[Towertalk] How To Hold Up A 20' Mast On The Ground?

[K7LXC@aol.com]

In a message dated 4/2/02 11:08:20 AM Pacific Standard Time, 
robin.midgett@vanderbilt.edu writes:

> I'm seeking constructive advice on how to hold a 20' mast upright on the 
>  ground while antennas are installed onto the mast. The plan is for a crane 
>  to place the mast & antenna assembly into the tower top once the tower is 
>  built & the antennas are on the mast. A stake through a plate driven into 
>  the ground is easy enough to keep the bottom of the mast from moving 
>  laterally; how should a person keep the thing upright without hindering 
the 
>  antenna installation?
>  I have an idea of using guy wires to hold the mast upright & of using 
>  scaffolding as a work platform to install the antennas, working from the 
>  top of the mast downward. What say you?

    WAY too much work and screwing around. Since you're going to have the 
crane there, have him do all the work. What you need is a man-basket and 
someone in it. To install the mast, you need to be on the tower as the crane 
lowers it. You just have to guide it in. Make sure there are no pieces of 
galvanizing to prevent lowering it through the thrust bearing (inspect every 
inch and file if necessary) and use a LONG sling (the crane operator will 
have them) so the headache ball is above the top of the mast and it'll hang 
vertically. Of course you did check the TB/mast fit on the ground beforehand. 

    Then the crane delivers the bottom antenna as you're standing on the 
tower. That's a slamdunk. 

    Use the man and the man-basket to pick up each of the other antennas 
until you top out and the antennas are done. You can hang them from the 
headache ball or man-basket - just rig them so that you can work on them at a 
decent work height so you can attach them to the mast. Have someone on the 
ground help you line up the booms. 

    It doesn't matter which way they're all pointed since one of the last 
things you'll do is rotate and calibrate the beams to a known direction 
(probably north - DON'T ASK - hi) and then tighten the rotator mast clamp. 

    You should have jumpers that extend from the feedpoints to the top of the 
tower; then all you have to do is use barrel connectors and hook up each coax 
to the shack. Please wxproof appropriately. 

    This whole process will take about an hour or so - much less time than 
you'll spend fooling around with the mast on the ground. Couldn't be easier. 

Cheers,
Steve    K7LXC
TOWER TECH - 
Professional, affordable tower services for industry and amateurs