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Re: Velocity Factor



If this is correct then I agree with you.  If you want to get real critical,
at VHF frequencies, the diameter of the radiating portion will affect the
length.  The larger diameter, the shorter the radiator.  From the ARRL
handbook.

73, Roy -- W0SL
http://home.swbell.net/rdwelch
----- Original Message -----
From: "Howard Long" <howard@howardlong.com>
To: "Howard Long" <howard@howardlong.com>; "el bachir zantou"
<el_bachir_z@hotmail.com>; <amsat-bb@AMSAT.Org>
Sent: Thursday, February 07, 2002 19:07
Subject: RE: [amsat-bb] Velocity Factor


> 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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