[TowerTalk] Coax Choke Balun Effective Lengths

[Tim Duffy K3LR]

There is no question that the length of the coax used as a choke is part of the feed system. Also, when cutting lines for monoband operation I would suggest you use odd multiples of 1/4
wavelength feedlines as well. The current forcing that occurs with odd multiples helps to preserve stacking performance even though the antennas being stacked might have slight differences
in feed point impedance across their respective bandwidths.

73!
Tim K3LR

http://www.k3lr.com

Pat Barthelow wrote:

> Whoa....
>
> Again with all due respect...the coax coil balun requires the RF to transit
> the coax's complete length inside the coax, even that which is coiled into a
> choke... before performing it's choking function by presenting a high
> impedance to current flow on the outside of the shield.  Therefore IMHO the
> length of the coax coil IS significant and must be counted in calculating
> lengths in phasing harnesses....If all that is required is equal lengths of
> two runs, and if the two coax choke baluns are precisely equal lengths, then
> I guess their lengths  can be ignored, because they are equal.
> Do a google search combining  K1TTT     +Choke Balun and you will find an
> excellent Choke Impedance/number of turns/frequency chart for various choke
> designs..
>
> 73, de Pat AA6EG   aa6eg at hotmail.com
>
> >From: "W3YY" <w3yy at cox.net>
> >To: "TowerTalk List" <towertalk at contesting.com>
> >Subject: [TowerTalk] Re: [Force 12 Talk] C-3 Stacking
> >Date: Thu, 3 Feb 2005 01:46:20 -0000
> >
> >VERY interesting.  With all respect to the writer, I'd like to hear other
> >opinions on this one, i.e., the coil baluns should be treated a zero
> >length.
> >
> >----- Original Message ----- From: "Keith Dutson" <kjdutson at earthlink.net>
> >To: <Force12Talk at qth.com>
> >Sent: Thursday, February 03, 2005 1:46 AM
> >Subject: RE: [Force 12 Talk] C-3 Stacking
> >
> >
> >>I think coil baluns should work fine.  Just remember that the coils do not
> >>figure into the phase relationship.  Treat them as zero length.
> >>
> >>Keith NM5G
> >>
> >>-----Original Message-----
> >>From: Force12Talk-bounces at qth.com [mailto:Force12Talk-bounces at qth.com] On
> >>Behalf Of W3OA
> >>Sent: Wednesday, February 02, 2005 7:09 PM
> >>To: Force12Talk at qth.com
> >>Subject: [Force 12 Talk] C-3 Stacking
> >>
> >>I presently have a C-4E and am using a coax coil for an RF choke at the
> >>feed
> >>point.  I'm planning to add a C-3E and use a Stack-2 box from Comtek
> >>Systems
> >>(http://www.comteksystems.com/) to connect them.  In view of the
> >>importance
> >>of using equal length feed lines from the Stack-2 box to each of the
> >>antennas, will using coax RF chokes on both antennas degrade performance
> >>from that expected with using pre made baluns, such as the Force 12 B-1,
> >>on
> >>both antennas?
> >>
> >>Tnx and 73 - Dick, W3OA
> >>
> >>
> >>
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> >
> >
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> >
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>
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