Hi Group, I have been dithering over choosing Ethernet cable and modular faceplates for months. I decided to go with cat7a cable for future proofing even though it's a massive over-kill for the performance I am going to need. I plan on using it for analogue telephone cable as well since it's going to run along side mains cable for part of it's route and the braiding and foil screening of cat7a would provide maximum protection from interference. I only need around 140 meters and almost every retailer is selling 350 or 500 meter reels. I found one retailer selling Nexans cable in custom lengths. This cable doesn't have a drain wire though, neither for the foil or braiding. Does this matter? I don't think it would make any difference to the quality of the braid screening but I can imagine a copper drain wire running through foil would increase the conductance to drain away the interference since copper is a better conductor than silicon. Also I believe drain wires make it easier to connect the screen to the terminating module. I was told by a retailer that you shouldn't really terminate using the drain wires anyway, but should connect the foil itself into the module. Is this correct? Can anyone advise on drain wires or perhaps suggest more retailers who sell in custom lengths. Very many thanks, David
Hi saspro Thanks for this. This is cat7 cable though which is an old standard. I really want to get cat7a cable. Very many thanks, David
The drain wire won't improve shielding, it's only for termination, so whether you need one or not depends on the connectors you use. I've never dealt with Cat7a cabling before, so I couldn't tell you if the connectors typically require a drain wire or not.
On Telco installations, the drain wire was always there so you had something to run to the ground bar. Everything else though (including coax) you just clamp around the braid or some variation thereof to get your drain. If you look at STP patch panels, the surround on the jack is actually metal and makes contact, which provides your ground (the RJ45 should be metal too). You still need to attach a ground to your patch panel though, obviously. All that being said, why in the devil do you want shielded anyways? It's a b1tch to terminate and cat6 utp is being certified for the new upcoming N-BaseT standard (5gbit) to the full 100M, so unless you live beside a tv transmitter or are into ham radio, stp is pointless.
Many thanks for these responses. That's really helpful. I was told that so long as the patch panel is metal, it will provide enough of an erth without having to actually earth into anything external, like the mains. I'm not sure what I'm going to do in the way of patch panels yet. I want to find a double gang wide, 6 gang high box that I can clip Euro modules in to. There is copper plumbing, mains and a spare earth leading back to my consumer unit near by but I don't understand the risks of electricuting my equipment if there's ever an electrical fault in the house and the mains earth becomes live. I don't need cat7a, but if I'm going to get holes drilled through joists and would have to rearrange furniture especially in a lodgers bedroom to upgrade cable later on, and the amount I need is not going to cost much, I'd rather future proof so I like the idea of cat7a. It will run around 20mm from a mains cable for around 12 feet in one room and a bit less in other rooms. I believe the phone cable will be more effected by noise than the ethernet. Okay... it's all a massive over kill but not being sure of the interference and the money not being a factor, that's what I feel more comfortable with. I like the idea of the braiding around the cat7a which I understand provides a better screening than the foil screening that most cat6a is available with in the UK. I'd have felt more confortable if I could find anyone in the UK selling custom cut lengths of cat7a with a drain wire. Very best wishes, David
Full stop. Worst idea ever. 1: An ungrounded cable shield is... wait for it... A GIANT FRIGGIN ANTENNA. 2: A properly built and maintained ground is connected to... ground and will have the same potential as the earth. You bond things to ground so that they never have different potentials (it's not voltage that kills you, it's differences in voltage). At least on this side of the pond, ground and neutral are tied together, such that if the live wire makes contact with something grounded, you blow your breaker/fuse and nothing terribly bad happens. Please, if you want to use shielded cable, you need to do it properly. You are far better off just sticking with UTP.
Why are you worried about interference - where do you live that has so many signals floating around? It's perfectly feasible to wire a standard house with Cat 5e and not worry about interference, as long as you keep your runs under 100m. Make sure that there's at least a 12-18 inches between your Cat5 and any electrical cables, and if they have to cross, make sure they do so at right angles to each other. Trust me, if you don't get your shielding termination right, you're going to suffer from much bigger problems than anything you might imagine about interference. Source: I used to flood-wire homes with Cat5e for home automation. No problems reported, ever.
I've got around 30 runs of Cat5e running through my house carrying all types of signals (data, phone, sensors, rfid) and I've never had an issue, I know you are thinking of future proofing but as others have said they have already started on multi gigabit tech over Cat5e and Cat6. If it's coming back to a rack then the rack and equipment should be grounded to stop unwanted floating voltages between equipment and connectors. For reference the mess that is my comms cupboard currently:
