[Microwave] AZ/EL setup for offset dish?

[Dr. Gerald N. Johnson]

Barry used an electric scissor jack for the elevation drive. Some 
electronic read out levels can be split and the read out remoted.

A yagi elevation rotor should work with the DirectTV dish and comes with 
a readout, but maybe not adjustable in 1 degree increments needed for 
peaking the 5 degree beamwidth. Unless the elevation rotor is gear down 
to move a smaller angle and slower.

There are tons of DC motored linear actuators, some were used on C band 
TVRO dishes for azimuth, Burden's Surplus Center generally has a 
selection of lengths and strengths. Some have reed switches triggered by 
a magnet on the screw so the controller gets to count the pulses and 
knowing the direction you or your computer control can figure the 
position angle. Usually the geometry is two fixed sides of a triangle 
with the third side variable, so all three angles change, but knowing 
the length of the three sides its not too hard to compute the important 
angle. There is a formula for solving the angles of a triangle given the 
lengths of the sides.

A cable could come down the tower to a linear actuator or a small winch 
at the tower base. A tag on the cable could run next to a scale on the 
tower leg.

A windshield wiper motor could use a short arm crank to move the dish a 
small distance or a worm drive motor could be slowed more by a cogged 
belt or chain drive.

I think Paul Wade has a description of his elevation mechanism in his 
fly swatter article on line. Barry's scissor jack was in a CSVHF 
proceedings a few years ago.

Getting wilder a hydraulic cylinder could provide remote linear motion, 
as could an air cylinder. Surplus Center has both and Marlin P. Jones 
and Associates has air cylinders. Trouble with air is its a better force 
that position device.

The trouble with an exposed screw like driven by the electric screw 
driver is keeping it lubricated and free of ice, and it takes a bit of 
fabrication to allow the nut to pivot as the angle changes.

And as has been used for EME for ages, a potentiometer can be coupled to 
the pivot axis, or can ride on the antenna with a pendulum on the shaft 
to hang down by gravity, which works best out of the wind. And that pot 
could be a resistive joy stick from RC aircraft or early graphics 
computers before mice became common.

Every EME station has solved this problem on a larger scale unless the 
operator has a slave to move the antenna manually.

73, Jerry, K0CQ

On 4/24/2014 4:17 AM, Scott wrote:
> Goes anybody have a link to a decent and fairly inexpensive setup for
> swinging a modified DirecTV dish for 10 GHz that is tower mounted?
> Especially interested in how the elevation is controlled...maybe
> something like a cordless screwdriver and threaded rod of some sort?
> What feedback method is the best get az/el info back down to the shack?
>
>