RE: [amsat-bb] Calibration of AZ-EL

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

>Subject: [amsat-bb] Calibration of AZ-EL
>How are most of you calibrating your Az/El? With a compass and level? I
>have heard of putting a solar cell at the end of a 2 or 3 foot tube
>mounted to the boom, then aligning for peak voltage when facing the sun.
>Once this is done, the local time and position are entered into a
>computer program. This sounds like a good method to me. Any others? Ben
>K9BF

A lot of solutions given so far.

But the easiest is to point your dish at the sun so that the feed casts a
shadow in the center of the dish.  It is now pointed very close to the
sun's position. If you are using an offset feed dish then the shadow falls
at the center of the lower dish edge when properly pointed.

Now point the dish at the az and el given for the sun by your tracking
program.  If it is not still pointing right at the sun, adjust the dish and
rotator until it is.  I usually like to do this a few hours within local
noon so the sun is fairly high in the sky.

Now this assumes that your feed is properly positioned on your dish for
proper focus and centering...if not then the RF radiation peak will be
offset.  You can test that by observing for sun noise on 2.4 GHz.  You
should see about 1/2 to 1 S-unit rise in the noise floor when pointing at
the sun versus pointing away from the sun at cold sky.  Be sure that the
sun is far above the horizon for this.  Near the horizon you will see the
noise floor come up and mask the sun's noise.  On my dish that occurs below
10-degrees elevation.

Pointing the UHF beam is pretty much lining it up with the dish.  You might
be able to look at the antennas shadow on the ground if the sun is bright.

This is much easier than using a compass or levels.  No fancy photo tracker
needed.

Ed - AL7EB

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