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[TowerTalk] Measuring Coax Length

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