To extend from Ian's remarks:

In some critical applications, the use of coax cable with braided outer Cu
conductor can cause problems.

RF charge flow (current) in the braid experiences a non-linear circuit
resulting in harmonic distortion or IM or both. Just made coax can have a
very low level of non-linearity with the effect increasing with age (and
probable corrosion). Ag plated Cu braid seems to have less of the
non-linear effect - perhaps because of a poorer mechanism for current to
move from one wire to another.
The effects are small, but can be important in certain applications.
Solid Cu outer conductors have advantages beyond mechanical and
power-handling.
73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Ian White GM3SEK" wrote in message
snip


Then it gets worse. Even the thinnest film of corrosion can disrupt the
contact between copper strands in a braid. Unless the current density is
large enough to break down this film, it means the RF current is forced
to flow into the interior of the braid. Again the exact geometry is hard
to visualize, but again the physics dictate that if an isolated
'filament' of current is forced to flow beneath a conducting surface,
the voltage drop per unit length must increase - in other words, the RF
resistance must increase.

Scientific deduction has told us that all these effects must exist.
Whatit cannot tell us is how big they are in real braid, or how
important they are in practice. For that we'll need some measured
numbers.

You have two choices he either look for existing measurements from
people who have demonstrated their competence and scientific approach;
or do it yourself.



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