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From: wsmith@cs.umn.edu (Warren Smith [Randy])
Newsgroups: comp.dcom.lans
Subject: Re: Summary: physical ethernet testing
Keywords: ethernet physical testing layer 1
Message-ID: <1991May11.025631.15340@cs.umn.edu>
Date: 11 May 91 02:56:31 GMT
References: <1991May10.175032.20303@hellgate.utah.edu>
Organization: University of Minnesota, Minneapolis, CSci dept.
Lines: 20

If you want a really CHEAP (in both senses) method of testing signal
quality you can use an oscilloscope and a simple packet generator
running on a workstation.  Assuming you have a scope handy the cost is
nothing.  By having one station blast the packets out as fast as it can
and triggering off the start of the packet you get a pretty good idea
what the packets look like.

We've used this technique to get a look at signal quality.  I wrote a
program on a Sun to blast out packets and modify the data bits every
100 packets or so.  We could see this pretty well with a 40 MHz scope,
however I think you probably need a 100 MHz scope to get a really good
look at the signal.  We could see the signal deteriorate as we increased
the length of the run (can't remember what we were testing though - maybe
twisted pair?).  Its no NQA, but then what is?

-Randy
-- 
Randy Smith
wsmith@cs.umn.edu
...!rutgers!umn-cs!wsmith