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RE: [10GBASE-T] RE: EMI Discussion

Geoff and Dan,
Yes, I was in the middle of it. Apologies in advance because there were about 100 people involved in 10BASE-T and I'm going to hit only a few of them here. We were doing something similar to what some of you want to do - characterizing existing cable so that it could be used beyond its intended and specified frequency range.
Don Johnson of NCR did a lot of work characterizing noise on cable in existing installations (including the famous, to 10BASE-T at least, Dayton YMCA). Hardware was left in place for days that would capture and count noise impulses over a threshold. Traces of various sample noise were taken and analyzed for frequency content.
Bob Conte, AT&T, did a lot of testing and analysis of cable as did Bill Kind, HP, and Bob Snyder, Wang. Crosstalk characteristics were studied on a wide sample of cables. Efforts were made to identify the 99% cable characteristics and to find cable for testing that was at the challenging edge of the range for testing. Modeling and simulation was done of the crosstalk by those people and others. Quite a lot of this was done and we had confidence in our results when we had theoretical and test results that were matching from multiple sources. For instance a lot of work went into finding the noise distribution and demonstrating that the self-crosstalk was a truncated Gaussian (that truncated way above our target BER). (At more than half the meetings we would have a newcomer 10BASE-T wouldn't meet the required BER because it didn't have enough SNR. It wouldn't if the noise was Gaussian but it wasn't - part of the price of breaking new ground.)
Multiple engineers from DEC and 3Com, including Ron Crane, put work into characterizing the noise from a source we had identified early on as our worst disturber - analog phone ringers.
There were also EMC tests done for both emmissions and suceptability (with lots of discussion of how you lay out cable in the chamber for a valid test).
Fortunately, at 10 Mb/s the wavelength was big enough that the connectors were not much of a contributor to the problem. At 100 Mb/s, the connectors became important and required testing. I don't know how many of you remember, but the initial Cat 5 deployments were done with pretty much the same wall jacks, connectors, etc as Cat 3 and some installations had to be redone to support 100 Mb/s after the redesigned connectors became available. Connectors made a big difference in the EMC testing for 100 Mb/s but not for 10BASE-T.
Everything was distributed on paper back then. By the end the presentations took several feet of file drawer space. I think the industry spent more per page developing the 60 page 10BASE-T standard then any other standard we have done. But our investment per unit shipped is pretty good so we probably don't mind. :^)
Even with all that work, we had a nasty surprise near the end when we found that for some cable insulation types the attenuation rose steeply above 40 degrees C. Once we figured it out we had to add a caution that some cable types had a temperature problem.
-----Original Message-----
From: Geoff Thompson []
Sent: Wednesday, August 13, 2003 4:41 PM
To: DOVE,DANIEL J (HP-Roseville,ex1)
Cc: Geoff Thompson;
Subject: RE: [10GBASE-T] RE: EMI Discussion


At 12:02 PM 8/13/2003 -0700, DOVE,DANIEL J (HP-Roseville,ex1) wrote:
Hi Geoff,

Good point of clarification.

I was not directly involved in that effort. At the time I was working on
802.4 (rf modems,CATV,etc) but I know a number of the folks who worked on it
and actually have an original copy of the massive binder full of work done
by Bob Conte et al. It was an impressive effort and I think we are looking
at something similar here.

I wasn't really involved in it. I was working on fiber a the time. Pat was in the middle of it. The guy who did the major work in the field was Don Johnson of NCR at the time. I have seen him recently in wireless meetings so he might possibly be available to provide war stories.

It was HARD!




> -----Original Message-----
> From: Geoff Thompson []
> Sent: Wednesday, August 13, 2003 10:49 AM
> To: DOVE,DANIEL J (HP-Roseville,ex1)
> Cc:
> Subject: RE: [10GBASE-T] RE: EMI Discussion
> Dan-
> At 12:03 PM 8/13/2003 -0400, DOVE,DANIEL J (HP-Roseville,ex1) wrote:
> >In the case of 10BASE-T, where we were
> >applying high speed (10MHz?) signals to CAT3 wiring which
> had been installed
> >for phone support, a *huge* quantity of testing was done to
> verify signal
> >integrity, EMI compatibility, and noise immunity.
> Actually it was not CAT3, The installed base was AT&T DIW (or worse).
> We considered DIW as the baseline.
> The TIA CAT3 spec was not approved until after the approval
> of 10BASE-T.
> Geoff