Topband: 160 Shunt-Fed Tower Readings

Charlie Cunningham charlie-cunningham at nc.rr.com
Wed Dec 10 17:11:44 EST 2014


>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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