On 9/17/2012 10:17 AM, Frank wrote:
R. Morris wrote:
On 09/17/2012 09:10 AM, Frank wrote:
I fail to see why a ground is needed at all. Surely the lower two
feet of tower is firmly embedded in dirt with the concrete anchor
above that.
You may want to look at some tower base diagrams. Never have I seen
any suggesting "two feet" in dirt.
That is because they are doing it wrong.
Ever wonder what happens to the rain water that collects in the tower legs?
Mine drains into the soil. If you block the ends of the tower legs with
concrete, the rainwater rots your tower legs from the inside out. My
tower has been up since 1976 with no sign of corrosion.
Not quite. It requires Oxygen for rust so they will rust at and a bit
above the water.
In "the old days" tower bases were set in concrete rather than using a
base plate or pier pin. However the bottom of the hold was supposed to
have about 6" of pea gravel, small tone, or even crushed rock and the
bottom of the tower legs set in this material so they could drain.
That single base is just not enough to drain off lightning strikes. With
my old tower which only had a few ground rods, I had a fair amount of
lightning damage. With the newer, 100' 45G which has each leg tied into
a ground system starting with an 8' ground rod about 3 to 5 feet out. I
have a ground system that ties two towers plus two masts and a common
point ground together at the house entrance with a grounded bulkhead
panel and Polyphasers. That tower has been struck more times in 10
years, than most ham stations will in a lifetime. Probably more than 5
stations. We (the neighbors and I) can account for 17 visually verified
direct strikes and no equipment damage.
Yes, over 600 feet of bare #2 X 7 or 9 CadWelded(TM) to 32 or 33 8'
ground rods is likely a bit of overkill, but *so far* and I emphasize
the "so far" it has worked. Lightning is unpredictable and nothing can
guarantee 100% immunity from damage, particularly if you take one of the
"super strikes".
But I think you will find that most of us strongly believe in a good
ground system topped off by a single point ground where everything
enters the house.
73
Roger (K8RI)
Maybe they just want to sell ground rods and cad welding equipment and
tower sections.
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