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Re: [TowerTalk] Measuring Coax Length

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Measuring Coax Length
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>
Date: Tue, 28 Oct 2014 23:54:35 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Likewise!

I used to believe that if you properly weatherproofed the connections on 9913, all would be OK. Then the tower took a direct lightening strike that removed all the weatherproofing and plating from the connectors. A few minutes later I had water running out of the 2-meter rig and onto the desk. It also ruined the desk.

I gave away all the 9913 I thought I had, which was about 1500 feet, plus a few hundred feet of unused. A couple years ago, the SWR went up on the 40 meter center fed, half wave sloper. When I disconnected a splice in the junction box where the cable came in, water ran out, so I had missed a piece.

I replaced all of the free swinging coax to the slopers with Davis BuryFlex (TM) Although I have used 8X successfully to the 40 antennas running the legal limit with no failures. I prefer the 8X in that use as it has low wind resistance.

73

Roger (K8RI)

On 10/28/2014 9:31 PM, john@kk9a.com wrote:
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@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)

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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--

73

Roger (K8RI)


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