> Please advise what I may need to adjust and or change from
my present setup
> Im doing..
Dave,
In all of that I didn't see anything where you motioned the
power line connections or computer connections in your room.
The idea of a single point ground is EVERYTHING metallic
entering the area or cluster of interconnected gear has one
single reference point that every cable or conductor passes
on the way to the equipment.
This means the power line must directly pass that point, the
telco lines, any water pipes that connect to or pass by
gear, any heating ducts that connect or pass by gear. All
grounds must be bonded together at that one common point
with the shortest possible lowest impedance leads.
I actually have multiple common point grounds or hubs. Every
electronic center is treated as a system or hub.
Outside there is a repeater shed under a 318 foot tower
400-500 feet from the house. That shed has every cable
entering through a metal plate. Coaxial lines on
feedthroughs, power lines in a metal box that has MOV's that
clamp to ground (a 30 volt MOV on power line neutral to
ground, the safety ground directly grounded, each power line
lead with a 130VAC rated MOV). The control and metering
leads have low voltage MOV's and the cable shield is bonded
to that plate. The repeater rack bonds to that plate. That
plate goes to the tower ground.
That's an equipment cluster.
In the family room I have a collection of consumer gear in
one corner. Every cable and wire entering that area is
bypassed to a common point that centers around a lightning
protection outlet strip.
That's another cluster.
In my radio room all the power leads come past an entrance
plate. The cables all pass through that plate with shield
grounded to the plate. My power lines pass that plate,
ground to it, and then distribute to the gear in the shack.
The telco and ISDN lines pass that plate and the RF bypasses
(series 100uH chokes and shunt .01uF caps) ground to that
plate. That's another single point ground. Nothing in this
room metallic that gets near the radios or amplifiers does
so without being somehow bypassed or bonded to that one
point.
That's another single point ground cluster.
Now I have different grounds outside, for example the entire
house has a halo ground around it. Every "zero voltage"
conductor entering or leaving bonds to that ground. That
includes the propane tank and line, the water line, the TV
antenna tower and dish.
At the "yard area" boundary, there are grounds for cables
entering from different directions. Since that area is
hundreds of feet wide, it is too far to do a single ground
for all of it. Instead each cable cluster entering the yard
area is treated to a single point ground of a few copper
pipes.
Where radials pass into the yard, they are grounded to the
nearest yard entrance ground if within 6 or 8 feet.
The in-ground swimming pool metal outer wall bonds to
radials that pass near it. It has a halo ground around the
fence area, and the pool and fence posts ground to that
halo. That ISN'T really a single point ground, but it
ensures any large currents passing by the pool don't have to
follow a high resistance earth path.
I think you get the idea.
The idea of a single point ground is to treat things in that
area or cluster in a way that every conductor entering that
area or leaving that area points to a single small area
focal point. If the area is 10 feet wide it better be a wide
flashing or plate acting as the single point. You don't have
a single point ground unless the mains ground for your
equipment and everything else ties directly with very low
impedance short leads to that common point.
That copper pipe along your desk is mostly an operator
safety thing. To protect the gear you MUST have all telco,
power, and any other conductor near or connected to the
shack gear all passing one point or area where all grounds
are bonded.
This is really very easy to do. I use an "extension cord"
that plugs into a 240V outlet to power my gear. My operating
desk has a distribution panel that all outlets are fed from.
That panel grounds to the feedlines with an almost zero
length lead. The telco jacks plug into a cord that runs to
that same point, and that is where the RF bypassing is. Even
though there are multiple entrance points into this room,
everything in this room (except overhead lights) bonds to
one common single point ground. From there it branches out
to the gear. The supply side lines are kept away from
sensitive gear.
This not only greatly reduces voltage between devices during
a strike, it does so without regard for the quality of the
actual earth ground. This cluster format is why I don't
loose modems or anything else during hits. I take perhaps a
dozen good sized hits directly on the 300 ft tower each year
that I know of. There are four 135 foot wire verticals, high
dipoles, a 190 ft tower, a 160 ft tower, and a 50 foot TV
tower. There are certainly dozens of area hits near my
antennas, since all my receiving and transmitting antennas
occupy an area about 3500 feet by 2000 feet. Being in middle
Georgia we have about 2 or 3 lightning storms a week except
from October through March when things thin out.
I go years without TV set, modem, or shack gear damage. The
most common damage is melting of cable shields outside the
perimeter grounds, and with those cables connected to gear
inside the house things just don't get hurt. This is because
I use grounding clusters to a single point. The quality of
ground at that point means significantly LESS than how
things are wired, as a matter of fact some clusters (TV sets
and computer areas) have no ground at all other than what
the power line safety ground provides.
73 Tom
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