"tianli_" (and jd) wrote in message
...
Nice jd!

(( Comments inserted between text ))


Many folks here are missing the point. It doesn't have to be 2X
wavelength
or
even 1X wavelength. Just string up a horiz. loop anywhere you can and as
long as you can make it. Don't worry about height above ground or if it
is
in a
circular, square or trapezoid, or what have you, configuration. If it is
anywhere
near as high as your proposed longwire or dipole it will work just as well
but
over a much broader swath of frequencies. Think of its performance as
much
like a discone antenna at VHF & UHF - no gain over a half-wave vertical
but
very broadbanded. The H-loop "generally" has omni-directional
characteristics
where as a dipole or longwire has definite nulls and peaks around the
compass.

I would guess that my H-loop is about at least 70-75 meters in
circumference
at an average height of about 20 ft. It is strung around the edge of my
roof in
a large "L" configuration with the wire tucked under the roofing shingles
at
strategic locations - invisible! It has survived several seasons of
severe
weather and hasn't budged. I use it for SWLing as well as transmitting on
80-10 meters using a vintage Johnson Matchbox - sweet!


--
While it sounds like you have little more than a cloud warmer there (if
otherwise please do advise), you're right that it costs very little to run a
few hundred feet of wire anywhere you can get it. The result could be a
good listening antenna. What it won't normally be is a good transmitter,
unless it meets mimimum design conditions.

Also, don't you worry what kind of RF you illuminate the house with? It
looks to me like people inside could be as close as 2 or 3' from your
antenna, and at most HF frequencies that is way too close to 100+w transmit
power.
--


Compared to a dipole or a longwire it doesn't experience those "dips" in
reception on certain bands. Any "dips" that do occur are not as deep and
an antenna matchbox will easily make up for it.

Where anyone obtained the idea you must use dozens of 75+ ft telephone
poles
around 100 acres of real-estate has simply never built or used a horiz.
loop.


--
That would be me. I have seen one in use, just never replicated by a
hobbyist (yet). Without the near 1/2 wave design-elevation, a horizontal
wire antenna becomes NVIS (or cloud warmer). We've all heard of people
doing this with their rain gutters for years, but that doesn't translate to
a worthwhile effort when compared to most achievable antenna designs.
--

Granted, it would undoubtedly work better at greater height, my
horizontal
loop encircles a small section of my woods at varying heights of
anywhere
from 6 feet to (maybe) 15 feet. I ran about 475 to 500 feet of wire,
hanging it off available tree branches as I went, in what is more or
less
a
square with somewhat bulging sides. I couldn't tell you exactly how much
wire I used, other than I used enough to form a loop through the woods.
I
couldn't tell you it's impedance. I feed it with coax through a
home-made
1:1 transformer. I have no complaints with it's performance.

I think there's this expectation by folks new to the hobby that
everything
has to be "labratory" perfect or it's a waste of time. In my experience,
I
have found that wire antenna's are *very* forgiving of imperfections.
Granted, they will not perform as well as something carefully
constructed
in a labratory environment, but they will *still* work - and there's
even
odds (or better than even) they will work better than expected!

My rule of thumb is: "As much wire as you reasonably can, as high as you
reasonably can." In different situations, that could be 30 feet of wire
at
house-eave level -or- a 2wl horizontal loop at 1wl above dirt. Just do
what you can, and are interested in trying, and don't sweat the details
until *after* you establish a baseline.

-=jd=-

True enough.

Jack