On Nov 21, 3:46*pm, SoaringXCellence wrote:
To all you communication experts,

I have a Schreder hp-15/18 I am rebuilding. *I need to install a
communication radio antenna...

I'm not a radio expert, but I have installed and tested four or five
antennas in an HP-18. The only one that has worked very well was an
external 1/4-wave whip installed over the aft fuselage. I tuned it to
an SWR of about 1.4:1, at 123.4, which was about as good as you could
expect.

The troubles with installing an antenna in the winglet are that there
is not a good ground plane for a 1/4-wave whip, and not enough
vertical height for a 1/2-wave dipole (two 1/4-wave whips opposed). I
suppose you could put a rubber ducky antenna out there, but there's no
point since you could have the same antenna in the cockpit and do away
with the 25 feet of cable.

Anyhow, the other antennas I tried were a commercial 1/2-wave dipole
strip antenna in various orientations in the fuselage (SWR above 2.5
in all cases), a 1/4-wave whip on the gear door (again, poor SWR and
poor demonstrated performance), a Sebald-type combo 1/4-wave whip and
Nicks tube (good SWR but pointless, since the ship has a Nicks tube
elsewhere), an internal 1/4-wave whip the original builder had
installed on the most forward metal bulkhead (poor SWR), and a rubber
ducky installed on the cockpit rail (reasonable SWR, poor overall
performance).

At one point I played with the idea of building an Aramid fiber
ruddervator and installing a Jim Weir style copper tape dipole inside
its trailing edge. I know that the performance directly forward would
be very poor, but the overall performance might have been decent. But
in the end I just stuck a whip antenna on it and got on with life.

Thanks, Bob K.