A 1/2-wave dipole will have to mounted inside the aircraft, which as you point
out, will be blocked in the forward direction. What this actually causes will
depend upon the performance of the xponder. Microair and the King KT-78 are
a bit weak in xmit; the Microair is relatively weak in receive according to
their
specs. I see now why they fuss over length of the coax, which is a factor
in mounting the antenna way in the back -- at 1gHz, coax losses can be very
significant.
The general rule is you get what you get. For VFR, practical fringe distance
from
ATC's interrogating antennas lets you whack out about 75% in performance from
your installation and be still able to report all seems OK. For IFR, especially
at minimum enroute altitudes, it can be a different matter entirely, the
way their grid of interrogators are set up.
Regards,
Fred F.
> IMHO you will get better performance from a Bob Archer dipole antenna.
> We mounted ours somewhere back of the baggage bay to one side.
> It needs to be able to shine forward past the engine and back past the
> tailplane steam tube etc.
> Fred F might have better ideas? He knows more than I do about these
> things, I guess Bob knows even more, bobsantennas@earthlink.net
>
> Graham
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