I'm on another mailing list with some network types who regularly have 
to test various devices with several lengths of CAT5 cable...  Seems 
like the common way to do this is just to have premeasured cat5 
terminated both ends to the bench.  Unfortunately, this is a *lot* of 
cable, and takes up a lot of room.

 Somebody today asked about how to build a simulator since they are 
regularly testing dozens units at a time on 100m cable lengths... i.e. 
kilometers of cable under the benches, which is getting to be a big 
pain.    I found a couple of companies which sell ready-to-go units, for 
about $200US each.   Realizing that a CAT5 cable is pretty complex in 
it's pair-to-pair interaction, this doesn't seem too bad, but I always 
wonder if it is possible to build something which simulates most of the 
effects for quite a bit less.

So, what I'm wondering is:   Is there a schematic floating around which 
does a good job of approximating the effects of a certain length of CAT5 
cable including pair-to-pair crosstalk and the like?   Including things 
like when the CAT5 is used in unbalanced mode, etc?

-forrest


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