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From Sunny North Lincolnshire uk

 

 

 

lat 53.596 Long -0.725 Grid IO93po WAB SE81: Operator Martin.

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Building a G5RV antenna My Early Projects   A Simple lightening arrester   

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A SIMPLE LIGHTENING ARRESTER BY MARTIN G8NQN

Here is a lightening arrester idea that's not totally of my own making, but has been modified by me to make it simple and easy to make, basically my idea's are that by using the earthing rod that all good radio shacks should have, an excellent arrester can be made that should not only deter a strike in the first place but provide a good path to earth should you still have the misfortune to get a strike. I'm sure everyone is familiar with the fact that lightning travelling to earth needs to get to ground, there are many theories about the path it takes and why. But one thing is known (continued Below)

 

That is that it will usually strike high objects that become statically charged prior to a strike  hence the reason most high building have lightning conductors from the highest point to ground, In a radio shack without a lightening arrester of some sort outside the building, the coaxes from the antenna come straight to the rig, and the rig is then earthed via its earth terminal to the earthing rod outside, this means that in a lightening strike a lot of the electrical charge will enter the house via the coax to the rig and attempt to find ground through the rig.

You will now see the benefits of a lightening arrester especially where the antenna's are not mounted on a steel mast or structure fixed to ground, let me explain my simple system then, the coaxes are passed by the earth rod and taped to it for about 1ft, after this point each coax is passed through a PL259 through feed, the back to back connectors from each coax are then connected together by a copper 1/2" strap which is fed to the hot end of a spark plug any will do and these are available from all motor accessory shops, the cold side of the spark plug is then strapped to the earthing rod, the principal is that as static electricity builds up on the Antenna's and coaxes it will arc to ground via the spark plug before reaching high levels and becoming attractive to a lightening strike, should a lightening strike still occur however, it will find a capacitance ground via the 1ft length of coax taped to the earth rod and arc through the coax screen to the earth rod and to ground, reducing further the amount of charge entering the shack.

The spark plug could be omitted if earthing the screen of the coaxes to ground outside of the shack is not detrimental to the SWR or Performance of the antenna, but remember this puts the director elements of say a YAGI antenna at direct ground potential as it would be if mounted on a steel mast, but in effect turns it into a lightening conductor with only the coaxes for the charge to find ground through, so in my opinion leaving the spark plug in the circuit is essential as it leaves the antennas without direct earth potential.

Even with these protective measures in place it is still wise to disconnect from the rigs during a severe storm or electrical storm as with a direct strike onto the antenna's some static could still get by the arrester and cause damage not only to the radio equipment but those nearby.

Martin (G8NQN)

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