Unless you live at low latitudes, an X/Y system has twice the problem as the AZ/EL does directly overhead, because it has moved the "axis" problem to the horizon directly North and South. So if you are at reasonably high latitude and trying to track the ISS across your south, you have the same problem. It takes the X/Y a LONG time to go from 179 degrees to 181 degrees azimuth since the Y motor has to go a full 180 degrees to get across the X axis (south).. If the system operates at 1 RPM, that can take a full 30 seconds.
The X/Y is best for tracking things that do most of their work "overhead" but are bad for things that swing through south with a low horizon (assuming you are in the northern hemisphere.). And since all LEO spacecraft spend 98% of their entire pass times well below 70 degrees and so they are definitely -not- "overhead" type space applications.
For example, the ISS has maybe one "overhead" pass above say 70 degreees only once every few days, which might have a few second problem in tracking, but the signal is so strong as to be inconsequential. Whereas the ISS will go through at least 2 or 3 pasess every day through south where the X/Y will have the same significant delay, BUT the delay is ocuring when the spacecraft is down on the horizon where you need the gain the most because it is 10 dB farther away.
See the real-world geometry of a LEO orbit and it is quickly obvious why there is very little "overhead" operations in the Amateur Satellite Service with LEO spacecraft. http://aprs.org/LEO-tracking.html
The thing about leo satelites (and the ISS) is that when it is directly overhead (a problem for the AZ/EL) it is 10 dB closer and very strong and needs no gain at all. And the duration of any pass above 70 degrees lasts only a few seconds.
We have a 12 meter X/Y and we are at 39 deg North Latitude and cannot track the ISS on any low southern crossing. We have to choose one side or the other and lose the other side. But this was back in 199? when we were one of three successful uplink stations to the Shuttle on STS-37 with Amateur TV color Video.
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Daniel Cussen Sent: Monday, October 13, 2014 6:15 AM To: AMSAT Subject: [amsat-bb] New Rotator X/Y as opposed to Azimuth/Elevation SPX X-Y Rotor
New Rotator X/Y as opposed to Azimuth/Elevation SPX X-Y Rotor
I am thinking of purchasing a new tracking system design, which uses an unusual way of pointing the antenna. I was wondering if anyone else has used this product or even the nearly identical non XY model?
Youtube video at the bottom does not work.
The benefits of it are supposedly better/faster positioning at the elevation peak, due to the "two elevation, one over another" design.
There is a good description of why it might be good here: Scroll down to conclusions http://www.microwavejournal.com/articles/2937-selecting-a-pedestal-for-tra cking-leo-satellites-at-ka-band
There are other benefits: 630 Euro plus shipping including USB computer interface (cheaper than Yaesu) Fast motor movement (50 seconds for 360 degrees) Can be compatable with Yaesu GS232 protocol or SPID driver
Downsides Low strength 80nM only suitable for light antennas (such as the arrow etc) Brand new model may have bugs or weaknesses 1 degree max position accurancy sensed by reed switch. Not 0.1 degrees as per some expensive systems. Cheaper computer interface/features compared to more expensive models. Not available from anywhere else (yet) 3 weeks minimum delivery time Strange to understand design Strange to understand config. The az & el degrees are converted to XY positions.
The main reason for taking the risk, is I want to do some small dish tests for HAMTV from the ISS, and even most expensive tracking systems, are too slow at fast peak elevations, particularly with narrow beamwidth dishes.
So has anyone used one of these or any thoughts/comments on the design?
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