[TowerTalk] Coax Life Expectancy

[Jim Brown]

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