The TDR will tell you where there are impedance
bumps among other issues (such as opens and
shorts). If the center conductor is migrating (called
cold flow), the impedance will change and you can
find that location with the TDR.
Cold flow occurs whenever the cable is bent or looped,
but is usually a slow process. Exceeding the minimum
bending radius will speed up this process. Certain types
of low loss coax (e.g. air dielectric with spacers) will have
increased impedance bumps because of spacing.
I have used 9913 (standard, not flex [I believe the major
difference is stranded vs solid center conductor]) and hate
the stuff. It has a memory and is difficult to straighten out.
I never shot ti with a TDR, but I believe cold flow would rear
its ugly head faster with this tye of coax than with convnetional
RG8-type products.
73,
Bob AA0CY
----------
From: Ron Youvan[SMTP:ka4inm@gate.net]
Sent: Saturday, August 28, 1999 1:06 AM
To: Tower Talk
Subject: Re: [TowerTalk] BELDEN 9913 COAX PROBLEMS?
Hi:
<< as we all know we can use our TDRs to find where the loss is located. Gosh,
I
forgot we don't have a TDR system. >>
I have a Tektronix 1505, all I can measure is the surge impedance along the
cable
I find nothing in the IB about the `loss' of the cable.
73 (= Best Regards) de Ron ka4inm@qsl.net
VISIT my HAM WEB SITE at: http://www.qsl.net/ka4inm
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