Hi Stu,
Thanks, both, for your replies. That is a pretty close frequency, presumably both systems need to use the same limited "public use" part of the spectrum
Correct
but I presume that greatly increases the likelihood of interaction if the antennae are too close. I had tried some experiments with the PAW and ADSB antennae and from that concluded that there was no significant effect on ADSB reception provided PAW was about 3 inches away from it - but of course ADSB is listening for powerful signals and the two systems are over 10% apart in frequency. Due to absence of PAW targets I could not test if the ADSB antenna was having any effect on PAW reception.
Close proximity of the 1090MHz (ADSB) antenna is unlikely to affect P3I due to the frequency difference and the fact that the ADSB is receive only.
As regards mounting an antenna on the underside of the aircraft, that probably is worth considering, I probably slipped into assuming an "on top of canopy" installation as a natural evolution from my present set up where they hang below the top of the canopy arch. However, I think there is one important consideration that very much favours a "top-side" installation rather than a belly-mount. Even inside the canopy, the antenna is very high above the top of the engine so it should have a view ahead down to perhaps 15 or more degrees below the horizontal, and of course unlimited view above the horizontal. A belly mount would have unrestricted view in the downward arc but would only be only a few inches below the engine 6 feet ahead of it so would barely be able to see above the horizontal at all. I think that is too high a price to pay. The other option I may be forced to consider is a fin-tip installation. That would give good separation though the cable runs would; be lengthy.
All good thinking on antenna placement. It's generally best to keep cable leads as short as possible, though Keith has had good results using the standard 3m extension leads to feed 1/4 wave whips on the underside of his Sportcruiser. If you decide to test a fin-tip option, it might be advisable to use lower loss co-ax (which will be a bit thicker) with appropriate connectors or adapters.
BTW - is there any received wisdom re the pros and cons of the red-box FL@RM unit vs the FL@RM Mouse? I have read a thread here somewhere taht said the GPS antenna in teh mouse is small and is a bit of a poor perfomer - not good if teh mouse becomes your primary GPS source for all the conspicuity and nav app systems, so the red box plus a GPS dongle sounds to me a better idea (but of course more wiring!)
Richard is correct re the GPS issue. It was me that had some GPS problems during testing with my FlarmMouse, though it did work fine for most of the tests and seems to be working again since. Lee sent my track logs for the flights in question off to LXNav in Slovenia, who commented that due to the small size of the inbuilt gps antenna in their (matchbox size) device, gps performance
could be poorer than when using a 'full size' gps antenna, but I don't think we have had anything further back from them yet. Lee subsequently reconfigured the PAW software so that if you have FLARM gps available, PAW will use this, but if you also plug in a PAW gps (in my case the mouse) then PAW will use that instead. I have had no problems since reconfiguring my setup along these lines and am getting sound glider fixes, so the inbuilt FlarmMouse gps seems fine when doing what it is designed to do. My previous comments were related to concerns where a couple of users were going to rely on the FlarmMouse gps as the sole source to feed Flarm, PilotAware, ADSB Out and IIRC a glass panel system, which I felt I could not recommend. Just too many eggs in the one (very) small basket for my liking.
I have no personal experience of the LXNavigation FLARM Red Box, so would bow to Richard's experience in this respect.
Regards
Peter
