Just in front of the vertical stab is still a very good location (mine is
about 18 inches forward of the vertical stab). Since the vertical
stabilizer is quite narrow and parallel to the antenna there will be very
little interference or reflection off of the leading edge. It's the folks
who have mounted the ELT antenna underneath the fiberglas tail intersection
fairing that are really limiting their usefulness. In that location the
antenna is mounted horizontally on the aft turtle deck bulkhead (RV-6/7/9)
projecting out into the 90 degree corner created by the intersection of the
vertical and horizontal stabilizers. That creates an excellent waveguide
effect, blocking the signal from reaching half of the area on the other side
of the aircraft.
Jerry, I understand the thinking about putting the antenna on the bottom and
it's another one of those multitude of "what if" scenarios that we RV
builders run through our heads so many times while we're building. I guess
to answer that somebody has to do some research on how many downed RVs have
ended up on their backs. I have heard of several but don't know just what
percentage of ALL RV accidents they actually make up. If you put it under
the wing and you stay right side up in a crash, you will be attenuating a
good bit of the signal and shortening the range at which you can be
detected. If you put it between the trailing edge of the wing and the
forward edge of the horizontal stab (top or bottom of fuselage) your range
should be quite good (right side up or upside down). Then you have to start
thinking about how to keep the antenna from being ripped off in the crash
(Tim Bryan's idea). And so the thought process goes... sometimes being a
safety analyst makes my brain hurt but, more food for thought.
Dean Psiropoulos
RV-6A N197DM
> -----Original Message-----
From: "Tim Bryan" <n616tb@btsapps.com>
Subject: RE: 406 MHz ELT
I have my antenna mounted just in front of the vertical stabilizer. My
thinking was in a rollover the stabilizer *might* protect the antenna from
being smashed. Now I am wondering if the stabilizer causes any shielding of
the signal. Dean, any thoughts on that?
Tim Bryan
RV-6 Flying
N616TB over 100 hours now
