earthing an aerial mast

[dave m]

I'm fitting an anenometer to a TV aerial mast and they recommend earthing it (the mast). Is it OK to earth it to the regular house earth or am I better to give it its own earth, just in case it ever did get hit by lightning?
Thanks,
Dave

[Fat Tone]

I think you mean a lightning conductor, that goes straight to ground outside your property. If you house has one then I would think it's ok to use it as long as you bond really well to it. If it doesn't then I would install one. Fatter ones are better as they have lower inductance.

HTH

Tony.

[Greebe]

Earth ground it seperate!!!

I've seen far to many tied to the house ground and when struck BlamO replace most if not all interior wiring including everything that's plugged in at the time.

[Fat Tone]

Just to clarify, Greebe & I are saying the same thing. The lightning conductor is completely separate to the house mains earth, and should be kept so.

T.

[Technoid]

Originally posted by Greebe
Earth ground it seperate!!!

I've seen far to many tied to the house ground and when struck BlamO replace most if not all interior wiring including everything that's plugged in at the time.

Not to mention the risk of fire

[dave m]

I think we have a consensus on that one, thanks guys, a separate ground it will be.

Dave

[Fat Tone]

Why do you want an anemometer? I have used many different types in my years doing environmental research. What type will you be using? From my experience if you are placing one in an area where vandalism may be a problem, separate cups & vanes make a harder target for projectiles than the vanes with propellors on the front. Ultrasonics are definately the coolest, but beyond most peoples pockets.

T.

[KvHagedorn]

This one's a tough nut to crack. I would read the National Electrical Code section 810 before doing ANYTHING. This is the US electrical code, though. Since you are in the UK, you might find something similar, though I wouldn't know where to look.

Panamax has some good articles on grounding, particularly this one:

http://www.panamax.com/literature/pdf/groundbondcatv.pdf

Others to be found here:

http://www.panamax.com/literature/

The antenna itself is what proves the problem, as it connects to your home's electrical system. If you use an antenna amplifier/preamplifier it may connect more directly.

Personally, what I would do would be to take a 0 gauge INSULATED copper ground rod and run the thing from about 3 ft above the top of the mast (with the top foot exposed) directly into the ground beneath. Then I would feel a bit more comfortable doing what the NEC tells you to do.

We do install antennas and occasionally satellite dishes, but we never install dishes on the roof or above the roofline anywhere. The only antennas we do are inside the attic. If your anemometer was a standalone unit with no connection to the house's electrical system, I would say it's a no brainer. Direct ground it.

[Greebe]

The problem with installing a ground lead above the antennae is that it will effectively produce a corona around it which commonly deflects a potential strike due to it being a single point. The flipside of the coin is that antennas and and or dishes distribute this corona around many points which effectively weaks the corona to the end that it acts like a lightning magnet. As with your suggestion, older homes with lightning grounds prove ineffective do it the spiked point.

[dave m]

Tony: It's part of the Oregon Scientific WM918 weather station, curently marketed in Europe by Huger; so it's a combined weather vane and cup anemometer, for some amateur weather watching. Hopefully vandalism won't be a problem around here.

KvH: Every house in our street has at least 4 feet of aerial mast sticking up above the roofline. The Anemometer will be wired back to its control box, so they recommend earthing the pole. Thanks for the links, I'll have a browse.


Greebe: could you clarify; are you saying it is better to ground the pole and/or put up a separate lightning conductor

Dave

[The PIT]

I've got to admit I haven't got ours grounded. Our weather station (Davy instruments Weather Monitor) is protected internaly and I have a seperate opto isolator for the computer connection. We've been struck once in three years and it just resulted in a mornings lost data. The consol locked up recording a Max temp of 600C.

[Greebe]

the ground block typically used for aerials coax should be terminated to it's own earth ground... this would include the mast.

also note that the ground lead from one to the other must be a seriously large gauge wire... anyone seen the old Lightning protection/grounding used on farm houses throughout the midwest?... typically they're ~1" square and twisted