"Nick" wrote in message
...
Hi,
I want to install a vertical, fed with an SGC230 at the bottom, but
concerned about minimising chance of a lightning strike on a bare
conductor.

Would it give more protection / solve the problem, if I encased it in a
fibreglass yacht mast which I happen to have ?

I plan it to be approx 40' high with the top 25' being a fibreglass yacht
mast with the wire running up the inside. Top would be insulated / sealed
so no ions could spray out, attracting a strike ... am I going the right
way ?

Thanks,
Nick
Nick

With the voltages involved in a lightning strike, the fibreglass mast will
not make much, if any, difference. Rain fall and dirt deposits will create a
conductive path along the mast a few days or weeks after it has been
erected. Lightning is attracted to the highest pointiest thing in an area,
no matter what substance it is made from. Churches and trees are made of
insulating materials and they attract more strikes than anything else on
land. It was common to have to regularly rebuild the towers and steeples of
medieval churches before lightning conductors were installed. The average
steeple usually lasting no more than a century before suffering catastrophic
damage from a lightning strike. At the time, this was just accepted as a
sign that the parishioners were insufficiently pious, or had transgressed in
some way.

The fibreglass mast is ideal as a support and to provide weather protection
for your antenna element(s), but do not count on it reducing the chances of
a lightning strike it it is the tallest structure within 400 yards or so.
Various tables and maps are available on the internet showing the frequency
of lightning strikes per year per square mile or square kilometer for most
areas in earth. These should help you evaluate the risks in your particular
area. Forty feet is not particularly high and if you live in an area with
less than 20 lightning days per year, I would evaluate the risk of a strike
as being low. There is always a statistical risk and that's a chance you
have to accept when dealing with any force of nature.

Try to ensure that there is a good earth connection at the base of the
vertical antenna using earth rods and/or buried radial wires so that in
event of a strike, the lightning energy is dissipated into the ground rather
than transmitted along the feedines into your house. A switch to disconnect
and earth the antennas when equipment is not in use is always a good idea. A
look through the MFJ catalogue will give you an idea of what equipment is
available.

Mike G0ULI