That is certainly right. But there is another aspect that might play a role here.
Many fast digital bus concepts have been designed with Class A limits in mind. That means when applying the (chip) manufacturer's reference design, the final product meets A limits only. Only with enhanced effort Class B limits can be met. Some chip-sets do never meet Class B, as there outputs have substantial common mode currents in their outputs ( thinking of Ethernet here). More and more EN standards now require Class B and also worldwide the trend is towards Class B. The application of ETSI standards for transmitter and/or receiver equipped electronics does not even allow for a Class A escape route. The new RED (Radio Directive) in the EU brings a whole new category under Class B (for example GPS equipped designs). If you are trying to approve a HDMI product into a Class B world, there is almost no margin to comply, and any EUT design flaw problem will show as non-compliance. Regards, Ing. Gert Gremmen Approvals manager ------------------------------------------------------------------------------------ + ce marking of electrical/electronic equipment + Independent Consultancy Services + Compliance Testing and Design for CE marking according to EC-directives: - Electro Magnetic Compatibility 2014/30/EC - Electrical Safety 2014/35/EC - Radio & Telecommunication Terminal Equipment 99/5/EC Web: www.cetest.nl (English) www.ce-test.nl (Dutch) www.cetest.fr (under construction) Phone : +31 10 415 24 26 ------------------------------------------------------------------- This e-mail and any attachments thereto may contain information that is confidential and/or protected by intellectual property rights and are intended for the sole use of the recipient(s) named above. Any use of the information contained herein (including, but not limited to, total or partial reproduction, communication or distribution in any form) by persons other than the designated recipient(s) is prohibited. If you have received this e-mail in error, please notify the sender either by telephone or by e-mail and delete the material from any computer. Thank you for your co-operation. -----Original Message----- From: John Woodgate [mailto:jmw1...@btinternet.com] Sent: Saturday 14 January 2017 11:14 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] lowest emissions 4k TV? I think the key words 'poorly-constructed' should be noted. Any manufacturing defect that creates an impedance discontinuity in the signal conductors causes mode conversion of the differential signal, creating a small, but significant common-mode signal. With best wishes DESIGN IT IN! OOO - Own Opinions Only www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England Sylvae in aeternum manent. -----Original Message----- From: ce-test, qualified testing bv - Gert Gremmen [mailto:g.grem...@cetest.nl] Sent: Saturday, January 14, 2017 9:57 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] lowest emissions 4k TV? Exactly : Once the signal is unbalanced (whatever the reason) only shielding can attenuate the emissions. But any unbalance is caused by the EUT at the sending or at the receiving end, not by the cable. Gert Gremmen -----Oorspronkelijk bericht----- Van: Brent DeWitt [mailto:bdew...@ix.netcom.com] Verzonden: zaterdag 14 januari 2017 2:17 Aan: EMC-PSTC@LISTSERV.IEEE.ORG Onderwerp: Re: [PSES] lowest emissions 4k TV? I did some experiments with equipment (Blu-Ray players and TVs) that showed that the introduction of an off-the-shelf, poorly constructed, short, cable to cable adapter caused a 25 dB increase in radiated emissions at 742.5 MHz in 1080P HDMI. The slightest introduction of skew/imbalance on the signal combined with a non-ideal shield system introduces enough CM noise back onto the outside of the shield to cause problems. It takes only a very percentage of the HDMI specified differential current drive to translate to CM to make a 1.5 meter cable shield look like a pretty efficient antenna. Brent DeWitt, AB1LF Milford, MA -----Original Message----- From: Ralph McDiarmid [mailto:ralph.mcdiar...@schneider-electric.com] Sent: Friday, January 13, 2017 12:19 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] lowest emissions 4k TV? " I suspect this is just equipment originated CM current, that cannot be cured with a better cable; but needs a better equipment CM design. (Or a bunch of heavy ferrites)." I suspect that is the crux of the issue, as it is for many ports on all kinds of products. Ralph McDiarmid Product Compliance Solar Business Schneider Electric -----Original Message----- From: ce-test, qualified testing bv - Gert Gremmen [mailto:g.grem...@cetest.nl] Sent: Friday, January 13, 2017 1:01 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] lowest emissions 4k TV? Exactly. Nowadays it's easy to filter high speed ports, and in the case of shielded cable this is even more easy. One aspect that can be a problem is cable length. USB and HDMI are limited in length, and in large rooms that can be a problem, needing repeaters, that can form a new problem themselves. About the cable radiating: If the signal arrives correctly at the end in an approved cable, the cable is not radiating. I mean it's not the mere fact that data is running that make the cable radiate. That is why these cable are approved and characterized. A radiating signal cable (if due to the signal) has problems with signal transfer also, especially at this data rates. In the case of HDMI the external screen is not needed to protect the signal as the data internally is grouped and internally screened (3 or 5 groups). I suspect this is just equipment originated CM current, that cannot be cured with a better cable; but needs a better equipment CM design. (Or a bunch of heavy