Jon, Richard, Test radiated emissions at both speeds and with each cable type. Per ANSI/IEEE 802.3 and 802.3h, 100BaseTX has 1/2 the pulse height of 10BaseT (to reduce EMI).
Whether to earth the shield (or semi-shield) is an eternal question. These four possibilities can occur (since a hub uplink connects to another hub) with floating shield: 1) STP cable earthed at AE end only - emissions are produced by AE, not EUT 2) STP cable earthed at EUT only - emissions will be from EUT 3) STP cable earthed at both ends - higher emissions due to ground loops (ground planes of both units are connected to the shield). If you add caps, the emissions can actually increase. 4) STP cable floating at both ends - minimal effect on emissions So long as you can justify your design and test methodology either approach is acceptable. David Sterner -----Original Message----- From: Stone, Richard A (Richard) [mailto:[email protected]] Sent: Wednesday, October 17, 2001 8:22 AM To: 'Jon Keeble'; [email protected] Subject: RE: 10/100 base interface in a plastic box Jon, if your running high etherent freq. and the shield is NOT grounded, you might fail class A FCC/Cispr 22. Richard, -----Original Message----- From: Jon Keeble [mailto:[email protected]] Sent: Wednesday, October 17, 2001 1:05 AM To: [email protected] Subject: 10/100 base interface in a plastic box RJ45s come in shielded, unshielded, and shielded with integral magnetics (and probably other flavors as well). Has anybody got any suggestions / experience / whatever re the use of one or other of these parts in a product that will live in a plastic box, power by an external mains adapter / internal regulator. The intention is to use UTP cable. I've read Intel's appnotes regarding layout for PHY / Magnetics / RJ45. In a situation with no chassis to call chassis ground, I suspect the shield is irrelevant. However, I'm rather attracted to the 'integral magnetics' solution, and these all seem to have shields. Given that the planes are void under the connector I suppose that means this shield will just have to be 'not connected. Has anybody got a recommendation regarding voids under the 'integral magnetics' part? Regards Jon Keeble ------------------------------------------- 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: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- 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: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- 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: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server.
