[ARDF] Does anyone have a good design for a Halo Antenna?

[Dale Hunt WB6BYU]

I strongly recommend reading W4RNL's articles on omnidirectional
horizontally polarized antennas - probably in the VHF/UHF
section of his website.  A lot of background information,
radiation patterns, and notes on tuning adjustments, element
diameter, etc.  I think he ended up getting best results
using triangular loops, but there were two different models -
one with close spacing between the open ends and one with
wide spacing, and neither had a non-reactive feedpoint
impedance.

The most critical design criterion, however, is how close
to omnidirectional you need the pattern to be.  I think the
IARU Region 1 standard is within 1dB, which is a challenge
with a standard turnstyle without careful adjustment.  (In
practice it would surprise me if most competition antennas
were actually that good.)

On the other hand if you are just having informal practice
sessions, I've had good luck with a stiff wire dipole bent
in somewhat of a circle... or not.  Only rarely do we run
into problems with being in the null off the ends of the
wires, and a bit of modeling should come up with something
that is perhaps only 6 to 10 dB from omnidirectional.

If you need gain from your horizontal omnidirectional
antenna that would be a different design, possibly
starting from one of the designs for TV transmission
like a slotted cylinder, or a spiral conductor wrapped
around a metal cylinder.  But those are probably too
large for what you have in mind.

Good luck!

- Dale WB6BYU





On 19 May 2008, at 14:57, Jay Hennigan wrote:

You should very definitely peruse the following:

http://www.cebik.com/content/ao/ao16.html

The site now requires registration and requires a mailable e-mail
address, but you can use mailinator.com to generate a throw-away for
such things.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
Your local telephone and internet company - 805 884-6323 - WB6RDV
_______________________________________________
ARDF mailing list
ARDF at kkn.net
http://www.kkn.net/mailman/listinfo/ardf