FW: [SI-LIST] : EMC quiet serial device???

Johnson, David (david.johnson@intel.com)
Tue, 9 Feb 1999 14:19:06 -0800

A further suggestion...
Try testing with (a) the modem still connected but turned off (unpowered),
and (b) the modem cable still connected to the PC, but no modem on the other
end of the cable. These kinds of tests can help to pinpoint whether or not
the problem might actually be the cable acting as an antenna rather than
anything specifically attributable to the modem itself. Hanging any kind of
long "wire" onto a high frequency source can often make a very effective
antenna for EMI emissions, even if the "wire" appears to be well shielded
and/or grounded at the point of attachment. It may not be a good RF ground
at all.

---- Dave W. Johnson

-----Original Message-----
From: Douglas McKean [mailto:dmckean@corp.auspex.com]
Sent: Tuesday, February 09, 1999 12:54 PM
To: si-list@silab.Eng.Sun.COM
Subject: Re: [SI-LIST] : EMC quiet serial device???
Importance: High

Roland,

As you are probably already aware, modems are *supposed*
to be Class B devices. If you can't get anywhere with
the manufacturer (since they are leading you to believe
you do in fact have a Class B device), you may be suffering
from CM (common mode) noise. A *possible* quick fix might
be ferrites.

For further investigation, you might try signing onto
the EMC-PSTC listserver group. All info for said group
is found at the following website ...

http://www.rcic.com/cnf/pstc.htm

Contrary to what some may be lead to believe, having trouble
with Class B peripherals is NOT an uncommon problem.

Regards, Doug

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