If you have a "random wire from a high structure, I would suggest a
popular antenna from the 60's:
Cut it to 133' and insulate the rest.
Depending on the convenience, break the 133' 49 feet from either end,
and attach ladder line. Use tuner in the shack.
On 75/80 it will radiate like a dipole strung identically. On 40, will
have a 4 node cloverleaf at low angles, with nulls off the ends and at
right angles. It radiates off the ends at high angles. If it's tilted
down and inducing secondary radiation in the tower, the pattern on 40
will start to become indistinct, with a strong lobe in the direction
of the tilt.
I suspect the lack of results with the random wire has something to do
with getting power into it, and its orientation. The setup above WILL
accept power from a tuner and will exhibit impedances at the end of
the feedline that the tuner will find manageable.
Using the boom as 40 m dipole is good if you can actually get up there
and do the work.
73, Guy.
----- Original Message -----
From: "Chris Hurlbut" <hurl8957@uidaho.edu>
To: <towertalk@contesting.com>
Sent: Thursday, March 28, 2002 12:42 AM
Subject: [Towertalk] I need to be louder on 40 and 80.
> Hi everyone,
> Maybe some of you can help me out. I'm looking to improve the 40
and 80
> meter signal here at the University of Idaho, W7UQ. Right now the
antenna
> is a ladder line fed inverted vee wire of unknown origin, up about
50 feet
> on the side of a wood chip silo. I've been thinking up ideas, but
I'm not
> really sure what would work out best. Maybe some of you out there
have
> experience with one or more of these and could help me out. Here is
what we
> have here at W7UQ:
>
> On top of the powerplant on campus is our tower with a TH7 on top.
I am
> guessing the tower starts at 50 feet, and is 50 feet tall. This
puts the
> TH7 at about 100 feet. There isn't much room to stretch out wires
or
> anything on top of the tower that would go out.... but something
might be
> worked out with the powerplant people. Just below the TH7 is a
random wire
> that seems to be worthless, but it is very large. I've never used
this
> antenna effectively on any band. My goal is to be loud for DOMESTIC
> contests... such as NAQP, SS, and the sprints. Very rarely would I
ever do
> a DX Contest seriously from here. There is limited space, but a
wire
> pointed east/west is doable (ie dipole, etc).
>
> I have had a few suggestions already about what might work, but I'm
not sure
> if some of them would be worth the trouble. On the other hand, they
may
> turn out to be great. Here is what I have thought up, or people
have
> suggested:
>
> 1) Loading the tower for 80 meters, and hanging radials off the side
of the
> silo. Sounds like a great idea to me, just not sure if the
powerplant folks
> would go for it. Would it be THAT much better than a dipole? What
about
> effectiveness in a domestic contest setting? Would it work at all
with 50
> feet of tower and a tribander? Hanging radials?
>
> 2) Loading the guy wires as a sloper array if they're long enough,
shorting
> at the breaks in them. Not sure how this would work, but it sounds
cool.
>
> 3) Dipole on each of 40 and 80, up as high as I could get them.
(Seems like
> the best to me?)
>
> 4) Other wire type inverted vee array such as a double extended
zepp. Maybe
> it has more gain than a dipole?
>
> 5) HF2V butternut vertical. We have one of these in the shack +
coax ready
> to go up. Aren't they supposed to be ground mounted with a ton of
radials?
> Not sure we could get it on the ground, or up in the air with enough
wire
> for it to work.
>
> 6) 2 element 40m yagi fixed to states (I WISH! heh) But maybe a
wire yagi
> with close spacing? It would have to be pretty close spacing... no
more
> than about 12 feet I think, if that much.
>
> I really like the idea of the tower turned into a vertical, but I'm
not sure
> if hanging radials would even work? I'm no antenna expert. Dipoles
seem to
> work OK, at least better than some non-resonant wire.
>
> Any help would be appreciated, and it might even get you an extra
mult in
> NAQP :)
> Thanks,
> Chris KL9A
> kl9a@qsl.net
> http://www.qsl.net/kl9a
>
>
>
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