If you can TDR from both ends of the cable, knowing the exact VP doesn't matter. The fault will be in the middle between the two readings. I've used this to find faults in twisted pair audio cable using a coax TDR.
------Original Mail------ From: "Gregg Eshelman" <g_ala...@yahoo.com> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Sent: Fri, 10 Oct 2014 00:07:41 -0600 Subject: Re: [Emc-users] Oscilloscope + logic analyzer (PC based) On 10/9/2014 12:36 PM, Gene Heskett wrote: > Dunno, I suppose if one wanted to test the quality of a new and unknown > quality cable it could be useful. But in troubleshooting existing cables, > I have yet to see anything work slicker than a good TDR. You can have a > bullet burnout someplace in a 2100 foot run of high powered coax, take a > look at it on the TDR and tell the tower crew within 5 feet of where to > take it apart. The 5' error? Probably the operator, not knowing the > exact propagation velocity of that particular line & using a SWAG instead. Five feet is good. How about 500 feet or more? The line my DSL is hooked up to has always been real iffy. Supposedly I'm able to use any modem I want but only the ones provided by the ISP will work - at my house. I've taken them to the ISP's office and to homes of other employees of the ISP and *there* they'll work. Almost every day, sometimes twice a day, I have to turn the modem off and on to reboot it so data will download again. Recently it just completely quit. One of their techs checked the line and found the pair I was on had a dead short. Instead of replacing that whole piece of defective multi pair line, he just swapped wires at both ends of that section to a different pair. Nevermind I still have the same problem as before and it's steadily getting worse. I expect that when this pair shorts out they'll just move it to another unused pair, if by then there is a "good" pair still unused. I know that this kind of suspended cable is expensive, but poor quality of service costs even more. In any business, when you have broken equipment, you repair or replace it ASAP because letting a problem go will cost a lot more money. Even more fun was the day that simultaneously a squirrel and a backhoe operator cut both sides of a redundant loop separated by many miles, cutting off several entire towns from the net until they got it repaired. Still more fun was the day a squirrel decided a fiber optic line with 100 or so strands would make good nest material. One of their new hires got to learn how to splice fiber on his 3rd day at work. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ------------------------------------------------------------------------------ Meet PCI DSS 3.0 Compliance Requirements with EventLog Analyzer Achieve PCI DSS 3.0 Compliant Status with Out-of-the-box PCI DSS Reports Are you Audit-Ready for PCI DSS 3.0 Compliance? Download White paper Comply to PCI DSS 3.0 Requirement 10 and 11.5 with EventLog Analyzer http://pubads.g.doubleclick.net/gampad/clk?id=154622311&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Meet PCI DSS 3.0 Compliance Requirements with EventLog Analyzer Achieve PCI DSS 3.0 Compliant Status with Out-of-the-box PCI DSS Reports Are you Audit-Ready for PCI DSS 3.0 Compliance? Download White paper Comply to PCI DSS 3.0 Requirement 10 and 11.5 with EventLog Analyzer http://pubads.g.doubleclick.net/gampad/clk?id=154622311&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
