[time-nuts] Distance between GPS Antenni

lists at lazygranch.com lists at lazygranch.com
Sun Dec 18 11:44:33 EST 2011

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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