[TowerTalk] Measuring Coax Length

[john at kk9a.com]

I would not use Belden 9913 outdoors, especially if underground. Some
years back I also purchase 9913 but I threw mine away because it was too
susceptible to water ingress.

John KK9A


To:	Towertalk Reflector <towertalk at contesting.com>
Subject:	[TowerTalk] Measuring Coax Length
From:	Mike Fahmie via TowerTalk <towertalk at contesting.com>
Reply-to:	Mike Fahmie <wa6zty at yahoo.com>
Date:	Tue, 28 Oct 2014 21:15:55 +0000 (UTC)

Some years back, I purchased a 500' reel of Belden 9913 and used a bit
here and
there over the years.  Now I needed four 70' runs to the base of my tower but
didn't know how much 9913 remained on the reel.
My DVM can measure capacitance so I connected it to the free end of the reel
and measured 6300 pF.  Belden says that 9913 capacitance is 24.6 pF/ft so
dividing that into 6300 pF implied that I had 256 ft remaining.  That was
enough for three 70' runs but not enough for four,  oh well.
I cut three 70' lengths from the reel, 45' of cable remained.  (3 x 70) +
45 =
255.  That is just 1 ft less than what was predicted by the capacitance
measurement !!!  Isn't it nice when the numbers work out so well.  Will I
rely
on that technique in the future?  Nope, gotta see it work out like that a few
more times first!
-Mike-WA6ZTY
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