Army interferes with garage doors.

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wrote:

Try the news in Orlando.. Nothing compared to NYC, but there is a shooting every night! Crime has been on the rise here for the last 4 years or so. I'd rather have no news and low crime.
Mike
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Not really. The garage door openers are "Part 15" devices - they don't have a reserved frequency allocation. Instead, they (and other low-power devices) are allowed to use a wide range of frequencies that are primarily allocated for other radio services.

A lot of unlicensed (Part 15) devices such as garage door openers and car-alarm keyfobs use frequencies around 433.920 MHz.
The primary usage allocation for this frequency band is government echolocation (radar). Ham radio operators have a secondary allocation (i.e. they can use it as long as they don't interfere with government radar). Unlicensed users are tertiary, and have *no* legal protection against interference from licensed, or other unlicensed users.
The transmitters for these Part 15 devices use very low power, by design and law. The receivers for them are, well, let's say "inexpensively made" - they tend to be reasonably sensitive (so that they can pick up the weak signals from the transmitters) but are not at all selective.
Strong signals from other transmitters, on the same or nearby frequency bands, can overload (saturate) the RF front end circuitry in these receivers - a phenomenon known as desensitization or "desense". When this happens, a strong transmission can completely block the weaker one, even if the actual frequencies of the two transmissions don't overlap at all. It's sort of like trying to hear a low-pitched voice speaking quietly in the next room, when somebody is blasting your eardrums with a piccolo :-)
--
Dave Platt < snipped-for-privacy@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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re: some may have paid for other repairs by mistake, one would assume.
You know what happens when one assumes...
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