On 6/14/2011 12:46 PM, K0DAN wrote:
> It was already black when the mower got to it. The problem could have
> been there for several years.
>
> Some years back this feedline had a Carolina Windom (off-center fed
> 260' dipole), feedpoint had coax terminated in a choke. On occasion I
> would have trouble getting a good match at QRO on 160M which led me to
> believe I might have saturated the choke and burned it up. Eventually
> the antenna blew down and it was a moot point. However the blackened
> braid which we speak of was near the junction of the "feedline" and
> the end of the choke. If I did burn the choke or have arcing in the
> coax, it could explain the blackness, however the dielectric and
> center conductor are in good shape and there is no smell/feel of
> typical carbon burns. I suspect this is corrosion but cannot rule out
> a HV event. CSI and antenna forensics!
In that case I'd concur that it's most likely moisture that got in from
the choke end. It takes some mighty fine water proofing to keep the
stuff out of cable ends. Even when well sealed the braid may "wick"
moisture in. You almost have to saturate the braid that the open end of
the choke to keep moisture out of it.
For those who use Silastic (TM) RTV or any RTV for that matter, they are
not moisture proof. Event he stuff you use for aquariums is not moisture
proof. Water proof? Yes, but not moisture proof which makes it a poor
weather proofing for the ends of coax. Even if you use the Alcohol based
that is non corrosive.
73
Roger (K8RI)
>
> 73
> k0dan
>
>
>
> ----- Original Message ----- From: "K8RI on TT"
> <k8ri-on-towertalk@tm.net>
> To: <towertalk@contesting.com>
> Sent: Tuesday, June 14, 2011 2:08 AM
> Subject: Re: [TowerTalk] Black
>
>
>> On 6/13/2011 11:07 PM, Martin Staffa wrote:
>>> It is water infiltration toss it, or cut it back until shiny and use
>>> it for
>>> jumpers. Martin
>>
>> it may or may not be. I've had surplus coax braid turn black just from
>> being stored in a shed that would get quite hot in the summer.
>>
>> The signs are not good either way, but black is one of the few colors
>> that is hard to pin down just by looking at it.
>> OTOH it it was wet when the lawnmower cut the jacket (did it peel a
>> piece, or cut it in two) it would turn black in short order. (IE a
>> couple of days)
>>
>> 73
>>
>> Roger (K8RI)
>>> _______________________________________________
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