[wxqc] Grounding of anenometer mast

[dshelms at comcast.net]

Hi Dennis,

I don't know if this actually helps, but... My anemometer is 15 feet above my roof, which is about 25 feet above the ground (e.g. anemometer is 40 ft AGL).  I lashed a 10 ft PVC pipe onto my 10 ft aluminum Rohn tripod mast (5 ft overlap) and placed the plastic anemometer on the top of the PVC pipe.   I'm hoping that use of non-conducting materials at the top of the anemometer mast minimizes the lightning strike potential, and so far (knock on wood) I have not had a strike yet.   

However, I did have a strike with an earlier configuration where I used the old TV antenna mast (iron?) for the anemometer mast.  That strike took out the anemometer and the Ultimeter 2000 console requiring replacement.  I think Peet has since included a fusable link in the anemometer to reduce the frequency of nuked consoles from lightning.   

All this discussion is moot for the folks with the high-speed wireless sensors (one day, I'll go wireless, but Peet has not such animal).  

Dave
CW0351


 -------------- Original message ----------------------
From: Gerry Creager N5JXS <gerry.creager at tamu.edu>
> Dennis,
> 
> I've a couple of thoughts.
> 
> 1.  I'd strongly recommend grounding the mast as you're presenting a 
> nice target for stray lightning.
> 
> 2.  Almost certainly, the TV antenna is mechanically bonded to the mast. 
>   Very few of the antennas are isolated and antennas design tends to 
> require a ground-poise to make the antenna work.  A floating antenna 
> without a ground reference is a poor performer.
> 
> 3.  Using the shield of the coax as the sole lightning ground return is 
> a bad idea from a lightning protection standpoint as it's not a real 
> low-impedence return for that much energy and your TV or more exotic 
> home entertainment hardware will almost certainly suffer some damage. 
> If you're in a real lightning prone area, I'd be looking at 
> gas-discharge tube lightning arresters (Poly-Phaser is sort of the index 
> brand) to protect expensive hardware.  It's what I use in ham radio and 
> wireless installations.  They also make a version for ethernet that 
> could be used to pass the data from the wired VP hardware.
> 
> Lightning is an interesting issue to have to deal with.  Having lost a 
> fair bit of ham gear some years back to a poorly prepared mast, I'm a 
> bit more sensitive to how to prepare now.
> 
> gerry
> 
> Dennis Maier wrote:
> > As soon as it's safe to climb up on my second story garage roof I intend to
> > extend the height of my anemometer from about 7' to maybe 15' or more above
> > the roof.
> > 
> > At the present time the Davis Vantage Pro anemometer is connected to their
> > Wireless Anemometer Transmitter mounted on the mast just above the tripod.
> > Also mounted on the same mast a couple feet below the anemometer is a large
> > TV antenna used to pickup On-Air HDTV. The TV antenna coax is routed into
> > the garage through the roof eaves vent down to the ground floor and into a
> > metal patch panel enclosure and grounding block then into the house. The
> > enclosure and a coax grounding block are grounded with #4 copper wire
> > through the wall outside to a ground rod. I did it this way to preserve the
> > appearance (no unsightly wires) of the newly vinyl sided house and garage.
> > At this time the mast is not grounded.
> > 
> > Was this, routing the wires inside the building before the ground block, an
> > unsafe decision from a lightning standpoint?
> > 
> > Because of occasional missed data packets from the Wireless Anemometer
> > Transmitter when I extend the mast I will probably hardwire the anemometer
> > to the Davis ISS and do away with the Wireless Transmitter. So that will be
> > additional wires running from the mast to inside the home.
> > 
> > I live on the waters edge of Saginaw Bay off Lake Huron in the Thumb of
> > Michigan. A few years ago lightning struck the electrical wires entering my
> > home at the utility pole, so I know it likes my area.
> > 
> > What are forum members thoughts about grounding the mast? I worry that
> > grounding the mast will just attract more lightning strikes.
> > 
> > 
> > Dennis Maier
> > CW4869
> > 
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> 
> -- 
> Gerry Creager -- gerry.creager at tamu.edu
> Texas Mesonet -- AATLT, Texas A&M University	
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