In a message dated 97-01-28 12:35:45 EST, you write:
>I am in the process of putting up an 80 ft. tower with a couple of HF
>Yagi's stacked on top
Hi, Dave --
What kind of tower? What county are you in?
>
>The plan is to have a TH7 about 2 ft. above the top and an a3ws (12/17m)
>about 8 feet above it. I figured to nest two sections of mast so the A3
>would be accessible from the top of the tower with the two sections
>collapsed. The problem/question arrises in that that puts the
>TX2 rotor down about 6 feet into the tower and I will have to cut the Z
>braces at that point to get the mounting plate and rotor in place.
What kind of mast? Size, wall thickness, etc.? What do you mean "nest
two sections of mast"? Why/how does it "collapse"?
Are you talking about the problems of Rohn 25G/T2X compatibility? I
think you only have to cut one diagonal to get the T2X in and out. Don't
butcher anymore than you have to. The other problem is that the Rohn
accessory shelf will only fit in a couple of places on the tower, limiting
where you can mount it. Please provide more details of your planned
installation.
>
>Is this advisable or will it cause an unacceptable weaking of the tower
>at tat point?
>
The main tower failure component are the legs (assuming that everything
else is installed per the manufacturer's specifications). Since they take
the compressive load, your surgery won't adversely affect the leg capability.
Of course this is not ever a good idea but many hams have successfully used
this technique WITH CAUTION.
BTW, install the TH7 right at the top of the thrust bearing rather than
2 feet up. You'll reduce the moment of forces on the mast and besides 2
additional feet really doesn't buy you anything.
73, Steve K7LXC
TOWER TECH -- professional tower supplies and services for amateurs
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