Dual-bearing ham radio antenna rotators are used in amateur radio applications in which amateur satellites are used for communications. Dual-bearing rotators permit an antenna array to be rotated left-to-right (azimuth) with one control signal from a controller, and also up-and-down (elevation) with another control signal from the controller. Once locked onto a satellite, the controller slowly changes the azimuth and elevation to remain connected. Such a rotator should be mounted at the very top of a tower with the bolts torqued to withstand both linear (vertical) and lateral (side-to-side) stress from wind loading of the antenna matrix.
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Things you need
- Tower climbing harness
- Lineman's belt
- Bolts, lock washers and nuts (sized to match the rotator holes and the holes in the rotator mount plate, with the lock washers extending at least 2 inches further than the diameter of the bolt heads, 2 lock washers per bolt)
- Open-ended wrench set
- Torque wrench (capable of 10 foot-pounds of torque)
Put on the tower climbing harness and the lineman's belt. Place the nuts, lock washers, bolts and torque wrench into the lineman's belt, and strap the rotator to the belt as well. Carefully climb to the top of the tower.
Set the rotator atop the rotator mount plate at the very top of the tower and line up the bolt holes in the base of the rotor with the holes in the rotator mount plate. If the holes don't line up between the two, acquire a drill and correctly sized drill bit to drill the holes necessary for mounting the rotator to the rotator mount plate and drill them.
Install one lock washer onto each of the bolts to be used in mounting the rotator, then slide the bolts through the holes of the rotator and the rotator mount plate. Once the bolts have been installed, place another lock washer and a nut over the ends of each. Hand tighten the nuts until firm.
Tighten each of the bolts to a minimum of 10 foot-pounds using a torque wrench. Use an open-ended wrench to hold the nuts while turning. If the rotator will be installed in an area where winds can gust to between 100 and 120 MPH, apply an additional five foot-pounds of torque to each of the bolts for added stress amelioration.
Install the azimuth and elevation masts according to directions included with the rotator and its antenna assembly requirements. Rotator manufacturers perform complicated engineering studies on their dual-bearing satellite rotors for maximum efficiency and safety, and this specific information should be adhered to without any diversion.
Connect the directional antenna arrays to the masts as needed, then connect the control and power wires to the rotator. Have a partner operate both the azimuth and elevation controls of the controller while observing operation to ensure the dual-bearing rotator is able to freely move the elements up and down, left and right, without any clearance issues. Use longer elevation and azimuth rotator masts if necessary should there be any clearance issues, but for every additional five feet of length in any given mast, tighten the bolts mounting the rotator to the rotator mount plate one additional foot-pound of torque each to accommodate the additional wind load stresses.
Tips and warnings
- Choose a dual-bearing rotator that is rated for highest average wind loads in your area. Even though great care is taken in this article to ensure structural installation safety, bearings are also engineered with rated wind load capacities and the bearings themselves can be damaged from excessive winds. Contact the local national weather service office (NOAA) in your area and ask for the highest recorded winds over the past 10-year period. Use this information to make wise dual-bearing rotator purchasing decisions for your geographical area.
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