Ed wrote:


It is technically true that the dielectric losses are a little bit
lower than for the same solid material; but dielectric losses aren't
important anyway, so using foam makes almost no difference to the
overall cable loss.


While I have no disagreement with everything else Ian stated, I do take
some exception to the above comment about foam. Just take a look at RG-8
for example. With all other aspects of it remaining the same, there
certainly is a significant difference in loss figures when the dielectric
is changed from solid to foam.

Detailed specifications, please?

It is impossible to change only the dielectric and have literally "all
other aspects remaining the same". If you want to keep the same
characteristic impedance, at least one more thing has to be changed -
either the centre conductor diameter or the shield diameter (or possibly
both).


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek