A long yagi without a F/B and a 3 db loss over the max gain is
basically a nonsense, expecially at HF and for general amateur use.
It's a much better idea to use two independent rotating staked yagis in
phase, and then to select any pair of directions (not only opposed)
where to beam.
Done it, one can decide if to keep the two directions and then
selecting a single one to receive better (better S/N) signals from
different headings, or if to align the antennas on a single heading.
Aligning (with proper spacing) there is a gain of about 3 dB over the
single antenna and 6 dB over the hypotesis of 1 driven element with
directors on both ends of the boom.
Moreover, stacked antennas at different heights can cover better
(smoother) a wider range of elevation angles when phased or reduce
interferences when used independently.
Last but not least, opposed in heading and phased 180° off, two stacked
yagi show a straight up radiation.
73,
Mauri I4JMY
> ---------- Initial message -----------
>
> From : owner-towertalk@contesting.com
> To : "Bill" <w9ol@billnjudy.com>, towertalk@contesting.com
> Cc :
> Date : Wed, 14 Mar 2001 07:52:30 -0600
> Subject : Re: [TowerTalk] back to back yagis
>
> Way back when we used to use radio linked packet cluster out here in
the
> black hole I toyed with this idea for VHF link antennas. Decided that
the
> best design would be 1 driven element with directors on both ends of
the
> boom. For HF of course front to back would not be possible with this
> design. Never thought seriously about it to try to model it though.
>
>
> At 07:42 03/14/2001 -0600, you wrote:
> >After watching a cluster debate over whether the signal was lp or sp
I
> >wondered if anyone ever modeled a longboom back to back yagi.
> >How would you feed it?
> >and
> >How would you set your rotor presets?
> >
> >LOL but wondering if it's ever been tried?
> >
> >
> >
> >------------------------------------------------------------
> >Eat right. Stay fit. Die anyway.
> >------------------------------------------------------------
> >
> >Bill H. in Chicagoland
> >w9ol@billnjudy.com FireBrick@telocity.com w9ol@telocity.com
> >
> >
> >
> >--
> >FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> >Submissions: towertalk@contesting.com
> >Administrative requests: towertalk-REQUEST@contesting.com
> >Problems: owner-towertalk@contesting.com
>
> Jim Rhodes K0XU
> rhodes@evertek.net
> jim@rhodesend.net
>
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
>
>
--
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