[RFI] Twisted pair for mobile power

[Jim Brown]

On 4/29/2013 9:40 PM, Michael Germino wrote:
> How often should you twist a pair of power cables, for a mobile setup?

The best answer is "always,"  but I don't think that's what you're 
looking for. :)  I've never understood the standardization of both the 
high futility world on (glorified) zip cord for speaker cables, and of 
the ham world for DC power cables. Zip cord, glorified or not, is VERY 
poor at rejecting RF coupling, while twisted pair strongly rejects RF 
coupling. The differences are HUGE -- several tens of dB. Lots of RFI 
problems with home entertainment systems have been solved replacing 
(glorified) zip cord speaker cables with twisted pair.

It's really funny, in a sad way  -- hams worry about RF filters on power 
wiring, but use zip cord for power.

> Is there a optimal twist rate or twist as much as you can?

More twists per inch, and more uniform twisting, is better.  Don't go 
nuts.  2-3 turns per inch is practical and in the ballpark.

73, Jim K9YC