[Elecraft] elecraft,RJ45 Standard

[Jim Brown]

On Mon,5/9/2016 9:41 AM, Lynn W. Taylor, WB6UUT wrote:
> If we're talking DC levels, sure, no problem.  Low rate signalling 
> just won't matter.

You're missing the fact that although these conductors INTENTIONALLY 
carry DC and low rate signals, they also can PICK UP RF and AF noise. 
Twisted pair, when used to carry a signal, is at least as powerful at 
rejecting RF and AF noise pickup as coax, but ONLY if the pair is 
dedicated to a circuit. That only happens when both ends of the cable 
are correctly wired. That is, OR and OR/WH will reject noise, but OR and 
GN will NOT.
>
> At audio levels, the shielding from twisting the wires might be helpful.

It is VERY helpful.

>
> If we're actually using them for Ethernet, then the twisted pairs 
> aren't wires, they're transmission lines.  100 megabit ethernet is 
> running at 100 megahertz.

Right. AND -- they are transmission lines at RF frequencies even when 
the INTENDED signal is AF or even DC.  THAT'S HOW they reject RF and AF 
noise.

>
> Wire the cable randomly and you don't have twisted pairs (transmission 
> lines) at VHF frequencies (or above).

And you don't have them at AF or HF either.

Bottom line -- CAT5 and similar cables are excellent for control wiring 
and even for RF, but we must  ALWAYS wire them so that every circuit 
uses a pair. Wiring them any other way is a recipe for noise and RFI.

73, Jim K9YC
>
> 73 -- Lynn
>
> On 5/9/2016 8:42 AM, David Robertson wrote:
>> As long as you maintain the same standard or a standard you create on 
>> BOTH
>> ends of the CAT 5 cable this cable could be used anywhere, regardless of
>> the system used.