[CQ-Contest] Life of Coax

Tom W8JI w8ji at w8ji.com
Sun Jul 29 08:15:36 PDT 2012

> What would you do?  Replace the outdoor stuff?  Use shack stuff? Use the
> un-used roll?  Throw it all away and start fresh?

I would measure it, which is easy to do accurately with a dummy load, radio, 
and a movable power meter.

I have 20-30 year old cables that are well within new cable loss specs. The 
primary cause of excessive cable loss is tarnish on a woven braid. Usually 
if the braid is not tarnished, it is good. Contrary to myth, it is NOT the 
closed cell foam soaking up water, or the dielectric. The overwhelming part 
of HF cable loss is in the copper, and usually in a woven conductor that 
tarnishes. Way up at VHF or UHF, the dielectric starts to dissipate power.

Foam cables can have less loss at HF, but that is because the center 
conductor can be thicker, not because of less loss in the foam.  :-)

73 Tom 

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