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Chad,
You are correct with SIGNAL cable. However loaded large DC power cables
work differently. EMI can be an issue. If I remember correctly a uniform
twist can reduce the problem. But I work mostly with -48VDC in large
power plant / load environments and we do not twist power cables. They
are however always run side by side as a pair. Bob Knucklos may have
more relevant information on this subject but I have never looked at his
books. I mostly reference Bellcore / Telcordia standards for DC power
signal and grounding since I have access to them.
Bobby
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Chad Robinson
Sent: Thursday, February 16, 2006 8:14 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Radio noise saga
Bobby J. Hughes wrote:
I would bet you found the problem. DC power leads should always be run
as a pair. A nice uniform twist is also good but I do not remember how
many twist per foot is recommend.
Twisted pair only reduces noise in signals transmitted THROUGH the wire,
and it only works if the receiver uses a differential signal. It doesn't
help with power wires. The curious can drop by:
http://www.duxcw.com/digest/Howto/network/cable/cable4.htm
It's a fairly good, brief description of what goes on. You'll usually
only find twisted pair in LAN cabling.
Regards,
Chad
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