On Mar 14, 11:51*pm, WaltWX wrote:
Does anyone have success finding an aircraft installed 406 ELT for a
Schempp-HIrth glider (i.e. internal installed antenna somewhere in
fuselage)?

A quarter wave of 406.25 is about 6.9", so a quarter-wave whip antenna
optimized for that frequency would stand about 7" tall. A dipole would
be about 14" tall. It's probably a vertically-polarized signal, so you
want the antenna standing vertically, and not horizontally.

If your glider has a fiberglass fuselage, it is relatively transparent
at the MHz frequencies, so you can use either an internal dipole or an
internal quarter-wave whip with a ground plane. The dipole is probably
the better bet.

If it's an all-carbon fuselage, it is pretty much opaque to the MHz
frequencies, about like an all-aluminum fuselage. No internal antenna
could offer anything like reasonable performance.

If the fuselage is primarily carbon, there may be a few places where
you might make an antenna work. Sometimes the vertical fin or rudder
are fiberglass or aramid; you might be able to put an antenna in one
of those places. I used Jim Weir's design guide to design the internal
123 MHz dipole antenna in the rudder of Brad Hill's Tetra-15
sailplane, and it seems to be working pretty well. The turtledeck area
might also be fiberglass or aramid, so you might be able to install
something there.

Thanks, Bob K.
http://www.hpaircraft.com/hp-24