Testing the channel with a “Golden Patch Cord”
With some cabling projects, there is a desire to test the ISO/IEC 11801 Class EA installation in a Channel configuration rather then Permanent Link configuration. (Typically easier to PASS a Channel test) In this case, a random patch cord – even though from the same manufacturer - is used to test the entire installation. This is a serious violation of the channel test model (ISO/IEC 11801 Standard) which assumes the user patch cord stays with each Channel that is tested. Different patch cords will yield different results - even from the same vendor. Sometimes it can change a FAIL to a PASS. Doing this allows you to go through your bag of patch cords and find out which one gives you the best result. For that reason, the standards bodies define a Permanent Link for the installer which has a test lead with a known/consistent performance.
The Channel performance cannot be guaranteed by using two randomly picked patch cords. Nevertheless, the practice of using a “Golden Patch Cord” is widespread. For those wishing to continue to test with a "Golden Patch Cord", there is a better option than picking two random patch cords. This option should only be carried out if instructed by the vendor offering the cabling warranty or the owner of the cabling system.
The user can select ISO11801 Cl Ea Qualification as a test limit but test using the DTX-PLA002 without a nag screen coming up saying they are using a Permanent Link Adapter with a Channel Test Limit. Why is this better than two random patch cords? Project "Salsa" as it is referred to in the standards bodies set out to create a test plug with consistent electrical performance. This test plug is being used in most laboratories today to verify connecting hardware performance. This same "Salsa" test plug is found on the end of the DTX-PLA002.
Using the manufacturer's patch cord to test the links best represents real world performance. Not true. Each patch cord has a different electrical characteristic. The principle issue here is how well the RJ45 plug has been terminated. The quality of this termination will vary from cord to cord and from vendor to vendor and so will the result from your field tester. Use a longer patch cord and you will see your NEXT margin improve - try it for yourself.
The Class EA Permanent Link test limits are still changing and I cannot trust them. The Channel limits have never changed, so some users feel they are better off using Channel Limits. That argument could have been justified before the last ISO/IEC 11801 meeting in October 2008 (The draft came out later). In draft 25N1599, we now have what many consider as the "final" numbers for the Permanent Link. You can update your DTX CableAnalyzer to these new limits by clicking here.
Testing in the Permanent Link is often considered expensive because an entire adapter needs to be replaced as the test plug wears out. Not true. With the DTX-PLA002 Permanent Link Adapter, only the very tip needs to be replaced. This can be done in the field. And reports from the field suggests that the tips last well beyond the stated >5.000 insertions found in the user manual.