[RFI] Ethernet RFI
aa4lr at arrl.net
Sun Jan 30 09:09:56 EST 2005
On Jan 22, 2005, at 8:41 PM, Ford Peterson wrote:
> One of my pet peeves is when computer technicians wire cat5 cables
> incorrectly. There is a right way and a wrong way to do it. The
> right way is the most difficult. Guess which way most people do it?
> The 8 conductors in that cable are actually 4 pairs of twisted cables.
> Each pair is a "hot" and a ground return. When you hook up the
> cables to keep the colors all the same on each pin at each end, you
> will have conductivity between the correct pins, and the network will
> work, but you completely lose any shielding benefits of the twisted
> pairs. You should not be hearing anything from that cable.
For a standard 10/100 Base-T Ethernet run in CAT 5 (or CAT 3) cable,
only two of the four pairs are used for signal. One is a differential
pair running to the hub, the other a differential pair running from the
hub. The other two pairs are typically not used, but do provide some
shielding to the run.
I have about 300 feet of surplus CAT 3 (!) cable running through my
house, and it all runs 100 Mb/s with no errors, and no interference.
It's all installed and wired correctly, and I'm proud to say I did it
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
More information about the RFI