[RFI] Grounding the Operating Position
EDWARDS, EDDIE J
EDWARDS, EDDIE J" <firstname.lastname@example.org
Fri, 29 Sep 2000 09:32:24 -0500
> -----Original Message-----
> From: David Jordan [SMTP:email@example.com]
> Getting ready to set-up a ground buss behind all the equipment on the
> operating table. Running a six ft piece of 1/2 inch copper pipe which
> is connected to the ufer ground system.
> Want to ask whether 1/2 inch flat silver tinned braid strap is OK to use
> to interconnect the equipment to the copper pipe. I expect the jumpers
> will be from one to two feet long.
> I vaguely remember reading that braid was not preferred when trying to
> reduce unwanted RF currents. If my memory serves me correctly it was
> stated that a piece of #16 guage wire was better than using 1/2 inch
Braid does give a large surface area for grounding, but todays comm
stds are to not use braid in the grounding especially outdoors where you
will get corrosion. The reason is when it starts to corrode between all the
little strands you start to get external rectification or "the Rusty Bolt
effect". This can lead to IM & other EMI/RFI problems.
Use either a #6 bare with green insulation or a 1-1/2" copper strap
if available. Cu strap made by Polyphaser can be bought from most Ham
outlets now. Run all grounds to a Master Ground Bus or MGB connected
directly to a single point ground system. To learn more about single point
grounding visit the Polyphaser web site at http://www.polyphaser.com and
click on the Technical Documents link. The PTD1016.pdf is just for hams,
but lots of good stuff there so be prepared to do some reading!
de ed -K0iL
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