I believe that if you are feeding the delta at the middle of one side, then
the antenna's radiation pattern is vertically polarized and the horizontal
parasitic won't do anything for you. I made a quick NEC model just now
that indicates a vertical placed behind the antenna could be tuned to act as
reflector, producing about 10 db F/B and about 3 db forward gain optimizing
for length only - the performance did not seem to be very sensitive to
position. An interesting idea might be to explore one on either side, each
length-tuned as a director, then add switchable loading so that one would
act as director and the other as a reflector with 180 degree switching....
one could also just build a pair of phased verticals for the same effort I
guess...
FYI about 10 years ago I built something similar for field day using a 40m
wire vertical hung from a tree with a parasitic V-shaped vertical wire
dipole reflector behind it - kind of like a vertical jungle job except that
I could move the tensioning rope almost 360 in a circle around the vertical
radiator to change the direction of the pattern since the spacing was fixed
by the top support rope which was shared with the vertical. Anyway, the
antenna worked very well and I made over 750 QSO's on 40m that evening just
following the propagation.
Hope this info is useful & good luck on your project!
73
Matt
KM5VI
Interesting ideas though.
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Tom
Osborne
Sent: Monday, September 21, 2015 11:13 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 80 meter wire antenna question
If you get some answers directly sent to you, I'd sure like to see what they
have to say about this. Thinking of doing something like this with a
40 meter delta loop. 73
Tom W7WHY
On Mon, Sep 21, 2015 at 6:25 PM, Dick Allardyce (N4RA) via TowerTalk <
towertalk@contesting.com> wrote:
>
> Hi all,
>
>
> I need some advice about a wire antenna for 80 meters. I have two 85'
> towers that support a nearly-square80 meter full-wave loop broadside to
EU.
> It fits nicely, but the bottom is only about 10' off the ground. It's
> fed in the center of one vertical sidewith a 1/4 wave of RG/11. It works
well.
> I'd like to hear of opinions or experience with adding awire parasitic
> element at this low height. Specifically, I'd like to add a half-wave
> wire yagi element spaced about .15WL that would be switchableto 3
> different
> lengths: phone director, CW reflector or phone ref/CW dir. I change
> the physical size of the loop for CWor phone. I'd like to remotely
> switchdirection (and mode) of the resulting antenna by changing the
> length of theyagi element.
> Any opinion as to the usefulness of a parasitic element ofthis design
> with the whole thing so near ground? The yagi element will probably
> only be about30' in the air. I don't expect 2 elementperformance, but
> I don't want to bother if someone already knows it would be awaste of
time.
>
> 73
> Dick
> N4RA
>
>
>
>
> _______________________________________________
>
>
>
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