The problem is that ANY length more than 1/4 WL grounded
WILL act as a parasitic reflector. A near resonant reflector
at 0.15 WL can provide 4-5 dB gain (at least in a Yagi) but
a longer (detuned) reflector will still provide around 2 dB gain
and 4 dB F/B at 0.15 WL spacing. For other spacings,
I suggest doing your own model to determine the effects.
Tom N4KG
On Tue, 6 Aug 2002 22:59:31 +0200 "Henrik Weiss" <ozling@mail.dk> writes:
> Another question related to the topic which is of actuality to me
> right now
> is HOW MUCH would one need to detune a tower from for instance a
> Inv. L for
> 160 M. that is supported by the same.
>
> If the tower itself is very close to resonance on the operating
> frequency is
> 100 Kc detuning then enough ? and how can one measure the L antennas
> degree
> of interaction with the tower other than to see no change on the
> feedpoint
> impedance ?
>
> Henrik
> OZ1ING
>
> -----Oprindelig meddelelse-----
> Fra: towertalk-admin@contesting.com
> [mailto:towertalk-admin@contesting.com]På; vegne af RCARIELLO
> Sendt: 6. august 2002 21:07
> Til: towertalk@contesting.com; mwdink@eskimo.com
> Emne: Re: [Towertalk] Interaction of Verticals
>
>
> Dink,
> Why bother putting up two antennas?
> Put up the full size 1/4 wave vertical for 80 meters. Then use it as
> a base
> feed 1/2 wave vertical for 40 meters.
>
> Rich AA2MF
>
> ----- Original Message -----
> From: <mwdink@eskimo.com>
> To: <towertalk@contesting.com>
> Sent: Tuesday, August 06, 2002 6:33 PM
> Subject: [Towertalk] Interaction of Verticals
>
>
> > Hello All
> >
> > I am looking at putting up two verticals as spare antennas
> > on the 40m and 80m. These are meant to be something for
> > use in SO2R, a multiplier radio, or just another choice
> > in a growing antenna menu.
> >
> > What's the feeling on how close I can mount two separate
> > verticals without interaction? These would probably be
> > full size 1/4 wave antenna's and I hope to be able to
> > put 18-24 inches between them. Only one would be used at a
> > time.
> >
> > If there is a problem with interaction, what if detune
> > the vertical not being used?
> >
> > 73
> > dink
> >
> >
> >
> >
> >
> > _______________________________________________
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>
> _______________________________________________
> Self Supporting Towers, Wireless Weather Stations, see web site:
> http://www.mscomputer.com
> Call 888-333-9041 to place your order, mention you saw this ad and
> take an
> additional 5 percent off
> any weather station price.
> _______________________________________________
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> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> _______________________________________________
> Self Supporting Towers, Wireless Weather Stations, see web site:
> http://www.mscomputer.com
> Call 888-333-9041 to place your order, mention you saw this ad and
> take an additional 5 percent off
> any weather station price.
> _______________________________________________
> Towertalk mailing list
> Towertalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
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