Alan Adamson wrote:
My solution to Comm Antenna ground plane
Got this idea from someone else on the LML.

Alan,
I am no expert, but all I've read says that ground planes don't work inside
carbon fiber bodies--it needs to be on the outside of the carbon to be
effective. Other comments/thoughts?  Bob Pastusek

On my IV-P belly (carbon), I painted on external ground planes.  I measured
the resistance of the ground planes and the resistance from one ground plane
to another......the ground planes are round and do not touch.  Using a
Biddle DLRO Meter (Digital Low Resistance Ohmmeter), I measured .040 ohm
near the antenna bases, .096 to .134 ohm from one side of the circle (ground
plane) to the other, and .112 to .130 ohm from one ground plane to another.
I sanded the carbon skin down to carbon before painting on the ground plane.
As you can see, there is very little difference between the ground plane
resistance and the carbon. With this data I am at a loss why ground planes
make a difference. Now the resistance of epoxy is infinite so maybe that is
the issue. I know a lot of people have had good luck with aluminum internal
ground planes. I also know of several people that like the painted on
external ground planes.  One of the com experts on this list told me ground
planes should be round. The com should be 36 inch diameter, the transponder
and TCAD should be 12 inch diameter.  I have 16 and 18 on the transponder
and TCAD and 36 and 30 on the Coms.
Craig Berland