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| I have recently encountered a problem with a standard CAT 6/FT6 cable running at 1000Mb/s. The cable was working fine but has now dropped to a 100Mb/s connection. I tested the cable and found the cable failed insertion loss by 22db and return loss by 6db. We replaced the jack at the user end and re-terminated the cable in the TR which made no difference.
I know however that the cable is run through an underfloor conduit for approx. 130' and inside this conduit is a small amount of rusty water which I feel must be the cause of this problem.
Any feedback would be appreciated.
Thanks,
Ryan Garner, RCDD
Ryan Garner, RCDD
Marcomm Integrated Business Solutions
(905)706-5453
ryanadamgarner@gmail.com
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| RyanGarner (3/10/2010)
I have recently encountered a problem with a standard CAT 6/FT6 cable running at 1000Mb/s. The cable was working fine but has now dropped to a 100Mb/s connection. I tested the cable and found the cable failed insertion loss by 22db and return loss by 6db. We replaced the jack at the user end and re-terminated the cable in the TR which made no difference.
I know however that the cable is run through an underfloor conduit for approx. 130' and inside this conduit is a small amount of rusty water which I feel must be the cause of this problem.
Any feedback would be appreciated.
Thanks,
Ryan Garner, RCDDRyan, I think you are probably right. IMO, I think the solution is to pull that cable (trash it), blow the conduit clear, and install new cable that is suitable for a wet environment. Even if you get the water out today, more will accumulate. Doug
Doug Weis, RCDD, ESS |
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| | I have seen standard CMP and CMR UTP cables fail from complete corrosion of the copper pairs that were installed in conduit in concrete slab on grade within 1 year of installation. In general we specify the use of outdoor rated cable in concrete slabs on grade piped homerun to telecom rooms. Even conduits that are not directly on the finished grade / dirt may contain water from condensation, but most often this happens with slab on grade conduit pathways. On another related subject I have also have had issues with floor boxes being daisy-chained with power conduits rendering the floor boxes intended for data useless without saw cutting the slab and installing a new conduit, often not an option when an owner is ready to occupy the space. Just one more thing to keep in mind. |
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| | I'm not sure what test equipment you have, but if you were to have a frequency based tester, you should see the Return Loss fail at the lower frequencies. In addition to that, you should see that all four pairs following each other on the trace as in the example below: 
This is a classic sign of water in the cable. With 100BASE-TX being full duplex, you will run into problems with 100BASE-TX. 10BASE-T may work but probably not that well. It can be so bad that your telephones will have trouble as well, since most of them are full duplex these days. In the case of the DTX CableAnalyzer, you can then use HDTDR to locate where the water is in the cable, as in this example below. We'll look at one pair to make life a little easier: 
We'll zoom in on the vertical axis to get a better picture: 
What you see is the impedance changing dramatically at 64 ft and at 69 ft. The area between these two spikes is where the water is. I'll use the marker feature to indicate this: 
This is a common easy diagnosis. Get a couple of these a week. It happens a lot more than people think. And yes, the cable has to come out and you will need to figure out how to dry out the conduit if it is conduit. I'm told a small piece of shamwow on the pull cord is very effective. If you have a DTX, you can send the FLW LinkWare file to support@flukenetworks.com for confirmation.
Kind regards
Adrian Young
Senior Technical Support Engineer
Fluke Networks Technical Assistance Center
Did you accidently delete results from your DTX? |
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| Thank you Adrian for all of that great information. My test results were very similar to the ones that you had shown on the post there. I find it funny though that the new CAT 6 cabling we installed last year is already having problems and the 15 year old CAT 5 cables that are in there are still working fine. Unfortunately the conduit in question is a 2" zone conduit stuffed with approximately 50 cables so that ought to be interesting.
Thanks again everyone for your feedback!
Ryan Garner, RCDD
Marcomm Integrated Business Solutions
(905)706-5453
ryanadamgarner@gmail.com
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