[TowerTalk] Buried section base...and lightning protection.

[Roger (K8RI) on TT]

The base for my LM470, is the first base where I've  used rebar.
The guyed 100' 45 G has a minimal (~1.5 sq yds) high strength base in 
hard clay.   3' in dia and a bit over 5'6" deep.

I've had 50 and 60' guyed, ROHN 25Gs mounted on dirt bases for over 25 
years (some with relatively large antennas) with no problems.
I had the antennas and 50 to 60 feet was all I could afford.

We had an ice storm that had the element tips of my 5L 20 meter KLM 
pointed at the ground.  Fortunately it warmed enough for the ice to fall 
off before the wind hit.  The wind removed a large Winegard VHF/UHF TV 
antenna off off the roof.   That antenna was hag bolted into a thick 
wood plate under the roof boards.  I was on the roof at night, in 
torrential rain and high wind, pumping Silastic RTV into the holes left 
by those lag bolts.  At least there was no lightening, but that rain 
sure was cold.  Calking gun in one hand and a flashlight in the other.  
There was no damage to the big antennas or towers which had dirt bases.  
BTW, when the ice fell off those 20 meter elements, they all went back 
to where there were supposed to be.  I figured I was going to lose that 
antenna when I saw the ice.

73

Roger (K8RI)

On 1/5/2016 Tuesday 3:09 PM, jimlux wrote:
> On 1/5/16 9:42 AM, Ken wrote:
>> I am totally amazed at  how concrete has weakened over the years.
>
> More that people care more about edge cases and unlikely scenarios.
>
> All the changes in regulatory codes are usually in response to some 
> "bad event" and a desire to "make sure that can't happen again".
>
> In a commercial environment (which is what Rohn, et al, design for and 
> what local codes contemplate when making tradeoffs), the incremental 
> cost of a cubic yard of concrete against the total job cost (including 
> labor!) is pretty small.
>
> By and large, businesses and regulators don't contemplate "homebrew" 
> implementations with self provided labor when making the tradeoffs. 
> You see this all the time with building codes.
>
>>
>> When I put up my 64' UNGUYED Heights tower in 1970, 4'x4'x4' was all 
>> that was required and that held a tribander and other antennas for 
>> years (rebar wasn't mentioned and it was hand mixed concrete).   For 
>> a 50' guyed tower, all I used was 30" square and 8" deep.
>>
>> But that was back  before we had modern computers to tell us it 
>> wouldn't work.
>>
>> Ken WA8JXM
>>
>> On 1/4/16 12:59 PM, Jim Brown wrote:
>>> Rohn recommends more. 3 ft x 3 ft, 4 ft x 4 ft.  More mass in the 
>>> ground is better when the wind blows.
>> 73 Roger (K8RI)

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