[TowerTalk] question of the day

[Roger (K8RI)]

jimlux wrote:
> Roger (K8RI) wrote:
>
>>>
>>> W3GM had six 100' Rohn 25g towers, all of which used a ground 
>>> mounted  rotor.
>>> Ham 4 and Tailtwister, as well.   They were turning things like a 3  
>>> element full sized
>>> 40m yagi.    The "mast" was 2" irrigation pipe.   Wasn't 
>>> particularly  heavy, nor thick
>>>   
>> I hope he had the rotators mounted independently of the 25G. IOW, the 
>> rotator mount affixed to the concrete and not the tower (It did say, 
>> ground mounted).  A full size 3L 40 could likely over stress the 25G 
>> in shear with a base mounted rotator attached to the tower.  In 
>> addition the 25G is a pretty light tower for that much wind load
>>
>> I'd not put a 3L 40 on anything smaller than a 45G
>>
>> 73
>>
>> Roger (K8RI)
>>
>
> Having six 100' towers implies a fair amount of open space, where a 
> failed tower might not do much damage other than to the tower.  He 
> could just gamble that a big wind won't come up, and if it does, and a 
> tower gets tweaked or falls down, you can just replace it.
True.  Over the 47 years I've been a ham I've never lost a tower to wind 
or ice. Very early one I did lose a wood mast that went into oscillation 
and literally exploded.  None of the pieces made it to the house and it 
only supported an inverted V so the only thing I was out as some time.

OTOH of the two current towers, the big one is only 10' from the corner 
of the garage and about 30' from the master bedroom. I'd hate to have a 
tower section or boom come through the ceiling of the bedroom, or even 
the garage for that matter. It's also slightly less than 40' to the 
operating position out in the shop.  The second and much smaller tower 
is on the West end of the shop and all it holds is the AV640 at 40' and 
crossed dipoles for TV at 30-32'. It it goes down about the only damage 
might be my wife's fence in the back yard.  Of course that fence cost 
more than some of my antennas. <:-))
>
> Just looking at rough ballpark numbers.. 10 feet of 25G costs about 
> $125, 10 feet of 45G costs about $250, so, for a 100 foot tower, the 
> cost difference is around $1250.  If labor is free(!), and you get a 
> big wind every 10 years, then the annualized cost of cheaping out on 
> the tower is zero. (aside from the cost of breaking the antenna)
>
> Not everyone needs a tower that is suitable for commercial 
> installation next to a preschool.
>
Like the 90' American Steel with a dirt base,  supporting my tribander 
and the repeater antenna I had up for years. <:-))
Incidentally the 40' Aluminum tower is on a dirt base with 3 sections of 
25"G bracketed to the end of the shop roof  and on a home made dirt 
base.  The 25 G serves as a raising fixture for the 40' Aluminum tower 
so I can raise and lower it by my self to work on antennas.

73

Roger (K8RI)
> Jim, w6rmk
>
>