Topband: Coax VF
stan at aqity.org
Wed Mar 28 15:45:11 EST 2007
> On 28th March, Mike wrote...
>> "...it 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.
More information about the Topband