George, W5YR wrote:
At the risk of seeming to rain upon the parade, let's keep in mind that the
931 can at most provide a low-impedance path to "ground." Whatever that
"ground" happens to be is what determines the success or failure of using
the 931.
George is correct. The way I like to look at is that there are at least
four different 'grounds' that you have to worry about, and you need to
provide for them separately.
1) The electrical safety ground. This is to prevent shocks in case the
chassis of some equipment becomes 'hot' from the AC line. Electrical
codes should be followed in shack wiring, all gear should have 3-prong
plugs, and other grounds should be tied into this.
2) The lightning protection ground. This provides a low-impedance path
for static discharges and lightning strikes to antennas. Requirements
are quite stringent to do this correctly.
3) The RF ground. If you have an unbalanced antenna such as a long wire
or vertical monopole, there needs to be a ground return for RF. This is
what the radials of a vertical and the MFJ 931 are for. If your antenna
is a dipole or beam with a balun, you probably don't need an RF ground.
4) The 'shack common' ground. All of your equipment should be connected
with low-impedance straps to a common ground bus (which of course will
be tied to the safety ground). The purpose of this is to insure that
all the gear will be at the same RF ground potential and reduce the
effect of the unavoidable ground loops created by interconnecting cables.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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