[TowerTalk] shunt feed

[Craig Clark]

>
>OK, with all this talk about shunt feeding - maybe I am ready to take the
>plunge.  I am usually not so stupid but I have read about shunt feeding and
>end up with more questions than answers.
>
>My tower is a 45G with an Optibeam OB17-4 on top (40 foot boom - 17
>elements) and then a WARC-7 (7 elements on a 14 foot boom) about 12 feet
>about the Optibeam.  So, quite a bit of top loading and with 80 foot tower I
>have wondered about shunt feeding for 80 and esp 160 meters.
>
>Can someone point me to a good step by step resource and will you also
>answer my questions afterwards?  I would love to do better on 160 meters.

How high is the tower? Do you have guy wires? Are they insulated from 
ground? If not, stop here and develop a plan B.

Put lots of radials down.

Run a wire or wire cage (6" - 12" on a side) to the top of the tower 
spaced 2-3 feet.  Ground this cage to the top of the tower.

Put a step-up L network at the base; you are matching 50 ohms to 
~~200 ohms (series L, C to ground on the antenna side.)

Tune for minimum SWR

You are good to go.

Craig K1QX
73, Craig Clark, K1QX

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