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Buried Antennas - Which Parts need to be Non-metallic?

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wsimpso1

Super Moderator
Staff member
Joined
Oct 18, 2003
Messages
11,353
Location
Saline Michigan
Fiberglass airplanes have a bunch of neat features, one of which is that antennas can be buried inside the airframe, and I am taking advantage of that feature. Trouble is that then you have to be careful about where you put long pieces of metal, lest your radio's speech and hearing be messed up.

My big questions have to do with which parts really need to non-conductive.

Here is the airplane:

Low wing monoplane;

Two seat side-by-side, two part push/pull rods out each wing for aileron control with an idler at the break between inner and outer wing panels, a bellcrank to run the motion, and a short push/pull tube to the aileron;

Flap control is a torque tube and short actuator push/pull rods at the fuselage wall, and probably fiberglass tubes as well;

Two part push-pull rods through the fuselage belly for elevator control with an idler in the middle, direct acting on the elevator;

Two cables for rudder control;

Quarter wave V dipole antennas in outer panels for NAV, but they can never be more than about ¼ wavelength from the aileron bellcranks. There are also position light and strobes on the wing tips, so the antennas can not really be near the tips either. Running the wiring along the aft spar and running the open part of the dipole V forward still makes me want to place the vertex of the V at the bellcrank and use fiberglass tubes for everything.

Quarter wave straight dipoles on the fuselage wall and vertical fin for COM. The elevator rods will be less than ¼ wavelength from the lower legs of the di-poles, so I think that they have to be fiberglass too. The rudder cables and light wiring can be run down the middle of both di-poles, but I am not so certain about the rudder cables. A candidate for Vectran through that part of the airplane, perhaps?

The other side of the fuselage and between the two COM antennas would be the ELT antenna.

Does this sound like a good plan? Or is it overkill? Perhaps not enough? I am a structures geek, not a raio geek, so please help me out.

Billski
 
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