Laying a CAT6 network

Working on just the garden or door jambs quickly becomes disheartening, especially if you're waiting for a tool to turn up or for it to stop raining.

Our place has always been covered in semi-operational LAN (local area network) CAT5 cables (internationally categorized wiring, like telephone wires but higher specification for computer to talk down at high speeds).

I spent forever reading up on networks and was even thinking of running fibre around the house to make it future proof. Fibre optic is one of those technologies, like thick ass wires in the national grid to carry megawatts, that is all but impossible to improve on. By the way, a single fibre optic has the bandwidth to carry more information than your spinal chord. Amazing hey.

CAT6 is the newer version of CAT5 and supports more data per second than CAT5, it's also cheaper than CAT5 depending on where you pick it up. So this monkey picked up a 1000ft (330m) spool to install while I rip the house apart. Data rates for CAT5 are around 100 mbs, where CAT6 is more like 1000 mbs.

Wires have two important properties - inductance and capacitance.

Capacitance is created by the wires being so close to each other. It's like rubbing a balloon on a jumper and putting it near some bits of paper - there's a charged stored up on the balloon. In the same way, applying a voltage to a conductor beside another, but not touching it, will create a stored charge. That's an issue, because for the voltage to change, it has to neutralize that charge as it goes, making it an effort. Computers send signals based on pulses of current, not voltage.

Enter inductance, which is an issue. As the electrons move down the copper, they produce a magnetic field around it, like an electromagnet. The faster you expect the signal to vibrate (transmit data), the more it tries to dump energy into things around it through that magnetic field; to the signal, as it vibrates millions or billions of times a second, the wire becomes a worse and worse conductor, until it's just as easy for the signal to break out of the copper and couple to something nearby, regardless of what it is. That creates electrical noise around wires and degrades your signal.

Inductance is a property that is only important with regards to the flow of electrons, the current. It also increases the more you expect the wire to deviate from a straight line. If you wrap the wire up into a coil, you have an electromagnet, and a terrible high speed conductor. The wire doesn't need to be in a spiral to achieve that effect, just making bends in it will do it. When laying network cables, you'll get the highest bandwidths by not looping the cable all over the place.

The last thing to thing about is noise getting into the network cables, from electrical wires nearby. The rules for this are that if you don't want it to happen, you lay cables so they cross over each other at 90 degrees and they don't run close and parallel to each other; the latter allowing the magnetic fields from them to couple between the conductors much better, causing them to crosstalk with each other.

There is a raging war on the internet about whether or not it's okay to lay things like CAT6 near power or TV cables. Despite searching, a lot, I found absolutely no concensus on it. In fact, the arguement is very two sided.

I won't know until I have my network tested how it's performing, but power and TV lines are two different things. The frequency power is transmitted at is extremely low, so low you can easily hear high power equipment humming at 50Hz in the UK. The low frequency means it doesn't break out of conductors anywhere near as happily. It's also well below the frequency a LAN will operate, so it's unlikely to cause any corruption.

TV signals are between 5 - 1000MHz, which is much more likely to be an issue. It'll couple out of it's conductor well and it's vibrating at about the same speed as the signals in a LAN.

What seems to be causing confusion for some is that LANs use cable that contains a twisted pair (it's called UTP, unshielded twisted pair). The idea is that by using two wires in a pair to carry each channel of the signal, any noise that gets picked up on the wires as they carry the data to where it needs to go, nulls it's self out at the other end by having a mirror image of it's self superimposed over it. It's complicated to explain, but imagine your a noise signal trying to walk down a wire, you goal is the kettle where you'll be making me a brew. You walk to the kettle, noise transmitted, but then I ask you to walk back to where you started, net result, you haven't moved.

Measuring the signal on a single conductor out of the pair to test for noise won't work, because the conductors work in pairs normally. It's also worth noticing that commercial operations often run thousands of meters of UTP cable all bunched together in cable runs. If crosstalk is a major issue, these runs as thick as you leg would undoubtedly be having problems.

So why have Shielded Twisted Pair? My guess is for extremely strong local signals that'd actually damage the equipment on the other ends.

But enough nerding it up.

My plan was to base the network and TV box (virgin V+) in the loft, then drop LAN and TV cables down into the bedrooms and downstairs from there. In a 1920's house, that is effort.

I needed to first get the cables across the loft floor. I crawled around under the eves in the cupboards armed with a drill and spade bit, like some kind of stawkler from a horror film, making a hole in there. My plan was to use a drain rodding kit to pull the cables from these cupboards across to a hole I could drop them through to the next floor. Only problem is, there's a mountain of junk under the floor joists, as well as a lot of chicken wire that's used to pin down the insulation (fibre glass blows all over the place if it's not held down and there's a fire). The rodding idea came to a skin itching end when it snagged on something under there. I got very annoyed.

A flash of inspiration came to me as I looked at the partially removed skirting board and the massive gap under it where the plasterboards are intentionally not flush against the floor; to prevent moisture wicking up. I pulled the rest off and found that some hammering and pointy thing action meant I could channel the cables along there, foam the gap up when done and fit the board to hide it all.

Check out the length of cable on the DeWalt rotohammer, think that's enough? Well, I love it, since it means I don't have to trail the plugs around in the air or across the floor with me. More tools like this make John a happy boy.

I also found the DeWalt 90 degrees drill really helpful for spade drilling through the joists where I needed to run the cables perpendicular to the span of the joists.

Notice I have no cordless tools? I hate them. I see the point if your a trade guy and don't always have a socket around, but at home, corded all the way. Cordless can't come close to the power levels of corded, and having a battery run out on you makes them feel like toys. The only cordless tool I might get is a drill/driver, but I doubt that. They also cost a fortune for a power and duration level that's still a lot less than I get with a cheap corded tool. Even if you're doing trade work, you could afford a cool portable generator and the tool for the price of a lot of the better cordless.

What's that fibre glassly looking stuff? Sound proofing from when I routinely received noise complaints when playing my guitar. The black stuff in the middle of the fibre is barium containing rubber, making it dense and so great at absorbing acoustic noise (you heard of a barium meal?). Not cheap, but works great. The other material is shredded car tyres all stuck together with some extra rubber. Use it for mechanically isolating things that vibrate, like speaker cabinets from the floor. You might also see some long metal things on the floor in the loft. They're also soundproofing, but go under plasterboards so they hang off the wall, rather than being tightly fixed to it.

I'm waiting for my snap and seal tool and coax stripper to turn up before I advance anymore with this. I also need faceplates for the cables that will give a tidy network (CAT6 rated) & tv outlet in each room. I'm using cable rated to Digi 100 for the coax to keep the signal clear over the long runs I'm using.

THE END!