Dan,
If you can get the end of the cable cleaned up well enough to make a
reliable connection, check the loss of the run at the highest frequency
where you can make an accurate measurement. If the shield is compromised
over a significant portion of the run, then I would expect that the
measured loss of the cable to be significantly worse than the published
specification. If the loss and impedance characteristics are still good,
then your probably okay to use the run as-is (unless you are using the
cable for some sort of duplex repeater application where passive
intermod (PIM) might desense a receiver).
73, Mike W4EF..........
On 6/13/2011 7:42 PM, K0DAN wrote:
> So you think the "black hair" I see might be contamination from the jacket
> versus oxidation?
>
> This could be significant, as I might have a chance to use a solvent to
> clean contamination, but cleaning oxidation is probably hopeless.
>
> Guess I need to get out there with the scrap pieces and see what steel wool
> does versus cloth + solvents.
>
> I think it's a lost cause, but am willing to put in a little more time just
> in case.
>
> As to "old cheap coax" this was supposedly "new expensive good coax"! Or so
> the marketing would have me believe!
> 73
> Dan
> K0DAN
>
> ----- Original Message -----
> From: "Jim W7RY"<w7ry@inbox.com>
> Cc:<towertalk@contesting.com>
> Sent: Monday, June 13, 2011 9:19 PM
> Subject: Re: [TowerTalk] BLACKENED BRAID?
>
>
>> It's most likely the jacket. I've had some old cheap coax that did the
>> same
>> thing. RG-213 with the non contaminating jacket was to keep the shield
>> from
>> decaying. As well as the center dielectric.
>>
>> 73
>> Jim W7RY
>>
>>
>> --------------------------------------------------
>> From: "Al Kozakiewicz"<akozak@hourglass.com>
>> Sent: Monday, June 13, 2011 5:46 PM
>> To: "'K0DAN'"<k0dan@comcast.net>
>> Cc:<towertalk@contesting.com>
>> Subject: Re: [TowerTalk] BLACKENED BRAID?
>>
>>> Maybe it's the soil ph or something...
>>>
>>> I've taken to using black PVC water pipe. It's cheap and is almost as
>>> easily buried as coax. I jump on a flat bladed shovel to sink it full
>>> depth; yank the shovel back to expose a crevass; shove the PVC pie in
>>> place and drive the 4x4 over the top to relevel the grass. In a few
>>> months the damage has disappeared.
>>>
>>> That way replacing the coax is easy if it's ever needed.
>>>
>>> Al
>>> AB2ZY
>>>
>>> -----Original Message-----
>>> From: K0DAN [mailto:k0dan@comcast.net]
>>> Sent: Monday, June 13, 2011 8:38 PM
>>> To: Al Kozakiewicz
>>> Cc: towertalk@contesting.com
>>> Subject: Re: [TowerTalk] BLACKENED BRAID?
>>>
>>> Hmmm...interesting. We too have the invisible dog fence, and I have
>>> something like 100' of 14 or 16 gauge insulated household wiring as the
>>> buried loop. Have not had any occasions to dig it up or splice, but what
>>> you describe is what I see on the shield of my sliced RG213/U.
>>> Interestingly, the center strand (twisted) is OK but the shield is
>>> gnarly.
>>>
>>> As suggested by others I'm gonna pull it back til I find clean copper,
>>> but
>>> I have a feeling the whole run is gonna have to be replaced.
>>>
>>> So much for "Mil Spec" and "direct burial". Caveat Emptor.
>>>
>>> 73
>>>
>>> Dan
>>> K0DAN
>>>
>>>
>>> ----- Original Message -----
>>> From: "Al Kozakiewicz"<akozak@hourglass.com>
>>> To: "'K0DAN'"<k0dan@comcast.net>; "K8RI on TT"
>>> <k8ri-on-towertalk@tm.net>
>>> Cc:<towertalk@contesting.com>
>>> Sent: Monday, June 13, 2011 7:27 PM
>>> Subject: RE: [TowerTalk] BLACKENED BRAID?
>>>
>>>
>>> FWIW, we've always had one of those invisible dog fences. The antenna
>>> system for those is basically a loop of insulated #14 AWG wire shoved
>>> into
>>> a
>>> slit in the lawn cut with an edger.
>>>
>>> Early in their lifecycle they are prone to damage from the lawn mower
>>> when
>>> frost heaves or whatever expose a section. That wire is always black
>>> under
>>> the insulation after only a year of burial and is a bitch to get clean
>>> enough to solder.
>>>
>>> Al
>>> AB2ZY
>>>
>>> -----Original Message-----
>>> From: towertalk-bounces@contesting.com
>>> [mailto:towertalk-bounces@contesting.com] On Behalf Of K0DAN
>>> Sent: Monday, June 13, 2011 8:01 PM
>>> To: K8RI on TT
>>> Cc: towertalk@contesting.com
>>> Subject: Re: [TowerTalk] BLACKENED BRAID?
>>>
>>> Thanks...will see what we have. I have a vision of peeling the braid all
>>> the
>>> way back to the hamshack! Could be this "direct burial" stuff really
>>> wasn't,
>>> and the jacket allowed moisture to get into the shield.
>>>
>>> 73
>>> k0dan
>>>
>>> ----- Original Message -----
>>> From: "K8RI on TT"<k8ri-on-towertalk@tm.net>
>>> To:<towertalk@contesting.com>
>>> Sent: Monday, June 13, 2011 11:56 AM
>>> Subject: Re: [TowerTalk] BLACKENED BRAID?
>>>
>>>
>>>> On 6/13/2011 12:39 PM, K0DAN wrote:
>>>>> Seems I saw a post here within the last year that diagnosed the cause
>>>>> of
>>>>> blackened copper shield?
>>>>>
>>>>> My case: I have a buried run of Cable Experts RG213/U Mil Spec,
>>>>> supposedly
>>>>> good for direct burial. It recently got nailed by the lawnmower (thanks
>>>>> to
>>>>> the XYL!), but there's enough stub left above ground to repair and add
>>>>> a
>>>>> connector, salvaging the buried run.
>>>>>
>>>>> I looked at a few of the chopped up pieces and the copper braid is
>>>>> BLACK.
>>>>> The center conductor looks normal, slightly dull copper color but in
>>>>> good
>>>>> shape, easily cleaned with steel wool for solder/connector.
>>>>>
>>>>> I would expect to see some kind of green or brown corrosion, but black?
>>>>> Is
>>>>> this maybe silver plate braid and I'm seeing silver oxidation? Web site
>>>>> says
>>>>> it's copper, not silver.
>>>> IIRC Copper Oxide is black. Sulfide (fertilizers and atmospheric crap
>>>> are *usually*green). Water varies depending on what's in it.
>>>>
>>>> Cut the jacket back until the braid is clean and shiny copper. Oxide is
>>>> a bear to try and solder. Don't let water get in there. If you can't
>>>> fix it right away, seal it thoroughly.
>>>>
>>>> 73
>>>>
>>>> Roger (K8RI)
>>>>> The cable otherwise looks in decent shape, and I do not believe it
>>>>> burned
>>>>> due to high SWR or lightning.
>>>>>
>>>>> I don't really want to replace the whole run but don't know the cause
>>>>> or
>>>>> extent of the blackened braid. I have doubts I can clean it up and make
>>>>> decent electrical connections but am willing to try.
>>>>>
>>>>> RF loss is not an issue, any antennas on this line will be below 7 Mhz.
>>>>>
>>>>> Ideas?
>>>>>
>>>>> Tnx es 73
>>>>>
>>>>> Dan
>>>>> K0DAN
>>>>>
>>>>>
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