The linear loading allows the 7 MHz length to be SHORTER tip-to-tip.
It is an easy exercise on EZNEC (or ...) to show the movement of
secondary resonances when a 7 MHz element is folded. When you model it
just use a single wire element in free space, and to keep from
violating some modeling caveats, keep the wire spacing in the folds to
a half foot, and make the segments no more than one foot long.
It will demonstrate the concept.
At NY4A, we use folded elements on a 4 element 80m wire yagi to keep
from detuning the 40m and 20m elements directly below it on the same
catenary. It's not a 3rd harmonic problem like 40/15, but the class of
problem, and the solution, is the same.
The 40m current on the 80m elements is down 25db or more, even though
in some spots there's less than ten feet separation. The isolation at
a multi/multi station has its own value per se, but if there's
effective isolation, then one antenna can't "pull" the other off
design.
73, Guy.
----- Original Message -----
From: <kk9a@arrl.net>
To: <TOWERTALK@contesting.com>
Sent: Sunday, August 08, 2004 10:29 AM
Subject: Re: [TowerTalk] STACKING
> Why would moving the linear loading further out and having longer
elements
> change anything? Wouldn't it still be the electrical equivalent of
a 1 1/2
> wl dipole on 21 MHz?
>
> ----- Original Message -----
> From: "Pete Smith" <n4zr@contesting.com>
> To: <N2TK@arrl.net>; "'RICHARD BOYD'" <ke3q@msn.com>;
> <towertalk@contesting.com>; "'Jose Castillo'" <N4BAA@cox.net>
> Sent: Sunday, August 08, 2004 01:07
> Subject: RE: [TowerTalk] STACKING
>
>
> Yes, exactly, but the 240/230 doesn't use the N elements, so far as
I
> know. The N element antennas are much bigger and heavier.
>
> 73, Pete N4ZR
>
> At 06:22 PM 8/7/2004, N2TK wrote:
>
> >Pete,
> >The MAG240N and EF240S seem to be two different type antennas. The
"N"
> >series has the linear loading moved out away from the boom.
> >
> >N2TK, Tony
> >-----Original Message-----
> >From: towertalk-bounces@contesting.com
> >[mailto:towertalk-bounces@contesting.com]On Behalf Of Pete Smith
> >Sent: Saturday, August 07, 2004 5:38 PM
> >To: RICHARD BOYD; towertalk@contesting.com; Jose Castillo
> >Subject: Re: [TowerTalk] STACKING
> >
> >The 240 part of the F12 antenna is, I believe, the same as an
EF-240S. At
> >6 foot spacing from my top tribander, I had to turn my EF-240S 90
degrees
> >to prevent significantly affecting the SWR of my F12 tribander on
> >15. Advice from Force 12 was at least 12 feet spacing, but each
unique
> >combination of antennas brings its own set of problems.
> >
> >73, Pete N4ZR
> >
> >At 02:53 PM 8/7/2004, RICHARD BOYD wrote:
> >
> > >As I often do, quoting others more expert than myself, the main
issue
> seems
> > >to be detuning of the 15M yagi by the 40M yagi. I asked W3LPL
how far a
> 15
> > >and a 40 should be apart. He thought 30' would be good.
> > >
> > >Most of us would not be able to get that much distance and still
have
> them
> > >both rotating on a mast at the top. One of them would either
have to be
> > >sidemounted lower down the tower, or you have to accept the
potential for
> > >degradation of performance by having them closer.
> > >
> > >In the real world, many people put their tribander and 2-el 40
within a
> few
> > >feet of each other and are satisfied with the performance.
Obviously,
> more
> > >is better. While it's a different situation, different bands, I
have 20
> >and
> > >15 yagis 8' apart and they've always worked well. It's the
> > >interaction/degradation problem that causes people to pair 40/10
and
> 20/15
> > >on two towers -- alternatively, 40/20 and 15/10. But not 40/15
together.
> > >With a tribander for 20/15/10 that's not the situation you have.
15 is
> the
> > >one that suffers, typically.
> > >
> > >Probably 6-8-10' separation between the tribander and 40 is worth
a try
> and
> > >see if it works satisfactorily for you. The resonant point
and/or
> pattern
> > >of the 15 may change.
> > >
> > >You might try putting up the tribander first and do good
performance
> plots
> > >across each of the three bands. Then put up the 40 at whatever
> separation
> > >you can achieve and repeat the plots to see what effects you can
observe.
> > >
> > >73 - Rich, KE3Q
> > >
> > >
> > >----- Original Message -----
> > >From: "Jose Castillo" <N4BAA@cox.net>
> > >To: <towertalk@contesting.com>
> > >Sent: Thursday, August 05, 2004 7:54 PM
> > >Subject: [TowerTalk] STACKING
> > >
> > >
> > > > Hello,
> > > > I am planning on purchasing a SteppIR 4 element yagi.
> > > > I also have a Force 12 240/230 (2 ele on 40 and 30 meters)
> > > >
> > > > How high above the SteppIR would be adequate?
> > > >
> > > > 73
> > > > Jose - N4BAA and YI9BAA
> > > >
> > > > _______________________________________________
> > > >
> > > > See: http://www.mscomputer.com for "Self Supporting Towers",
> "Wireless
> > > > Weather Stations", and lot's more. Call Toll Free,
1-800-333-9041
> with
> > > > any questions and ask for Sherman, W2FLA.
> > > >
> > > > _______________________________________________
> > > > TowerTalk mailing list
> > > > TowerTalk@contesting.com
> > > > http://lists.contesting.com/mailman/listinfo/towertalk
> > > >
> > >_______________________________________________
> > >
> > >See: http://www.mscomputer.com for "Self Supporting Towers",
"Wireless
> > >Weather Stations", and lot's more. Call Toll Free,
1-800-333-9041 with
> > >any questions and ask for Sherman, W2FLA.
> > >
> > >_______________________________________________
> > >TowerTalk mailing list
> > >TowerTalk@contesting.com
> > >http://lists.contesting.com/mailman/listinfo/towertalk
> >
> >_______________________________________________
> >
> >See: http://www.mscomputer.com for "Self Supporting Towers",
"Wireless
> >Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041
with any
> >questions and ask for Sherman, W2FLA.
> >
> >_______________________________________________
> >TowerTalk mailing list
> >TowerTalk@contesting.com
> >http://lists.contesting.com/mailman/listinfo/towertalk
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers",
"Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041
with any
> questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers",
"Wireless Weather Stations", and lot's more. Call Toll Free,
1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
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