[SECC] Coax replacement

[Kevan Nason]

I like Jeff's, W4DD comment about posting at least once a month.

Here's something I put in another clubs newsletter about current activity
at N4XL:

·         Truth or fiction?  It came to my attention while preparing a
presentation on different types of feedlines for our local club that most
coax cables, including the non-contaminating type, have a finite lifetime
of between 15 and 25 years. After that, the loss begins to creep up. I
didn’t care enough when I first set up this station to record station data
so have no idea what SWR or reflected loss changes have occurred over the
years. It seems likely any changes due to aging coax would be waaayyy to
slow for me to notice over the 20 years that have passed since I installed
my coax runs; and to that point I can’t say I actually do have excessive
loss. So, I started looking on the internet. Most posts say it should be
replaced.  I ran across a discussion about this on the TowerTalk reflector
(at least I think it was that one) where K3LR (I think) said he doesn’t
replace his unless he sees a problem. He has quite a station so maybe it
doesn’t need to be replaced.



Looking at my exposed coax it is rough feeling and no longer shiny and
black. For the most part, it is Davis Buryflex. I bought some new Buryflex
for a doublet I installed a couple years ago. The 20-year-old cable seems
to be more flexible than the new. Also, when I put the Rigexpert antenna
analyzer on the 175 ft run out to the elevated vertical it says the 7 MHz
return loss is a bit over 1 dB (one way) higher than the specifications say
it should be. Since most coax runs were installed at the same time I assume
they all would read similar loss.



It is getting harder to work as these bones get older. About 200 ft of my
coax is buried in clay. Beginning with the tower, I decided to replace all
the coax rather than waiting a few more years. I’ll rent a trencher next
spring when the grass starts growing again to replace the buried runs. Is
it worth the cost and effort to replace? At the very least I’ll feel better
about my system when I’m in the heat of the contesting battle. At best,
I’ll remove or prevent a couple dB loss in my antenna system. Loss that I
might not be up to fixing 10 years from now. Those crimp on PL-259’s we
talked of last newsletter are working out well.
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