Re: [amsat-bb] Velocity Factor

["Dr. Jim Akers" <jakers@xxxxxxxxxxxxxxx>]

CN8ZE,

The fact of the matter is that radio waves travel at a different rate in a
transmission line than they do in free space.  The ratio of the velocity
in the line to that in free space is the VF of the cable.  That is

VF=V/C .  

You didn't say what cable you are planning to use but for most of the
cables that hams use, like RG-8, RG-58, RG-11 and RG-59, VF is about 0.66.

Hope this helps.

73...Jim...W5VZF.

Dr. Jim Akers
Dept. of Electrical 
and Computer Engineering
Miss. State Univ. 


On Thu, 7 Feb 2002, el bachir zantou wrote:

> Hi everybody,
> I'm up to build a quarter-wave antenna using a coax cable. Then a colleague 
> of mine told me that the length of the radiating inner wire is not just the 
> quarter of the wavelenth, but it should be multiplied by the VF(velocity 
> factor) constant of the coax cable witch depends on its type. Could anyone 
> bring to me more information?
> Thanks in advance.
> el bachir ZANTOU
> CN8ZE.
> 
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