[TowerTalk] Measuring Coax Length

[Mike Fahmie via TowerTalk]

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