How often does front end overload make the news?
w3hwn at comcast.net
Mon Dec 4 21:03:16 CST 2006
As noted, this sort of thing isn't exactly news. A certain one of the bands
the FCC has made available to Part 15 (non-licensed) devices, and often used
by garage door openers, is primarily allocated to the military. There was a
case a few years ago where the Navy installed an LOS link in California from
a newly arrived ship to a tower overlooking a valley. Soon garage doors all
over the valley either were non-functional or they spent the day flopping up
and down like a landed fish. The manufacturer tried to get the FCC to inter-
vene but was reminded that Part 15 devices have no status -- if they get QRM
it's tough toenails. The Navy eventually took pity and re-tuned their link.
Garage door openers may not be a threat to national security, but the reverse
is not always true. :-)
At 09:12 AM 12/4/2006, Karl W4KRL wrote:
>DENVER - What do remote-control garage door openers have to do with national
>security? A secretive Air Force facility in Colorado Springs tested a radio
>frequency this past week that it would use to communicate with first
>responders in the event of a homeland security threat. But the frequency
>also controls an estimated 50 million garage door openers, and hundreds of
>residents in the area found that theirs had suddenly stopped working.
>"It would have been nice not to have to get out of the car and open the door
>manually," said Dewey Rinehard, pointing out that the outage happened during
>the first cold snap of the year, with lows in the teens.
>Capt. Tracy Giles of the 21st Space Wing said Air Force officials were
>trying to figure out how to resolve the problem of their signal overpowering
>garage door remotes.
>"They have turned it off to be good neighbors," he said.
>The signals were coming from Cheyenne Mountain Air Station, home to the
>North American Aerospace Defense Command, a joint U.S. and Canadian
>operation set up during the Cold War to monitor Soviet missile and bomber
>Technically, the Air Force has the right to the frequency, which it began
>using nearly three years ago at some bases. Signals have previously
>interfered with garage doors near bases in Florida, Maryland and
>In general, effects from the transmissions would be felt only within 10
>miles, but the Colorado Springs signal is beamed from atop 6,184-foot
>Cheyenne Mountain, which likely extends the range.
>Holly Strack, who lives near the entrance to the facility, said friends in
>the neighborhood all had the same problem.
>"I never thought my garage door was a threat to national security," she
>David McGuire, whose Overhead Door Co. received more than 400 calls for
>help, said the Air Force may be able to slightly adjust the transmission
>frequency to solve the problem. If not, it will cost homeowners about $250
>to have new units installed.
>"The military has the right to use that frequency. It is a sign of the
>times," he said.
>By ROBERT WELLER Associated Press Writer
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Richard Barth *** W3HWN(at)ARRL.NET *** Silver Spring, MD
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