We're having our office rewired; old Cat3 and Cat5 wiring is being replaced with a shielded Cat6. (The reason for shielded is another subject completely and is a done deal, so please, no "Why Shielded? You don't need it" posts. I will say that having a shielded solution is of lesser importance today, but will take on greater importance in the future.)
My concern has to do with the proper way to implement a shielded ethernet solution. We got two quotes. One was very specific about materials, from someone whose expertise I trust. We sent his itemized list of materials to another company and asked them to match the materials and give us a price. Their quote was less detailed, but since it was supposed to be based on the first quote I assumed they quoted the same or equivalent stuff. The cost was similar. For reasons of business politics too complicated to go into, we selected the second company's "equivalent" quote.
Now stuff is starting to arrive. Where the first quote explicitly provided a shielded solution from end-to-end, some of the materials arriving are indeed not shielded products. Instead of shielded patch cables we're getting unshielded. Instead of an empty multimedia panel into which shielded jacks would be installed, we're simply getting a cat 6 patch panel, which I haven't been able to verify supports a shielded solution (I'll check it out when it arrives).
This leads to my questions:
- I am assuming that a shielded patch panel or jack provides the means of connecting all the shields from the horizontal cabling and the patch cables, effectively creating a single ground point for all cable segments from end to end. Is this correct?
- If I'm only concerned about EMI in my horizontal cabling locations, and think EMI will not be an issue in my rack or office locations at present, is it appropriate to use unshielded patch cables, as long as the shielded horizontal cabling is properly grounded to the patch panel (which is itself grounded thru a properly-grounded rack)?
- If the cable shield is ungrounded, does the shield simply provide no benefit, or does it create the potential to cause harm? I've read speculation that an ungrounded shield could act as an antenna that actually increases EMI exposure to the pairs inside.
Please understand, I'm not asking for an opinion about whether EMI is likely to pose a problem in my environment; I'm asking for sound ethernet grounding theory.
Thanks in advance!
Bryan