RE: [amsat-bb] New to Satellite and having problems

["A.J. Farmer" <ajfarmer@xxxxxxxxxx>]

Over the past few weeks, I have been working on building a computer
controlled Az/El rotator out of two low cost TV rotators, one mounted
sideways on top of the other.  I have the project to a point now where it is
working very well.  I will be posting details of the project to my website
soon.  Basically, since a TV rotator does not give a calibrated position
reading in the shack (only a geared dial that gets out of alignment easily)
you need to build a simple circuit to feed position data back to the
computer.  I used a potentiometer mechanically coupled to each rotator.  As
the rotator turns, so does the potentiometer, thereby changing the voltage
in the circuit.  By reading the voltage at the 0 degree mark and the 360
mark for the Az rotator and the 0 mark and 90 mark for the El rotator, the
computer can then extrapolate the voltage readings in between to determine
the position.  This is the same way that the Yaseu rotators work.  The data
is fed into the Nova satellite tracking program using a LabJack USB
interface which is natively supported and very easy to configure for a
homebrew rotator.  I dismantled the control boxes and installed four relays,
one each for CCW, CW, UP, and DOWN so that the computer can turn the
rotators.  It is working very well and is hands off at this point.

The rotators were bought on eBay for $20 - $30 each and the Labjack is $120.
I haven't totaled up the misc electronic components yet, but I estimate it
was in the $50 range for everything including precision potentiometers,
relays, etc.  Add in some creative engineering and you have a fun project
that rewards you with a computer controlled Az El rotator for a hardware
cost of about $100, plus the cost of the Labjack interface and Nova
software.

I'm using this setup to point my Arrow antenna.  No fancy high gain antennas
(yet)!

Again, this is a basic summary of the project.  I will have pictures and
details of the system on my website soon.

73!

A.J. Farmer, AJ3U
http://www.aj3u.com


-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org] On Behalf
Of Brian L. Chaffins
Sent: Wednesday, August 04, 2004 4:19 PM
To: AMSAT BBS
Subject: Re: [amsat-bb] New to Satellite and having problems


This is perfect. I recently picked up a low cost Radio Shack rotor from 
ebay ands its just waiting for me to figure out what to do with it. I 
was wondering it anyone figured out a simple way to properly track a 
bird with a standard rotor. When I was young(er) we use to build 
telescope equitorial mounts from water pipe.

It looks like I have a new project.

Thanks again
Brian
KC8ZBC

Emily Clarke wrote:

> At 08:57 AM 8/4/2004 -0400, you wrote:
>
>> Thank you for your reply. That helps. I had not even thought about 
>> the power being transmitted by the ISS. After all they are running a 
>> D700 also. I' guess its time for another antenna. My wife is going to 
>> be so excited. *smurk*
>
>
> I may have a solution for you if you are willing to live with some 
> compromises.  I live in an apartment so everything is a compromise for 
> me...
>
> I use two small Yagi antennas made by Diamond - the A144S6 (9db gain) 
> and the A430S10 (13 db gain) which are $59 and $69 respectively at 
> HRO.  These are beam antennas, and with beams you need to rotate them 
> and control elevation.  However, I have mounted them at a fixed 
> elevation 27 degrees which puts the 1/2 power beam width below the 
> horizon. I traded this off against a null in the antenna above 75 
> degrees (which is statistically only about 4 percent of all satellite 
> passes.)  I'm sure I lose something on the ground, but I can still hit 
> 70cm stations 200 miles away and 2m stations 300 miles away, so I'm 
> probably not giving up much.
>
> I rotate by hand, but you could use one of the inexpensive radio shack 
> rotators since these antennas are very light (less than 1.5 pounds 
> each) and can be mounted in most places that you are mounting a 
> vertical.  They are small (less than 39") also, so you don't need a 
> lot of room to swing them around.
>
> Hope this helps.
>
> 73,
>
> Emily
>
>
>
>> Oh, and I already read the artical you suggested last night.
>>
>> Thank you very much
>> Brian
>> KC8ZBC
>>
>> Emily Clarke wrote:
>
>
> ---------------------------------
> W0EEC - CM87tm
> AMSAT Area Coordinator - San Francisco Bay Area
> http://www.projectoscar.net    http://www.PlanetEmily.com 
> http://www.emilyshouse.com/experthams/ao7/
>
> Help Pay For Echo - http://www.amsat.org/amsat/sats/echo/index.html
> --------------------------------- 
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