Re: [amsat-bb] RE: Leo Class stations

[Emily Clarke <w0eec@xxxxxxxxx>]

Thanks David for raising this up again.  I'm going to repeat the URL here 
because it's very important for newcomers to read this, understand this and 
also realize that they don't have to be super rich to afford this hobby:
http://web.usna.navy.mil/~bruninga/rotator1.html

Newcomers and maybe seniors (those among us who are moving from landed 
properties into condos and the like) should read and understand this 
paper.  Bob is right on! The real meat is in the cumulative percentage 
between 20 and 30 degrees!  I finally settled on about 26 degrees - but hey 
- I still adjust things.   Anyone who doesn't believe this should just drop 
me a line - I'm an advocate and don't mind answering questions.

My technique for working amateur satellites is almost wholly based on this 
brilliant Bruninga article with a few small differences. Bob originally 
proposed the Arrow, but like David I started out with a omni (covered in 
plastic ivy so when it wasn't elevated it looked like a plant).  I 
graduated to a Cushcraft 3x3 yagi (not the best design, but better) and 
eventually modified it to be 3x5.  I used that on FM, but it desensed in 
duplex so I changed again.  Now  I use small but high gain Yagis (both by 
Diamond and under 40" boom length with higher gain and less cost than the 
Arrow).

The other difference is that I rotate by hand.  I'm thinking of the 
RatShack rotator though, but the problem is how to mount them to the peak 
of the condo without hitting Condo Nazi territory.  But we are close to an 
agreement because it will get rid of what is now 15' of unsupported 
aluminum mast and replace it with 3' of supported mast.

You can see the whole transition I went through by clicking on the 
"Antennas" gallery here:
http://www.emilyshouse.com/gallery/

Bob Brungina's theories in this one paper are not to be dismissed 
lightly.  The Big Guns will poopoo it, but without this one brilliant 
explanation of an entry level system I (and I suspect many hams) would have 
abandoned the entire effort as being an elitist hobby that was 
unobtainable.  I am now gradually investing more heavily in the hobby, but 
without an entry point that gave real results I don't think I would have 
bothered.

So hats off to you David, and thank you Bob.  It's a great solution to a 
problem that isn't as difficult as people make it out to be.

73,

Emily



At 10:14 PM 2/24/2004 +0000, you wrote:
>Steve,
>
>I'm currently am in the midst of experimenting with various LEO antenna 
>arrangements to expand my portable operation.  One idea that I currently 
>like is the idea
>of using a simple az-only TV rotator (available at RadioShack,etc for 
>~$60) to rotate a small vertical beam.  The beam is tilted upwards 
>slightly with respect to the horizon.  This provides good gain for the 
>lower elevation parts of the pass, and as the bird gets up higher its 
>increasing signal strength compensates for the beam's reduced sensitivity 
>at higher elevations.  The relatively low gain of the system makes 
>pointing requirements not all that stringent.
>I believe Bob Bruninga has described this setup in the past.  You might 
>find some relevant info at http://web.usna.navy.mil/~bruninga/rotator1.html
>
>Hope this helps,
>David Carr
>KD5QGR
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---------------------------------
W0EEC - CM87tm
AMSAT Area Coordinator - San Francisco Bay Area
http://www.projectoscar.net    http://www.PlanetEmily.com 
http://www.experthams.net/ao7

Help Launch Echo - http://www.amsat.org/amsat/sats/echo/index.html
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