[TowerTalk] CDwelding a tower leg

[K8RI]

On 9/17/2012 11:33 AM, Frank wrote:
> I'm still an amatuer with 60 foot tower and 4 element beam located in a
> secluded valley.
>
> Your set up sounds professional.  You have more steel in the air than my
> zoning laws would allow.

The theory:  An overhead charge moves along through or with the clouds.
An opposite charge moves along on the ground. The charged area on the 
ground maybe hundreds of yards across. Towers, trees, and power lines 
provide vertical extensions to this charge.  The static does not just 
build up on the tower or antenna, that is only an extension, and/or 
connection to a much larger charge.

Because the tower is part of a charged area the static usually does not 
build up "on the tower" which makes it 	quite different than 
precipitation static building on an ungrounded tower.
Snow on a cold and windy day can turn the ungrounded vertical or tower 
into one whale of a Van De Graaff  Generator with startling results at 
the other end of the coax that could put the most powerful ignition 
system to shame.

The tallest object might be the most likely to take a hit, but it is 
only a tiny bit closer to the overhead charge than the surface. So it's 
not good to go against the odds, but those same odds come with no 
guarantee.

The one predictable thing about lightning is its unpredictability.

It was 130 feet to the top antennas in 
http://www.rogerhalstead.com/ham_files/Tower29.htm
which I've shown many times.  I've also said that the tower and antennas
took 17 visually verified hits the first 6 years it was up.
It has taken none the last 4 that anyone has seen.

On several occasions nature must have had poor aim as a stroke 
completely ignored the tower and hit a power pole just to the North and 
East out by the road. That strike was almost at a 45 degree angle to the 
top antennas.  It wiped out a bunch of stuff in their house including 
the transformer on the pole IIRC.  It also hit a young spruce tree about 
100 feet to the East of the road with largest piece being about 3' long. 
  There have been other "close ones" that did not hit the tower.

73

Roger (K8RI)

>
> No wonder you got hit.  You have my sympathy and envy.
>
>
> Cqtestk4xs at aol.com wrote:
>
>> I assume you don't live in the lightning capitol of North America,
>> central FL.  I understand very well about lightning and static build
>> up as do others who have posted here.  I have three 199.99 footers as
>> well as  several other smaller ones.  Unless you live in an area of
>> little t-storm  activity you have been very lucky.  Having a lightning
>> hit your tower is  not if, but when.
>>
>> I have spoken to several EEs who work at the local surge protection
>> mfg company and since I have followed their advice I have had no
>> damage even though  the towers have been hit over the summer.
>>
>> Bill K4XS/KH7XS
>>
>>
>> In a message dated 9/17/2012 2:53:22 P.M. Coordinated Universal Time,
>> frankkamp at att.net writes:
>>
>> Nope,  never been hit by lightning in over 30 years of hamming.
>> Evidently  you have had that misfortune.
>>
>> Ever wonder if there might be something  you don't understand about
>> static build-up?
>>
>> My tower is grounded by  virtue of the tower leg bottoms stuck in sand
>> and dirt below the  concrete.  I don't need any additional grounding.
>>
>> The tower acts  like a big lightning rod.  Contrary to popular belief,
>> lightning rods  don't attract lightning, they dissipate static charge.
>> At least mine  seems to work that way.  Your milage may  differ.
>>
>> Cqtestk4xs at aol.com wrote:
>>
>>
>>
>>> You ever take a lightning  hit?  I have several times and it was
>>> uh....exciting.   Towers were extensively grounded but not to a common
>> ground with the
>>
>>> house.  Three tower legs are not an extensive ground and   will not
>>> dissapate a direct hit and will likely make a beeline to your  shack on
>> the coax to
>>
>>> finish the job on its way to your home  grounding system through the
>> house.
>>
>>> You are living on  borrowed time with that attitude.  Extensive
>>> grounding is  your best friend and the insurance company's.
>>>
>>> Bill  K4XS/KH7XS
>>>
>>>
>>> In a message dated 9/17/2012 1:17:23 P.M.  Coordinated Universal
>>> Time, frankkamp at att.net  writes:
>>>
>>> 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.  If it was  done that way those three tower legs should
>>> serve as some pretty  good ground rods.  At least my version of
>>> common sense  tells
>>
>>
>>
>>> me so.  I will have to admit that common sense has not  always  been
>>> kind.  Sometimes it does not make sense at all  and becomes just
>>> common bs.  I am wondering what it might  be on this topic?   Anyone
>>> venture a guess?
>>> _______________________________________________
>>>
>>>
>>>
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>>>
>>>
>>>
>>>
>>
>>
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