My C31XR came with the insulators/spacers. After seeing some comments about
big winds whipping elements around. I noticed that if i worked at it and
while the antenna was on the groound that I could still make the 20/15 DE's
touch, I fabricated a second set out of fiberglass glass and installed it
further out toward the end of the 15M DE.
Price of making this? about $1.00 since I had to buy the plexiglas at
home depot. I doubt the wind would ever have caused a problem but for a
buck I decided not to take the chance.
I am as happy with my C31 as Jerry is with his stepIR. I too will consider
a stepIR when i see one survive a winter on top of W3LPL's 200 foot tower an
a full year of heavy duty contesting. Personally, I hope none of you guys
buy a C31 cause i don't need the competition
73
Chet N6ZO
Chet N6ZO
----- Original Message -----
From: "Jerry Keller" <k3bz@arrl.net>
To: "Gene Smar" <ersmar@comcast.net>
Cc: "Towertalk" <towertalk@contesting.com>
Sent: Wednesday, November 10, 2004 10:07 AM
Subject: Re: [TowerTalk] Force 12
>
> ----- Original Message -----
> From: "Gene Smar" <ersmar@comcast.net>
> To: "Jim Lux" <jimlux@earthlink.net>; "Darrel J. Van Buer"
<darrel@vanbuer.net>;
> <jimjarvis@comcast.net>
> Cc: "Towertalk" <towertalk@contesting.com>
> Sent: Wednesday, November 10, 2004 12:41 AM
> Subject: Re: [TowerTalk] Force 12
>
>
> > TT:
> >
> > I have a Bencher Skyhawk with the older open sleeve feed system
> > (similar to F12's. Ahem!) Both F12 and Bencher Yagi's have available a
set
> > of phenolic spacers that keep the DEs in the same spatial relationship
over
> > their entire lengths. The need for these spacers is to minimize SWR
> > fluctuations during high winds that cause the elements to whip around,
> > dramatically changing the feed impedance on the various bands.
> >
> > Just a thought but maybe F12 folk whose Yagis don't include these
> > spacers ought to install a set to maintain the design impedance during
windy
> > conditions.
> >
> > 73 de
> > Gene Smar AD3F
> >
> > ----- Original Message -----
> > From: "Jim Lux" <jimlux@earthlink.net>
> > To: "Darrel J. Van Buer" <darrel@vanbuer.net>; <jimjarvis@comcast.net>
> > Cc: "Towertalk" <towertalk@contesting.com>
> > Sent: Tuesday, November 09, 2004 10:56 PM
> > Subject: Re: [TowerTalk] Force 12
> >
> >
> >>
> >> ----- Original Message -----
> >> From: "Darrel J. Van Buer" <darrel@vanbuer.net>
> >>
> >> > I had a lot of trouble tuning 10m once with a C4XL (and changing
element
> >> > length was really bizarre - small changes act as expected, but at
some
> >> > point there would be a big jump to a wildly different resonance),
they
> >> > after taking it down to replace cable on crankup tower it was fine.
I
> >> > THINK the problem is that the drive cell is really sensitive to
spacing
> >> > and parallelism between the elements. If so, then it means loosening
> >> > the U-bolts and shifting element position.
> >> >
> >> >
> >> > >
> >> > >Seriously, has anyone had difficulty with their 3 band matching
> > system,
> >> operating on 15m? There is a C4XL which we finally gave up on after
two
> >> years and put in three separate feedlines. Then, we gave up on that
and
> >> replaced it with an optibeam. Works great.
> >> > >
> >> > >At V26DX, there's a C3 with a 40m kit on it....well, it HAD one. It
> >> never tuned, either, and we finally gave up on it. Seemed to tune ok
on
> >> 20-10, and had
> >> > >reasonable f/b.
> >> > >
> >> > >n2ea
> >>
> >>
> >> I think Darrel is right.. The drive scheme for these relies on really
> > tight
> >> coupling between the driven element (i.e. the one that's actually
> > connected
> >> to the feedline) and the other parasitic driven elements. I was doing
> > some
> >> modeling of this scheme to get a better understanding of what Force12
was
> >> doing, and found that very small changes in the spacing had very large
> >> effects on the feedpoint impedance (the performance as an antenna
didn't
> >> change all that much).
> >>
> >> Perhaps one conceptual model is to think of the three elements as a 3
> >> section LC network (with a lot of coupling between the components).
With
> >> just the right spacings and lengths, all the reactive components cancel
> > out
> >> at the three frequencies of interest (14, 21, and 28). However, change
> > just
> >> one component, and all the zero reactance points move around.
> >>
> >> It's worse than trying to tune a multisection filter, and if your only
> >> tuning tool is a SWR meter, you could spend a very long time trying to
> > make
> >> it work. With some sort of sweeper, and a bucket truck, you might be
able
> > to
> >> do it a bit faster. Very much a case of a clever design, that you pray
is
> >> assembled correctly and rigidly.
> >>
> >> For what it's worth, at the JPL amateur radio club (W6VIO) we have a
C3S
> >> that we used for field day to good avail. It tuned up fine on 10,15,
and
> >> 20, but we only used it on 10 and 20, since we had the Cal Tech club's
> >> (W6UE) 4 element monoband on another tower for 15. For all I know, the
C3
> >> was a fine dummy load on 15.
> >>
> >> Also, for what it's worth, this is an example of an antenna design that
> >> could make good use of a antenna mounted autotuner. As I mentioned
above,
> >> the antenna performance (F/B, gain, etc.) didn't change all that much
with
> >> small changes in the element orientation/length/position, it's just the
> >> reactive component at the feedpoint that's the problem. A well
designed
> > (!)
> >> tuner would probably be as low loss as the L/C inherent in the 3 driven
> >> elements.
> >>
> >> _______________________________________________
> >>
> >> 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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