On Apr 17, 2008, at 9:53 PM, Richard (Rick) Karlquist wrote:
> It is in Reference Data for Radio Engineers, Chapter 24,
> configuration N.
>
> Zo = [60/(epsilon^.5)]* ACOSH {[4D^2/d1d2  d1/d2 d2/d1]/2}
>
> where epsilon is relative dielectric constant
> D is center to center spacing
> d1 and d2 are the wire diameters
> ACOSH is inverse hyperbolic cosine
>
> Of course I wonder why would anyone deliberately use different
> diameters?
>
Hmm, it's different in my copy (4th edition (1956), chapter 20):
(276/(epsilon^.5) * log10 (2D/(2*d1d2)^.5) for d1, d2 << D
I suspect (but haven't checked) that the formula Rick gave may be
more general (without the d1, d2 << D restriction).
Bob, N7XY
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