I concur with Cortland. If you know that the application may be with the cable longer than 2 m, I would recommend to find the lenght and arrangement of the cable that maximizes emission and then fix it in the box. The standard says "at least 2m" which I don't read as a recommended length. I understand it may be hard to make it pass, but this is just my personal point of view, especially considering the application.
Neven > > Dries, it sounds very much as if that short shield is acting as a > (low-value) bypass capacitance. If, as you say, no shield is permitted, > then your customers will audit with no shield, and the product will fail no > matter what "tricks" you used to get around failure in your own tests. > Then you will still have to deal with the problem - and explain to your > bosses how you let it get by. If you are lucky! Avionics problems have a > way of turning serious 10 km up. Don't do it. > > It's best to fix the problem inside the equipment. This could be as simple > as 100 pF or so capacitance from each conductor to chassis (what, I think, > that short shield is doing) or a bifilar common-mode filter optimized for > the frequency range you are currently failing. > > > Cheers, > > > Cortland > > > Dries Vanduffel wrote: > > >> '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? > << > > ------------------------------------------- > 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: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > 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 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] 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
