Hi Stephen This kind of effect can be from the device you are using as a driver. = For complex transceivers where you have a lot of control you can create = that situation if you do not program them correctly. You can also have = simply a device that is not working properly. Do not concentrate only on = the PCB board. If you are using test equipment as a source, it is also possible in some = equipment to change the cross-over point from 50%. Jose -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] = On Behalf Of Stephen Greenhalgh Sent: Dienstag, 17. Januar 2006 10:03 To: Si-List (E-mail) Subject: [SI-LIST] Eye diagram Recently I saw an eye diagram in which all the crossovers occurred at = 70-80% amplitude rather than the ideal 50%. Apart from this obvious = defect, the eye looked pretty good. Ever since, I have been wondering = what would cause this effect. My first thought was some difference = between the +ve and -ve traces of the differential signal path, but I = cannot formulate a theory that explains this satisfactorily. For = example, if one trace were longer than the other, I would expect both = positive-going and negative-going edges on the longer trace to be = delayed relative to the shorter one, which would mean that some = crossovers were raised, and others lowered, from the 50% level. Is this a known phenomenon that I have somehow completely missed? I = would be glad for any explanation or suggestion that anyone can offer. Stephen Greenhalgh ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu