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Updates: Oct 2004: finishing up the mobile antenna shootout July 2004: Added antenna testing and more photos June 2004: |
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[Mobile Station] [Fixed] [Antennas] [Lightning] [Quick Reviews] [Walkabout] [Other Hobbies] [Links] |
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I have seen houses burned by lightning. I had my own minor experiences with a blown up water pump and a burned up pool heater. Equipment damaged, but easily replace and noone was hurt. But my amateur radio equipment is a bit more expensive and valuable. Given the equipment is connected to antennas which are great lightning targets, I wanted to take whatever precaution I could. Station Configuration: The fixed station is on the third floor of a wood frame structure. Clearly not the best place! This area is a loft above a bedroom with a small attic next to it. It was essential to get good grounds from the station, outside, in a safe manner. Inside System: All the equipment inside the shack is tied to a 1” copper pipe. No this pipe doesnt go anywhere, it is not part of the plumbing of the house, it just serves as a big termination point for a ground wire to each piece of equipment in the shack. Thus there are no ground loops anywhere: a single point ground. (The computer audio interface is opto isolated on control and trasformer isolated on audio.) Industrial clamps bind the wires to this short section of pipe. In addition there is a ground wire to the coax switch. Two large wires (one #8 and one #6) runs thru a hole in the wall inside PVC electrical conduit to the attic space. From there these two wires run down the outside of the house in 2” electrical conduit to ground level. This wire was expensive, but I think it was worth it. Outside System: The two wires from the station go each to a ground rod that goes into the ground about 7 feet. These rods are also tied together. Each rod is separated by about 2 feet. I just wanted to make sure I had a good connection. Each coax line coming into the house is terminated in this area with a lightning arrestor. Each of these have their own ground rods spaced from the others by about 2 feet and all tied together with lots of copper wires. (no single point failure here!) There are three coax lines that lead up in to the shack in a different electrical conduit. (There is one for the G5RV, the vertical/spyder beam and a VHF yagi.) Around the entire perimeter of the house, I buried and #6 copper wire. (Yes I know something like flashing would be better but I didn’t have any!) Every 10 feet this wire has a ground rod. There is also a connection to the main ground rod of the house, so that sneak currents cannot go thru the house wiring. (The idea is that this is a much lower impedance path.) The connections to the rods are made with a box that can opened for inspection. I did my best to make these connections but I didnt have materials for doing the “exothermic welds” In two places I have additonal wire that goes off away from the house buried in the ground. This is actually #1 wire that I obtained that was junked at work. (It is beautiful copper wire, a shame to bury it!) There are no other units connected to this grounding system. (Outside air compressors for air conditioning, pumps or motors.) I thought long and hard about that and decided the sneak paths from these units into the house would be more dangerous. In accordance with vendor’s directions, each of these units has their own ground rod installed. The routing of the “ham” ground is such that there is always a few feet between my ground ring and these rods. Does it work? Well I certainly don’t know. It is really difficult to take impedance measurements to ground. I do know we get alot of lightning and my radios keep on working. One of the arrestors had to be replaced so there is some indication it was hit. I do know I do get good signal reports when I transmit, so somethign is working right! |
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Links
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[WB2EWB Ham Radio] [Mobile Station] [Fixed] [Walkabout] [Other Hobbies] [Links] |
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Copyright 2004 by Philip P. Thompson, All rights reserved. |