on 1/14/03 8:45 AM, Jim White, K4OJ at k4oj@tampabay.rr.com wrote:
> ....another option mentioned on tower talk that has been used in the
> past at my stations was to mount that plate upside down at the top of
> the next to the last (top) section of tower.
>
> This is very easy to do when you are stacking sections...
Not a bad idea. With a short top section, there is plenty of room. We
actually assembled the top section, rotor plate and the final 10 foot
section of tower on the ground before hoisting it up. Made the jobe real
easy.
>
> By mounting it with the ears up, the flat plate will actually rest
> against the horizontals. As I remember there still was something thing
> had to be "cut in" but the beauty of this location was that the weight
> of the rotor/mast/antenna was NOT just support by the u-bolts in the
> corners.
Actually, if you mount it the "normal" way, it still ends up resting on the
top of the Z truss on the next lower section. It's attached almost
literally where the two sections meet. No cutting needed. Rohn wouldn't
design and sell something that needs to be hacked for proper install.
>
> There are "short top sections" available on the market as well, by
> using a middle thrust bearing as well you get the "ideal" mast location
> (in my opinion) - coupled with mounting the top guy sets down from the
> top of the tower near the rotor you create a tower which has a good
> place to work on the antennas....even better if you have a flt top plate
> which allow you to use the mast for stacking easily - you can stand on
> the top plate.
The ideal is to the the BPL25G, I think it is. I had a short, tapered, top
section that came with my tower so I didn't use this. The BPL25G is the
flat top plate you mention. It has "ears" on it bent down at 45 degree
angles for guy points - very nice. You mount your thrust bearing on this
plate and then you put your AS25G at the bottom where it and the next 10
foot top section meet. This is a great solution. No need for a guy bracket
on the top section then.
I don't have a thrust bearing since I don't have massive antennas. But if
you wanted to use a thrust bearing plate at the bottom of your short,
tapered top section, then you would need to mount the AS25G lower and then,
yes, you would need to hack it up. I would certainly cut the plate, NOT the
Z trusses on the tower. The plate will feet in between standard sections as
well, but the rotor may not. My Ham IV interferes with the Z trusses as
well. But the space at the bottom part of the top section leaves plenty of
room.
>
> With my size 13's I was never a fan of 25G but 45G and 55G with the
> above sheme work gud.
>
> Sure is cool here, cannot wait for the nice weather we get in April when
> we go mobile in the Florida QSO Party - by the way that's the 26th and
> 27th this year.
I laugh when you Florida people say it's "cool." :-) It was about 11
degrees F driving to work this morning. Y'all come up north here and we'll
show you what winter is all about!
73,
Jon
NA9D
-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)
Citizen of the People's Democratic Republik of Illinois
Life Member: ARRL, NRA
Member: AMSAT, DXCC
http://www.qsl.net/na9d <- Updated on 1/12/03!!!
"A life lived in fear is a life half lived."
|