RE: [amsat-bb] Velocity Factor

["Howard Long" <howard@xxxxxxxxxxxxxx>]

Folks - I may have misunderstood what el bashir was saying but here's what I
think is being asked...

Take a piece of coax. Separate the braid from the inner for 1/4 wavelength.
Stick the inner 1/4 wl vertically and use the separted braid as part of a
ground plane (or alternatively a counterpoise).

That's why I say the dielectric in the exposed radiating vertical 1/4 wave
has a VF of 100%, as the electric field is mostly going through air and not
the dielectric sheath.

            |
            |<-inner in dielectric sheath
            |
            |
coax        |
oooooooooooo+------------- Braid

So I say the length of the inner uses 100% VF but with the usual shortening
factor making it 95% of a 1/4 wl in free space.

Phew, this is hard work, and I'm not sure I've understood the question yet!!

73 Howard G6LVB ;-)

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