Topband: VF drift in coax

[Tom Rauch]

I don't believe for a moment long term VF drift in foam 
cable is any more of a concern in foam coax as it is in 
solid dielectric coax.
I can't even think of any reason that would be true!

Does anyone know why that would be possible or true?

I have a feeling it might be because people think water gets 
into the cable, but that isn't true. The cells are closed. 
It isn't a sponge. Any water simply follows the shield or 
the center (if it isn't a foam bonded to a solid center 
conductor and shield) so it affects solid cables just as 
much as foam.

Now I can see air core cable without a closed dielectric 
filling up with water, but that type of cable is a problem 
in any installation where it is not pressurized.

So where does the idea come from?

73 Tom