[TowerTalk] Inner conductor migration in Heliax(TM)

[Patrick Greenlee]

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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