Well, light in free space goes at about 30cm per nanosecond. It will go somewhat slower in the coax,
but to locate the break to 3cm accuracy you will need a pulse rise time of about 100ps, or less.
Suggest you have a look at Tek's Time Domain Reflectometry Measurements which you can download from
here
Craig
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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of cheater cheater
Sent: 28 June 2018 15:32
To: [email protected]
Subject: [TekScopes] Kludging together a TDR or similar?
Hi everyone,
I have a DOCSIS 3 150 Mbps cable modem which just stopped working after a substantial storm (i
replaced it to make sure). Apparently the cable is broken. While I'm waiting for the technician to
show
up next week, I was wondering if anyone had an idea how I could kludge together a TDR to see if I
can
find where the break might be? Am I right to think that you just inject a pulse from a sig gen and
measure the delay time to find out where the break is? Do I need to use any specific bandwidth
equipment, or will anything do? Is there an easier way to get this done? I don't have a TDR, but I
have
some 7000 series scopes and some non-tek sig gens that go up to iirc 20 MHz. The tek mainframe's
pulse gens will go higher (IIRC I have a 7904), but not sure if I can use those for this purpose.
Thanks
