[Hallicrafters] Antenna lightning protection

[SX-25]

My top antennas are at 130' and have taken an average of 3 verified, direct 
hits a year which includes the past two years with none. 



Roger,

I salute you for your grounding system! It sounds as though your system should be a model copied by every amateur radio station.

Back in college I worked in telecom, maintained sites with 300 foot towers and became very interested in lightning protection, which I have carried through to the present day and my dinky little ham station. Most compelling of my experience is how a direct lightning strike can VAPORIZE things made of plastic, copper and iron (like a set of headphones) when NOT EVEN CONNECTED TO ANYTHING....just setting on a table!

As a result of my interest born back in those days, I began compiling a 3-ring binder full of magazine articles dealing with the topic. Since my degree is in meteorology I got a lot of mileage out of the topic for term papers and so forth. Indeed your 3 hits per year is a sobering reality that too many hams either ignore or remain in denial as a potential hazard.

According to one article I have, the National Weather Service states the following about the probability of a lightning strike on a tower or airborne aerial (sic):

HEIGHT     PROBABILITY OF DIRECT STRIKE IN AREA HAVING 30 STORMS PER YEAR

50 feet        Once every 4 years
100 feet      Once every 2.5 years
200 feet      Once every 1.5 years
400 feet      Three times every 2 years
600 feet      Three times per year

The map contours of how many lightning storms per year can be found on many Internet websites however, as a very general rule, the "30 per year" contour line runs along the northernmost border of the United States. The contour line running through the middle denotes roughly 40 storms per year. The southernmost border of the U.S. 90 to 5 storms per year with the greatest number on the eastern side of the country, dropping to only 5 per year as you approach southern California.

So there is valid reason for concern and I urge all hams to use this "quiet time" during the winter months to get their "house in order" for the more volatile Spring stormy weather season (even though lightning occurs throughout our country throughout the entire year).

Vern WA9VLK
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