ferrites). Regards, Ing. Gert Gremmen Approvals manager ---------------------------------------------------------------------------- -------- + ce marking of electrical/electronic equipment Independent Consultancy + Services Compliance Testing and Design for CE marking according to + EC-directives: - Electro Magnetic Compatibility 2014/30/EC - Electrical Safety 2014/35/EC - Radio & Telecommunication Terminal Equipment 99/5/EC Web: www.cetest.nl (English) www.ce-test.nl (Dutch) www.cetest.fr (under construction) Phone : +31 10 415 24 26 ------------------------------------------------------------------- This e-mail and any attachments thereto may contain information that is confidential and/or protected by intellectual property rights and are intended for the sole use of the recipient(s) named above. Any use of the information contained herein (including, but not limited to, total or partial reproduction, communication or distribution in any form) by persons other than the designated recipient(s) is prohibited. If you have received this e-mail in error, please notify the sender either by telephone or by e-mail and delete the material from any computer. Thank you for your co-operation. -----Original Message----- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Friday 13 January 2017 04:27 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] lowest emissions 4k TV? If I am qualifying a device that connects through a cable to this TV, but not the TV itself, why would it physically have to be part of the set-up in the test chamber? Why could it not simply be support equipment in an adjacent chamber, providing the proper interface at the end of the cable? Ken Javor Phone: (256) 650-5261 > From: Doug Smith <d...@emcesd.com> > Reply-To: <d...@emcesd.com> > Date: Thu, 12 Jan 2017 16:32:06 -0800 > To: <EMC-PSTC@LISTSERV.IEEE.ORG>, Ken Javor > <ken.ja...@emccompliance.com> > Subject: Re: [PSES] lowest emissions 4k TV? > > Hi Ken, > > Unless you are required to include a 4k TV or other device as part of > your test setup! > > Doug > > On Thu, 12 Jan 2017 18:20:05 -0600, Ken Javor > <ken.ja...@emccompliance.com> wrote: > Not proffering a solution here, but the amount of traffic on this > topic has >> surprised me. Back in the day when most testing was on an OATS, I >> would have understood the concerns expressed, but nowadays most >> testing is performed in a SAC simulating an OATS. With the latter it >> is simple to use any off-the-shelf device in an external chamber just >> as the appropriate load interface for the test sample, and provide >> filtering external to the chamber necessary to clean up any emissions >> that could pollute the test chamber ambient. With a shielded cable, >> it might be as simple as running it through a stuffing tube and >> grounding out the rf current running external to the shield. Or there >> could be a high quality shielded cable used in the test chamber, >> which connects to a bulkhead-mounted and grounded adapter, and >> external to the chamber, the noisy support equipment and any crummy >> cable can be used. >> >> Lots of possible variations, but the point is that with a SAC, we >> don't have to be near as picky about the support equipment. >> >> Ken Javor >> Phone: (256) 650-5261 >> >> >>> From: Ralph McDiarmid <ralph.mcdiar...@schneider-electric.com> >>> Reply-To: Ralph McDiarmid <ralph.mcdiar...@schneider-electric.com> >>> Date: Thu, 12 Jan 2017 20:59:57 +0000 >>> To: <EMC-PSTC@LISTSERV.IEEE.ORG> >>> Conversation: [PSES] lowest emissions 4k TV? >>> Subject: Re: [PSES] lowest emissions 4k TV? >>>> I wonder if RF current on the coax coming in to the cable box >> then radiates >>> from the HDMI cable? All that overhead cable strung through >>> residential neighborhoods must pick up a lot of RFI on its outer braid. >>>> Ralph McDiarmid >>> Product Compliance >>> Solar Business >>> Schneider Electric >>>> - >>> ---------------------------------------------------------------- >>> 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 <emc-p...@ieee.org> >>>> All emc-pstc postings are archived and searchable on the web at: >>> http://www.ieee-pses.org/emc-pstc.html >>>> Attachments are not permitted but the IEEE PSES Online >> Communities site at >>> http://product-compliance.oc.ieee.org/ can be used for graphics (in >> well-used >>> formats), large files, etc. >>>> Website: http://www.ieee-pses.org/ >>> Instructions: http://www.ieee-pses.org/list.html (including how to >>> unsubscribe) >>> List rules: http://www.ieee-pses.org/listrules.html >>>> For help, send mail to the list administrators: >>> Scott Douglas <sdoug...@ieee.org> >>> Mike Cantwell <mcantw...@ieee.org> >>>> For policy questions, send mail to: >>> Jim Bacher: <j.bac...@ieee.org> >>> David Heald: <dhe...@gmail.com> >> >> - >> ---------------------------------------------------------------- >> 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 <emc-p...@ieee.org> >> >> All emc-pstc postings are archived and searchable on the web at: >> http://www.ieee-pses.org/emc-pstc.html >> >> Attachments are not permitted but the IEEE PSES Online Communities >> site at http://product-compliance.oc.ieee.org/ can be used for >> graphics (in well-used formats), large files, etc. >> >> Website: http://www.ieee-pses.org/ >> Instructions: http://www.ieee-pses.org/list.html (including how to >> unsubscribe) >> List rules: http://www.ieee-pses.org/listrules.html >> >> For help, send mail to the list administrators: >> Scott Douglas <sdoug...@ieee.org> >> Mike Cantwell <mcantw...@ieee.org> >> >> For policy questions, send mail to: >> Jim Bacher: <j.bac...@ieee.org> >> David Heald: <dhe...@gmail.com> >> >> > - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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