On Sun, 31 Jan 2010 08:56:41 -0600, Lostgallifreyan
wrote:

Fred wrote in
:


If I went into most places selling cables I'd get laughed at if I took
that line, they'd say 'hie me to a research lab, if not an actual
nunnery'. Not that you're wrong, but if you want a single general
purpose cable for HF and VHF especially if stocking it for general
sale, then there IS a 'best' cable, defined simply by that which most
likely serves the wide range of purposes at a low price. Currently in
the UK that cable seems to be RG6; few places like to stock more than
one type for RF if they think one will do. Perfectionism is NOT the
first base. It's reasonable to expect some standard without being told
to either become an expert or use a bell wire and stay in ignorance.
RG6 works, but they sell it for VHF/UHF, not RF. I'm not so concerned
with moderate losses, but SNR maintained by good shielding matters to
me.


You seem to miss the point that one shop's RG6 (or most other RG cables)
may well not be the same as another's. So there is no definitive answer
to you question.


No, haven't missed that at all. Most of my time is spent looking at all the
RG6's out there and examinng that. Besides, most advice out there implies I
have to buy it and try it to be sure, which is stupid because it's cheaper
and faster to get a better cable! RG6 is specified for UHF, I want HF.

I have 5 runs of RG-6 (foil plus braid) running in a conduit with 2
LMR-600 cables carrying 1500 watts of RF at HF. I also have 3
CAT6 network cables in there. None of them hear the others.


It is also very unlikely that 'good shielding' will have any effect on
SNR in most applications, other than due to increased loss if the
braiding is very very poor, or you are running the cable very close to a
source of broadband interference.


I've been told that braid makes a great deal of difference to common mode
noise pickup, and that while a thin foil and loose braid is fine at UHF it's
not to be expected to do the same for HF.

It's the shield, of which the braid is only part. Only if you are
running the RG-6 with other HF cables *might* you find a problem. As
I said above, I have 5 of them in the same conduit with cables
carrying 1500 watts of HF RF and there is no cross talk. That thin
foil is just fine at HF as well as UHF as long as it's not carrying
substantial power. Where you really need the extra shielding is at
very low frequency,or very high power. They do make quad shield RG-6
for receiving, but it's not a cable for high power transmitting. I'd
not put more than 100 watts into RG-6 of any configuration.

73 and good luck,

Roger (K8RI)



http://www.abccables.com/info-rg59-vs-rg6.html is one of the more descriptive
texts I read. No RG6 that I have found fits the description given there for
HF. RG59 does though, as does BT2002. I think I'll be going with that BT2002
anyway, never mind the expense. The waste of time trying to avoid it is alone
beginning to look more expensive than the price difference.