[TowerTalk] Strange coax failure

[Patrick Greenlee]

The problem was in a 6 ft jumper of RG-58U.  I cut it in half and then 
started to cut off an inch at a time to look for defect. Lucked out and 
spotted it immediately.  The center conductor was migrated out to the 
edge of the dielectric and at one small place probably stuck out and 
intermittently contacted the aluminized foil under the braid. I had no 
bad ohm meter readings but using the jumper to connect the meter to the 
dummy load showed super weird uninterpretable readings. The bad area was 
a couple inches in extent.

Comet doesn't do TDR nor give the sign of the J factor but still is a 
good machine.  I'm back on the air and able to use my antennas again,   
Y A H O O !!!!

Patrick    NJ5G


On 12/15/2014 4:12 PM, Jack Brindle wrote:
> May not need the Tek TDR. The RigExpert AA-170 has a very good TDR function that would be able to tell where the discontinuity point is in the coax. No idea if the Comet device has this functionality, but it’s worth a look.
>
> Jack B, W6FB
>
>> On Dec 15, 2014, at 1:58 PM, Richard Solomon <dickw1ksz at gmail.com> wrote:
>>
>> If you can find a TDR, like a Tektronix, you can see where the defect is.
>>
>> 73 es HH, Dick, W1KSZ
>>
>> On Mon, Dec 15, 2014 at 12:19 PM, Ray Benny <rayn6vr at cableone.net> wrote:
>>> Patrick,
>>>
>>> I had a case once of a shorted coax due to a manufacturing defect. The coax
>>> was a 100 ft piece. I had first cut off the connectors one at a time but
>>> found the coax still shorted. I cut the coax in half, one half open, the
>>> other shorted. I kept cutting the shorted section in half until I had about
>>> a 6 inch shorted piece remaining. I slid off the braid and found that
>>> during the manufacturing process the center conducted was bent outward and
>>> through the dielectric causing a direct contact with the braid. Don't know
>>> why the short was not caught in a QC check, but maybe only random
>>> pieces/rolls were checked.
>>>
>>> In the end, I still had 50ft of coax to use, plus a bunch of shorter
>>> pieces...
>>>
>>> Ray,
>>> N6VR
>>>
>>> On Mon, Dec 15, 2014 at 11:09 AM, Tom Osborne <w7why at frontier.com> wrote:
>>>> Hi Patrick
>>>>
>>>> Don't think I'd cut them in half.
>>>>
>>>> I'd just cut the plugs off and replace them and check the cable again.
>>>> Might be something in the plugs that are bad and you would be wasting a
>>>> bunch of cable.
>>>>
>>>> If still bed, then start cutting them.  73
>>>> Tom W7WHY
>>>>
>>>>
>>>> On 12/15/2014 8:09 AM, Patrick Greenlee wrote:
>>>>
>>>>> I'm going to cut the bad jumper in half and test the halves and then cut
>>>>> the bad piece in half and test those pieces.  Whichever is bad will
>>> then be
>>>>> dissected carefully to see, if possible, what was physically wrong with
>>> the
>>>>> coax.  This is a real head scratcher for me.  The good news is I'm back
>>> on
>>>>> the air with a pan adapter full of signals again and loving it.
>>>>>
>>>>> Patrick     NJ5G
>>>>>
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