In article ,
Lostgallifreyan wrote:

Ok, if I take that with the point about lower HF loss in RG6, it seems that
my easiest option of a copper-braid RG6 will be good, but this still begs one
question: If BT are using BT2002 double-braided copper and no foil, at
greater cost, what does it do for them that RG6 will not do? Would it be a
matter of transmission power, or something else?

One issue which may be relevant in some applications (transmitters and
repeaters) is internally-generated cable noise.

Foil-and-braid cable has developed a somewhat evil reputation among
repeater operators. The story, as I have been told it, is that the
braid, and the conductive layer on the foil, don't make particularly
good (or continuous) contact. As RF power flows through the cable,
some of the current can jump back and forth between braid and foil,
through imperfect connections each time. This leads to some amount of
discontinuity in the current flow (diodic junction effects or
"micro-arcing") and rectifies a small amount of the RF power into
broadband noise. The same effect might be capable of generating
intermodulation noise, if the cable is carrying two or more strong
signals at the same time.

In many applications this effect is irrelevant. In a duplex
application (e.g. an FM repeater) it can be nasty... the broadband
noise from the transmit channel goes right through the duplexer stage
into the receiver, and can swamp out the desired incoming signal. You
can lose several dB of receiver sensitivity due to this effect.

For this reason, repeater builders prefer to use a non-foil-shielded
cable. Cables with double silver-plated copper braid shields are
popular, as are heliax-type semi-hardline cables.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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