Re: [TowerTalk] vertical feedpoint and phased verticals

[Jim Brown <jim@audiosystemsgroup.com>]

Hi Kelly,

A common mode choke will be most effective if placed at the antenna 
feedpoint, but all practical chokes I know of THAT WORK must be placed 
at a point where the antenna is matched and fairly close to the Z of the 
choke. I've never used full wave loops, and don't know what the Z is at 
the feedpoint. If, for example, the choke is 1/4 wave from the antenna, 
any noise picked up on that 1/4 wave length of feedline will couple to 
the antenna.
A choke wound from a pair of enameled #12 has Zo of about 53 ohms; #12 
or #10 THHN is about 93 ohms; #12 Teflon is about 105 ohms.
73, Jim K9YC

On 2/21/2018 9:11 PM, Kelly Taylor wrote:
> Eclerity doesn’t want me to send this to Jim Lux for some reason, so putting 
> this out there:
>
> When one has created a full-wave loop and has cut a matching line to 1/4wl*vf, where 
> should a common-mode choke be installed? At the feed point of the antenna? At the 
> junction between the matching line and remainder of feedline? If at the antenna, does 
> the choke effect the matching line’s length?
>
> Any ideas? I’ve only ever seen designs that ignored a choke.
>
> 73, kelly, ve4xt
>
> Sent from my iPhone
>
> > On Feb 21, 2018, at 21:15, jimlux <jimlux@earthlink.net> wrote:
> >
> > > On 2/21/18 6:18 PM, Jamie WW3S wrote:
> > > Phasing 2 verticals, using the Christman method has detailed in several of 
> > > ON4UN book....using a radial plate with a bulkhead connector at the base, and a 
> > > 19 inch coax pigtail from the connector to the vertical....for measuring 
> > > purposes is that 19 inches part of the coax phasing length, or part of the 
> > > vertical antenna height?
> > part of the coax
> >
> >
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