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Re: Topband: Antenna Question

To: "rick darwicki" <n6pe@yahoo.com>, "Group Topband" <topband@contesting.com>
Subject: Re: Topband: Antenna Question
From: "Tom W8JI" <w8ji@w8ji.com>
Reply-to: Tom W8JI <w8ji@w8ji.com>
Date: Mon, 9 Dec 2013 14:23:43 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Do you think a Nye would tune my antenna to 160/80/40 if I extended it to 43 feet or so? Base voltage problems?>>

With 500 watts actually applied to a 43 foot vertical made of 1 inch tubing, the base voltage is about 14 kV peak.

With standard 1/4 inch bolts forming the arc electrodes, 14 kV will typically arc about 1 inch across the surface of any clean base insulator material in 60-70% humidity. Some types of insulator material can be worse, pretty much none will be better. Dryer air will be better.

Voltage changes by the square root of power change, so 1000 watts is about 20 kV and 250 watts is 10 kV peak.

This is the actual voltage **if** you can manage to get that power level into the antenna.

Doubling the antenna tubing size reduces voltage by about 10%.



73 Tom



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