[TowerTalk] Grounding systems etc. DE K0FF

[K0FF]

When I was preparing to retire a few years ago, I had the luxury of time on
my side, and a fresh QTH waiting for me in the countryside. We were going to
move to the "weekend" place and set up an antenna farm. My working career
involved setting up communications systems (voice, video, data) for gov't
and industry, so I decided to make a design for my own station, and slowly
build it to that design. It took 5 years but it's now pretty much finished.
All MF and HF bands as well as all VHF and some UHF bands are used, as well
as EME, and a Beverage hub. 7 towers so far and lots and lots of poles and
trees.

As important to me as the towers, and antennas was the grounding system. I
use a single point system, and you have to look at what is "ground" a little
differently when you do that.

I'll describe the whole system someday if there is any interest, but in
rough detail, I have 2 operating positions in the house and a transmitter
shack located about 350 feet away. Everything is set up in a star pattern
with the house in the middle, and the lowest frequency antennas being the
farthest away for feedline loss control.

The main grounding panel for the operating positions is located in the
basement directly below the main desk, which is in a little room on the
first floor. All of the coax cables, Heliax, and control wires land here
first, and their shields are grounded to this panel. Polyphaser lightning
arresters are mounted there, for coax and control wires,  as well as the
station's lowpass filters (yes here is the correct place, not at the rig).
On HF the rig's coax first goes to the panel, is treated with a Polyphaser,
and then goes back up to the amplifier. Also all antennas except the VHF go
through a relay switching system, and are disconnected and grounded when the
"big switch" is pulled. The telephones for the house go through the panel
too, and are treated and conditioned there. Finally this panel (It's 7 feet
tall) holds the station power supplies which include a Sorenson 12V at 150
Amp main unit and another Sorenson 12V at 50 A backup. 220AC supplied of
course. Additional small 12 and 24V supplies for switching are rack mounted,
and all equipment, panels and rack are grounded to the main shack ground,
which is in turn tied into the service panel ground, and the 2 towers at
either end of the house, and the TV antennas pole, and the VHF chimney
mount.

In the operating position itself, there is a 2 inch wide by 1/4 inch thick
copper bar running around the room. Each individual piece of equipment tied
onto this bar with it's own piece of 10Ga flex wire, with crimped copper
terminals. This "perimeter ground" then goes through the floor via a short
copper strap, and ties onto the single point ground. The shack AC line is
treated with a SERIES conditioner, which ties to the single point ground ( a
surplus commercial unit from a computer center) and then also with the usual
shunt devices. The main 220 has a large commercial device right in the panel
too. This type of arrangement is called a "star of stars" and you can see
that there are no loops.

Most of the information you need concerning grounding of radio stations is
contained in the book by Polyphaser, the ARRL Handbook and additional info
can be found in the "technical papers" section of the online webpage of
Broadcast Engineering company.

Geo>K0FF


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