Wing tip J Pole vs belly mount quarter wave

After spend a little time looking at the APRS forum here it seems interference issue while not wide spread are also not uncommon.

I had planned on using the j-pole in one of the wing tips, but if interference is even a sometimes issue, wouldn't it be better to simply mount a quarter wave antenna on the belly beneath the baggage area and bend it so it looks like an airplane antenna?

I would think the external antenna would mitigate interference issues.

What say the experienced users?

73
John
N13JP
WB9JPH

The belly mount antenna will give you the best results and more or less 360 pattern whereas the wing tip antenna won't have the best radiation pattern.

John - two considerations that may help narrow down your antenna placement. First, "what other antennas will you have?" and second, "where will you install the tracker unit?"

If the tracker is installed in the fuselage somewhere, then the belly will be easier to wire. If the tracker will be installed in the wingtip, then the j-pole will be easier.

If you have COMM, and NAV, and Transponder, and ADSB-IN, then you may run out of belly space based on separation.

Neither location will be an issue as far as the APRS transmission. If you co-locate receive antennas, then you may have interference depending on the quality of the RF electronics isolation.

humptybump said:

If the tracker is installed in the fuselage somewhere, then the belly will be easier to wire. If the tracker will be installed in the wingtip, then the j-pole will be easier.

Click to expand...

There is no reason to put a tracker in the wingtip if you aren't using a j-pole antenna.

Antenna placement

There are going to be a slew of antennas-don't have details worked out yet but there will be dual nav/coms, mode s xpdr, loc/gs, and a 2nd xpdr and a dme antenna for the dual band ads-b box + GPS antennas.


So what is best location for these antennas and the APRS antenna?

A wingtip J-pole will be horizontally polarized, so most probably be cross-polarized from most receivers. I know some folks have APRS antennae in the wingtip, but range will be compromised. Of course with altitude, range will be often several hundred miles. (at least I often get that range with a vertical whip in my -9)
Best regards,
John AF6QO N79LH