Thanks all for your comments, interesting stuff.
There is an external Garmin antenna on the outside of the aircraft which I guess I should ideally use, I've just not got round to making up a BNC connection lead I can use to join my GPS III to it yet - anyone have any hints as to the type of coax I should use for such a flylead?
IO540-C4D5D - I do have one of those rubber suction cup accessories but haven't really been able to find a spot that seemed worth using in the PA28 - thinking, perhaps in error, that it was best to keep the antenna vertical and the suction cup at the top of the windscreen means it's at quite an angle. Given so many of you reckon this will help I will of course try it next time I fly.
Mark 1 - I'm with you on this, my symptom is that one minute it's working fine with strong signals form approx 6-8 satellites and then over a period of around 30 seconds they all fade away to virtually no signal strength and I start getting the "power down and re-init" or "poor satellite coverage" error. I tend to do 90% of my flying west of London in the Midlands area (South of Milton Keynes, North of Basingstoke and East of Newbury). I too have wondered if strong local signals were to blame or specific jamming, those frequent NOTAMs you see citing "GPS Jamming Trials" seem to be a clue but it's a pig to work out the area they are supposed to affect and when they are operating.
Anyway, thanks again all, I'll take up some of these suggestions and report back.
Safe flying!
