[Antennas] Ground?

Sun Jun 28 18:58:13 EDT 2009

Group,
I was asked the following:
 > Bob-
 > To add to my education, please explain for me, with regard to the
 > part I marked with *** below--
 > Please complete the circuit for me-- RF goes FROM the radio, THROUGH
 > you, and TO where? Use the assumption that you are touching the Mic
 > case.
 > ***
 >> You can do the whole ground grid system and STILL get RF burns!
 >>
 > ***
My response:
The RF indeed DID go out the coax. MY lips got the RF burns from a
microphone, and my finger tips from the skirt of the knob! I am VERY
glad it was a barefoot SB-102!
My ground system was 12, 8 foot rods driven into the ground, connected
by 1/4" solid copper over 150 sq feet.
I learned a good bit about RF grounding from that night on. RF voltage
can float over most any metallic surface with surprising ease.
1) I use bus bar, 1/4" thick, 1 1/2" wide, and in lengths of about 5
feet. All HF gear is bonded to the bus bar. I use a MINIMUM of #12
solid, and use a toroid near the radio on the power cord. You could use
stranded in lieu of solid. You "can" use the wing nut ground provided
by the radio manufacturer, but I've been known to solder too the radio
now. I take both ends of the bus bar outside to the ground system with
1/4" solid copper too the grid system.
2) RF is NOT picky about where it will go. Find the path that it CAN
take - because it will!
3) I run coax out one hole through the wall, the ground out another.
I hope you can see what can happen, and why I wrote what I did. My coax
and ground ran through the same hole in the wall. RF can induce voltage
in a parallel conductor with great ease.
-- 
Bob - NØDGN