Hi Bill,
The general rule for EC antennas is to keep them as near vertical as possible. If antennas on two aircraft are at 90 degrees to each other - i.e. one set vertical and the other horizontal - there would be a 3dB loss in signal between the two (in plain terms transmission and reception would both be halved). we have to accept of course that aircraft do not always fly straight and level, so even in the best case there will be some loss of signal as aircraft bank or climb.
Obviously, externally fitted antennas generally provide the most reliable performance - especially mounted below the aircraft and clear of obstructions like fixed undercarriage to maximise interaction with our network of ATOM ground stations.
Best advice I can give you is to try to maximise outlook from the aircraft - especially towards the front - avoid obscuration by adjacent metalwork or bags of fluid (us!) and accept that in some situations we just have to put up with less than optimal positioning. i suggest doing a trial fit and fly, then look at the Vector plot for your aircraft (available on
https://pilotaware.com/knowledge-base) and repeat the trial until you find the optimal position.
Best Regards
Peter
p.s. If you haven't already done so, take a look at the Fixed Installations Forum. Nothing there yet on PA28s, but there is a lot of good info on other types which demonstrates the essential principles.
