NEXT and Return Loss

[OneSourceTelecom]

I am doing a cable certification project and am looking for some insight on NEXT and Return Loss.
What is the best solution for this?
Over the years I have re-teminated/re-pulled etc....
Any info will help, I will need to present this information with a solution to my customer within the next few weeks.

 

[cwc3]

Are you asking what to use to test data cabling ?

 

[SYQUEST]

The best solution is planning, and to install the cable and hardware properly, according to the manufacturer's recommendations and practices.

As far as measuring NEXT and Loss, that depends on the test equipment used.

....JIM....

 

[OneSourceTelecom]

Im using the Microtest Omniscanner for testing- testing all exisintg cabling throughout a school district.
I need to provide a repair report and solution.
Im looking for a solution for NEXT and Return Loss.

 

[cwc3]

you mean if the cable does't test to specs???
solution is you recable ?

 

[wires]

Im looking for a solution for NEXT and Return Loss."

Most of the time I have seen these problems it was related to poor terminations. Either the hardware or workmanship did not meet standards.

I used to spend a lot of time with a Omniscanner on networks I took over checking all the runs. These days I simply install managed switches and look at the error counts after a couple of days or weeks. Invariably the bad runs will have high error counts and I'll fix those. Much more cost effective than scanning each cable.

 

[SYQUEST]

Per "wires" remarks, as I said also. If the proper materials are used and installed correctly, you should have NO NEXT or loss issues!

....JIM....

 

[wires]

The quote below is from Belden's site. Be aware that the term "split pair" is referring to the wires terminating on pins 3&6 not a true split pair where wires from different twisted pairs are intermingled.

Since OneSourceTelecom is having problems with both NEXT and RL this info explains how the two are related. In short the place to look is how the wires are handled and how the connector is constructed on pins 3&6.

"Connector Return Loss
Connectors are a weak link in the channel's performance. Specifically, the split pair in the RJ-45 type connector is the major culprit. The physical separation of the conductors degrades the RL performance by disturbing the pair geometry. This separation of the pair generates an impedance discontinuity, causing signal reflections. Additionally, the near-end crosstalk (NEXT) compensation that some manufacturers performed on their older connectors aggravated the RL performance of the split pair. However, large improvements have been made to the new versions of connectors and this is becoming less of an issue making the cable performance more critical."

http://www.belden.com/pdfs/Techpprs/imprltp.htm

As SYQUEST says you shouldn't have problems with this if your materials and installation are up to spec.

Another issue may be with your test tool. The Omniscanner has been out of production for quite some time. This instrument requires regular calibration to be accurate. It is possible that the NEXT/RL fails are a due to the instrument not the cabling.



Good luck!