by sonex1374 » Thu Sep 08, 2016 10:55 am
Don,
If you've tried all those changes (new plugs, wires, caps and rotors, beads), it may be something simpler. How is your radio antenna routed up the sidewall and behind the panel? If the antenna feed line crosses other wires they can affect each other. An example of this could be your cigarette lighter plug feeding noise into your radio, or your radio feeding noise into your EFIS causing fluctuations every time you transmit. The key point here is that routing makes a huge difference. You should review your antenna routing and look for ways to change or improve separation.
Next, check the condition of your antenna ground to the ground plane. Is there corrosion starting under the antenna base? Or under the ground lug? Bad antenna grounds will de-tune your antenna and may be a problem.
Also, where is your radio antenna mounted? You may need to move it to another spot. Try removing your antenna from the airplane, mounting it on a temporary aluminum ground plane (i.e. a 12-24" square or diameter piece of metal, or crossed strips, or whatever), and moving it away from the plane a bit. If that improves things, maybe a new location on the plane will help.
Lastly, check the condition of your antenna feedline. Damage to the line or a badly crimped connector can let RF noise in or out. Inspect it carefully for kinks (breaks in the insulation), abrasions, or bad ends.
Good luck with your troubleshooting.
Jeff