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RE: [amsat-edu] Results of el/az rotator query

Dear Christopher,

I congratulate you got to a final solution as give you best wishes as your
project seems very interesting.

Have you consider using an automatic controller for Satellite Communication
Stations which controlls both the el/az system and the doppler shift on the

Please be so kind to take a look at our PrimeSAT Controller at:


We've been receiving many good critics on reviews from magazines like Radcom
and CQ, and there are other releasing on Funkamateur and CQ-DL.

Looking forward to hear from you.

Kind regards,

Armando Claro da Fonseca

> -----Original Message-----
> From: owner-AMSAT-EDU@amsat.org 
> [mailto:owner-AMSAT-EDU@amsat.org] On Behalf Of Christopher J 
> Galbraith
> Sent: terÁa-feira, 7 de MarÁo de 2006 20:23
> To: amsat-bb@amsat.org; amsat-edu@amsat.org
> Subject: [amsat-edu] Results of el/az rotator query
> Hi gang,
> Thanks to many list members, we got a ton of valuable 
> feedback on az/el rotator requirements and systems.  I've 
> summarized the comments (below) in case it is useful for 
> others planning a station.
> In the end, we chose the Alfa Spid system which offers the 
> pointing accuracy and mechanical robustness needed for future 
> work with physically larger arrays and small beamwidth 
> antennas.  If we were only planning to use 2 or 3 Yagis, the 
> Yaesu G-5500 would have been the winner.
> The AMSAT lists are excellent examples of hams helping other hams.  
> Thanks again, VY 73, Chris KA8WFC
> ----- BEGIN SUMMARY -----
> The original question posed was (paraphrase):  
> "What sort of azimuth and elevation rotator system is needed 
> for VHF/UHF Yagis and a dish for the microwave bands?  The 
> application is for current LEO amateur satellites, with an 
> emphasis on the ability to expand in the future."
> Main points on assessing requirements:
> 1. A good rule of thumb for needed pointing accuracy is half 
> of the antennas
> 3 dB (half power) beamwidth.  For Yagis, this means a 15 
> degree accuracy is good enough.  For dishes with gains well 
> over 30 dB (and beamwidths on the order of a few degrees), a 
> more accurate system is needed.
> 2. All of the available commercial options are reliable 
> enough for most ham installations, with increased load 
> capacity and reliability, and pointing accuracy coming with a cost.
> The systems considered, many suggested by list members, included:
> Format: [System] [Cost] [Number of recommendations]
> 1. Yaesu G-5500 [$800 with an external PC interface] [7 
> votes] 2. M2 system composed of a OR-2800P (azimuth) and 
> MT-1000 (elevation) [$3,000] [0 votes] 3. Alfa Spid az/el 
> system [$1,500] [5 votes] 4. EMOTO EV-800-DX [$3,300] [1 vote]
> Hardware specific notes:
> 1. The Yaesu G-5500 is best suited to VHF/UHF work although 
> many also use it with small (32" or less) dishes.  It uses 
> potentiometers for position sensing and planetary gears with 
> some backlash, so its accuracy is roughly 5-10 degrees.  Many 
> have had systems based on the G-5500 (or G-5400) up for
> 10+ years without any problems.
> 2. The M2 system is overkill for anything less than 
> medium/large (above 1m) dishes and EME arrays.  It uses worm 
> gears and has claimed accuracy of 0.5 degrees.
> 3. The Alfa Spid system uses worm gears and magnetic position 
> sensing like the M2 at roughly half the cost.  It has a 
> claimed accuracy of 1 degree.
> ----
> Via the amsat-edu mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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