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.
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