Hello Tod!
The beads I use do not fit over RG8.
I use teflon double shielded cable that is either 50 or 75 ohm. This cable has
the outside diameter close to RG58 and is capable of handling the legal limit
with a engineered safety factor for mismatched loads. The exact cable is
detailed in the article.
As you point out, bead heating leads to several problems that occur in other
designs which I concluded were not acceptable for my application.
One must also take into account the length of cable introduced by these chokes
when using them in stack designs. Depending upon the stack criteria, I use even
or odd quarter wave feed line lengths to the main switch. This choice depends on
factors such as grounding unused antennas and other in phase/out of phase
combination choices.
Critical control of the design parameters and physical installation lessens the
chance of stack disappointment after everything is installed.
The W0IYH choke stayed at room temperature (its choking capacity was unchanged)
during heavy contest use tests and during 100% duty cycle tests in the lab.
73,
Tim K3LR
Tod - Idaho wrote:
> 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
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