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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.
----
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