Protecting Your Equipment Against Lightning By Ken Meyer, K9KJM, EC Door County A direct lightning strike to your antenna mast can be safely handled. It is not simple or easy to install a system to take direct strikes, but with some time and effort it can be done. I wish to dispel the old wives' tales about "Nothing can prevent a direct lightning strike from destroying your radio equipment." Tall buildings, like the Empire State building, take direct lightning strikes most every thunderstorm. These buildings are full of people and contain radio transmitter antennas on tall masts. Commercial radio and TV transmitter towers, public safety towers and cell phone towers are required to be on the air 24 hours, 365 days a year and do not shut down when storms approach. When properly installed, they do not suffer lightning damage. Years ago when some poorly protected stations had lightning damage, they were grounded with No. 6 copper wire, which was then state-of-the-art. Power companies did significant research and found No. 6 copper wire is heavy enough to handle over 97 percent of all lightning strikes. For the most powerful three percent of strikes No. 6 copper vaporizes. It was found to be cheaper for power companies to replace and repair the damage than to install heavier ground wires on all of its equipment. If a power company substation wants nearly guaranteed protection, it uses heavy 2/0 copper wire grounding on everything and connected it to an underground grid of bonded ground wires to many ground rods. Modern radio stations use flat copper sheet, the wider the better, run from a single-point ground panel where all coax and other wires are grounded, to the ground system. Copper sheeting can sometimes be found for a reasonable price from upscale roofing companies, which use it for roof flashing. True silver solder is the material required to make connections and bond it together. Silver solder is available at welding supply shops for about a dollar a stick. One stick will make quite a few joints. MAPP gas in a small hand held torch will supply enough heat to flow true silver solder. Do not use lead/tin solder! It turns to a white powder underground! Once the copper sheeting is in the ground, use heavy copper wire to your closest ground rods. Ground rods should be 8 long, copper-clad 5/8" rods, which are only about $8 new at home supply stores. Space the ground rods twice the distance apart as the depth, meaning 8-foot rods should be spaced 16 feet apart, 4-foot rods, 8 feet apart. Consider the ground wires connecting the ground rods similar to the roots of a tree. The closest wires to the shack, like the closest roots to a tree, should be of large diameter. As the roots go away from the building, smaller and smaller gauge wire can be used. The first wire to the ground rods should be 2/0 copper, then No. 6 copper to the next rods, then No. 10 copper wire out further. Rods and radial ground wires are effective up to about 75 feet away from the tower building. For underground use, there is no need to use new wire. Used copper wire salvaged from an old building, and stripped of all insulation will work as well as new wire and much cheaper. Ground enhancement systems can also be homemade. Old copper pipe, drilled full of holes and filled with rock salt can save significant money. Old copper automotive radiators, or anything else, which applies a lot of mass in the ground to dissipate lightning energy can be used. Installing such a system is more than a single year project for most of us. Start with a few rods, and add more as time and funds permit. Indoors, near the point where the coax enters the building, should be your single point ground plate where all lightning arrestors and coax switches are mounted. Polyphaser and I.C.E. (Industrial Communications Engineers) have some of the best arrestors. Polyphasers are sometimes found on E-bay for far less than full retail price. Any radio equipment you intend to use during a thunderstorm should have such an arrestor inline. The cheap way to protect any equipment not used during a storm is to have a coax switch that directs all antennas to ground. I use the old B&W (Barker & Williamson) Protect series for HF use, and the Alpha-Delta strip line for VHF/UHF. Whatever you do, do not disconnect the coax and just leave it lay! If you insist on disconnecting, which in itself is very dangerous, at least install an old SO-239 connector to a good ground connection and connect the coax to that! Leaving coax unconnected, or just as bad, inside an old glass jar, is like leaving a stick of dynamite on your floor! There was a great series of three articles on proper lightning protection in QST magazine a few years ago. Good information on Polyphasers can be found at http://www.polyphaser.com/ppc_ptd_home.aspx. The best site I have found about lightning protection in general is http://members.cox.net/pc-usa/station/ground0.htm. For those of you who wish to use your radios with full safety during a severe thunderstorm, cross-band repeat is a good solution. Set up your base VHF/UHF radio to cross-band mode and use your HT to talk directly to your repeater of choice. Always also monitor your output frequency by scanning with the hand held radio to make sure all is working properly. But, save yourself and your equipment and install a proper ground system!