Case Study 5 – NEXT Fails on DSX Cable Analyzer due to a termination issue

See a video example of this case here.

In this case study, the installer was failing NEXT when certifying a number of category 6A permanent links. With the DSX CableAnalyzer, it is possible to discover why these links were failing.

After the TEST, the installer was presented with the following DSX CableAnalyzer test result. The DSX will show the same results screen as left from the previous test. In this case, the WIRE MAP screen. Select FAULT INFO to quickly identify the cause of the failure.

 

 

Let's take a look at how the DSX CableAnalyzer diagnosed a problem with the local connector.

 

Step 1

Find out which pair combination of NEXT is causing the FAIL.

• Tap "Performance"
• Tap "NEXT"
• Tap the Right Arrow of PAIR to identify the worst pair combination

 

 

In this example, we see that the 1,2 - 3,6 pair is the cause of the NEXT failing.  Make a note of the failing pair.

 

Step 2

Look at the HDTDX Analyzer trace for this marginally performing pair. X for the NEXT failure.

• Tap the back arrow in the top left corner 
   
• Tap the FAULT INFO tab 
   
• Tap the HDTDX ANALYZER button 
• Tap the Right Arrow next to the PAIR to select just the 1,2 - 3,6 pair

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Step 3

Analyze the trace. What you are seeing is where the crosstalk is happening in the link. The cursor automatically goes to the largest source of crosstalk. In this case, the largest source of crosstalk occurred in the first connector, at 0.0 meters. The two yellow dotted lines represent the ends of the test leads of the DSX CableAnalyzer, so you can assume the lines are the location of your first and last connection.

You will note there is a “Value 53.05” on the screen as well. This is the value of the peak at the place of the cursor. In an ideal world, the value should not exceed 35 units, 30 if the link is less than 15 meters in length. Clearly, that has been exceeded. Looks like the near end connection needs to be reterminated (assuming the connector is really a Category 6A connector). Before we do that, let’s take a look at the far end of the link for the same pair, 1,2 – 3,6 on this link by moving the cursor to the near end finding the largest value, in this case “Value: 9.77” at a distance of 13.6 meters. 

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This is a good connection, much less than our limit of 35. This is what you would expect to see on a mated connection. Choose your connector carefully, terminate is carefully, making sure to minimize the untwisting of the pairs and the jacket removal and you can expect to see these small values.

If you have the “Store Plot Data enabled in your DSX CableAnalyzer, these graphs will be available to analyze in LinkWare PC software.

Conclusion:

The termination at the near end of the link is supect. Be careful though. The HDTDX is telling us that the NEXT FAIL is due to the connection at the near end of the link. It could be any of the following reasons:

1. Bad termination (twists not maintained)
2. Non component compliant Category 6A connector
3. Catefory 5E or Category 6 connector used in a Category 6A link
4. Bad Connector

The order above indicates the most likely cause, with 1 being the most likely.