Topband: TOP HAT

[BILL MCHUGH]

Can anyone tell me how I can calculate how much effective length a top hat
of given size will add to a vertical of given height?  I recall seeing an
article in QST once which had some calculations to that effect but I can not
locate the article. If I recall correctly, it showed how to figure the
effect in degrees, which would be great.

The particular top hat I am dealing with is 6 spokes, 8ft diameter.  I am
lengthening an antenna by several feet and would like to see in advance what
changes I am going to have to make in my tuning unit after I put this top
hat in place.

Anyone help with either the formula or the source of the article?

Bill, VE3CSK



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