Hi Al,
I have been looking at the antennas on composites airplanes (Lancairs, Glas
airs, etc) for years and the fact is that most builders install al
l antennas inside the airframe for obvious drag reduction, except for XPDR
and DME antennas. Of course I am talking about glass, not carbon fiber air
frames. XPDR and DME works in the 1030- 1090 MHz frequency range and are th
erefore more sensitive to shadowing and any less than perfect installation.
Best practice is to install the antenna outside, pointing downwards, on t
he belly of the aircraft, with the appropriate ground plane. Minimum size
of the ground plane is 4 wave length in diameter. 10 inch diameter, .025 i
nch thick aluminum is suggested in the litterature. Another thing is to mak
e sure your BNC connectors (both center wire and shielding) are soldered no
t just crimped, as this warrants a better contact in the long term and a be
tter reliability.
Good flights
Remi
From: "AlStills" <astills@cox.net>
Subject: Europa-List: Ground Plane
Hi all,
I've been having a little problem with ATC reading my transponder all the
time. I suspect a bit of shadowing.. I have the 2 1/2"-3" transponder
antenna mounted
upside down on a shelf on the rear corner of the baggage bay. I have a 6"
steel ground plane mounted to the antenna. What size ground plane have
others used
successfully and where is your antenna mounted. ATC reads me better out of
KGEU with a feed from Luke AFB while KDVT (where I'm hangered) gets their
feed
---From Phoenix Sky Harbor airport. By far KDVT is worse than KGEU. I know
there is difference in the feed from the different radars but need to get
rid of most of the
shadowing if possible. Sure would make me more presentable to the guys at
KDVT. (One of the busiest GA ariports in the nation)
Have about 8 hrs on the plane now and the grin is still in place. Gets even
bigger the more I fly!
Al Stills
N625AZ
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