Topband: 160 Shunt-Fed Tower Readings

[Larry K4AB]

>Why do you feel a need to improve it?

Thanks for the response, Charlie!

I'm concerned about a few things:

1) I'm thinking the antenna is electrically too short.  After all, the
Yagi at the top really isn't adding too much top loading.  And I'm thinking
adding a couple of top loading wires connected to the tower
might be beneficial.

2) What exactly is the analyzer telling me when it says C:15893pF?
I'm far from an engineer, but something tells me that's way high.  Or is it?

73,
Larry K4AB


On 12/10/14, Charlie Cunningham <charlie-cunningham at nc.rr.com> wrote:
> From your description and your measured data, Larry, I don't see how you
> could improve the antenna noticeably!  Why do you feel a need to improve
> it?
> I appears  to be resonant, well-matched and it appears  to have an
> excellent
> ground image system! I think you might be kidding yourself if you change
> anything! As the old adage says n "If it ain't broke -don't fix it"!
>
> 73,
> Charlie, K4OTV
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Larry
> K4AB
> Sent: Wednesday, December 10, 2014 2:41 PM
> To: topband at contesting.com
> Subject: Topband: 160 Shunt-Fed Tower Readings
>
> The antenna is a 94' Rohn 25, with a Force 12 24'boom Delta 6BA on top.
> Note
> that the elements are insulated from the boom. The base of the tower is
> grounded.
>
> 73 radials are attached to the base ranging in length from 130'-250'.
> 15,000 feet of radials, average length of ~200'.
>
> It is fed through a  series 1000pF 10KV Jennings vacuum variable.
> The shunt is a 4 wire cage about 3" in diameter and attached at ~45'
> level.  It is spaced about 3' from the tower.
>
> Here are the readings I get from a RigExpert AA-30 at the feedpoint:
>
> 1.830 kHz
> Series model: lZI: 59.7 Ohms
> R:59.5 Ohms
> SWR: 1.23
> X:5.6 Ohms
> C: 15893 pF
>
> What are these reading telling me,and how can I improve the antenna?
>
> Thanks, in advance!
>
> 73,
> Larry K4AB
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