W4des wrote:
>I am seriously considering placing a ground rod through my basement
>floor, concrete slab. I have my shack in the basement near one of the
>basement windows. I previously had the rig and other equipment grounded
>to the 8ft. ground rod immediately outside the window by the shack with
>about a 9-10ft run of ground strap. However, I have a deep basement and
>consequently the ground rod was vertical to the station and just outside
>on the otherside of the concrete wall. With a field strength meter I
>determined the ground strap and rod were both radiating RF. Now my
>antennas are on my 50ft tower at the end of the house and the tower has
>three ground rods at its base, connecting to the legs and the lightning
>arrestors, at the base and top of the tower. The previous problem with
>the ground rod out the basement window seemed to be related to a ground
>loop situation.
Hi David:
You may want to try something else first before drilling holes into your
concrete floor. It doesn't sound like your tower ground system and shack
ground system are tied together? If not, I would make these a single ground
system by tying them together. And depending on the soil conductivity in your
region, you may want to increase the number of ground rods on your tower and
put them in a ground radial configuration if possible. Be sure everything in
the shack is grounded to a single point, which could be a ground just outside
the basement window or the rod in the basement floor if you so desire or need
this solution after creating a proper ground system.
Also the rod outside the window, if it's the minimum 8 ft length, should be at
least 4 ft away from the foundation if possible. Mine's only a little over
three because of a concrete patio so it may not be possible all the time. The
idea is to have as much "ground" or earth around the rod as possible. Think
of each rod in terms of it creating an electrical "sphere" of influence the
diameter of the rod length around the each rod.
For 8ft rods, they should be spaced no further than 16 ft apart and no closer
than 14 ft. For 10 ft rods, no further than 20 ft apart and no closer than 18
ft. If they're too far apart, they won't act like a single grd system; too
close together and the ground may become saturated during a lightning strike
sending more energy into the shack than you'll want.
Another thing to consider is the AC power system safety ground (you know, the
green wire or third prong). How is it grounded if at all? Is it only
grounded to a cold water pipe like mine was? This is bad especially if the
pipe has to snake its way to the other side of the house before it sees any
earth! Your AC breaker panel or the feed at the meter or entry point should
be well grounded AND it should also be tied to your radio station system
ground outside the house!
Another thing often overlooked are the telco and cable TV grounds. Tie these
also to the outdoor ground system. The ideal is to have a ground ring with
properly spaced ground rods all the way around the house and everything tied
to it on one side of the house only, but this is usually not practical in a
residential environment due to sidewalks, driveways and things like XYL
restrictions! I just have a ground buss along the backside of my house with
everything tied to it, and whenever possible as much stuff tied to the same
ground rod as possible!
If any of this sounds familiar to list readers, I got most of it from
PolyPhaser's book "The Grounds for Lightning Protection". Pretty good book
and very few sales pitches for PolyPhaser products which are pretty good too.
We use them on our Comm sites at the utility I work for.
Good luck with your ground system upgrade!
73,
de ed -- K0iL
k0il@qsl.net
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