Amund, Cortland may be right, a chamber 'may not' be needed, high ambient considerations to be put aside for the moment, even if the emission is measured to be on the " 24dBuV/m @ 3m, freq.band 155MHz-165MHz". I am just curious, what are the limits (or standards) are you trying to meet? From what I read here, is it CISPR22 (or EN 55022) or something like that (Class B) scaled back to 3 m? I note that it is about 20dB below FCC limits for class B (at 3m).
If it is a single frequency line emission you can use a home made E or H field probe and work in the near field. Douglas Smith (who post frequently in this forum) have some good articles on DIY 1Ghz probes. You would need a E-field probe to 'sniff' out the CM portion of the emission and a H-field 'loop' to sniff out the offending loop before you can hug a 'return wire' to the offending signal line to cut the return loop down to size. I like to use the (thinisy, i.e. small gauge) wire-wraping wires for this. Good luck and hope that EMC don't always meant that it lead to Even More Coffee for the all nighter. Tim Foo Cortland Richmond <72146.373@compuserve. To: "am...@westin-emission.no" <am...@westin-emission.no>, ieee pstc com> list <emc-p...@ieee.org> Sent by: cc: (bcc: Wan Juang Foo/ece/staff/npnet) owner-emc-pstc@majordo Subject: Decoupling - capacitor values (ESR, layout, CM filter) mo.ieee.org 04/20/02 05:39 AM Please respond to Cortland Richmond Cortland Richmond <72146....@compuserve.com> 04/20/02 05:39 AM Amund, You do not HAVE to be in a chamber to keep working on this. Since there is only one Vcc pin (which processor IS this? - be SURE there is only one Vcc pin; you may have an unfiltered, unconnected Vcc pin or two) you are limited in how many capacitors you can attach to it. This doesn't matter; if you filtered power, and got 7 dB, you've done there what CAN be done there and should look look at other things. Troubleshoot the board. I too have thrown solutions at problems without knowing what exactly was wrong. It takes too long and costs too much. Find the source. A small 'scope probe, with the end taped over, makes a serviceable E-field probe. <snip> ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"