A good screen room acts as a Faraday cage, it doesn't need a ground for rf performance. The ground is for safety. I drove a ground rod adjacent to a room I built and it didn't make any difference at all whether I was connected to it or not.
I would take a small loop around the interior walls (especially seams, especially the door seam) and sniff for hot spots. Also once you get your room working to your satisfaction, it cannot be used to check for radiated emissions against a three or 10 meter limit. All you are doing is building a look up table of frequencies to be checked on an OATS, or perhaps troubleshooting the highest emission levels. If you mode stir the chamber and put your analyzer on peak hold you can at least level on peaks and not troughs (at frequencies where the room is resonant), but again the values measured do not directly correlate with those on an OATS or SAC. From: "Jeff Chambers" <[email protected]> List-Post: [email protected] Date: Sun, 11 Jun 2006 19:19:17 +0100 To: <[email protected]> Subject: Seaward 'Screened Room' Firstly thanks for the replies re the Laplace Instruments Analyser - it looks good value for the price. Now, we have here a Seaward 'Screened Room', about ten years old, which is basically a 'tent' of metallised fabric draped over a metal framework, with a metal floor. It was sold for emc work, has a solid-looking door, plus a filtered mains inlet. Its about 5m x 3m x 3m, and I'd like to use it to provide confidence that designs are well within emissions limits, rather than try to justify things close to a limit. Its literature of the time claimed 60dB to 80dB attenuation. But... it doesn't seem to offer much attenuation to FM radio signals! It's only ground is via the mains inlet, i.e. not much of an rf ground. Otherwise it's just sat on the factory floor. I have a building girder very close by emerging from the floor - should I ground the room to that? This might bring a smile to those lucky people out there with state of the art anechoic chambers, but I have to use what I can! Any thoughts? Regards, Jeff Chambers Jeff Chambers Engineering Manager System Technologies Morecambe Road Ulverston, Cumbria LA12 9RN www.SystemTechnologies.com <http://www.SystemTechnologies.com> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
