February 28, 1964 Electronics
[Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Electronics,
published 1930 - 1988. All copyrights hereby acknowledged.
In the early 1960's, the U.S. Air Force's Air Defense Command began installing high power AN/FPS-24 long range radar units in some of the country's major seaboard and northern cities. Designed to watch for ICBM's and intruding long-range aircraft from the U.S.S.R., it operated in the VHF band at a 7.5 megawatt peak power output. Once operational, nearby residents immediately began lodging complaints about severe bleeps of interference on radios (AM, FM, mobile radio, wireless surveillance) and television that occurred once every 12 seconds - the rotation period of the radar's 120-foot-wide by 50-foot-tall antenna. The USAF's response was to blame the problem on crappy receiver design by all the manufacturers, and refused to take any action to mitigation the problem. Many science and engineering magazines reported on the heated battle, and eventually the government was forced to yield. Other than instituting blanking in the direction of specific key off-site commercial broadcast installations, I do not know what, if any, other actions were taken.
I have told the story before about how the S-band airport surveillance radar (ASR) I worked on in the USAF caused my car radio to beep with each antenna rotation when within about half a mile of the system. See a reader response to this article.
Radar Adds Beep to Home Sets
Pittsburgh residents are complaining to Air Force that the new AN/FPS-24 long-range radar outside of town is causing audible beeps every 12 seconds on their TV, radio and hi-fi sets. And since Air Force, with FCC backing, blames the problem on set design, manufacturers can expect some customer complaints - and not just from Pittsburgh. Air Force is installing 24 of the big radars around the country, as part of an up-dated detection network.
Investigations have put the blame on home-equipment overload and audio-system detection of the powerful radar emission rather than spurious signals from the radar. Air Force sends complainants mimeographed instructions on how to modify their sets and tells the set owners they must pay the cost-$5 to $25 a set. The modifications don't always work. Some die-hard audiophiles, according to one report, are even moving to locations shielded from the radar beam by natural obstacles.
FCC's Buffalo, N.Y., office, which is fielding the Pittsburgh complaints, says it isn't taking any specific action. It classes the beeps with interference from ham radios, citizen's band, industrial and other r-f equipment. The solution, FCC indicated, is better interference-prevention design in the sets, such as additional bypassing and shielding.
Posted September 7, 2018