[RFI] stealth RFI

EDWARDS, EDDIE J eedwards at oppd.com
Tue Jun 17 09:00:47 EDT 2003

A couple of other things that may help.

A good site for grounding information is www.polyphaser.com which has
several tutorials about grounding and lightning protection if that's an
issue in your location.

Some basic grounding/bonding rules:

-- Never use braided cables for grounding (especially outdoors!) since
corrosion will eventually create thousands of P-N junctions and possibly
cause noise problems and external rectification creating more RFI/EMI
problems.  It may be OK to use at the operating position/desk in a
controlled environment (constant temperature, low humidity), but even
there they should be replaced every few years before corrosion becomes a
problem.  Unless you move equipment around a lot, I'd stick with either
copper strap or solid as first choice same as outdoors.  Less future

--  More ground rods offer a better ground, but placing them to close
can be a waste of copper and money.  8-ft rods can be placed 12-16 ft
apart and still offer lightning protection as well as additional RF and
safety grounding.  You need to think in 3-dimensions to picture the
influence surrounding a ground rod.

-- As Rob stated, do not allow any sharp turns or bends in grounding
cables/wires.  Always use 8-inch radius bends.  Create a cutout out of
cardboard to use as a guide.

-- Use of a Low Pass Filter is Mandatory at all times especially when
running amps.  It's good engineering practice which is required by FCC

Good luck!

73, de ed -K0iL

-----Original Message-----
From: Rob Atkinson, K5UJ 
Are you running a low-pass filter in your 
feedline to your antenna?  If not, I'd get one and give it a try.  

In my experience, a 1 kw amp needs a pretty good 
ground.  Depending on where you are, one rod may not be enough.  I'd put
at least two more, each at least 4 or 5 feet away from the one you
have in.  The one in now should be the center rod with the others coming
it, each with its own strap from the center, i.e. don't daisy chain
It's better to have all this below grade also.

your 10' ground run is just about a 1/4 wave antenna.  If 
possible, try to make it shorter, as in about 5 or 6 feet (hard to do I 
know) so your gear sees a lower reactance on that band.  I would also 
recommend using either a heavier gauge cable such as 2/0 gauge from Home

Depot, or better yet, some 3" wide copper strap which is available in
from AES and perhaps other vendors.   Try to avoid sharp bends in your
to the rods.  

Please report back to the list on the outcome.

Rob Atkinson

From: Ted Bohrer <N7QY>
My buddy has a RFI problem in the TV and home stereo. Here's the
"I turned on TV, sat the wife down, asked what channel was the worst,
did a baseline test with Icom linear on (500w), voice and CW. The TV
does a little herringbone on key down full 500w and the speakers mumble
SSB, worse with processor on."

More information about the RFI mailing list