On Sun, 15 Jun 2008, Ken Elliott wrote:
> Eben King wrote:
>> Would wrapping them in Al foil help? My electrical intuition says the
>> Al shied would emulate a Faraday chamber, so it should.
>
> The issue is often crosstalk between strands. Wrapping the assembly in
> aluminum foil would only help shield it from external RF.
Why would twisting them prevent/reduce internal crosstalk?
> Wayne's statement:
>> It takes time
>> for electricity to propagate through a wire, and Ethernet devices will
>> only wait so long before assuming the segment isn't in use and begin
>> transmission of their own.
>
> Well, this is a bit confusing. I assume Wayne intends something other that
> my interpretation of his words.
>
> Electricity travels at the speed of light, so there is no way that it could
> timeout. Longer lines do a great job of capturing RF, and this confuses the
> network device. Often, this RF causes packet corruption, which will cause
> multiple retransmission of the packets. So untwisting the cable does not
> slow down the raw signal speed, but packet corruption does cause the data
> transmission rate to drop. I had a client next to a radio tower, and you
> had to get everything right on the wiring to prevent excessive packet loss.
I think this is how it fails:
The signal reflects a bit off each jack, and more off the end of the cable.
(This is, I believe, why you need terminators at the ends of some cables.
Phonenet, and Thinnet come to mind. Maybe SCSI.) If the cable is too long,
some devices may get the reflection at a plausible time for the next cycle
(1/signaling rate).
--
-eben QebWenE01R@vTerYizUonI.nOetP http://royalty.mine.nu:81
"God does not play dice" -- Einstein
"Not only does God play dice, he sometimes throws
them where they can't be seen." -- Stephen Hawking
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