rf_engineer
join:2003-08-04
USA
| reply to Paulg
Re: Rats
You're taking the unshielded twisted pair nomenclature too literally. It's a general understanding in electrical engineering circles that copper twisted pair is self-shielding. Untwist the wires and the self-shielding properties go away, along with its bandwidth characteristics, and crosstalk between pairs goes through the roof. |
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whizkid3
Premium,MVM
join:2002-02-21
Queens, NY
 ·Earthlink Cable Mo..
| said by rf_engineer  :You're taking the unshielded twisted pair nomenclature too literally. It's a general understanding in electrical engineering circles that copper twisted pair is self-shielding. Untwist the wires and the self-shielding properties go away, along with its bandwidth characteristics, and crosstalk between pairs goes through the roof. Self-shielding???
Go back and check Maxwell's laws. A twisted pair is going to accept interference like any other unshielded wires. However, because of the twisted pairing, both wires will have virtually the same exact interfering signal injected on them. Differential receivers (in the Ethernet chips), can then eliminate the interfering signal. |
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rf_engineer
join:2003-08-04
USA
| said by whizkid3 :said by rf_engineer :You're taking the unshielded twisted pair nomenclature too literally. It's a general understanding in electrical engineering circles that copper twisted pair is self-shielding. Untwist the wires and the self-shielding properties go away, along with its bandwidth characteristics, and crosstalk between pairs goes through the roof. Self-shielding??? Go back and check Maxwell's laws. A twisted pair is going to accept interference like any other unshielded wires. However, because of the twisted pairing, both wires will have virtually the same exact interfering signal injected on them. Differential receivers (in the Ethernet chips), can then eliminate the interfering signal. That's true, noise introduced into the line will be in phase on both lines and will be "cancelled" at the end, while the intended signal is 180 degrees out of phase on each line. But compare a twisted pair to two conductors spread apart six feet, like a power line. This is the meaning of shielded versus unshielded in the context of the original post. |
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