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Re: Topband: 160 Shunt-Fed Tower Readings

To: "Larry K4AB" <>, "Charlie Cunningham" <>
Subject: Re: Topband: 160 Shunt-Fed Tower Readings
From: "Tom W8JI" <>
Reply-to: Tom W8JI <>
Date: Wed, 10 Dec 2014 18:50:54 -0500
List-post: <">>
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.

If you run any power, you will likely start to have problems with arcing at the Yagi antenna elements where they cross the boom.

This is because of the poor insulation, and because of the high voltage at the boom when on 160.

The cure for that is to ground the elements to the boom though air coil inductors. Just five or ten uH would work OK, and not upset the antenna operation. This would also add 160 top loading.

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?

It is meaningless. It just means you are measuring almost where the antenna is resonant.

73 Tom
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