about variations on the theme of the R-390A receiver. A 24 volt watertight version was produced for mobile operation. A lightweight version was produced for airborne operation. Specialized versions for remote operation, very low frequency (VLF) operation, and for use with frequency synthesizers, etc. were also produced.


Provides links to reports, manuals, books, videos, web pages, magazine indexes and other periodicals

Systems and Accessories

Provides information about R-390A communications systems, accessories used with the R-390A and some current accesory information.


Provides information about tube line-up, restoration, modification, operation and maintenance

Send Comments to the FAQ-Meister: (root[at]r-390a[dot]net)
Version: 15 - - Last revision: 2015-May-12