Another Newbie Question

[Electro960]

Sorry in advanced for the dummy question. So I finally made the move to buy a c-band satellite system but I'm trying to figure out how the dish moves before I install it with the actuator. I'm assuming that the actuator arm is solely responsible for moving the dish in an east/west direction but what I'm trying to figure out is how the dish adjusts in elevation since the satellite belt is on an arch. I've read over lots of useful literature recommended by this board but still can't get this understanding. Is there another device that needs to be added?

 

[B.J.]

Sorry in advanced for the dummy question. So I finally made the move to buy a c-band satellite system but I'm trying to figure out how the dish moves before I install it with the actuator. I'm assuming that the actuator arm is solely responsible for moving the dish in an east/west direction but what I'm trying to figure out is how the dish adjusts in elevation since the satellite belt is on an arch. I've read over lots of useful literature recommended by this board but still can't get this understanding. Is there another device that needs to be added?

I think it overly confuses things to think of the satellite belt being on an arc. Better to think of the satellite belt being on a PLANE, ie the earth's equatorial plane.
If your polar mount has it's rotation axis parallel to the earth's rotation axis, then the dish will also describe a plane when it rotates, however that plane will be a plane that is a couple thousand miles above the earth's equatorial plane, assuming that you are at some north latitude. So what you do is tilt the aim of the dish down a bit (declination) so that it can see the sats in the plane below. This would be perfect if we were located on the earth's axis, but since we're not, the declination of each sat is slightly different, so we adjust by using the so called "modified declination" and tilting the rotation axis slightly to compensate (this is a slightly more complicated concept.... best to understand the non-modified explanation first).

Bottom line though, is since your rotation axis is tilted by an elevation equal to 90 minus your latitude, when your motor turns, it changes both the azimuth and the elevation that the dish is aiming at, so only 1 motor is needed.

 

[ForestKlown]

They're moving in a straight line through space. Space is curved via gravity.

 

[14karat]

As B.J. stated, they are in the earth's equatorial plane, 22K miles up, in geostationary orbit (they don't move)... in a band called 'The Clarke Belt'.
Once your elevation and declination adjustments are set on your mount, they will never change. The mount compensates for the curve of the arc as it travels E/W.

Have you happened to read thru these pages? They may help you get a clearer view of how it all works...
- > Footprints by Dish Size - Adjusting the Polar Mount for Prime Focus Antenna - C/Ku-Band Satellite Systems - Tuning, Tracking, Azimuth, Elevation, Declination Angles, F/D Ratio, Focal Distance, Inclinometer, LNB/Feedhorn Assembly, Actuator Assembly, C

Sorry in advanced for the dummy question.

There are only 2 dummy questions I know of... the first one is the one that's not asked, and the second is the one that is asked over and over by the same person after it has been answered...

(I don't think this one falls in either category!)