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Originally Posted by ahoss2000
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One question I want to ask the experienced folks here is that, once I set the motor elevation per Sadoun web site ( HH90 motor, motor elevation= latitude ), I never visited this adjustment again, and in all the posts I have read there is no mention of fine tuning this adjustment. With the strongest transponder on IA5, my max signal was about 73. So, I am thinking, maybe I should fine tune this adjustment. Unless when we fine tune dish elevation, then it does not matter much if motor elevation was less than a degree off. Thanks. |
First, relative to your "elevation=latitude" statement, I know what you're trying to say, but actually elevation = 90-latitude. I think a better way to say it is that your scale is indicated in latitude. Basically, if your scale has smaller numbers when it is
aiming closer to the southern horizon, then you have an elevation. If you have smaller numbers when aimed higher in the sky, it is a latitude scale. For most accurate alignment, this latitude scale should be about 0.6 degrees greater than your latitude (0.7 deg up north, 0.5 deg down south).
"In my opinion" (I know there are opposing opinions here), if you spend a little extra time making sure that this elevation is set as accurately as possible to start, then you really should never need to touch this again. Basically, either the motor elevation or the declination (dish elevation adjustment) should be set as accurately as possible and never touched again, whichever you feel can be done most accurately. With a big dish, often the declination is easier to adjust accurately, so you'd set that, and never touch it again, but with these small dishes, the consensus is that the motor angle is most accurately set. So set that, and I recommend getting an inclinometer at the hardware store, and find a surface on your motor that is parallel to the rotation axis of the motor, and verify the scale with the inclinometer.
The combined angle of inclination and declination is set quite accurately by peaking on your southern sat, so whatever errors remain after the inclination setting will be compensated to a large degree by the declination being off a bit. Ie it will compensate perfectly for sats near south of you, and will be off a bit for sats to the extreme, but will not be off enough to matter.
Fine tuning is OK, but I really think it is best to keep your fine tuning to just one of the elevation/declination parameters, not both. Once you start changing both, things get out of control fast. If you must do fine tuning, tune your dish elevation on a sat to the south, and tune your motor's due south setting on a west sat (or east sat, but not both). But NEVER try adjusting your elevation or declination while aimed at an east or west sat. Only fine tune dish elevation while aimed south.
These small dishes have a resolution of approximately 2 degrees or even more for some of the smaller dishes. So if you are off by 1/2 degree, it's not just that you can settle for that being good enough, it's really a case that this is the best you can do, because you can't tell the difference in reception well enough for fine adjustments to be more effective. Kind of like trying to fine tune the aim of a flashlight on a wall to aim at a 1/2" circle drawn on the wall, when the flashlight has a spot of 2 or 3 inches by only measuring light intensity. Ie, what is important is not that the spot is perfectly centered in the beam of the flashlight, but as long as the circle is always within the 2" beam, that is as good as you can do, if all you have as a measuring tool is brightness on the circle.
Anyway, if you can most accurately set your motor elevation, I really would never touch that again, and if any fine tuning on southern sats is necessary, do that always with the dish elevation, just like 10 years ago, I adjusted my declination on my big dish, and I haven't touched it since. Any time my south sats get off (usually in the spring with freeze thaw cycles), I just touch up my motor elevation, which for you would be done with your dish elevation since that is the least accurately set initially.
{For more random discussion, see
http://www.megalink.net/~wejones/inst&align.html
and
http://www.megalink.net/~wejones/Small_offset_issues.html