was in 1984. As the military procured newer receivers, many R-390As were released to surplus while others were destroyed. Some receivers were retained by the services, however, when they found that the R-390A's vacuum tube circuitry could easily survive an electromagnetic pulse. There are reports, possibly apocryphal, that R-390A receivers are still in use aboard U.S. Navy submarines since the receiver can withstand the strong radio frequency fields found aboard ship. Many of the R-390As that exist today are in the hands of vintage amateur radio collectors and amateur radio operators who contend that few modern solid state communications receivers can equal its performance. There is a wealth of information, both printed and electronic, devoted to R-390A restoration and maintenance, as the R-390A is widely considered an example of the best of vacuum tube technology. See also ART 13 transmitter ARC-5 BC-348 BC-654 Collins Radio Hammarlund super pro National HRO Vintage amateur radio 75A-4 and KWS-1 References Further reading External links Amateur radio receivers Military radio systems of the United States Military electronics of the United States Equipment of the United States Air Force Models of radios Telecommunications equipment Military equipment introduced in the 1950s