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Author Topic: Cheap / Homebrew AZ-EL  (Read 8093 times)
AE5NE
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Posts: 91




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« on: June 22, 2010, 11:56:51 AM »

I want some kind of az-el rotator to point beams at satellites.

I am thinking something based on the cheap jack screw drives used for the common broadcast satellite equatorial mounts.... Basically mount the antennas on a hinge, and mount the jack to an arm that lifts them as the jack extends (or contracts).

Really, the Azimuth part is easy to handle with a common rotator.  The Elevation part is what I am looking for.

I can build and write control hardware/software to accept any format spat out by a sat tracking program, and to convert shaft counts to angles, etc...  so I am not really worried about that part.   I am looking more for physical design ideas.

Or a source for cheap pre-made units.


Thanks for any help!
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W5DQ
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« Reply #1 on: June 30, 2010, 03:27:23 PM »

The jackscrew idea won't work as the ham satellites are not in geosynchronous orbit so their ground track changes constantly. Most, if not all, ham sats are in a polar orbit I believe so there is that too to prevent the jackscrew method. You will need some sort of horizontal rotation to accomplish the elevation part of the pointing at the same time the vertical component handles the azimuth. That is why most successful arrangements use AZ-EL computer controlled system to track sats.
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
WB0KSL
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Posts: 94




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« Reply #2 on: June 30, 2010, 11:12:13 PM »

I was last on the sats back in the early 90's, but I seem to remember a few stations using a jackscrew arrangement for the elevation portion of an az/el tracker.  As I recall, the factor which makes it feasible is that the actual useful arc covered in elevation need not be a full 90 degrees.  The vertical beamwidth of common antennas used does not require that the antenna point all the way to the horizon.  Likewise, few passes are straight overhead.  Speed of the jackscrew movement, and programming, would be the major issues, IMHO.

73 - John - WB0KSL
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KA1DBE
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Posts: 122




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« Reply #3 on: July 02, 2010, 09:40:19 AM »

I use just an azimuth rotator and my beams are positioned at a 20 degree angle.  I can usually stay with the bird through the pass with the exception of the first and last 5 degrees of the pass. 

73's, es GL
Jeff
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W3JKS
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Posts: 203


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« Reply #4 on: July 02, 2010, 10:05:19 AM »

Here is an interesting homebrew az/el:   http://ka6puw.tripod.com/azimuth1.html

And here is another one: http://aa5fr.com/elcheapoazel.htm

I've seen some pretty good inexpensive az/el mounts using older outdoor pan-tilt mechanisms from the vidicon tube days of security cameras.

At the other end of the spectrum, I just picked up (with help!) a tracking mechanism formerly used for the electro-optical targeting system on a British warship.  I'm going to mount it onto my Mobile Communications Unit.  Roll Eyes

73,
john W3JKS/AAT3BF/AAM3EDE/AAA9SL
http://www.armymars.net/ArmyMARS/MCU/index.html
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K8POS
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« Reply #5 on: July 03, 2010, 04:14:01 PM »

I used my telescope drive.  Even tracks them too
http://melvinweather.com/sat.html

Bob
K8POS
someday the will up date my call
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W3JKS
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Posts: 203


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« Reply #6 on: July 05, 2010, 08:00:12 AM »

I used my telescope drive.  Even tracks them too
http://melvinweather.com/sat.html

Bob
K8POS
someday the will up date my call

I have a question (I haven't used a telescope since I was a kid visiting the Mt Cuba Observatory one night).  What kind of telescope would be useful for spotting satellites using a low-light camera?  I'm thinking of mounting some sort of optical capability coaxially with the usual 70cm, 23cm, 13cm antennas.  I think that it would make evening contacts a little more interesting.  Cool

73,

john W3JKS/AAT3BF/AAM3EDE/AAA9SL
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K8POS
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« Reply #7 on: July 19, 2010, 08:42:00 AM »

Not sure about the photography part.  Satellites travel pretty fast across the sky, and are very small even in a large telescope.  here is a place to look that will show what you could capture.
http://www.satobs.org/telescope.html.

Good luck
Bob
K8POS
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K0JEG
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Posts: 679




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« Reply #8 on: September 12, 2010, 11:06:24 AM »

I used my telescope drive.  Even tracks them too
http://melvinweather.com/sat.html

Bob
K8POS
someday the will up date my call

I was wondering how well this works. I have an Orion Teletrack mount that I use for taking gigapixel images with my DSLR. After I got it working, my 2nd thought was to use it for tracking Satellites. I know it is fast enough to track a LEO satellite and has plenty of tourque. I'm using a Bluetooth to serial adapter module for the auto-pan software, and I'm sure there's a way to get gnome predict (Linux sat prediction software) to work with it, but I'm not enough of a coder to get it going.

Are you using custom software or does the "brain box" that comes with your mount have the ability to track sats? It wasn't all that clear on your page.
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