Mailinglist Archive: opensuse (1777 mails)

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Re: [opensuse] Moving to IPv6
  • From: John Perry <j.e.perry-t@xxxxxxx>
  • Date: Tue, 14 Sep 2010 04:52:06 -0400
  • Message-id: <4C8F37B6.9080106@xxxxxxx>
On 9/13/2010 4:29 PM, Carlos E. R. wrote:
On 2010-09-13 01:48, Ilya Chernykh wrote:

Why do you think cable TV coaxial(or anything) is better than UTP? To have
cable TV you also have to make wiring.
Coaxial is more capable than twisted pair. But quite more expensive, too.

Actually, no.

Coax is much easier to build as a true constant-impedance line, but it has higher loss, especially at higher frequencies, which is the true limiting characteristic. If you can build a twisted pair to a very high standard of consistency, it will give greater ultimate range due to the lower signal loss. Coax needs less signal conditioning over shorter distances, and less complex conditioning over any distance because it's normally better controlled (that's why short instrumentation cables like oscillosope probes are almost always coax), but twisted pair gives greater range and acceptable signal fidelity once you've done the signal conditioning.

That's also why the ancient Ethernet cables were coax, but limited essentially to 10Mbps and short distances, and we had to go to twisted pair (cat-5, cat-5E, cat-6) to get higher bandwidth and signal fidelity over longer distances. Manufacturers are building Ethernet cables much more carefully than they do short-range, low-frequency twisted pair, and for longer distances the transceivers are more complex to compensate for the poorer signal fidelity,.

Those cable systems that still use coax have frequent repeaters with frequency-dependent loss compensation.

Pedantic John Perry


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