Hi, Here is some information about some of the material being talked about
here.
There are a myriad of manufacturers, each with different quality standards.
There are numerous PVC (Polyvinylchloride) and other jacketing compounds
produced by chemical companies and purchased by wire/cable manufacturers.
These components vary in quality and price. They vary in their resistance to
Ultra Violet (UV) resistance and chemical interaction breakdown. Our
commercial success requires that we be astute in Polymers.
There is much confusion with the terms "UV resistant" and Non-Contaminating
Vinyl ("NCV"). NCV refers to the polymer composition of the outer jacket of
a cable. There are plasticizers in PVC and other types of jackets that can
contaminate via leaching or migrating through the shield and then into the
cable dielectric or into the jackets of adjacent cables. If plasticizers
from the outer jacket migrate/leach into the dielectric, this contamination
can alter the chemical composition of the dielectric or adjacent jackets,
thus affecting the electrical and longevity characteristics of the cable(s).
The way to avoid contamination is to use an NCJ or NCV rated jacket, i.e.
non-contaminating. However, not all chemical compounds rated NC are as good
as others. With regard to UV protection, i.e. the breakdown of the outer
jacket due to UV rays, one needs to obtain quality PVC (likewise if certain
other jacket materials are utilized). A good NCJ compound does not
necessarily mean good UV protection and vice-versa.
A PVC cable should NOT be buried, even if it is a non-contaminating type.
Direct bury cable is achievable using polyethylene (PE) and other jackets.
Also, PE does not contain plasticizers therefore it is non-contaminating and
also it is highly UV and abrasion resistant (due to its higher durometer and
density). For a high grade, low loss, flexible 50 ohm cable, see our
BURY-FLEXTM PE jacketed coax. If has a 20 year life and is a strong
competitor to LMRTM and HeliaxTM, at significantly less cost (57 cents/ft
avg.). Even if you don't need to bury it, it's a wise choice. BURY-FLEXTM
was designed by DAVIS RF Co. and is produced by our closely affiliated
manufacturer, Advanced Digital Cable, Inc. We are particularly greatful to
our associates Steve Payne, General Partner of Advanced Digital Cable and
Press Jones, N8UG, The Wireman, Inc. for their contribution to final
refinements of BURY-FLEXTM and other superb cables.
We closely scrutinize the chemical compounds available for the applications
we are fulfilling. We specify to the manufacturer what we know is most
appropriate for the desired, high quality, outcome. Part of the need for
this is due to the fact that we design cables and wires for everything from
cables reinforced with KevlarTM for monitoring drilling of polar ice caps
(where drill bit lubrication slurry can play havoc with insulation), to FDA
approved jacket materials inserted inside patients. We work with our
manufacturers to effect a highly efficient, quality, long life cable at
highly competitive pricing.
Why would you want a highly efficient, quality, long life cable at good
pricing verses buying an "equivalent item" at one to a few cents cheaper per
foot (a savings of only $3.00 per hundred feet)? Our answer is this: first,
cheaper cables usually are not quality "equals" to our cables. Secondly, we
have been handling, using, and communicating with cable for years. We also
have experience in bouncing signals off the moon, setting ARRL contest
records, and working with other RF engineers who design antennas. What we
have learned is that RF power out and receiver selectivity, sensitivity, and
noise elimination are paramount. These points, however, are immaterial if
the cabling is not providing maximum performance. We feel that the entire
antenna system is the most important aspect of RF communications (assuming
that the rest of the system is operating properly and compared on a watt for
watt output basis and conversely on a comparable receive signal level
basis).
Cable usually does not "stop working". However, depending on it's
construction, it certainly "ages" causing inefficiencies over time. A well
constructed PVC cable will last 9-14 years depending on the environment. A
good PE will last 18-24 years. Poor cable may last only 30 to 70% of the
life of quality cables.
The above information is from: http://www.davisrf.com/amateur.htm Davis RF
Co.
I wanted to provide some information about the subjects being talked about.
I do not have any affiliation with Davis RF Co.
Bob N3DOK
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