glantaff
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Information for newbies - Why you lose a signal certain times of the day within a luna month outside the normal beam:
Although geostationary satellites are nominally fixed in the sky when seen from the Earth (i.e. Astra 2D @ 28.2°E), they do in fact wander slightly, tracing out a figure of 8 over 24 hour period. This movement is because geostationary satellite orbits cannot be made exactly circular with exactly 0° inclination. In time, even the most perfect geostationary orbit will become increasingly non-circular and inclined to the equatorial plane.
This is due to external gravitational disturbances resulting from the gravitational attraction of the sun and moon. The station keeping on the satellite is designed to periodically compensate for these disturbances by correcting the orbit. For current geostationary satellites this wander is kept less than +/-0.1° in both the N-S and E-W directions (+/-0.1° in a figure of 8).
In simple terms, if you were to stand within a circle on the ground and start to turn your body clockwise or anticlockwise, you will slowly move towards the edge of the circle and there will come a point where you will need to change your position slightly to keep within the circle.
You could invest in an automated tracking system to keep your dish pointing at the strongest signal from your selected satellite, then again, if you can afford an automated tacking system, it would be cheaper to invest in setting up cluster of antenni to compensate for the gravitational shift.
Hope this explains why at certain times of the day in good weather, you can lose a signal from a satellite. Don't forget, these sat's are around 35,000km's away, so moving the dish manually is not advised.
Although geostationary satellites are nominally fixed in the sky when seen from the Earth (i.e. Astra 2D @ 28.2°E), they do in fact wander slightly, tracing out a figure of 8 over 24 hour period. This movement is because geostationary satellite orbits cannot be made exactly circular with exactly 0° inclination. In time, even the most perfect geostationary orbit will become increasingly non-circular and inclined to the equatorial plane.
This is due to external gravitational disturbances resulting from the gravitational attraction of the sun and moon. The station keeping on the satellite is designed to periodically compensate for these disturbances by correcting the orbit. For current geostationary satellites this wander is kept less than +/-0.1° in both the N-S and E-W directions (+/-0.1° in a figure of 8).
In simple terms, if you were to stand within a circle on the ground and start to turn your body clockwise or anticlockwise, you will slowly move towards the edge of the circle and there will come a point where you will need to change your position slightly to keep within the circle.
You could invest in an automated tracking system to keep your dish pointing at the strongest signal from your selected satellite, then again, if you can afford an automated tacking system, it would be cheaper to invest in setting up cluster of antenni to compensate for the gravitational shift.
Hope this explains why at certain times of the day in good weather, you can lose a signal from a satellite. Don't forget, these sat's are around 35,000km's away, so moving the dish manually is not advised.