A tutorial by cwk9
Every thing you wanted to know about UTP buy were afraid to ask
A few questions that need to be answered before we get started.
Q: What does UTP stand for?
A: UTP (Unshielded Twisted-Pair Cable).
Q: What does UTP look like?
A: It’s that blue cable that’s always running around computer labs.
Q: Were can I find a video of a man shooting a TV?
A: Try here http://www.howstuffworks.com/what-if-shoot-tv.htm
Q: Is there STP (Shielded Twisted-Pair Cable) cable to?
A: Yes but it is more expensive and is rarely used in computer labs.
Q: How is UTP different from Cat5?
A: UTP is a type of wire; cat5 is a TIA/EIA standard. But for the purpose of this tutorial I will mostly be referring to cat5 cable. There are also Cat 5e Cat6 and Cat7 but most networks are still cat5.
Q: Why are your writing this don’t you have anything better to do?
A: No.
Let’s start with what’s in a UTP cable. If you cut open your standard UTP cable you will find that it is not one wire but 8 wrapped in a blue outer jacket. The 8 wires will be twisted in pairs. In addition each pair of wires is wrapped around each other UTP must follow precise specifications as to how many twist are permitted per foot of cable. Each wire is a different color so that you know witch order to place them into the RJ-45 connector (more on this latter). There are two reasons for the twisting. One is to reduce crosstalk.
Definition from Cisco
CROSSTALK: When electrical noise on the cable originates from signals on other wires in the cable, this is known as crosstalk. NEXT stands for near-end crosstalk. When two wires are near each other and untwisted, energy from one wire can wind up in an adjacent wire and vice versa. This can cause noise at both ends of a terminated cable
The other is to limit signal degradation RFI (radio frequency interference) and EMI(electro-magnetic interference). Some things you should try and avoid to minimize EMI and RFI are.
-Televisions
-Radios
-Microwaves
-Heaters
-Welders
-Computers
-Motion sensors
-Motors
-Fluorescent lights
This wire twisting technique works so well you will rarely need STP wiring to deal with RFI/EMI. Once as a test I tried running some cat5 into ceiling then wrapped around a Fluorescent light 20 times and then back down and it still worked perfectly. So just what is in the 8 little wires? Copper of course. Either 22 or 24 gauge with an impedance of 100 ohms to be exact. If you are wondering why UTP CAT cables are so popular and most other cables have died out there a few compelling reasons.
-CAT is cheap, cheap, cheap.
-you don’t have to worry about terminators (not the terminators for the movie the BNC kind)
-UTP has a diameter of about .43cm so it’s easy to work with. If you have ever seen an old thicknet (garden hose coax) cable you would understand what a god send 0.43cm must have been.
-Works with RJ connectors
-Fastest copper based networking media.
-Its blue
Of course it’s not perfect there are a few draw backs.
-More prone to EMI/RFI than coaxial cable and STP.
-Can only go about 100 meters before it needs a boost from a repeater or other networking device. You might want to keep it less than 70m just to be safe. Some coax cables can go 500m and fiber goes even further.
-Its blue
Back to those color coded wires. If you buy the wire in bulk you will need to attach it to something. Cables will most often connect to an rj-45 connector (phone is rj-47) or patch panel. What order you place the wires into the rj-45 determines weather your making a straight-through cable or crossover cable. Straight-through cables maintains the pin connection all the way through cable. Hence pin 2 on one end will be pin 2 on the other. Cross over cables are specific to Ethernet, pin 1 at one end should be connected to pin3 at the other end; pin 2 at one end should be connected to pin 6 at the other. Crossover cables are used to directly wire two computers together or connect to a networking device that does no perform the cross over for you. Devices that need a roll over cable are usually designated with an X near the port. For everything else there’s straight-through cables. Placing all those wires in to the rj-45 in the right order is a bigger pain in the ass than you might think. It’s not to be attempted by anyone with lousy dexterity or a short attention span. Here are some links to help you build your own cables.
http://www.informit.com/content/inde...9200FBE28F9%7D
http://howto.lycos.com/lycos/step/1,...+20002,00.html
The first layer of the OSI model is the physical layer which means that no layer above it can function with out it. Because cables are in that layer we can make the logical assumption that your network is only reliable as the cabling used in it. To save your self some trouble you might want to get a cable tester so you can test the cables you’ve made before you start running them through the walls. Cable testers (sometimes called time domain reflectometers or TDRs) vary in complexity. Some only have a red and green light on them others will tell you what kind of cable you have, what wires are working and how long it is. Of course if you don’t need to worry about wire testing that often you can just connect two computers and have them ping each other.
A little more Q and A to answer any questions you might still have.
Q: What Ethernet specifications use UTP?
A: 10BaseT, 100BaseT, 100BaseTX and 1000BaseT use UTP. 10Base2 and 10Base5 are coax. 100BaseFX is fiber
Q: I want to wire my LAN with pink wires. Does Ethernet cable come in pink?
A: I have seen yellow cross-over cables but other wise there all blue. You could always use spray paint.
Q: is there anything more boring than talking about Ethernet cables
A: Yes http://radioqualia.va.com.au/freeradiolinux/a
