When you say your j-pole doesn't seem to work do you mean that it doesn't work at all, or that you aren't getting the APRS transmission range you expect?
Wingtip-mounted dipole antennas have some limitations, but a lot of APRS-equipped RVs use them and they seem to work reasonably well. You've probably checked your coax and connectors but if not, I'd do that before changing out antennas. If you have a ham radio friend with an antenna analyzer, you can almost certainly bribe them with food and/or beverages to bring their analyzer to check out your installation. A quick sweep with the analyzer can help pinpoint coax issues or a poor antenna impedance match - both of which will reduce your APRS range.
Hope this helps. Please check back if it doesn't and we'll try some other tricks.
EAA Technical Counselor/Flight Advisor
RV-7 N701ED FLYING!
Nashua, NH (KASH)
Last edited by Thermos : 09-01-2020 at 05:35 AM.