[TowerTalk] vertical feedpoint and phased verticals

[Jim Brown]

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 at 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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