There is a reason that 12M Yagi's interact with
tribanders and 10 and / or 15 meter beams...
12M self resonant elements are only 14% longer
than 10M self resonant elements and 12M Directors
are ~9% longer than a 10M DE so they make fairly good
REFLECTORS to the 10M Driven Element
12M self resonant elements are only 18% shorter
than 15M self resonant elements and 12M reflectors
are ~13% shorter than a 15M DE so they can act as
short DIRECTORS to a 15M Driven Element.
When they are placed only 6 ft from a tribander,
the are CLOSELY COUPLED to the tribander,
being only 0.125WL away on 15M and 0.166 WL
away on 10M, i.e. your typical Yagi element spacing.
Tom N4KG
On Mon, 4 Feb 2002 "Robert Shohet" <kq2m@mags.net> writes:
>
> Hi Dave,
>
> This is an instance where an understanding of "real-life" situations
> is
> important, as well as realistic expectations.
>
> I would expect two antennas 6' apart to have interaction even if the
> model
> says otherwise.
> Having made that very generalized (and sometimes inaccurate)
> statement,
> tribanders are even more complicated than monobanders and therefore
> can be
> expected to have far more complex interaction issues.
>
> I suggest to anyone to ask about issues like that on this reflector
> BEFORE
> actually putting up the antennas. Of course many people are not
> aware of
> this reflector and/or don't subscribe to it, but that's a different
> story.
>
> No one should entirely rely on a model for the same reasons that no
> one
> should entirely rely on their experience either.
>
> 73
>
> Bob KQ2M
>
> >
> > Please don't rely entirely on modeling when designing and
> installing an
> > antenna. Remember its just a tool to see if an antenna works in
> theory.
> > Unless you can build real world interactions into the model or
> schema then
> > its not an end all. I got an excellent model for a W2PV
> > 3 el 12 meter beam but putting it up 6 feet below my KT34XA really
> went
> > askew. The 12 meter beam went to 25.9Mhz and both the 10 and 15
> meter
> > portions of the VA went haywire.
> >
> > 73 Dave K4JRB
> >
> >
> >
> >
>
________________________________________________________________________
> > Where do you get ICE bandpass filters & beverage matching boxes?
> The
> > same place that pays for the hosting of this list: The eHam
> Store.
> > Order online at http://store.eham.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
> >
> >
> >
>
>
>
________________________________________________________________________
> Where do you get ICE bandpass filters & beverage matching boxes?
> The
> same place that pays for the hosting of this list: The eHam Store.
> Order online at http://store.eham.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
>
________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today! For your FREE software, visit:
http://dl.www.juno.com/get/web/.
________________________________________________________________________
Where do you get ICE bandpass filters & beverage matching boxes? The
same place that pays for the hosting of this list: The eHam Store.
Order online at http://store.eham.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
|