Hi Andy, Most of the ports are linking to offsite support equipment or looped back to get link. The response seems consistent regardless of how it is linked. There is also some tuning; broadband humps up a little higher in one spot or another but not a real big factor. I have tried 50 ft and shorter 3 to 10 ft on all ports, and tried ferrites on the offsite portions of the cables. Using STP on the offsite portion of the cable will be an interesting test. Thanks for the input. Rick Linford -----Original Message----- From: Andy White (EWU) [mailto:andy.wh...@ewu.ericsson.se] Sent: Wednesday, October 09, 2002 3:39 PM To: Rick Linford Subject: RE: Ethernet Radiated Emissions Hi Rick, Is the problem only when you link more than 2 cables together? What is the length of link cabling when adding cables? I susepect that the BB noise is directly associated with the increased cabling and the lengths becoming resonant. If cable lengths are the issue for the BB, the RE problem is not that easy to resolve. Changing to another UTP will not really improve it, a section of STP (on a link or some of the links) would probably help. I would give it a try. Perhaps a cable ferrite may work on a link cable as well to reduce the BB lump amplitude. 100bT uses a 25MHz source so it may be possible to add some filtering at the pcb but this will probably affect the ENET operation/functionality. Hope you find a simple solution. I liked your 'thanks to the marketing dept for the opportunity to learn' comment - classic :) all the best Andy ____________________________________ Andy White, Staff EMC Engineer Ericsson Wireless Communications Inc. San Diego, CA 92121 Tel 858 332 6214 / 877 877 7799 ext 26214 Fax 858 332 7311 e-mail andy.wh...@ewu.ericsson.se ____________________________________ -----Original Message----- From: rlinf...@sonicwall.com [ mailto:rlinf...@sonicwall.com] Sent: Wednesday, October 09, 2002 1:55 PM To: emc-p...@majordomo.ieee.org Subject: Ethernet Radiated Emissions Having worked on Ethernet (100 MB UTP) EMC for a few years, I now find myself lacking understanding of Ethernet communications and how this may be affecting radiated emissions. What is seen on the OATs is broadband noise between 50 and 150 MHz. With two cables connected and linked, broadband is not even out of the noise floor. With the third and subsequent cables linked the broadband increases With all cables attached and not linked there is no broadband. Reducing the resolution shows peaks every 60 kHz. Probing on a linked signal shows peaks every 30 kHz with every other peak (60 kHz) being 20 dB higher. Probed several other types of Ethernet equipment, NICs and switches and this seem consistent across all products and manufactures. I feel the filters and layout is quite good, in that, with cables attached but no link there is no emission. In probing on the board it self the 30 kHz signature is present only on the transmit and receive all other signals and voltages appear clean. Is this the nature of Ethernet 100 MB over Unshielded Twisted Pair? Could this be the fault of the UTP cables? If so any suggestions on the type of UTP cable to purchase? Thanks in advance for your time and responses. Rick Linford And thanks to a marketing department for this opportunity to learn, by believing 6 ports of 100 MB is need in the home.
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