On Fri, 21 Mar 2008 15:50:45 -0700, Jim Lux
wrote:

Buck wrote:
This is an interesting antenna. It is a mobile stealth magnetic loop
antenna.

http://stealth.ae/plugins/custompage...categories=136

Isn't this like the Q-Mac antenna sold in Australia?
http://www.qmac.com/mobile_antennas.html


They sure look the same.


Since the roof of a house is fairly large, a more conventional random
length loop tuned with something like a LDG or SGC autotuner at the
feedpoint might be a good approach. Icom IC-AH4 could probably also work.

That is certainly an idea I hadn't thought of. It sounds cheaper and
easier to build. The same concept could be used with raising and
lowering the antenna, but instead of a 'loop', it could be a wire.

Thought: let's assume one puts up a loop on the roof. The ground side
is a single wire running over the peak of the house roof, folds up at
90 degrees for 3-6 feet, back across the roof 6 foot above the peak
and back down to the hot lead of the autotuner. Would that not
circumvent the need for the capacitor at the far end? and would the
loop have to be trimmed to a particular size to operate the various
bands, or could the tuner actually operate with most any size loop.

Disclaimer: I know from experience that some random lengths might not
work on all bands, but some do appear to. I recognize that there
could be inefficiencies...




I wonder what the size and cost of the Vacuum variable is to make a
similar antenna??


size of a pickle jar
Several hundred dollars, depending on size, power handling, and source..

http://www.surplussales.com/VaccumVarCaps/VVC5.html
http://www.mgs4u.com/RF-Microwave/va...citors-500.htm

plus you'll need to cobble up a motor and drive system.

the $300 or so for a autotuner starts to look like a good deal.
http://www.hamradio.com/web/newcat/hrocat7.pdf



I tend to agree with you here




Buck
N4PGW

This is what I was fishing for. Maybe the antenna design isn't the
best, but the discussion is introducing variations of thinking that
could be useful.

Thank you
Buck
--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."