See my previous postings on the Force 12 EF180BV. This is a 37 foot high
linear loaded vertical. I used a pair spaced 30 feet (one-eighth
wavelength) to get top 5 80M single band finishes in CQWW and ARRL DX from
a small lot in UK. The array survived several 80mph windstorms. With lots
of short radials, the array only occupies a 60 foot square piece of real
estate. If really space challenged, one EF180BV with say 60 x 25 foot
radials will deliver a good punch from a tiny lot. The array was beaten
out by the many 4-squares in UK, but not by much - 1/2 - 1 S unit
estimated. On the other hand if you have space for a delta loop at 90 feet,
that probably will beat out the single vertical.
I'd anticipate the Sigma 80 doing a good job, depending on soil conditions
in its vicinity. Even though it does not itself require radials, in poor
conductivity soil conditions, I'd want to lay a mat of wires to get the
near field conductivity up; and if you have the real estate, some really
long wires to impove the far field (the Sigma is a half wave, so far field
conductivity is more important than it is with a quarter wave). So it may
not save the work of laying radials - but will get out way better than the
quarter wave verts with no radials :-)
Dave
WJ6O
G3WGN
80m op at M6T
----------
From: n4kg@juno.com
To: TOWERTALK@contesting.com
Subject: Re: [TowerTalk] Force 12 Sigma 80 (and alternatives)
To: <towertalk@contesting.com>
Date: 10 February 2002 16:53
I'm not sure I agree that a base loaded 35 ft 80M vertical
with a good ground system "would work nearly the same
as a full size antenna" as W8JI suggests.
My friend KZ4V had an HF2V vertical which is
essentially base loaded on 80M with 120 radials
(exact length unknown but at least 30 ft) that worked
very well on 40M but SUCKED on 80M where she had
to struggle in pileups to work DX.
A vertically polarized Delta Loop and Inverted Vee, with
apexes at 90 ft each were MUCH more effective when
installed a few years later. I expect a TOP loaded vertical
would also be much more effective than a base loaded vertical
The MFJ 1792 80 / 40 vertical is one reasonably priced option
which is full size on 40M with an isolating coil and top hat
for Top Loading on 80M and priced around $160.
Another option is to shunt feed a short tower / Yagi combination
or use my Elevated GP approach shown in JUNE 1994 QST or
the ARRL Antenna Book and Handbook which uses a Yagi as
a Top Load for an 80M GP.
Tom N4KG
On Mon, 21 Jan 2002 "Tom Rauch" <w8ji@akorn.net> writes:
>
> > Have any readers had experience with Force 12 Sigma 80??? I am
> > considering a vertical due to small lot and dissatisfaction with
> my inverted vee for DX. The info on F 12's site looks interesting but
> > $600 for a 80M vertical !!!! WOW. Opinions??
>
>
> Why not just build a vertical Brad?
>
> While linear loading is generally not as efficient as lumped loading
>
> using properly designed inductors or a small capacitance
> hat/inductor combination, you'd almost certainly never notice the
> difference (expect perhaps in a yagi). By far the bulk of losses are
>
> generally in ground systems, so concentrate on a good earth
> ground. If you have a really good ground system, a 35 foot base
> loaded vertical would work nearly the same as a full size antenna!
>
>
> If you could just erect a 30-40 foot push up mast, and make
> guylines to the top load the mast, you could have a really nice
> broad-band and efficient vertical for less than $100.
>
> Another choice is the 80/40 meter MFJ vertical. While it is narrow
> banded on 80, but works quite well. It is top loaded and about 34
> feet or so high. You could also modify it and make a better 80
> meter antenna out of it by using a larger "hat" at the top.
> 73, Tom W8JI
> W8JI@contesting.com
>
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