[Towertalk] AB-577 Mast and Windloading

[K4tmc@aol.com]

>From the AB-577/GRC manual:

Chapter 1, Section II, Description and Data

1-5.  Purpose and Use

a. Mast AB-577/GRC is an eight-section antenna support that can be extended 
as high as 48 feet (14.63 meters) above the ground.  Extension Kit, Mast 
MK-806/GRC is a five-section mast kit that is mounted on top of the 
AB-577/GRC to produce a total height of 75 feet (22.86 meters).  WARNING: The 
use of more than one 25-foot mast extension kit (MK-806/GRC) on the Antenna 
Mast AB-577/GRC is hazardous and is not authorized.

b. In some applications, the AB-577/GRC supports Antenna AT-903/G, a 
horn-type directional antenna (size: approximately 20 x 24 x36 inches).  The 
AB-577/GRC (and the MK-806/GRC) may be used to support two AT-903/G's when 
they are mounted on  Antenna Support AB-720/G or AB-957/GRC (T-bars).

1-6.  Technical Characteristics 

a. AB-577/GRC

Type - Sectionalized, tubular
Material - Aluminum
Height: 
    Maximum extended    - 48 feet (14.63 meters)
    Collapsed (launcher height) -   95 inches (2.41 meters)
    Each mast section - 64 inches
Guy rope lengths - 39 ft., 47 ft., and 56 ft. (11.88, 14.32, & 17.07 meters)
Stability - +/- 5 % of original setting for winds up to 75 mph, under 
conditions of 1/2 inch ice loading
Rotation - Azimuth rotation, 360 degrees, controlled from ground
(end of quote from manual)

There is no specification on actual antenna weight that can be supported.

>From the manual for its bigger brother, the AB-621/G, which uses 6 inch tubes:

Resistance to wind velocity -
(guyed at 3 levels with anchors located 35 ft from the mast center) 100 mph 
Maximum antenna weight - 190 lbs (86 kg), at 12 inches from center of mast

Hope this helps.

73, 
Henry Pollock - K4TMC
Raleigh, NC