Hi Keith,
Alan and I did some 'Bridge' testing today. A nice change from testing Mode S. Results were very favourable, though even with years of fiddling with aerials as a 'Radio Ham' - I was surprised how significant aerial placement can be on this frequency and how easily signal can be attenuated by pilots/aircraft bodywork/engines. We got good cover in our initial test to well over 5+miles ( which I would consider a perfectly reasonable range for P3i detection) with no loss of signal (in my case using a FLARM dipole inside my flexwing pod). Unfortunately weather/ time precluded further testing.
Supplementary note to avoid confusion to other readers - I am NOT trying to imply that this is P3i's maximum useable range, simply the maximum distance apart we got during our short test flight with 'test' aerials. As I say, weather precluded further flying and I have no reason to doubt previously reported results. In any case even as a worst case scenario for plane to plane detection, 5 miles is further away than most of us can see a light aircraft in anything less than perfect conditions.
Regards
Peter
p.s. congrats on the RAeC Award!