[wxqc] Grounding of anenometer mast

[Ken.A.Brown at noaa.gov]

Dennis,

Before I answered this I wanted to make some tests.  I, like you, 
have some wind sensors (Peet and T-238) located on a tripod mast 
on the roof along with a HDTV antenna.  My mast is grounded with 
a heavy cable to a 8 foot ground rod.  One thing I was concerned 
about is the fact that most TV antennas are designed for 300 ohm 
twin lead.  When we connect them with coax we use a 300 ohm to 75 
ohm balun transformer.  I just checked a couple of baluns and 
there is no DC path between the 300 ohm section and the 75 ohm 
section.  Thus, your TV coax shield is grounded but the antenna, 
and thus the mast, is not.  Now, with a direct hit, nothing is 
going to survive.  But with lightning hitting a tree across the 
street or down the block there will still be a high induced pulse 
on any exposed and elevated metal structure.  Even in clear 
weather if it is dry, windy, and dusty, you can get a high static 
build up on the mast.  So to reduce, even a little, the 
likelyhood of damage, and protect your HDTV which probably cost 
more than your weather station, I recommend a good connection on 
the mast with as direct a path as possible to a good ground.

Ken Brown