[Moon-net] 5500 ROTATORS FOR EME ELEVATION

[John Fridenstine]

Hi All,

Russ (K2TXB) pointed out that these rotators move too fast to easily move 
larger arrays.  I use one to elevate my 4x12 two meter array but it is speed 
reduced by the use of a lever system.  5500 elevation rotators can move 180 
degrees from stop to stop and nowhere does the Moon rise higher that 90 
degrees.  Using a lever ratio of two to one,  I can move the antenna slower 
and easier than directly mounting the crossboom inside the rotator.

I mount the crossboom on the azimuth mast through a sleeve bearing 3 feet 
long.  On the other side of the mast I mount the rotator with rotating 
center pipe parallel  to the boom.  In my case the boom is 2.5 inches in 
diameter and the pipe in the rotator is 1.25 inches.  Levers on each side of 
the rotator are mounted on both the boom and on pipe in the rotator.  The 
levers have a 2 to 1 ratio.  In my case 4 inch levers on the rotator and 8 
inch levers on the boom.  Equal length arms connect the levers on each side. 
The antenna now moves at half the speed and half the effort.  When the 
elevation indicator reads 100 degrees, for instance, the array is at 50 
degrees elevation.  It now moves slowly enough that there is little bounce 
when the rotator stops and starts.  Also the weight and twisting torque of 
the array is on the much stronger bearing and not the rotator.

This system has worked well for the last 2+ years.  Of course my antenna is 
less that 20 feet to the top antennas and it is tied down when not in use. 
If any one would like pictures look at W8PAT on QRZ or email and I can email 
some closeups.

73 and GL
John W8PAT
EN81vg