Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!purdue!gatech!emory!stiatl!rsiatl!jgd
From: jgd@rsiatl.UUCP (John G. De Armond)
Newsgroups: comp.dcom.lans
Subject: Re: Cable testers
Message-ID: <99@rsiatl.UUCP>
Date: 13 Jun 89 05:28:56 GMT
References: <2021@wasatch.utah.edu>
Reply-To: jgd@rsiatl.UUCP (John G. De Armond)
Organization: Radiation Systems, Inc. (a thinktank, motorcycle, car and gun works facility)
Lines: 34

In article <2021@wasatch.utah.edu> haas@wasatch.utah.edu (Walt Haas) writes:
>I'm shopping for a good way to test coax and twisted pair cables used in
>Ethernet, Arcnet and broadband.  One way would be to spend a lot of money for
>a large, heavy TDR that would give me lots of information.
>
>In particular I'm looking at a thing
>called a Cable Scanner built by a company called M-Test.  Does anybody in
>netland have one of these?  

I've observerd the Cable Scanner in use and have used it a bit.  My general
impression is that it is useful for determining the length of a known good
cable and for finding catastrophic failures (cuts, shorts, etc) but for
the problems we've had, it has been of little use.  The catastrophic 
failures can usually be observed visually (someone ran a chair over the
cable, etc).  When the failures are marginal or intermittent, these little
pocket instruments leave a lot to be desired.  A crushed cable or an
intermittent connector or an improperly crimped connector will not show
up on these boxes unless the condition is bad.

What you have to do is determine whether the threshold of detection is
in the same ballpark as when the tranceivers quit working.  I've found
little to beat the 'O-scope based units, especially the ones like the
Tektronics scope with the strip-chart option.  You can literally 
detect non-intrusive bending of a cable with this unit.  Connectors - even
correctly crimped ones - show up clearly.  And since you can make hardcopy,
you can build a history file of each cable.  This history is the
absolute best way to quickly diagnose changes.  You can also quickly 
detect unauthorized new taps with little trouble.

If your budget can handle it, get both instruments.  If you can only
afford one, get the scope.  It is more than worth the effort in 
handling.

John