[Hallicrafters] Antenna Lightning Protection

[Troglodite at aol.com]

In a message dated 1/7/2009 8:52:30 A.M. Central Standard Time,  
n0jmy at hayseedhamfest.com writes:

My tower  never showed any signs of having been hit over the 13 
years I lived there.  But my well, which was about 50' away and protruded 
out of the ground  about 18", got blasted on a regular basis.
    That is very interesting. The same phenomenon  seems to take place at 
cave entrances. They get hit much more often than  surrounding terrain at higher 
elevations. I think your well may be subject to  the same phenomenon.
 
    Here's my theory: The "feelers" that precede the  actual discharge travel 
along the path of least resistance. If all other factors  are the same, the 
strike will hit the point of highest elevation. But the  resistance of the 
atmosphere is not a constant. It depends on how saturated it  might be with water 
vapor or other substances.
 
    In the case of both the well and the cave  entrance, these portals may 
have a considerable thermal differential with the  surrounding air. So they 
"breath" as the surrounding temperature changes. This  can be seen clearly in the 
winter, where cave entrances may be spotted by  the water vapor clouds that 
form near them. I would imagine the same thing  happens with a well.
 
    So in both cases, the air exiting the  openings may be saturated with 
water vapor, and could be warmer than the outside  air due to the huge thermal 
mass of the cave or well. In this case the vapor  would rise, and thus present a 
lower impedance than a higher (but dryer)  location.
 
    Anyone else have a theory? I have personally  witnessed this phenomenon 
at cave entrances, but have not been around enough  wells to observe a strike.
 
Regards,
 
Doug Moore KB9TMY
 


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