[TowerTalk] New Tower Construction - Questions - grounding

[K7LXC@aol.com]

In a message dated 08/31/2000 9:08:58 AM Pacific Daylight Time, N8NGA@one.net 
writes:

> The lesson here as I see it is that many hams have no rebar cage, and
>  only one to three ground rods.  Where this occurs, my logic tells me
>  that the concrete can in fact be exploded in a direct hit, and that
>  the ground system is inadequate.  My recommendation, after reading the
>  Polyphaser data is to make a rebar cage in ANY tower base, whether 
required 
> or not, and use it as part of a complete grounding system.  Rebar is
>  CHEAP compared to having a tower come down when the base explodes, or
>  not having the best ground possible for my station.

    Thanks for quoting the PolyPhaser book - they are experts in their field.

    A lightning strike is going to look for the path of least resistance and 
ignore high resistance paths. In the case of adequate tower leg grounds, it 
should follow the leg connection to the ground rods and will ignore the 
rebar/concrete/earth interface which has higher resistance. Running a big 
wire from the leg thru the concrete to a ground rod at the bottom of the hole 
might be one way to really make it work as a good low resistance path and 
avoid some of the rebar cage bonding problems. Warning: if you have potential 
differences, that's where the arcing will take place so bonding everything is 
the way to minimize it.

    As far as only using an Ufer ground, it's commonly used where there isn't 
enough earth around the tower base for a full-sized ground system; i.e. where 
you might only have enough room for the tower base at the site. 

Cheers,   Steve    K7LXC
Tower Tech

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