On 13 Jan 2005 10:38:09 -0800, "ELIPPSE" wrote:


I made all of the antennas for my Lancair; com, VOR, glide-slope, and
transponder. You can make a simple 1/2 wave com or VOR dipole out of
sheet aluminum shaped like a bow-tie. The experimental ones I made had
a VSWR of less than 1.2:1 over the full 108-136 range.

ELLIPSE, I am impressed. I've played with RF for some 45 years, and
have a hard time getting a true 1.2:1 VSWR into a resistive dummy
load, much less into an antenna over a bandwidth exceeding 20%. I'd
like to get with you and see what we can do in getting a patent on
your invention; you will be a wealthy man.

By any chance have you also done any radiation patterns on this?
Since it is vertical, I suppose it is perfectly circular, but I wonder
about the bank angles; does it work well when you are in steep banks?
From your skills at attaining that VSWR, I bet you get spherical
radiation with a 5 or 6 dB gain.

These currents can often
get into the microphone feed and cause squeeling and distortion during
transmit.

So you have had some problems with VHF signals conducted on the
feedline getting into the microphone circuit and causing audio
feedback?

Make
each element about 15" long, tapering from 1/2" wide at the feed to
about 12" wide at the end. They can be either triangular or
sector-shaped, in other words straight or curved ends. Separate the
feed ends by about 3/8". Attach the shield to one feed end and the
center conductor to the other.

Hm, I thought the driving point impedence of a 1/2 wave dipole was
substantially different from 50 ohms ... your balun handles the
balanced to unbalanced conversion; what does the impedence
transformation?

Do you have a webiste detailing this design, especially with
supporting measurement information? It has many applications far from
aviation, as well as in aviation.

George