Re: Wacko beams focuses on Las Vegas?


Message posted by lone wolf on February 22, 2004 at 11:12:18 PST:

They have the ea6b jammer, but I don't know the frequencies that it jams. The article is more or less accurate except for WIFI being in the same band as the keyless remotes. [WIFI is 2.5 and 5.4 Ghz)

It used to be pretty common to read about garage doors and vehicle unlocking in Hawaii when the Navy was doing exercises. Over the years, these SRDs (short range devices as the FCC likes to call them) have got more sophisticated so that random bits of RF won't trigger them. However, the technology that makes them robust (long coded sequences) makes them more prone to jamming. You can demonstrate this yourself doing a simple experiment. Try to see how far away you can get from your car and still get the remote to work. Do this test in an urban environment (which should be poluted with RF) and do the same test in the boonies. You should get more range in a quiet (RF wise) environment because the signal is easier to "qualify" (match the code) by the reciever. I stumbled across this while fidling with my remote while parked around the Meadow Valley wash. [I was tired from the hike, very glad to see the truck, and was trying to open it as I approached.]

So why didn't every remote fail? Well, the good ones use SAW filters, which is a fancy way to make a very narrow filter that is also very accurate in terms of being on-frequency. Then there is the other stuff that is not so good.

In the link provided, they list a few frequencies for these SAW filters, but I believe only 315Mhz is used in the US.

Attached link: murata saw filters & some freqs

In Reply to: Wacko beams focuses on Las Vegas? posted by SEZBRONCO on February 22, 2004 at 9:30:12 PST:

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