Lightning Strikes!

A few days ago we took a direct lightning strike to the LFA antenna. It was quite something and knocked out the electricity until we found and reset the breakers. It must have hit the driven loop as the 4″ square plastic balun box exploded with such force it knocked the reflector off and it fell to ground. Pieces of grey plastic and green unsulated plastic clamps were all over the place. The ferrite cores from the balun landed nearby still wrapped together but the wires missing. The remote switch was disconnected at the time but after it blew the 2 coax cables out of their plugs it continued down the 7/8 Heliax till it crossed an electrical wire going to a light. It decided it liked that better than the coax so ripped a hole in the heliax and jumped into that and removed a bunch of insulation from the garden wire in the process. We got off quite lightly really, got a computer that won’t boot up, a small TV that won’t turn on, and needed to replace the decoders and the cable modem. One splitter in the cable also needed replacing. The cable guys said the plug in the box on the street had also blown out of the socket. Every time we have had a lightning strike the cable system seems to attract the strike and suffers. Fortunately everything was  disconnected in the shack, but the AC plug was expelled from the socket.

The hole in the heliax

The hole in the heliax

Where it flashed into the electrical cable

Where it flashed into the electrical cable

 

bits on the lawn.Obviously the grounding was not up to snuff so we are redoing the grounds, adding more rods and running a new 70mm copper cable from the lightning rod at the tip to the central rod and tying it in to several other rods to better dissipate the strike in future.

THE 5 Element LFA. A credit to the material used by Henry in Holland because the reflector took no damage despite falling onto a tiled roof from 30 meters and breaking a few tiles. None of the elements appeared affected by the strike so we will reassemble it as a 6 element OWA yagi using all the elements. The LFA has been a phenomenal antenna for me but the band width is just a little tight (comes with the high gain figures!) so we will try the OWA configuration and see what we think. From the swr curve we should be good from below 27 thru to almost 29mhz. Awesome.

driven element minus the balun

driven element minus the balun

 

elements all good

elements all good

 

Boom still goodSince we needed the pipe the 1/2 wave vertical was on to dig the holes for the additional rods I thought I would replace the 1/2 wave with a sigma IV I had bought locally and never got around to erecting. Followed the markings exactly as there was no instruction sheet and surprise surprise she came in at 1:1 at about ch 40 with no further adjustment needed. Plenty of bandwidth and it seems to work very well. Currently up about 6m to the base but not sure if I can get it up much higher as a lot of antenna up in the air. it is 5.99m from the base of the ring to the tip. Worked France, Corsica and Greece and quite a few australian stations. I think it is a keeper. It doesn’t like power for very long…after about 15 minutes with 300w Pep the swr started to creep up to just over two…came back in 10 minutes and fired up again and back to normal. I guess the gamma match. Not much to it. May look at getting a better one some day..but not now.

Sigma IV

Sigma IV

 

Sigma IV 5.99m from the bottom of the cage to the tip

Sigma IV 5.99m from the bottom of the cage to the tip

It was time to pull one of my old radios out of the cupboard and warm it up. An old Magnum 257, with 1969 finals and turned down to 14w to run the KL203 stuck on top of it. Got to be the cheapest 100w radio out there.100w magnum 257

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2 Responses to Lightning Strikes!

  1. dd182003 says:

    Fixed the computer yesterday..one of the sticks of ram had gone bad and the pci firewire card seemed to have developed a glitch so changed that too. DDR2 ram is now worth more than ddr3!
    computer up and running well so all good.

  2. It’s a little setback to remind those of us who reside in the tropical regions to instal things properly!

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