4
same gray electrical conduit as is used for the two 10” masts. If the antennas to be mounted
are particularly heavy, you can make the horizontal boom more rigid by driving a standard 1”
diameter wooden dowel, available at hardware stores, into the conduit with a hammer. This
dowel is a snug but manageable fit into the 1” plastic conduit. For some antennas, depending
on their mounting configuration, it is important not to use conductive metals for the horizontal
boom, and this PVC + wooden dowel boom meets that requirement nicely.
If you want a boom longer than four feet, use a longer PVC tube. Here is how to make,
for example, an 8-ft. boom. Wooden dowel stock generally only comes in 4-ft. lengths, so buy
two dowel lengths, drive the first one into one end of the 8-ft. long PVC with a hammer. Cut the
second 4-ft. dowel in half, then drive the first 4-ft. dowel to the center of the 8-ft. PVC by driving
it further in with one of the 2-ft. dowels. Finish by driving the other 2-ft. dowel into the other
end. Not quite as strong as if an 8-ft. dowel were used, but probably strong enough, especially
if you put your heavier antennas on the inner 4-ft span.
It may be convenient, however, not to mount the full-length horizontal boom during the
testing and setup phase, as it will require a substantial turning radius, an inconvenience
indoors. While setting up the Az-El rotor indoors, it may be more convenient to use a short
length (~1.5 feet) of boom, made from the same 1” electrical conduit. We drilled a ¼” hole
transversely at one end of a such a short boom and inserted a 6” length of ¼” wooden dowel,
to serve as a “pointer”, a substitute for an antenna, to be able to see easily in which sky
direction a mounted antenna would be pointing.
This completes the rotor assembly.
Connecting the rotor controller to the wall power supply
Open the controller box by loosening the four corner screws in the box bottom to reveal
the controller board. The connections to the controller board are shown in the figure below.
Connect the wall power supply to the controller board. The power supply is 24 VAC from the
supplied wall-mount transformer. Use common lightweight stranded lamp cord, sometimes
called “zip cord”, to connect the wall-mount transformer to the terminals on the controller
board. Tinning the ends of the lamp cord wires with solder at both ends prior to attachment to
the transformer and the controller board will help avoid shorts due to wayward wire strands.
The power zip cord is connected to a two-pin
terminal block mounted along the top edge
of the controller board. The wall-mounted
transformer has a difficult-to-replace internal
fuse, so take care to avoid shorting the
transformer output.
Connecting the rotor controller to the rotors
and the computer
The eight wires to the two rotors go to
the eight-pin terminal block along the right
edge of the controller board. The four wires
from the azimuth rotor go to pins 1 – 4
consecutively. The aluminum casing of the
rotor has, adjacent to the area where the
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