[Towertalk] Coax recommendations

[Wendell Wyly W5FL]

Don't underestimate the old standard RG213 coax.

It DOES NOT have a foam dielectric and is much more rugged for normal use,
especially on towers and where it gets flexed around rotators and usually
also costs less.

While Foam Dielectric coaxes have a slightly higher velocity constant and
slightly less loss, they are more delicate and will cold flow (move) such
that the center conductor is no longer concentric with the shield where a
sharp bend in the coax occurs.  I have also had the center conductor on foam
type coaxes slide vertically inside the shield on a 100 foot run up the
tower.

More care is also required in attaching PL-259 connectors to foam dielectric
coaxes than solid dielectric, although you can damage either one quite
easily with too much heat.

There are tradeoffs, and loss is only one of them.

-----Original Message-----
From: towertalk-admin@contesting.com
[mailto:towertalk-admin@contesting.com]On Behalf Of Rob Atkinson, K5UJ
Sent: Thursday, August 08, 2002 12:13 PM
To: towertalk@contesting.com
Subject: [Towertalk] Coax recommendations



I went looking for a new feedline last year and wound up choosing the cable
experts cxp1318fx type of RG8 as a good balance, for legal limit amateur use
on HF at 100 feet or less, between the professional grade lines and the junk
sold in national consumer electronics chains.  It has a foam dialectric 84%
vf, a stranded copper center, foil/braid shield, direct burial jacket, .7 db
loss at 30 mhz/100ft, and if I recall correctly, it handles ~ 2.2 or 2.3 kw
at 30 mhz (so there's some wriggle room).  I'd recommend it for HF at
typical runs of 120 feet or less, as in out the shack, over to and up a 60'
tower. I don't think I would want to use it for a really long run.  Mine is
about 90 feet and I've been satisfied with it so far.  It's about
$0.70/foot; less for > 100'.  I will add (since a little humility never hurt
anyone) that they do a pretty good job attaching UHF connectors if you want
them to which is great for me because I guarantee you, I'm the world's worst
cable connector solderer.

Rob Atkinson
K5UJ
k5uj@hotmail.com



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