Lostgallifreyan wrote:


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.

Are their any good references with test numbers on this? Been googling a
bit, haven't found anything definitive yet

- 73 de Mike N3LI -

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.

On Jan 29, 7:56*pm, Roy Lewallen wrote:
....
If there was a "best" cable, there would be only one type. Some have
lower loss, some are more flexible, some have better weather resistance,
some have better shielding, some have a longer lifetime, some tolerate
temperature extremes better, some are more uniform, some are less
expensive, and so forth.

So deciding which cable is "better" requires a lot more information
about what your requirements are.
....
Roy Lewallen, W7EL

Well said, Roy. I just purchased 2000 feet of "RG-6" coax. My main
goal was that I needed hundreds of feet of flooded coax with (good
shielding) that I could afford. The Commscope CATV aluminum foil/
braided coax that was available on eBay fit my needs perfectly.

I'm feeding my remote Beverages with it, as well as running medium
power to an inverted L on 160. Works great.

I'm convinced that no other coax at any price would have worked any
better.

73 Mike
W0BTU

Lostgallifreyan wrote in
:

....
sense, but it is it so?

I wrote some notes that you may find interesting at
http://www.vk1od.net/transmissionline/RG6/index.htm .

Owen

Owen Duffy wrote in
:

Lostgallifreyan wrote in
:

...
sense, but it is it so?

I wrote some notes that you may find interesting at
http://www.vk1od.net/transmissionline/RG6/index.htm .

Owen


Very useful, though I'm still not clear about using it for HF. I found eBay
listing 270364333691 (worth seeing, low cost, good pictures and description),
but that shows a thin braid and film that I read might not be adequate for
shielding at HF. Low cost is great but I wonder if trying to get good
connections to aluminium braid will be more trouble than it's worth, if the
worth of a cable with a copper braid isn't that much higher. (Still looking
for one). The cable that seems most likely to work based on all I read is a
BT2002 cable with a double copper braid over a foam dielectric and stranded
core, but the cost is three times higher.