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Message
Christer,
Bear in mind the carbon fiber skin of a Lancair IV
is electrically conductive so, in general, placing an antenna inside the
aircraft doesn't work for the same reasons aluminum skinned aircraft
don't use internal antennas. I understand there is, or was, an
E-glass area in the vertical fin specifically to provide a non-conductive
window for a dipole type of com antenna but I don't know if that's present
in all L-IV kits. Other than an antenna behind an E-glass section
about the only other option is to use a conventional external com anteanna,
something like a Comant CI122.
You mentioned trying dipole antennas on the belly
of your airplane. Again, due to the carbon fiber, I wouldn't expect them
to work if they are placed close to the skin. As for better performance on
the ground that's probably the result of the earth itself acting as a
counterpoise for the antenna.
By the way, if you use an external antenna you'll
need to make sure it has an adequate counterpoise (frequently referred to as a
ground plane). I know some of the Legacy builders have had good results
using the carbon fiber skin as the counterpoise as long as the antenna base
makes good electrical contact with the skin. Other builders have used
conductive coatings or copper mesh. There have been a few threads about
this on the LML.
Tom Gourley
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