Every so often a vendor publishes a very useful little handbook. The "Copper Cable Troubleshooting Handbook" by Fluke Networks is one such handbook. Although the handbook is promoting Fluke equipment, it is still worth downloading a copy.
The introduction to the Fluke handbook sets the stage for the rest of the material.
Certification is the process of comparing the transmission performance of an installed cabling system to a standard, using a standard defined method of measuring the performance. Certification of the cabling system demonstrates component quality and installation workmanship. It is typically a requirement to obtain the cabling manufacturer's warranty.... Technicians must diagnose the failing links and after a corrective action has been implemented, they must retest to ensure the link meets the required transmission performance.
In the past, I owned a cable installation company. The installers varied in diligence for the cable installation. Documenting the testing, corrective actions, retesting and finally the labeling was usually but not always satisfactory.
I found that for large cable bundles, the installers would test the outer cable pairs. The outer pairs are more likely to be damaged during installation. If the outer pairs passed, then the installer assumed the inner pairs were performing properly and did not test them. So you should learn how cable tests and corrections are performed.
So what can be the trouble with a cable?
* Installation errors--damaging the wire twist (even removing 1/2-inch of twist can change the cable characteristics), bending the cable sharply, pulling too hard on the cable * Using the wrong connectors * Original manufacturer problems * The patch cable can be bad * The connector terminations are incorrect or poor * The test scenario is set up incorrectly * The test equipment software is not current
The handbook covers the basics that should be performed before testing begins. I learned that the temperature can have an effect on the test results, such as leaving the test equipment in a cold or hot location before use. It was recommended that cable testing equipment come to room temperature for about 15 minutes before use. I also learned that test equipment should be recalibrated every 12 months by an authorized service center.
Some of the problems I have encountered are also listed in the extensive lists provided:
* Wires open, broken * Incorrect pin connections or pair reversal * Crossed pairs * Split pairs * Cable too long * Excessive cable delay * Insertion (attenuation) loss (the signal is weak)
There are three pages of faults and likely causes to review. Various configuration models are described for testing scenarios.
I found that reviewing the handbook content gave me a newer appreciation of the results of good and bad installation practices. I found a single fault can manifest itself as several different problems, making the diagnosis difficult.
