Talk:GPS Dead Zone
I had a similar experience with a television tower, although i didn't test it as thoroughly as you apparently did. I tried two receivers (my page) one of them usually acceptable even under bad conditions, and both suddenly came up with very wild guesses. I will try that again. The only other time my pgm-111 got into insane-mode was a few meters near a motorized lawnmower, i guess it was the unshielded ignition spark then. --florianheer 17:02, 4 August 2008 (UTC)
I've seen this before on wi-fi as well as HAME radio and the trace losses seem to be consistent with that. It's definitely a signal jammer, whether unintentional radiator or not no one can be sure but there's definitely a signal capture from something else emitting in that area.
Thankfully 10 years later after this was posted SDRs are very cheap and work as a decent spectrum analyzer, the RTL-SDR covers both the L5 and L1 frequencies (there is even open-source software allowing you to use it as a GPSr) and going through the area while recording the waterfall display for later analysis usually helps figure out what the problem here is in most cases. Definitely something to consider for any future people that have discovered problem areas like this in their locale as well long after this article was written.