There are a couple of very different "real life" issues here. If you have volunteered to be in charge of sound for a choir concert at your local church, and it's fifteen minutes to showtime, and you've got hum in the PA system, you will doubtless pull every rabbit out of every hat you can think of. One rabbit may be floating a shield on the end of a cable. Forget EMC. Forget safety. The show goes on.
But, short of fear-driven panic patches, it is almost <never> appropriate to float shields on cables. Disconnect a shield on one end of a cable and you have transformed it into an efficient monopole antenna. It will be susceptible to inbound RF, and it will transmit RF very nicely in the same manner. A bad idea. At the lab, we work with several Pro-Audio clients who manufacture high-performance equipment. Shield floating is just not done. It is not necessary ... if the overall product design is well thought out. And yes, I do understand the reality of fighting hum problems in a crisis situation. In a previous life, I was Chief Engineer for several commercial radio and TV broadcast outlets. In situations (particularly setting up remote broadcasts with unknown equipment), anything goes. But we shouldn't carry that behavior back to the design teams. My comments may or may not reflect the opinion of my employer. Regards, Jim Ericson Senior EMC Engineer Acme Testing Company Acme, WA. work e-mail: [email protected] ------------------------------------------- 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] 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"
