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The full wave loop can be hung
verticle or horizontal and the sides don't have to be the same
length, although it will probably work best if they are. Actually
the best performance would be achieved if it were a perfect
circle but, of course this is next to imposable and the advantage
wouldn't be worth it. Do
not be concerned about getting it perfectly
symmetrical and one end can be higher than the
other. Just try and get it as high as
possible and you will be pleased.
The loop situated horizontal in
relation to the ground makes for a great antenna for 40 or
80 meters, especially for closer in work.
Some ref ere to this as a cloud warmer because a
considerable amount of energy is emitted directly
overhead. Although the horizontal loop really
shines for closer in work it will perform very
well for dx as also.
The loop can be tuned (with a
tuner) to any ham band higher than the
desired frequency. The pattern of a resonate loop is broadside
but will draw closer to the sides as the
frequency is raised. Of course if you are
using it horizontally this will mean a lower angle
of radiation making for a great DX antenna.
I prefer to feed them directly with
coax at a corner and situated in a diamond
configuration when hung verticle but, you can feed them in
the center of either side. If you feed a vertical
strung loop on the side it will be vertically
polarized and if you feed it on the bottom it
will be horizontally polarized. I prefer the
bottom mainly because it is more convenient. Of
course, if you hang it horizontal it will be
horizontally polarized no matter where you feed
it.
Now, if you really want to melt
antennas off of towers at 1000 miles then you can
add a reflector. You can do this by making A
closed loop and situate it directly behind
the vertically hung driven loop. Just make it
5% larger and put it about .15-.20
wavelengths behind the loop. This setup would be refered
to as a quad. To get the full benefits of a quad you should
have the center near 1/2 wavelength high. Not
very many hams have directional antennas on the
lower bands so you can expect others to ask what
kind of amplifier you are using even when you're
using low power.
A little known fact is that you can add a half
wavelength of wire behind the loop instead of the
closed loop. This comes in handy where supports
are not abundant.
I have routinely broke pile ups
with A 20 meter quad at 50 foot, even with
many big guns all calling at once. The quad has
the ability to hold the band open for dx longer than a
yagi. I have saw this many times, just tune across a
dead or dyeing band and many times the
loudest stations heard will be using a quad. I don't know
why this is so, but it's a fact. May be it's
because the loop has a broader vertical beam width,
has more capture area, is more resistant to
fading and has a quieter noise floor.
I have never had a problem with matching directly to coax on
frequencies below 20 meters. My 40 meter loop
hung at about 45 degrees covers most of 40 meters
with low swr. A quarter wavelength of 75 ohm
coax (RG-11) between your antenna and 50 ohm
coax will make for a better match on the higher bands.
When you add a parasitic element you will have no
problem matching. a two element quad is real close
to 50 ohms. A single loop is closer to 75
ohms.
Use the formula 1005 divided by the frequency
in MHz and it will be real close to your target
frequency.
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