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
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 < email@example.com> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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