[RFI] Ethernet RFI

John Pelham w1ja at bellsouth.net
Sun Jan 23 19:47:36 EST 2005

> On Sun, 23 Jan 2005 13:18:08 -0600, Ed -K0iL wrote:
> >But only one of those would place the "twisted pairs" into the 
> >correct EMC signal configuration.

I continued to misunderstand, but I get it now.

I thought Ford was saying his ignorant tech was wiring the RJ45s in a more-or-less random fashion.  I couldn't understand how that would work at all.  Now I see: Ford's tech must have been saying that it was OK to put any color on any pin, so long as one put the same colors on the same pins at the other end of the cable.

As has been said, of course that isn't good because, although it would check OK with an ohmmeter, it would not correctly hook up the signals to the proper twisted pairs in the cable.

Then Jim Brown wrote:
> Bottom line -- you cannot test data cables with an ohmeter, you 
> MUST test them with a specialized data-transmission test set that 
> measures end to end loss, crosstalk, and related parameters. These 
> test sets cost big bucks.

I would think one could accomplish most of the "specialized data-transmission test set" test by just eyeballing the RJ45s on each end and making sure the proper color code for the wires was followed.  That is, assuming the cable is good quality.

John W1JA

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