I'm going to be installing a Nav Antenna that i'm getting from SteinAir. I'm looking for advice on mounting it. I have seen here that many people put these in the wingtip. Questions:
1) What is the best way to attach the antenna in the wingtip - epoxy?
2) Does the orientation of the antenna matter?
3) What about ground-plane, if installing in the fiberglass wingtip?
Thanks!
Phil
The most common wingtip antenna is called an ‘Archer’, after its original designer, Bob Archer. Technically it’s a bent quarter wave, working against a ground plane, and fed by a gamma match. So
1. There is a ground leg on this antenna, which must be electrically connected to the metal end rib (the rib will serve as the ground plane). The instructions suggest using nutplates and the wingtip attach screws to connect the ground leg to the rib. Others have riveted an aluminum angle onto the end rib, and mounted the ground leg to the angle. Some just let the rest of the antenna lay inside the wingtip; some use tape or a strip of fiberglass/epoxy to keep it from bouncing around.
2. VOR and ILS signals are horizontally polarized, so the antenna should be horizontal. Note com signals are vertically polarized, which makes it harder to use wingtip antennas for com signals - there isn’t enough vertical room.
3. The ground plane is the vertical end rib.
The instructions say how to run wires to nav lights, if you must run them across the antenna. But it’s usually best to mount the antenna aft a bit, and avoid the wires altogether.
Some EAA chapters may have an ‘antenna analyzer’ you can borrow, to tweak the matching network (‘gamma match’) for optimum performance. But if you follow the instructions it’s probably not necessary.
Examples of installation errors I’ve seen:
1. Mounting the ground leg 8” away from the end rib. It needs to be close, and in electrical contact.
2. Reversing the ground leg and radiating leg! Expect poor performance!