This: “Given *NO* limits in some gaps, however, then it becomes possible that a product could wreak havoc with other products that are susceptible at those frequencies, so then the corresponding immunity tests would have to be changed.”
is simply untrue. Unless the potential victims are radio receivers, in which case there could be a problem. But there shouldn’t be any relaxations where the radio spectrum is in common use. Radiated immunity levels are at 1, 3 or 10 V/m. One cannot unintentionally radiate at these levels. Assuming just 1 V/m, and 3 meters, you are looking at 300 mW transmit power, and that’s assuming the radiating mechanism has a gain of unity, which is highly unlikely. It also ignores the 5.1 dB headroom required by 80% modulation. If you include that, you’re looking at an unintentional 1 Watt transmitter. For conducted emissions, it’s the same thing. The 61000-4-6 limit is 1, 3, or 10 Volts open circuit from a 150 Ohm source. That is half those potentials into 150 Ohms. Those levels are 60 dB or more over present power-line CE requirements, and there is no way that sort of outage will happen when you have to meet CISPR type requirements at nearby frequencies. And even if you don’t have any conducted emission controls, for instance on a signal cable, you won’t be able to meet radiated emission limits with common mode signals on the order of 0.5 Volts or more on these cables. And here is no way to have signals at such levels when you have to meet radiated emissions requirements >from 30 – 1000 MHz or higher, even if the limits look like Swiss cheese. In conclusion, allowing zones of no emissions control will not require reworking immunity levels. There may be other reasons it’s not a good idea, but you can’t base opposition on immunity concerns. Ken Javor Phone: (256) 650-5261 ________________________________ From: Bob Richards <[email protected]> List-Post: [email protected] Date: Sat, 5 Feb 2011 15:16:55 -0800 (PST) To: <[email protected]> Subject: Re: EMC spectrum 'gaps' Derek, If certain gaps in the spectrum have limits removed, then it would stand to reason that someone might end up exploiting that fact. Even unintentional radiators might position internal operating frequencies or harmonics in those frequency gaps. When I first thought about it, it made some sense. Given *NO* limits in some gaps, however, then it becomes possible that a product could reek havoc with other products that are susceptible at those frequencies, so then the corresponding immunity tests would have to be changed. It is something worth thinking about. Bob R. --- On Thu, 2/3/11, Derek Walton <[email protected]> wrote: From: Derek Walton <[email protected]> Subject: Re: EMC spectrum 'gaps' To: [email protected], [email protected], [email protected] Date: Thursday, February 3, 2011, 2:40 PM Thanks Ghery, this is why I'm trying hard to ELIMINATE limits that serve no purpose. Anyone interested in contributing, feel free to contact me, off list if you feel more comfortable. Thanks, Derek Walton - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
