[mythtv-users] quality shielded coax cable
Brian Wood
beww at beww.org
Mon Jul 3 17:03:56 UTC 2006
On Jul 3, 2006, at 10:31 AM, Greg Woods wrote:
> Is that an oxymoron, or is there a place (brick-and-mortar or web)
> that
> is good to look for this? I'm betting the answer isn't "Radio
> Shack" :-)
>
As opposed to "un-shielded" coax cable :-))
Not sure what type of cable you want, you don't say.
Because it really depends on what you want to do, a 75-ohm coax
designed for video (Belden 88281) does not do so good a job for
passing RF energy to 3Ghz., and a wire designed to hang in the air
from the pole to your house won't spool onto a reel very easily.
Cables designed for RF transmission are generally 50-52 ohm
impedance, RG-214U is great but costs about $6/foot.
RF cables also come in single, dual, triple and even quad shield, for
varying resistance to outside ingress and radiation from the cable.
Canaire makes some cables designed especially to be flexible and take
a lot of spooling and un-spooling, a favorite on TV remotes, although
the stranded center conductors are a pain.
Copper or Aluminum shields have different purposes. Times even makes
one with a 90% silver center conductor and 100% copper double shield
(hand *that* reel to a cable installer used to aluminum's weight :-))
Belden makes good cables, Times Wire and Cable (AKA Times Fiber)
does as well.
The normal communications and electronics supply outlets sell them
both, Newark Electronics, MCM etc. Pacific Radio in L.A. has always
had good prices (ever since they bought about 1000-miles of Belden
cable for the LA Olympics back in the 80's).
Essentially the old maxim applies - you get what you pay for, and the
good suppliers make the specs easily available.
It's also important that you use connectors designed for precisely
the cable you are using, the best cable in the world will perform
poorly if it has a 10-cent connector on it that has been crimped with
a pair of pliers, or not crimped at all. It takes skill to properly
solder a BNC connector or a PL-259, but if done correctly it will
work great forever.
If you have a specific purpose in mind let me know and I'll make a
suggestion or two, gratis and worth every penny :-)
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