[TowerTalk] Grounding against lightning

[radioada@ghana.com]

Name: Alex T Quarmyne
Call: 9G1TV
E-mail: radioada@ghana.com
Mail Address:  P O Box KA9482, Accra, Ghana

We are running a community FM radio station in a small town, perhaps I should 
say small village, called Ada, which is my home town.  If you have a map of
West 
Africa you might be able to locate Ada at the point where the River Volta
enters 
the sea.  On December 8 we got a direct lighting hit which destroyed our 
transmitter, two audio mixers and two minidisc machines.  To get an idea of
what 
a station like ours goes through in such a situation, one needs to know
that we 
have had to send the damaged items to Britain for repair.  The transmitter is 
back and the station is back on the air.  

Naturally, we are going over our grounding system to ensure that we do all
that 
can possibly be done in an effort to avoid a recurrence.

Before the lightning strike, we had on top of the 150-foot galvanized tower a 
lightning arrester which was grounded to the tower at the top.  The tower was 
grounded to earth at the bottom using a 10mm bare copper cable and a 3-foot 
copper rod burried 4 feet into the earth with a pipe inserted to allow weekly 
watering to keep the soil around the copper rod always wet.  The 7/8-inch  
heliax feeder was also grounded to the tower at the top and also at a point 
further down where it bends to leave the tower to enter the transmitter room.

Since the lightning strike, we have checked all connections to ensure that 
contacts are good and have now installed a 10mm copper cable diretcly from
the 
lightning arrester to the copper in the earth.  We have also now connected
the 
ground to the transmitter rack.  An enginner we spoke to has recommended
that we 
run another ground cable to the heliax feeder close to the point where it
enters 
the transmitter.  This will mean that the feeder will be grounded at three 
points.

We have also ordered a surge protector which will be installed on the mains 
coming into the building. 

We shall very much appreciate any comments and advice.

>From Ghana, A Happy New Year to You All !

Alex.


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