[TowerTalk] MA-550 Questions- Part 1

[thompson@mindspring.com]

: BillSavage, K3AN <k3an@qsl.net  asked:

>
>I have just moved to a country "estate" which consists of a house in the
>middle of a 3 acre yard.
SNIP
>There are no >antenna covenants; a few nearby neighbors have 8' satellite
dishes and/or >30' or 40' house-bracketed TV towers.
>
>I'm planning to install a free-standing U.S. Tower MA-550 crank-up tower
>with the manual crank option.  The MA-550 is the XYL's requirement.

Why stop at the MA550?   Go to the tallest model..the Force 12 is easily
supported and the low band dipole will work better.
>
>1.  I would like to use the '550 as a center support for an 80 Meter
>dipole, so I guess I want the MAB instead of the MARB base.  The MARB base
>puts the rotor at the bottom, and rotates the entire tower.  Is it feasible
>to put some kind of loose-fit "collar" on the mast that's above the top
>section, and tie the center of the dipole to some kind of arm extending
>from the collar?

You can use either base.  Fellow towertalker K4SB (then K4DJC) described
putting a dipole above a tower/rotor with a loose collar in Ham radio
magazine in the mid 70's.
>
>2.  If I go with the MAB mount, and put the rotator atop the tower, what's
>the maximum safe length of mast I can use and not overstress the rotator's
>bearings and other parts when I crank the tower over for antenna
>maintenance.  I'm planning on a Force 12 C3SS beam.  What would be your
>recommendation for the minimum rotator for this installation?  Would I be
>better off going to the next one up the capacity chain?

You can use either the Ham IV or T2X or similiar rating Create or Yaesu.  If
you put the rotor at the top with a mast out the top of the rotor you will
lose 40% of the capacity (another reason to put the rotor at the bottom on
this type of crank up).   The MA550 is the same as the old Wilson MT-61.
Use only a couple of feet of mast max.  Make the section out the top of
light material (a long fiberglas pole is ideal).
>
>3.  How do you go about ensuring that the base will be level, and the tower
>plumb, as you are pouring the concrete and letting it set?  Can you shim
>the base in some manner after the concrete has cured?  Will these questions
>be answered in the U.S. Tower planning information packet?

US Tower should provide a base layout and template along with instructions.
Anything less is not acceptable!   Wilson and Tristao (old names for US
Tower) provided good documentation...I would hope US Tower still does.
Just to be safe you might buy from a dealer who knows and installs towers.
One advertises in CQ and QST and offers assistance.


73, Dave K4JRB



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