RJ-45/8P8C Couplers

[disinfo]

I've always thought that use of these was bad practice, but have never really had any proof.

Was called out today to investigate why a customers backup job was running so slowly to their brand spanking new Windows Storage server.

The server was cabled into the network on a CAT5e link into a 1Gbps switch port.

I checked all of the obvious things, network card drivers speed / duplex mismatch and came up with nothing, so I put the cable certifier on and low and behold it failed the crosstalk test (NEXT) On testing the link speed it was averaging at around 17Mbps

After a bit of investigation (digging around in a rockwool filled suspended ceiling ) I came across this;

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• disinfo
• 31 Jan 2009
• 1

Replaced the thing with a proper IDC junction box and link speeds are now at 987Kbps which pretty bang on considering overheads.

To satisfy curiosity i've tested the coupler in isolation, it still fails the test badly and on cracking the casing open I can see why.

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• disinfo
• 31 Jan 2009
• 1

Maximum permitted limit for untwisting pairs is 13mm, as you can see the image above clearly shows that the couplers do not uphold this standard.

This is a plot of the NEXT test, red line is the limit

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• disinfo
• 31 Jan 2009
• 1

Moral of the story is don't use RJ-45 couplers!

I've just bought a few different types from eBay to test if this was a particulary bad one.

P.S. I'll be going back to rerun the whole cable rather than leaving the IDC JB bodge.

 

[EddyP]

Very interesting.

I've used some of these in the past, can't say i've noticed slow traffic, but unless theres something quite network intensive going on it would be easy to miss.
Will try to remove them and put IDC jobbies in now then, thanks

 

[plugwash]

If a coupler is not advertised as being compliant with any particular standard (or comes from a dodgy source like many ebay sellers) then it doesn't at all surprise me that it isn't suitable for gigabit ethernet (it would probablly be fine for 100BaseTX )

I have seen couplers from reputable suppliers that claim to be cat5e certified and would expect those to work fine with gigabit.

 

[disinfo]

If a coupler is not advertised as being compliant with any particular standard (or comes from a dodgy source like many ebay sellers) then it doesn't at all surprise me that it isn't suitable for gigabit ethernet (it would probablly be fine for 100BaseTX )

I have seen couplers from reputable suppliers that claim to be cat5e certified and would expect those to work fine with gigabit.

Well, i've bought a certified one. So will let you know the results when I get it.

This coupler by the way failed all tests and was not suitable for carrying any data under TIA or ISO/IEC standards.

 

[kjacko]

yeah i wouldn't use any couplers for data transfer either.
I only ever use them to connect our RJ11 phone cables to a cat5e patch lead which then plugs into the network.
RJ11 plugs are sods to extract from a RJ45 floor port.

 

[Igorian]

I personally don't like them and would rather replace the run, as you've stated.

 

[Lectrician]

They are ****e and non-compliant, some people will use them without issue, but the pro's out there know what to do with them!


Why has this been moved to hardware?

It was more suited where it was in "Alarms, CCTV and Telephones".

Perhaps it should be renamed "Alarms, CCTV & Datacomms", or "Alarms, CCTV, Telecoms & Data" etc.

 

[disinfo]

Perhaps it should be renamed "Alarms, CCTV & Datacomms", or "Alarms, CCTV, Telecoms & Data" etc.

Thanks, I'm glad someone else realised my logic in posting it in the section I did.

For my next test im going to use a CAT5e cable to run 100BaseT and use the other two pairs to run telephones, many people seem to think that this is ok.