"Michael" wrote in
:

I get a lot of noise from my random wire antenna. It transmits very
well but is very noisy in receive. My neighbor put up a 280 foot loop
antenna which he feeds with ladder line. He feeds the ladder line from
a 4 to 1 balun to coax. The coax comes from a tuner. His setup
performs very well on all bands down to 75 meters. I went over to his
shack last night and listened to his receiver on 75. I was really
impressed with the lack of noise. I can safely say the difference in
noise was profound. He has this loop surrounding his house at a 30
ft. height. It is arranged in a square.

Has anybody else had this experience with loops? It looks like I have
room to put up a triangular loop. Will this work as well?

Can I use the same tuner I have now and just feed a coax into a balun.
Or, should I put the balun in the tuner and come straight out with
ladder line? There is a lot of room in this tuner. It is an old remote
controlled tuner surplused from a ship.

Michael, a horizontal full-wave loop is actually quite a good choice for
LOCAL networking on 75m. The feedpoint impedance will depend somewhat on
the distance above ground and on the quality of the ground but should
range between about 200 ohms down to as low as about 50 (or even lower if
your ground is good). The shape of the loop is not all that important
and, if it's symmetric, the feedpoint can be anywhere. The ideal height
would be about 65 feet, but lower will still work well.

The radiation characteristic of an antenna like this is horizontal
polarization but with the main lobe directly skyward (which is actually a
good thing on 75m for LOCAL work). It does this, of course, at the
expense of radiation at low angles, so it is not a useful DX antenna
(though it may outperform a dipole at the same height). Being a loop, it
is also somewhat immune to near-field electrostatic interference such as
from nearby power lines (which may account for the lower noise pickup).


--
Dave Oldridge+
ICQ 1800667