Thanks Patrick. Makes sense to me. I do have a short length (maybe 60ft or
so) of properly stored near-new LDF4-50 so I can use that as the baseline.
Anyone actually attempted impedance or another measurement to check for
performance change?
73, David G3WGN M6O
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A tdr (without a scope for a visible display) needs to see a step function, an
impedance lump. A gentle variance will not be reported well. Comparing a
known good length of the same material to your material using a sensitive
impedance bridge should tell you if the center conductor has migrated as that
will change the impedance.
Velocity factor will be different too.
And now stand by for the folks who know.
Patrick NJ5G
On 4/12/2016 1:33 PM, David Aslin G3WGN wrote:
> Hi all,
> Looking for the TT brains trust to help me out with this issue:
> I have two drums of LDF4-50 and one of LDF5-50 which have been stored on
> their sides for around 10 years. This disobeys one of the prime directives,
> since Andrew/Commscope say they MUST be stored with the drums vertical. My
> understanding is that the horizontal storage may lead to inner conductor
> migration.
> QUESTIONS: How can I determine whether migration has occurred; if so to what
> extent; and what extent should cause me to avoid using the cable for the
> 50m/165ft+ runs to my HF towers?
>
> Of course, if there is gross migration, a continuity check from inner to
> outer would reveal a short, but would a TDR or other method reveal
> performance degradation from lesser amounts of migration?
> 73, David G3WGN M6O
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