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RE: 8b/10b and EMI

Hi Ron:

I believe so.  The 1000Base-CX is a copper cable which always gave me
unpleasant feeling.  Very often, we have to test several times with
improvement to pass EMI certification.

The shield of a copper cable is not perfect, which is serving attenuation,
but not stopping leaking.  Therefore, I agree, if one has high back ground
noise level, the additional 6 dB can give you trouble.

I would stay on fiber cable products.


Edward S. Chang
NetWorth Technologies, Inc.
Tel: (610)292-2870
Fax: (610)292-2872

-----Original Message-----
From: owner-stds-802-3-hssg@xxxxxxxx
[mailto:owner-stds-802-3-hssg@xxxxxxxx]On Behalf Of DOVE,DANIEL J
Sent: Friday, March 17, 2000 12:48 PM
To: stds-802-3-hssg@xxxxxxxx
Subject: RE: 8b/10b and EMI

Hi Ed,

>  From: Edward Chang [mailto:edward.chang@xxxxxxxxxxxxxxxx]
>  Tom, Rick and all:
>  So far, in the real industry-wide installations, no one has
>  the 8B/10B IDLE
>  EMI problem.  Furthermore, no one has proved that 8B/10B
>  IDLE signals will
>  cause EMI problem for 10 GbE in an enclosed environment.

Actually, I believe that there were some significant problems
getting 1000BASE-CX to meet FCC requirements and the first FC
optics also had trouble. Spreading the spectrum helps a lot.

I did some analysis for Gig E where I looked at the peak spectral
components of the IDLE sequence as opposed to a random stream and
the 1.25GHz component was substantially higher for IDLE than for
random data. I believe it was 6-8dB higher.


Dan Dove


Dan Dove