Its the weekend and math part of my brain isn't fully functioning so here goes. Is there a way to "cheat" setting up an HH motor so that the dish could be moved thru an arc of only ~70° however it would be between dish elevation of something like 1°- 40°
HH motor horizon limits
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It has a physical limit switch. You would need to disable that inside the motor and use DiSEqC 1.2 not USALS.
Good thought. I don't recall seeing a limit switch but i'll go have a look. What I was trying to think through was how to keep the motor on same arc but shift the dish position by say 20° east, thereby allowing the dish to go past elevation limit.
You can set "0" almost anywhere but you can't exceed the physical limit of the device. Some of them don't even have a full cut gear on the main shaft.
I recognize that I can't exceed limit of device which is why I'm trying to figure out if its possible to start of with dish shifted relative to true south yet maintain proper arc. Let me throw this out there. If I were to point motor at true south, rotate dish on motor shaft to satellite ~20° east and adjust elevation for signal. Would this keep me on the same arc and allow dish to be pointed lower on horizon? Thanks for the ideas. My brain is broken and I'm getting headache thinking about this. 
Short answer... NO When you set the dish on arc it is done with physical adjustments, azimuth, elevation and declination. If you change the calculated zero point you will stay on arc but USALS and preprogrammed positions are useless. If you change the azimuth or elevation you are no longer on the arc no matter where you set the zero point.I recognize that I can't exceed limit of device which is why I'm trying to figure out if its possible to start of with dish shifted relative to true south yet maintain proper arc. Let me throw this out there. If I were to point motor at true south, rotate dish on motor shaft to satellite ~20° east and adjust elevation for signal. Would this keep me on the same arc and allow dish to be pointed lower on horizon? Thanks for the ideas. My brain is broken and I'm getting headache thinking about this.
Longer answer... Yes but... You could set the motor with the elevation set so it's axis is correct for your latitude, including adjustments for a modified polar mount. Set the dish on the motor pointed towards any satellite you wish. The motor will rotate the dish on the arc. But the USALS calculations will be wrong for all the satellite positions. You would have to figure out the "fake" satellite positions and have them input for the orbital location. It would be possible, but do it for the challenge and not the convenience. DiSEqC 1.2 on the offset dish would be easier with the "crooked setup".
I think this is what Magic was saying.
Argh. I suspected it wouldn't work but at least now I understand why. Thank you for the explanation.
Wouldn't it be nice to have an H2H setup that tracks perfectly from horizon to horizon using USALs? Apparently it can't be done. I have given up striving for perfection! My loss of hair is not natural, its due to me pulling it out.
I cannot visualise what you are saying here. You mean the motor-zero is directed to south and set with correct latitude; and then the dish doesn't have to be in line with the motor south, but can have another azimuth?
I cannot see that the dish+lnb is following the arc properly, then.
So please elaborate a bit, so that I can understand what you mean here....
Can't it really? USALS is 'just' a computer program in the receiver, which wouldn't have absolute boudaries on that point I would say. See for instance this post: http://www.satelliteguys.us/xen/posts/2859684/
It seems to be just a boundary of the programmers?
The calculator on the bottom of this site goes from 70W to 80 E, apparantly: http://www.juras-projects.org/eng/software.php
I never used or tested it, though.
Greetz,
A33
The dish will be on the arc, but the dish will not be pointing where USALS thinks it is pointed.
Use the "Modified Polar Elevation" to give better tracking of the arc away from the zenith.
You need to think of the frame of reference from the motor and the polar coordinates set by the axis of the motor. The only thing the motor is doing is swinging an arc that defines a cone relative to the axis. If you can find the cone that intercepts the Clark Belt by aiming the dish from the motor, you're on it no matter where the motor is pointing.
We need to have the dish pointing at the zenith when positioned @ "0" so the mechanical system of the motor and dish are in agreement so the USALS frame or reference is valid. Shift the motor (rotate axis) or dish (point to another satellite) are not changing the cone's reference frame, just changing the USALS reference of where on the cone the dish is pointing.
Use the "Modified Polar Elevation" to give better tracking of the arc away from the zenith.
You need to think of the frame of reference from the motor and the polar coordinates set by the axis of the motor. The only thing the motor is doing is swinging an arc that defines a cone relative to the axis. If you can find the cone that intercepts the Clark Belt by aiming the dish from the motor, you're on it no matter where the motor is pointing.
We need to have the dish pointing at the zenith when positioned @ "0" so the mechanical system of the motor and dish are in agreement so the USALS frame or reference is valid. Shift the motor (rotate axis) or dish (point to another satellite) are not changing the cone's reference frame, just changing the USALS reference of where on the cone the dish is pointing.
Relative to the USALS reference, most motors will move beyond the satellites that are programmed into USALS by using DISEqC 1.2. I use my sg2100 with DISEqC to run to it's eastern stop where I find 30W just above the horizon here. No need to re-position the dish. The motor MUST be perfectly installed though; azimuth, elevation, and declination have to be dialed in as accurately as possible otherwise there will be too much error at large angles away from your southern (reference) satellite.
The software limits for USALS control are somewhat arbitrary. I'm not sure why they are set where they are. Most of my receivers return a "Beyond Limits" when programming for 30w, which is at ~9° elevation. My Amiko A3 will control down to 30w with USALS. It'd be nice if the programmers were not so conservative in setting the USALS limits.
USALS calculation limits are typically set to +/-60 or 70 degrees. +/-70 degrees is the theoretical horizon to horizon coverage. Some chipset SOC have the calculation limit hard coded to a smaller range.
Due to mechanical mount and dish assembly variances, USALS calculation become unreliable near the horizon. Even with receivers that calculate to */-70 degrees, I find the DiSEqC 1.2 is much more accurate for elevations less than 10 degree elevation.
Due to mechanical mount and dish assembly variances, USALS calculation become unreliable near the horizon. Even with receivers that calculate to */-70 degrees, I find the DiSEqC 1.2 is much more accurate for elevations less than 10 degree elevation.
So now that my brain is more hamburger than usual, are you saying a dish rotated on motor shaft 20 deg could remain on the arc and allow DISEqC 1.2.for positioning? I don't see how that's possible as once you rotate the dish on motor shaft, wouldn't the elevation would be off, ie arc shifted?
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gpflepsen:
I still don't understand what you mean.
Highest point of the arc is the exact south, so I don't see that you would follow the arc if you s....
Or did you mean something quite different with that sentence?
Greetz,
A33
I still don't understand what you mean.
Highest point of the arc is the exact south, so I don't see that you would follow the arc if you s....
That would mean the highest point of the arc is at the satellite you aimed at. So you don't follow the Clarke Belt anymore.
Or did you mean something quite different with that sentence?
Greetz,
A33
Don't let the bend in the motor shaft throw you off. The bend is only accommodating the dish mount's inability to be set low enough, to a 0 or negative elevation, as is needed when mounting on a "mast" that is inclined for a polar mount.
Say your due South is 97w. You can set the motor to zero, mount and aim the dish at 87w. Motor to what USALS thinks is 107w and the dish will be pointing towards 97w.
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