Been to Duxford today and not having our usual machine, took two handheld GPSs with us. As always, we put the lines on the map & being as it was a Good Day for Flying, the GPSs were not really necessary... But, around Daventry, both of them lost all signals. Mine has an active antenna and when working normally shows between 8 and 10 satellites with good strong signals. They were both off for about 10 minutes. Same thing happened coming into MAN over Macclesfield. The Garmin 430s in our usual mount have not (so far) had a problem. Now I know that there is the radio 4 transmitter at Daventry putting out about 400kW on 198 kcs, but would that block the signals?
Btw - Duxford's new hangar is Very Impressive - the standard of the aircraft there is 1st class. And there were LOTS of Pipers!