On Mon, 30 Jul 2007 18:47:13 -0500, JOHN PASSANEAU
wrote:


Hi Danny:

You are of course correct, but with RF in the shack problems levels are
important. If the level of RF is below some threshold it causes no harm.
Almost all Ham stations operate just fine with low levels of unbalance
and other defects in the antennas.
Just for interest sake I ran some numbers on a model ground system. Let’s
assume you have a perfect ground system and you connect to it from the
shack on the second floor using 12' of #6 wire. And it runs in a straight
line, no bends or curls. The self inductance of that wire is about
56.22uHy.
So what will be the reactance of that wire at 3.5 MHz? Doing the math I
get 1,235.7ohms. At the other extreme 28MHz, I get 9,886.52ohms. These
are numbers that hardly make me confident that I have any kind of a RF
ground.
By the way at 60Hz the reactance is 0.021ohms that I think is a good
ground.
Please excuse me for harping on this, but I run the electronics shop in
the Physics dept at Penn State University. I'm constantly seeing many
meter long thin wires tied to some cold water pipe or something in a lab
that is supposed to get rid of all the high frequency noise in some
experiment and it has no chance of helping. If physics grad students have
problems understanding grounding it's no wonder that Ham’s do too.

John Passaneau W3JXP

John,

You are absolutely correct. My error was I didn't address the second
story issue. At that location all bets are off and your statements
above are correct. Although using copper strapping with multiple runs
of different lengths from the station to the ground system should
work better.

My station here is on ground level. The distance from the connection
point of the outside ground system to the point inside were all
equipment is connected is about three feet of 3/8" diameter copper
tubing. My frequencies of interest is 80-10 meters. The ground system
consists of eighteen #8 copper radial wires connected to a eight foot
ground rod which serves as the anchor point. The radials are fanned
out over about 210º arc varying in length from as short as about
twenty feet up to seventy feet. It seems to work fairly well.

Thanks for the input and addressing the original poster's question. I
had taken off on a tangent based on the statement that a so called
balanced antenna wouldn't benefit from using a station ground.

Very 73,
Danny, K6MHE