If you feed your antenna as a dipole, then your counterpoise is the lower leg.
Your radiation resistance will be low if your antenna is short. You need
something to raise it to about 50 ohms which will be either a coil across the
feed point or a capacitor. I have found that there are so few stations with
good 80/75 meter antennas in Field Day and many sites are so noisy, either with
man made noise or atmospheric noise that it is hardly worth the effort to erect
an 80/75 antenna for Field Day unless you have a high transmitter count. Willis
'Cookie' Cooke,TDXS Contest Chairman K5EWJ & Trustee N5BPS
From: Jim Brown <j...@audiosystemsgroup.com>
To: elecraft@mailman.qth.net
Sent: Monday, July 20, 2015 12:14 PM
Subject: Re: [Elecraft] Verticals on mountaintops
Hi Al,
As it happens, W6GJB and I are building a custom 80M vertical for FD use
on a mountaintop. As part of the design process, I've compared it to an
inverted Vee at the height where we could rig it without trees. The
model, of course, is for "flatland," and while HFTA can tell us how
being on that mountain affected the horizontally polarized inverted Vee,
we have no comparable modeling for a vertically polarized antenna. So I
asked Dean Straw, N6BV, retired ARRL Antenna Book editor and author of
HFTA how he thought being on the mountain might affect the vertical. His
answer was "I don't have a guess."
Our vertical will be built from that modular army-surplus mast that
comes in 4 ft sections that fit together with a 40 ft telescoping tube
mounted to the top, with a wire taped to it. We will feed it as a
vertical dipole, and there will be loading both at the bottom and top.
Not at all suitable for backpacking. :)
73, Jim K9YC
On Mon,7/20/2015 9:58 AM, Al Lorona wrote:
> [I've re-named this thread. Was 'Miniature self-supporting HF Antennas'.]
> When the ground is perfect, that's the best case for a vertical antenna. If
> the ground becomes worse than ideal, then the losses increase and performance
> is not as good and the pattern changes: less radiation to the horizon and
> higher takeoff angle.
> But then, if the ground continues to get worse -- let it become the worst
> case, an insulator with zero conductivity-- don't the losses go to zero
> again? And does the pattern go to more like an isotropic, or ...??? If the
> antenna does look more like it's in free space, then this would support the
> statement that there's radiation below the horizon from a vertical on a
> mountaintop.
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