Topband: Lightning and Beverages

[Tom Rauch]

> Just wondering what effective measures anyone has discovered to avoid
> this problem, other than completely disconnecting EVERYTHING from the
> transformer when it is not in use: antenna, ground, feedline and all.

Having over 30 antennas is a good test bed for proving reliability of 
a system. I can't afford to constantly check and replace resistors 
after storms. Despite being in Georgia, with frequent afternoon 
thunderstorms, I almost never replace composition resistors that 
terminate my Beverages. At the most, I have to change one resistor a 
year. The only failures occur when an antenna has a direct hit on a 
tree it is attached to, and even then generally only that one antenna 
develops a problem. I've actually had wires blown in two without 
resistor damage, but I use the correct type of resistors!  
   
If I use a metal film or carbon film resistor, I generally replace it 
after every storm, even if the lightning is a mile away. Virtually 
all film type resistors, both metal and carbon, will not take much of 
a momentary overload.

One thing to remember is virtually all carbon resistors are now film 
type resistors. Just because the resistor is a big brown 2-watt 
carbon resistor, it does not mean it is a composition type! You 
either have to cut a sample resistor open and look inside, or know 
the exact manufacturer part number, to know if it is really a 
composition resistor.

Use carbon composition resistors (manufactured only on special order 
now) or metallic composition resistors (like standard Ohmite OX or OY 
series resistors), and constant open-resistor problems will 
disappear. 



Short of being able to trace the resistor 
You have to actually 

If you use a composition resistor, it will take almost a direct hit 
to damage the resistor 73, Tom W8JI
W8JI@contesting.com