R-390A

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The R-390A /URR is a general coverage HF radio communications receiver designed by Collins Radio Company for the US military.

R-390A radio receiver
R-390A radio receiver


Contents

[edit] History

The R-390A military shortwave radio receiver was the result of a project undertaken by the U. S. Army Signal Corps in 1954 to replace the existing R-390 receiver then in use. The R-390 had done its job so well that the Corps decided continued use of this type of receiver necessitated an improved, reduced-cost version.

Originally built by Collins Radio Company in Cedar Rapids, Iowa, the R-390A was designed by two teams. The mechanical team was led by Fred Johnson while the electronics team was overseen by Collins' Ernie Pappenfus, K6EZ. Besides Collins Radio, 12 other sub-contractors (including Motorola, Stewart Warner, Stromberg Carlson, Capehart, Teledyne, and others) built R-390As until the last one rolled off the assembly line in 1984. Banks of these radios served the country in all branches of the US military. Additionally, they found service with the CIA and NSA to monitor communications from behind the Iron Curtain. During the Cold War years, the R-390A was so valued it was classified top secret, a security measure which remained in force until the mid-1960s.[1]

[edit] Design

The R-390A is a general coverage radio receiver capable of receiving amplitude modulated, code, and frequency shift keying signals. Its tuning range is from 500 kilohertz to 32 megahertz, in 32 one-megahertz bands. The circuit is the superheterodyne type, double conversion except on the lower bands where triple conversion is used. It employs 26 vacuum tubes, a larger than normal count for most general-coverage receivers. The receiver weighs 85 pounds and can be operated on 120 volt or 240 volt supplies. It fits neatly into a standard 19 inch relay rack.

Tuning of the R-390A's radio frequency and intermediate frequency front end is synchronized by means of an ingenious mechanical system of racks, gears, and cams. When the front panel tuning controls are rotated, this system raises and lowers ferrite slugs in and out of the receiver's tuning coils. This ensures that all front-end circuits are tracked, meaning all circuits are tuned to the correct frequency to maintain excellent selectivity and sensitivity. The receiver's construction is modular for easy servicing. Each major area of the receiver is contained in easily removable subassemblies, and these can be repaired or replaced as needs be. Though the R-390A is mechanically and electrically complex, alignment and servicing were designed to follow simplified procedures published by the Signal Corps.

[edit] Use

The R-390A was deployed to most branches of the US military and remained in general use through the 1980s. The last major update to its documentation 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.

[edit] See also

[edit] References

  1. ^ http://www.r390a.com/html/history.htm R-390A History

[edit] General References

  • Rippel, Chuck. R-390A History and R-390A Overview. The R-390A/URR Home on the Web. (9-11 January 2003)
  • Couillard, L. W, Cost Reduction Program for Radio Receivers R-390. Cedar Rapids, Iowa: Collins Radio Company, 1952
  • United States Department of the Army, Technical Manual TM-11-5820-358-35: Radio Receiver R-390A/URR. Washington, DC: Government Printing Office, 1961.