[time-nuts] Distance between GPS Antenni

Brooke Clarke brooke at pacific.net
Sun Dec 18 15:17:05 EST 2011


Why limit the sniffing to GPS frequencies?

Have Fun,

Brooke Clarke

lists at lazygranch.com wrote:
> A few weeks ago when GPSs attached to cars were the internet rage, I attempted to "sniff" a GPS with my spectrum analyzer to see what leaks. (The idea here would be can a GPS detector be built.) The assumption here was the local might leak out the antenna. I couldn't measure any leakage off my Garmin. I tried this using a passive GPS antenna as the sniffer, as well as an amplified GPS antenna. The GPS I was trying to sniff was a Garmin GPSMAP60. I did manage to see the actual GPS signal on the spectrum analyzer with the amplified antenna. But like I said, I never sniffed an local oscillator leakage.
> I think that given the nature of GPS signals being so weak, the manufacturers don't allow much leakage since that would "desense" their own receiver.
> I do recall seeing a bit of L-band cellular coming off the passive antenna.
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