There is a nice little demo that one can usually see at the EMC Symposium where someone (don¹t recall who) has a small reverb chamber with some fluorescent lamps that come on and go off as the paddle is stirred.
Ken Javor Phone: (256) 650-5261 From: Ed Price <edpr...@cox.net> Date: Thu, 9 May 2013 10:04:56 -0700 To: <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: RE: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? I view the power density concentrations as varying density little clouds, chimera, moving regularly in 3 dimensions, and continuously changing their dimensions as they move. The presence of the ground plane, stirrer supports, antenna and EUT would have the motions not always linear. The motions wouldn¹t be ³darting² but more gracefully oscillating; it would make for one heck of an animation. One thing we haven¹t talked about is knowing the response time of your EUT. Most times, I was fortunate enough to be testing systems which had the courtesy of crashing rather quickly and completely, so a ³response² was obvious. But when your definition of a ³response² is ³any degradation of operation, any unintentional responses and nor any failure of intentional responses², then you have a formidable task before your testing just to learn how your EUT degrades. Ed Price WB6WSN Chula Vista, CA USA From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Thursday, May 09, 2013 8:10 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? Well, an area of constructive or destructive interference is going to have dimensions on the order of a half-wavelength. That sets the upper bound on the illumination spot-size. Clearly, the spot size decrease with increasing frequency. Ken Javor Phone: (256) 650-5261 From: Luke Turnbull <luke.turnb...@trw.com> Date: Thu, 9 May 2013 09:53:35 +0000 To: Ken Javor <ken.ja...@emccompliance.com>, "EMC-PSTC@LISTSERV.IEEE.ORG" <EMC-PSTC@LISTSERV.IEEE.ORG> Conversation: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? Subject: RE: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? The picture I have in my mind is that there¹s a (or several) relatively small hot spot(s) you could say will-o¹-the-wisp(s) that dart around the test chamber as the paddles move. Therefore my understanding is that a large system isn¹t simultaneously illuminated by the reverb method. Luke Turnbull From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Ken Javor Sent: 04 May 2013 17:52 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? Let me recode that sorry for the typos: The paddle must spin slow enough or stop and dwell - so that the test sample has time to respond to the peak field intensity. Since one doesn¹t know where in the chamber the peak is, only its amplitude, the rotation rate or dwell time must be such that the test sample response time is accommodated at every paddle position. This makes reverb testing take much longer than anechoic testing. Ken Javor Phone: (256) 650-5261 From: Ken Javor <ken.ja...@emccompliance.com> Date: Sat, 04 May 2013 11:49:23 -0500 To: <EMC-PSTC@LISTSERV.IEEE.ORG> Conversation: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? He paddle must spin slow enough or stop and dwell, so that the test sample has time to respond to the peak fed intensity. Since one doesn¹t know where in the chamber the peak is, only its amplitude, the rotation rate or dwell time must be such that the test sample response time is accommodated at every paddle position. This makes reverb testing much longer than anechoic testing. Ken Javor Phone: (256) 650-5261 From: Pat Lawler <plawl...@gmail.com> Date: Sat, 4 May 2013 08:36:58 -0700 To: <owner-emc-p...@listserv.ieee.org> Cc: <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? The issue of waiting to get the peak field intensity could be shortened by spinning the paddles at a higher speed. However, I wouldn't want to be inside a metal chamber with a 4'x8' metal plate spinning at 300 RPM. Sounds like an Edgar Allen Poe story -- 'The Plate In The Reverb Chamber'. Thanks to all who replied. This is a corner of EMC testing I've never been involved with. If EMC is called black magic by some, mode-tuned/stirred/stepped chambers sound like black magic^2. Pat On Mon, Apr 29, 2013 at 9:23 AM, Luke Turnbull <luke.turnb...@trw.com> wrote: Hi all, Our experience is that you get pretty much the same levels with either a reverberation chamber, or with high gain antennas in a regular anechoic chamber. It is possible to increase the antenna gain by 3 or 4 dB compared to ³traditional methods², and get up to the same levels achieved in a reverberation chamber. Our methods achieve a minimum 3000 V/m, 1-18 GHz in a regular anechoic chamber. Luke Turnbull Dr Luke Turnbull EMC Technical Manager TRW Conekt Stratford Road Solihull West Midlands B90 4GW United Kingdom Tel: +44 (0)121.627.3966 <tel:%2B44%20%280%29121.627.3966> email: luke.turnb...@trw.com web: www.conekt.co.uk <http://www.conekt.co.uk> <http://www.conekt.co.uk> <http://www.conekt.co.uk/> From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Ed Price Sent: 28 April 2013 17:53 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? <snip> You can take advantage of the multiple reflections in a chamber (actually enhancing the reflections through the use of the moving mechanical structures) to achieve higher E-fields. This allows you to get higher E-fields for a test like RS103 than you could get using traditional methods. <snip> Ed Price WB6WSN Chula Vista, CA USA From: Pat Lawler [mailto:pat.law...@verizon.net] Sent: Sunday, April 28, 2013 7:38 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference? All, Over the years, I've come across pictures of test chambers with descriptions such as mode-stirred, mode-turned, and reverberation. They seem to look similar, with metal walls and rotating metal paddles. Do these names reference the same basic design, or are they different animals? Which ones are used for which type of RF immunity test? Thanks, Pat Lawler Teset engineer - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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