[time-nuts] GPS fadeout
shoppa at trailing-edge.com
Tue Aug 21 19:36:37 EDT 2007
Hal Murray <hmurray at megapathdsl.net> wrote:
> I'm trying to check/debug some new software so I'm paying attention to the
> output of a Garmin GPS 18 USB.
> It's inside my house, not a great location. Mostly, it works. But every now
> and then it fades out for a few minutes.
> I'm only logging the data every minute or so, but I have counts of the
> good/bad seconds. On the glitch that just happened, it was going fine with 5
> satellites. Then it faded out to 0 satellites. Two minutes later it had 5
> satellites again. The total even was under 4 minutes.
> Are glitches like that common? Does anybody have a list of what causes them?
> The only thing I can think of is multipath off an airplane. Big jets are not
> uncommon overhead. I'm ~30 miles south of SFO.
Local VHF/UHF transmitters such as public service
base stations or even mobile units can desense consumer GPS antennas easily.
RFI-resistant GPS antennas (commercial and/or military) are available.
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