[TowerTalk] Re: Equation for Zo

[David & Barbara Leeson]

See pg 8-7 through 8-23 of Phys. Des. of Yagi Antennas.  Note that this is
the formula for the characteristic impedance, not the input impedance, of
the element.  This is used to get the reactance variation around resonance.

For a tapered element, you can substitute into the formula

Zo = 60 * (ln (2*h/a) -1) an equivalent radius ae such that

ln(ae) = SUM OF Ln ln(an/h), where Ln is the length of each section of
radius an.  This is most easily done by setting up a spreadsheet, with
columns for each section of the element and rows for section radius, 
section length, and Ln ln(an/h), which when summed across gives ln(ae).

Then Zo = 60 * (ln (2*h/ae) -1)

Dave, W6NL (ex-QHS)

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