Why do we get CAT6 Return Loss failures when the cable is installed in floor boxes that show signs of water in the conduit? The jacket of the cable has not been compromised so I am curious as to why a damp conduit would affect the impedance of the circuit.
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The problem is that water is an excellent conductor of electricity. Cabling will emit some energy. This problem gets greater as the frequencies get higher. The jacket on a cable has some insulation properties, but in unshielded environments, there is no shield to stop electrical current from being emitted from the cable. This is what we commonly refer to as "noise" in the channel. Noise can occur at various points in the channel. Near end cross talk is noise at the near end or where the signal is being introduced, for instance. Electricity that is emitted from the cables in an environment where water exists is even worse. This is because the water acts as a conductor, keeping the emitted noise from dissipating and increasing its ability to interfere with other cables or even the original cable.
This was first published in July 2004