On 2/14/2023 4:30 PM, Jim W7RY wrote:
Ultraviolet from the sun is what degrades PVC I believe... ?
That's my understanding as well, but I don't know it to be a fact.
I do, however, have additional experience with vintage coax from several
manufacturers that I, along with many of N6RZ's neighbors, helped his
widow remove from his station (indeed, to break down all of his station,
including several towers). I also helped her catalog his "stuff" and
dispose of it.
Much of his stuff was sold, but I took a lot of the coax to a meeting
the large contesting club of which we were both members, and offered for
the taking. Nearly all of it looked to be in good shape, nearly all of
it being pretty good quality stuff, but I'm guessing much of it was 20
years old. Everyone turned their noses up at it, so I took it home, made
stubs out of it, and measured them, plotting attenuation vs. frequency.
Out of several dozen stubs, only one showed any significant degradation,
the coax from which it was made came from a shed and the shield showed
significant oxidation from water intrusion. I think a lot of folks throw
away a lot of good coax for no good reason.
My conclusion was, and remains, that unless coax has suffered either
that sort of damage, or is of quality that is damaged by UV, it's going
to last a long time. I experienced significant water intrusion due to
construction of a dipole center insulator that allowed leakage into the
coax -- water flowed through more than 150 ft of coax to the entry
panel! Visual inspection showed oxidation of the shield had begun, and
loss measured with a VNWA had increased a bit in the 6-8 months since it
had been installed. This was RG11, either Belden 8213 or an equivalent
from Davis RF that measured like 8213.
73, Jim K9YC
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