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W8JI's new Contesting and Boatanchor Room
Antenna System and my house station
This is a typical installation:
Unless you have a very tall tower or underground utilities, lightning will most often strike utility lines. They are just a much bigger target, so the odds favor them being hit. Lightning surges follow the drop to the house entrance (D), where a very small portion of the surge is diverted to the entrance ground (C). The largest portion flows through the house wiring to the station equipment and out to the antenna (A) and station ground (B). The station ground and electrical mass of the tower and antennas looks like a better ground than the small rod at the service entrance.
With the most common hits or surges, good grounds installed at A and B actually increase current flowing through the house wiring and through radio equipment.
Some people disconnect antennas. If A is disconnected and B remains connected, the radio is still in the lightning path from D to B. Disconnecting the antenna doesn't do much, unless the tower or antenna takes a direct hit or has induced charges from a nearby strike. It does not eliminate the most common problem. Unplugging the radio equipment helps, but there is still a significant risk that lighting will flow though other paths from D to A or B.
The best solution to this problem is B has to be bonded to C with a much lower impedance path than any other path, including the house wiring. B and C should always be bonded together, this is even spelled out in the National Electrical Code.
"Common grounding is important to ensure an electrically continuous and uninterrupted path to properly dissipate lightning’s harmful electricity. Failure to make all of the required ground system interconnections is a common trouble spot cited in lightning protection system inspections."
Many amateur radio installations have an independent ground rod outside the radio position. Ground rods that are not bonded to the power mains ground outside the house can actually increase the chances of damage.
My Station Ground
Tower Grounds
The following is typical of my tower grounds:
Because this is the point where most of the lightning energy passes, the grounds are wide flashing high temperature silver soldered to the ground rods
Radials are also tightly wrapped and soldered with high temperature silver solder to a number 6 AWG solid buss wire. That buss wire follows the perimeter of the tower pad. The old flashing in the picture was installed in 1998. The older tower and its grounding strap has been removed, but during its life the silver soldering survived hundreds of direct hits.
To make the connections to the rods, we drill a tight hole in the flashing and force it over the rod. We slightly fold it upwards and fill the depression with high temperature silver solder using a MAP gas torch. You must use high strength high temperature solder, not traditional plumbing solder.
All four corners are grounded to the tower legs. Most of the real work in the ground system is done by the buried radials.
Workshop entrance and ground:
Receiving antenna, transmitting antenna, and control cable entrance at house:
Grounds and shields of all cables entering the house are grounded to wide copper flashing. The copper flashing connects to my station ground inside the house and to the utility company and circuit breaker panel ground. The perimeter of my house has a #6 solid copper ground wire that bonds to the water line, propane tank, TV antenna tower, satellite cable, and telephone and electric service ground rod.
This ensures everything in the house comes up at nearly the same rate during a lightning strike. Large lightning currents do not flow through the house.
House operating area entrance common point ground:
This is the receive antenna grounding block inside the house. Bottom cables are the entrance cables. This is an old picture; cables are now all F-6 with compression fittings. Transmitting cables go to a single point where an 8-position relay cross-over antenna switch routes cables and harmonic suppression filters to various radios. This switch allows any tower's grouped feedline or antenna feedline to be connected to any radio.
The transmitting antenna switch matrix is fairly complicated. I have three primary towers; a 160-foot rotating tower with antennas for 160 meters through 70cm, a 200-foot tower that provides a 160 meter omni vertical and an eight direction four square, and a 318-foot tower with multiple dipoles at various heights and directions for 160 and 80 meters. Each tower has a 5-position or 8-position antenna switch at the base. The 318-ft tower has an additional switch mounted 1/2 way up.
There are two additional 7/8th inch feeders out to areas for antenna experiments.
Feedlines are sized to keep loss below 1dB to any antenna feedpoint in the system.
Everything inside the radio room is grounded to the large copper flashing. This is additional assurance that everything in the radio room comes up at the same rate.
Despite this system having miles of coaxial cables spread over an area covering many thousands of feet, and despite all of these cables being connected 24 hours a day, I have never even lost as much as a computer modem or TV set in a storm! I have had a super-bolt melt the shield of heliax at my 318-ft tower base. Radio, computer, and TV equipment in the house were not damaged during that hit. The worse damage I ever have are coaxial cable shields outside the house that melt from direct hits.
Protection is really more about how things are connected than anything else.
For more grounding look at my contesting barn's entrance.