Topband: Coax VF

Stan Stockton stan at
Wed Mar 28 15:45:11 EST 2007

> On 28th March, Mike wrote...
>> " seems that I read in ON4UN a rather ominous recommendation that
> foam dielectric be avoided for use as phasing lines, the reason being that
> the VF does not remain constant with time & temperature. He recommended
> using only solid dielectric coax for that purpose. I know this isn't what
> you wanted to hear, but it may save you a lot of grief down the road.  I
> will try to find the exact paragraph in the latest ON4UN book."

I thought ON4UN simply pointed out that the only coax you could use was foam 
for certain applications - like four square if you wanted to use quarter 
wavelength lines to reach a center point in the array.  I don't remember 
anyone ever saying not to use foam provided you know what the velocity 
factor actually is.

Stan, K5GO 

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