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Re: "Precision" Antenna Pointing



Jeff,

That's an interesting way of doing things, as well as one I keep forgetting.

How about this for an idea? With a dish (with known focal point) correctly
mounted on the boom, could you place a small (non-flammable!) screen at the
focal point and move the Az/El until the Sun's image is in the middle of the
screen?

Then with the correct Almanac predictions (or any one of a number of Star
Tracking programs) you'd be able to very accurately check your Az/El
calibration without the need for a radio.

Indeed, you could do it without a dish on a sunny day. You could assemble
two pieces of paper, one behind the  other separated by a few inches, the
forward one with an aperture in the middle, mounted in the direction of the
antennas. Centering the image on the rear piece of paper would ensure you're
in line with the sun. You know, a bit like those homebrew eclipse
experiments.

Or maybe I'm being too simplistic. Not to mention bad at descriptions.

73 Howard G6LVB

----- Original Message -----
From: "jeff w griffin" <kb2wqm@juno.com>
To: <amsat-bb@AMSAT.Org>
Sent: Tuesday, January 09, 2001 2:40 PM
Subject: Re: [amsat-bb] "Precision" Antenna Pointing


> The best , and most accurate way to electronically align an antenna
> system is to perform a solar. This process uses the solar almanac data to
> precisely predict where the sun is at any given time at your location.
> The idea here is to use the Sun as an RF source. You then use received
> signal strength to  determine exact azimuth, and elevation of  the
> antenna system. This process is the best method I know of to az-el align
> an antenna system. I haven't done a solar in over 15 years, as I don't
> work on site , at radar sites anymore. This work is usually done at a new
> site, or after any antenna modifications were performed. I also
> occasionally request solar's to verify the tilt of an antenna.
> Azimuthally an antenna system is constantly checked by primary search
> permanent echo's. So the azimuth is usually not in question.  The antenna
> systems I deal with have a beam width of 1.8 to 3.5 degrees or so,
> depending on the exact model of the radar system, and mode of operation,
> Beacon or search.
>  I have never tried this at home, my S band down link seem's to be
> aligned,  thank you. Someone with a problem might want to consider this
> method. Also over the years the accuracy of the consumer grade az-el
> rotor control systems, has been questioned. My gut feeling is a best of
> about + or  - 2.5 degrees. Anyone ever test this?
>
> 73 Jeff kb2wqm
>
>
>
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