From: "Dennis J. Murray" <djmurray@BELLATLANTIC.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, February 20, 2003 1:40 PM
Subject: Re: [PIC]: How would I build a reflectometer?


> I'll tell you guys - I've been following this link since it's
inception and
> you REALLY have my curiosity piqued!!  I've used TDRs quite a bit in a
past
> life and I DEPENDED on the visual representation on the screen to
interpret
> what is really on the line!  I don't think I EVER had a clean line
that
> didn't require some interpretation - was that hiccup a sharp bend?
water in
> the line? an unauthorized tap?  A long-forgotten splice?  etc.
>
> How do you plan to accomplish this using a PIC or an oscillator
circuit????
> Or don't you?  Just looking to determine overall length to the most
> significant reflection??

I only wanted to measure the length of installed network cabling.  I'm
not really looking for wiretaps or anything that subtle.  ;-)  I'm
thinking that as long as the injection end is terminated to match the
characteristic impedance of the wire, there should only be one large
reflection and that would be from the far end.  I'm thinking that using
the latest arriving "echo" would represent the distance to the far end
of the wire.

michael

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