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

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

I watched the video and checked out the details. The antenna is
basically a loop with the roof of the car (the bottom of the luggage
rack) as the ground side of the loop, the antenna goes up, folds over
the top and back down to the other side of the roof where it feeds
thru a high voltage vacuum variable capacitor back to ground.

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



---------------------------
| |
|_ |
| |( coax conx) = Capacitor
| -|_____________|
^ (roof)
^
(feed)

I am not as good an artist as some of you, but here is my graphic
The coax feeds with a gamma? and is tuned by a stepper motor tuning
the vacuum variable cap. Depending on which of the three models, it
operates from 1.5-10 MHz, 2.7-15.5 MHz, or 4.5-22 MHz at up to 150
watts.

The technical notes have more interesting details:
http://stealth.ae/plugins/custompage...cles.php?id=10

It seems to me a homebrew version could be made for base use such as
for those in restricted homes. Placed on the peak of the house, the
ground side could be a wire across the top of the peak and the loop
lift up during use so it would not attract too much attention to the
neighbors.

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.



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




Buck
N4PGW