[TowerTalk] Yagi statcking order?

[Art Greenberg]

On Tue, Mar 17, 2020, at 12:53, sawyered at earthlink.net wrote:
> With 17ft of mast exposed, how much is in the tower?

Tower is a WT51. There is only one place to put the rotator where the manufacturer
placed welded rests for the plate, about 3 feet down from the top. Big, burly bearing
at the top plate.
 
> I have a Thrust bearing at the top of the tower and the rotor (Yaesu 2800)
> at the bottom of the mast.  I have a second thrust bearing mid section but I
> let it float unless I am doing maintenance requiring pulling the rotor.

This would be my preferred arrangement, but its not an option the way this tower
is made. If I had the expertise, I would consider adding rests for another plate
farther down, but I do not. In that case I would definitely add 40/30 to the SteppIR
instead of stacking two large antennas.

> I think the moment arm of the mast vs what's pushing against it in the tower
> is a big part of the question.

I understand that consideration. But as both the 3 element SteppIR and either of the
smaller 2-element 40m yagis are similar in weight and wind load, I'm not sure it makes
much difference what the stacking order is with respect to that issue. I think height
of the second antenna on the mast is more important. I don't think I can put either
antenna at the top of the mast (or anywhere near that high) for that reason.

Art
WA2LLN
art at artg.tv