I find this grounding system inductance lowering "arms race" a tad
obsessive. I think there is some confusion about shack grounding because
there are actually three grounding systems (at least) at work. Each
system has its own conductor size requirements. These systems are:
1. The Electric Code required equipment grounding conductor that is
part of the 120 volt power to the receptacle you plug your
equipment into (connected between the third prong in the outlet
and the ground rod at your service entrance) This is usually #12
copper for a 20 amp circuit.
2. The RF ground: This is to provide a path to ground for stray RF
currents. Here the length is much more important than the
diameter.
If skin effect were so important then why is ladder line, often
constructed of #16 or #14 wire the transmission line of choice when
low loss is of the utmost importance. We entrust wires of this
size
to get our signals to and from the antenna...surely it should be
sufficient to shunt some RF to ground. The impedance to ground is
effected much more by the length.
3. Lightning protection. Here is where big diameter is important.
The currents involve in a lightning strike can melt small diameter
wire. Its best to provide a path for lightning to ground before
entering the house for obvious reasons.
Of course, with three system involved there is plenty of potential
for ground loops. Bringing all the RF grounds from various equipment
to a single point (like on the tuner) will help eliminate some of them.
RF filters in power circuits and line isolators in coax runs should
eliminate the rest (Radio Works sells some relatively low cost line
isolators...don't have any personal experience with them).
73, Henry, W6GZ
hmauro@pacbell.net
"Dr. Gerald N. Johnson, electrical engineer" wrote:
>
> Actually a wide strap of flashing copper is far lower in inductance than
> 3/4" copper pipe though its not as easy to find these days.
>
> 73, Jerry, K0CQ
>
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