I don't believe shielding is in order, but you are allowed to "hide" the excess cable length above 2 meters by laying it directly on the ground plane and behind the test set-up. But even this is really only justified if the 2 meter length is aircraft installation length. One thing you can do is be certain the cable is no closer than 10 cm from the edge of the ground plane, because radiation efficiency depends on how close the cable is to the ground plane edge, as PCB designers know. What I am about to say is not in keeping with the spirit of the test, but if you have multiple cables, and some are benign and some are hot, you could put he benign ones closest to the edge, and the hottest ones farthest away (the spec says 2 cm separation between adjacent bundles). I have always worked for airframers or the Customer, so it has never been in my organization's interest to do such a thing, but I have seen some pretty complex test set-ups over the years.
on 2/18/03 11:16 AM, Vanduffel, Dries at dries.vanduf...@barco.com wrote: > > > I'm measuring RE02 according Mil Std 461C. > the Standard says that 'signal cables' have to be at least 2meters long lay > and on the table. > My cables are twisted pairs and not allowed to be shielded. Around 30MHz I > get hugh outages. > The total cable length is 3 meters (this length is only chosen to reach the > wallplate). > When I shield off the last meter from wallplate towards the table with > Alumium foil, the outages decrease drastically and my equipement is 'almost' > passing the test. (around 20MHz - 30MHz outages have to stay below 20 > dbuV/m!!!) > My question: Is this a legal trick to pass RE measurements? > and if so: Is it also allowed to actually connect this artificial shield to > the table (gives best result) or should it just stop there and not touch the > table? > I remember an official testhouse doing this trick to let pass a unit but the > standard doesn't mention about this of course...! so I wonder if it is > legal? > > It seems like there are standing waves on my cable cause a shorter (1meter) > cable does not give problems neither does a 3m 'overall shielded' cable. > It gives me a headacke trying to filter out these outages on the > interconnection board of the unit and I'm almost at the end of my ideas of > how to fix this. . I tried lots of filtering and Y capacitors to chassisGND > gives best results but not good enough.. > Any tips are welcome to solve this problem. > > > Dries Vanduffel > Avionics Design Technician > > BARCO View > Th. Sevenslaan 106, > B-8500 Kortrijk, > BELGIUM > > Tel. +32(0)56 / 23 3008 > Fax. +32(0)56 / 23 35 88 > > URL: www.barcoview.com > Email: dries.vanduf...@barco.com > > > > - - - - - - - - DISCLAIMER - - - - - - - - > Unless indicated otherwise, the information contained in this message is > privileged and confidential, and is intended only for the use of the > addressee(s) named above and others who have been specifically authorized to > receive it. If you are not the intended recipient, you are hereby notified > that any dissemination, distribution or copying of this message and/or > attachments is strictly prohibited. The company accepts no liability for any > damage caused by any virus transmitted by this email. Furthermore, the > company does not warrant a proper and complete transmission of this > information, nor does it accept liability for any delays. If you have > received this message in error, please contact the sender and delete the > message. Thank you. > > ------------------------------------------- > 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 > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > -- Ken Javor EMC Compliance Huntsville, Alabama 256/650-5261 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 Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
