Tim:
I suspect that the beads you used are the 1" long ones that have a large
enough diameter to fit over RG-8. As you point out the ferrite in the bead
is important. I used to make choke baluns using the W2DU recipe and then
found that if I started using high power on low frequencies the beads would
become warm or even hot. That balun (the W2DU) is only about 12 inches long
vs. your 48 inch one. The beads are usually resistive and reactive to give
the choking impedance -- it depends on the frequency. The lower frequencies
tend to be more resistive than reactive even though the overall impedance
remains high.
In the case that the choking impedance is mostly resistance, the greater the
resistance the less the heating (I^2 * R). The longer length of beads will
have more resistance resulting in higher impedance and also less heating.
The best way to go is the way you did it -- measure the darn things and then
select the BEST. Life is too short to even build everything we can think of
much less repair stuff that is under designed.
73, Tod, KOTO
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of Tim Duffy K3LR
Sent: Wednesday, July 16, 2003 2:18 PM
To: Jim Wilcox
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Antenna Stacking Question
Hello Jim:
The W0IYH balun uses the same physical idea for the choke, however he uses
larger and different beads to increase the effectiveness and the power
handling capability under various
impedances. Therefore, the W2DU design and the W0IYH design are VERY
different. I measured the W1JR balun and I believe the IYH design has better
performance.
There are NO commercial manufactures that are making the W0IYH choke to my
knowledge. The design is 48 inches long.
I do not have my lab notebook with me here in Oklahoma, however you can take
my stamp of approval for what it is worth.
I measured choke effectiveness, resonance and power handling capability
under several load impedances in my tests.
Many baluns do live up to their claim specifications. Several did not.
I was looking for the BEST RF choke I could make or buy. The W0IYH design is
what I use in my systems. Other stations have success with other
chokes/baluns.
I have measured the real world effectiveness of the IYH design in my antenna
feedlines under contest high duty cycle conditions and they live up to my
measurements in all respects.
Other baluns will work fine in most applications where the BEST is not
needed.
73,
Tim K3LR
Jim Wilcox wrote:
> Thanks for the info, Tim.
>
> I did some searching and see that there are some items about your article
in
> the TT archives--go there and do a search for
>
> K3LR and W0IYH "choke" baluns in the feedline system
>
> This indicates that the W0IYH balun is a Walt Maxwell (W2DU) bead balun.
> >From what I can determine (i.e., Jerry Sevick's books), this type
probably
> is bested by Joe Reisert's toroid balun.
>
> Please please believe me that I'm not trying to "get anything started"
here,
> but will you provide more info about what you mean when you say, "I have
> tested every available commercial balun and the IYH choke baluns work much
> better than any of them"? I believe that there are several commercial
> baluns that are precisely this (W2DU--W0IYH) type. Can you provide some
> data, e.g., actual measurements; how does the W0IYH design differ from
that
> of W2DU?
>
> Thanks!
>
> Jim, W3WV
> ________________________________
> Jim Wilcox
>
> ----- Original Message -----
> From: "Tim Duffy K3LR" <k3lr@k3lr.com>
> To: "Bill Tippett" <btippett@alum.mit.edu>; <towertalk@contesting.com>;
> <k2qmf@juno.com>
> Sent: Wednesday, 16 July, 2003 14:58
> Subject: Re: [TowerTalk] Antenna Stacking Question
>
> I wrote a detailed 2 part stacking article that was published in CQ
Contest
> magazine five years ago. I don't have a copy, but Comtek Systems does and
it
> details the baluns that I use. The
> Amidon part number and coax choice for both 75 and 50 ohms is listed in
the
> article. They were designed by W0IYH and I built and tested them using my
HP
> Network Analzyer. I have tested
> every available commercial balun and the IYH choke baluns work much better
> than any of them. I use them for lots of applications throughout my
antenna
> farm.
>
> The article also has lots of hints for stacking 2 and 3 high stacks as
well
> as a full design for the RF switch box I use for all of my stacks (which
> Comtek now sells).
>
> You can obtain information on the baluns and stacking information from
> Comtek at 704-542-4808.
>
> I have no financial interest in any product Comtek sells.
>
> 73,
> Tim K3LR
> http://www.k3lr.com
>
> Bill Tippett wrote:
>
> > <http://lists.contesting.com/mailman/listinfo/towertalk>k2qmf at
juno.com
> > wrote:
> > >
> > > My question is what is the best way to feed the antennas???
> > > Can I use 1to1 antenna balun on each antenna or do I need to
> > > connect the coax directly to the antenna and maybe use some
> > > ferrite beads instead??
> >
> > If you use a balun of any kind, make sure it is connected
> > the same way to both antennas. Many sealed baluns have phasing
> > marks and these should be aligned, otherwise your antennas will
> > be out of phase and will not work well. If your baluns are not
> > marked, check this post to determine phasing:
> >
> > http://dayton.akorn.net/pipermail/towertalk/2000-October/034295.html
> >
> > 73, Bill W4ZV
> >
> > _______________________________________________
> >
> > 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
|