RE: Spektrum Telemetry module and iPhone App.
From my past "tester" experience, I really like to maintain the same configureation and limit as many of the variable as possible. That said, I can report that the data losses WRT GPS are ALL in the same orientations and same locations at the same field... Most testing of the GPS has been done with my 1/4 scale RV-4 where the TM1000 antenna runs from just under the leading edge of the wing back to just behind the trailing edge.
The other plane that I have used is my RussiaStik... same exact orientation, and curiously, same location of drop out, however, the drop out areas were smaller (gives rise to the"Mask" theory)
If you envision a race track in front of your position on a flight line, I always lost the GPS data when doing a landing approach where I would make a left turn on to a base leg (facing East, and looking to my left). The GPS tracking arrow would not reappear until almost touch down, so it was absent for a good bit of the final approach after dropping out on the turn to base. The electric plane seemed to regain GPS sooner. There were also drops off to my right but these were of much shorter duration... The difference here is that at that end of the race track I was always at a higher altitude... (80 feet on the landing approach for a start... other end of the runway I'm between 200 and 300 feet.)
I'll post a picture and explain where I see the drop if that helps making some evaluations.
KKKKFL