Cabling concepts

I'll just add my 2 cents here...

As tfs quoted “the more twists per inch of cabling, the less susceptible the wiring is to EMI and crosstalk...” this is important why you should NEVER (and I know a lot of people do) stretch the cable. If it isn’t long enough make another cable (You can use the cable somewhere else), the more you stretch the cable the more it untwists, therefore eliminating the purpose of Twisted Pair cable! Thus making it susceptible to EMI and crosstalk (slowing your speeds of course)

Just thought I would like to add that in cause all too often at gaming LANs I see people jerking their cable around the place to make their cable reach their computers… Not a good thing to do

and then they complain that they lost because the latency was too high

okay I'm with you so far. Maybe I am just really stupid but I'm not finding out WHY twisting it is going to make it so that Cross over doesnt happen and EMI and RFI.

Thanks!

COnfused

Here is an explanation I found that might help clear it up:

Each cable pair forms a complete electrical path for signal transmission. The currents flowing through the wires in each pair are equal, but flow in opposite directions. These currents produce electromagnetic fields that could transmit electrical noise to nearby wires. However, the fields surrounding the two wires have opposite polarities. Twisting the wires together causes the fields to cancel out, which minimises the electrical noise, or crosstalk, generated by each cable
pair.

There are two types of twisted pair cable: shielded twisted pair (STP) and unshielded twisted pair (UTP). STP cable, which may also be referred to as ScTP (screened twisted pair) or FTP (foil-screened twisted pair), contains a conductive shield that is electrically grounded to protect the wires inside from electrical noise. STP cable is more expensive and more difficult to install than UTP

your a stud

Inductance and understanding what it is answers your question. It is as simple as the fact that electrical current creates a magnetic field. Changing current creates a moving magnetic field. Relative motion between a magnetic field and a conductor (wire) will induce a current in the conductor. This is the principal that generators operate on and the basis of transformer action, which is where AC current in one wire will induce AC current in another. In transformers wire is purposely wound on top of another to transfer electrical energy from one circuit to another.

This is the answer to your question. In networking cable it is undesirable to have current in one wire pair induce current in another wire pair. By twisting the wire pairs an equal amount of energy is induced into both wires. Since each wire in a wire pair is conducting current in opposite directions at the same time any external magnetic fields cause equal and opposite currents and are therefore canceled. This works well for external electromagnetic sources. By making each wire pair different in their number of twists per inch they act as external sources to the other wire pairs thus no voltages/currents are induced from one wire pair to another.

This is why following standards with regard to untwisting pairs as little as possible in terminating CAT5e (and especially CAT6) cable when making either RJ45 connections or punch down connections is critical. Books on AC electricity defining inductance, capacitance, and impedance would help explain the reasoning behind the twisting of wire pairs in CAT 5, CAT5e, and CAT6 cable.

On the other hand I tell those studying to be net workers just follow the standards of network cabling very closely. After all unless you want a double degree in electronics and computers you don’t need to worry about why.