On Fri, 26 May 2006 13:02:14 +0100, Christopher
wrote:

The way it is done is to attach the feed at a point so many inches up
from where the coax would be grounded to the fuselage. Although the
fuselage is at ground potential where it connects to the battery and
negative lead for the avionics if you find the right spot to attach the
coax the feed will both be matched and radiation will occur on a
vertical member as if it were insulated from ground.

I don't fly, but love airplanes and radio. The only thing I think is
missed here is that the aircraft band is wide (108-136 MHz, I
believe). While a part of that is receive only (for the plane), the
range that the transmitter must be able to talk to is still pretty
wide, 15% I believe. To get a fixed tune system that works well with
reasonably low SWR requires low Q; how well do those systems work?

I know the classic J-Pole is decent, and am not sure this differs in
concept.

Those nifty foil designs of Jim Weir's lower the Q by width, I
believe, as the thickness is slight.