[Elecraft] Horizontal Loop Antenna

[Terry Conboy]

At 11:58 AM 2005-12-21, Kevin, N8IQ wrote:
>I've been thinking about what kind of antenna to put up. With my height and
>deed restrictions, I'm quite limited. I've thought about putting up a
>horizontal loop antenna. Basically I was planning to run some enameled
>magnet wire around the perimeter of the roof (I have no plans on running
>more than 10 watts). The wire would lay under the shingles so it can't be
>seen. The antenna will be 1 WL long on 80 meters. I'll run coax down to the
>K2 + ATU.
>
>This is similar to "The Loop Skywire" described in the November 1985 issue
>of QST. Anyone have experience (or see a problem) with this antenna?

Kevin,

Just be sure that the high voltage points on the antenna are well 
insulated from your shingles.  The voltages are maximum at 1/4 
wavelength away from point on the loop which is opposite the 
feedpoint (and every 1/2 wl from those points on 40m and higher 
bands).  Even with 10 watts, you could see about 200 volts (rms) RF present.

When the shingles are damp, you may see a bit of detuning from 
increased capacitive loading (and a little extra loss).

I used a 30 foot high horizontal loop (1 wl on 80m) at my Seattle QTH 
and was quite pleased with its performance on 80m-10m.  One side ran 
closely parallel to the aluminum gutter above the second story.  The 
remainder of the loop was stretched to trees across a small 
creek.  Feed was through a short length of 300 ohm line and a 
link-coupled balanced tuner.

The loop was originally made from stealth #26 magnet wire, which was 
fine for RF (100 watts), but was often trashed by falling tree 
branches.  It was later upgraded to bare #22 and the mechanical 
problems were nearly nonexistent (and it was still nearly 
invisible).  When I started to get ice buildup, I connected the loop 
to a low voltage DC supply which warmed the wire enough to melt the ice off.

ARL 61,
Terry N6RY