Lightning Strike Damage July 19 2006

I took a direct but relatively weak lightning strike on Wednesday July 19, 2006 during a vicious lightning storm. At 4:30 pm EDT lightning struck my 50 foot Rohn steel push up mast. The mast has a large porcupine/spline ball air terminal installed and is grounded by seven 10 foot ground rods and my 80-10 meter inverted V antenna is grounded to the same seven 10 foot ground rods.

NOTE!!! Once again the installed porcupine/spline ball air terminal failed to prevent a direct lightning strike. That is ten direct strikes in ten years to a 50 foot steel mast. At one time I was a proponent of "charge transfer systems". However after research I came to the conclusion that they don't work, not even somewhat, they just can't. Check out the following .pdf file. http://www.kn4lf.com/WhyChargeTransferSystemsDoNotWork.pdf .

Most of the charge went straight into the ground via the mast but some also followed the 107 feet of 300 ohm window line feed line then to ground. The antenna is grounded just outside of the service entrance of the radio shack but a bluish white colored bolt of lightning plasma still came through the aluminum window frame into the radio shack.

The lightning bolt knocked an Oregon Scientific wireless hygro thermometer off of the window ledge and it also knocked a glass of ice tea off of my radio operating desk. I normally would have been sitting 1 1/2 feet from where the glass of iced tea sat but I always leave my radio shack at the first sound of thunder. The lightning bolt struck about two seconds after I walked out of the radio shack. As I had my back to the electrical charge I didn't see it directly but I did see a blue flash, heard the snapping sound of electricity and felt static electricity, plus smelled ozone and burning wood.

I conducted an inspection of the radio room at 6:00 pm EDT and luckily discovered that I lost no radio, weather or computer equipment, the TV is okay too. All of my equipment was unplugged from the power mains, internet cable modem, antenna and ground but I feared (EMP) electromagnetic pulse damage. But speaking of EMP the 48" TV in the living room was damaged. It was not plugged into the cable or power mains but was sitting approximately 20 feet away from the Rohn 50 foot steel push up mast, which is partially supported by the eave of the house. It's now been replaced with a new 61" TV by my home owners insurance.

I had an Oregon Scientific wireless hygro thermometer sitting on the window ledge of the service entrance as well as a plastic cup of iced tea sitting on my operating desk. Both items have melted mark on them but the hygro thermometer is still working.

Is there a lesson that Ham's can learn by this incident? Absolutely, when you hear thunder ground out your antenna(s) unplug your radio station equipment and leave the radio shack. Secondly, no matter how much lightning protection and grounding you have implemented it's probably not enough.

This is the outside of the service entrance of my radio shack. The board is a 1" thick x 3" tall x 3' long piece of oak. The #14 gauge copper clad steel 300 ohm window line to the 80-10 meter doublet is soldered to the pins of a female dual binding post. It's hard to see but the very end of the window line is swollen due to heating. Just above it on the wood and aluminum window frame you can see scorch marks.

This is the inside of the service entrance of my radio shack. Just above the female dual binding post there is a melted spot on the black foam insulation strip. Above that on the aluminum window frame you can see a scorch mark.

This is the cumulonimbus lightning spitting thunderstorm beast before it moved through my area.

This the top of the Rohn 50 foot steel push up mast after the direct lightning strike. On top is a very large hawk that likes to sit on top of it daily and crap. In the background you can see a mammatus anvil cloud left over from the storm. You can't tell in a photograph but the #14 gauge stranded double coated 135 foot flat top wire of the antenna and the 107 feet of #14 gauge copper clad steel 300 ohm window feed line stretched and sagged due to heating effects.

This is the base of the Rohn 50 foot push up mast with a hole blown in the ground by the direct lightning strike. The two 10 foot ground rods are hard to see.

This is the grounding system for the 80-10 meter doublet antenna. I use 1" wide tinned flat copper braid to three 10 foot ground rods spaced five feet apart. I bought some 2" solid flat copper strapping at the 2006 Orlando Hamcation that is supposed to replace the tinned braid but I haven't gotten around to it yet. I may have had less lightning plasma enter the radio shack if had of had the copper strapping installed.

This is the back of the Oregon Scientific wireless hygro thermometer. The shiny surface is the melt spot caused by the lighting plasma as it entered the radio shack. The instrument was sitting on the service entrance window ledge and was tossed across the radio shack and hit the closet door.

This the plastic cup that I had iced tea in. You can see the melt mark caused by the lightning plasma. It was sitting on my operating desk only a couple of inches away from the Ameritron AL-811 amplifier and about 11/2 feet from where I had been sitting seconds before the lightning bolt struck. The plastic cup was also thrown across the radio shack and hit the closet door. Needless to say tea and ice went everywhere.