Discussion
I can never find the lounge site, anyway, quick question, so not a long drawn out post.
My satelite dish broke one of its mountings last night in the wind, so one side sort of sprung out, altering the angle of the dish, result, no signal.
In anticpiation of the return of Fringe tonight, I managed to wire it back and it works fine.
Trying to explain to the OH how much the dish would be out of alingment if it was altered by as much as 2 degrees, I couldnt remember the formula, ie at the satelite distance, could be pointing at a point miles away from it.
Question, given that the satelites are around 20,000 miles away from earth, (I think), how much of an offset would 2 degrees be at that distance, ie by how much would it be missing the satelite? I am sure one of our knoweldable readers knows the answer, and maybe the formula. tks guys.
My satelite dish broke one of its mountings last night in the wind, so one side sort of sprung out, altering the angle of the dish, result, no signal.
In anticpiation of the return of Fringe tonight, I managed to wire it back and it works fine.
Trying to explain to the OH how much the dish would be out of alingment if it was altered by as much as 2 degrees, I couldnt remember the formula, ie at the satelite distance, could be pointing at a point miles away from it.
Question, given that the satelites are around 20,000 miles away from earth, (I think), how much of an offset would 2 degrees be at that distance, ie by how much would it be missing the satelite? I am sure one of our knoweldable readers knows the answer, and maybe the formula. tks guys.
Is this just a random guess thread?
3000 miles up + 20% out by degree + taking into account latitude offsett, I would say it's out by only about 20 feet. Out. Parabolic dishes have tangentel alteration built into the set up meaning you can have a degree offsett of around 10% before signal clarity is effected.
Some of the above may not be true.
None of the above is true
3000 miles up + 20% out by degree + taking into account latitude offsett, I would say it's out by only about 20 feet. Out. Parabolic dishes have tangentel alteration built into the set up meaning you can have a degree offsett of around 10% before signal clarity is effected.
Some of the above may not be true.
None of the above is true
GTIR said:
Is this just a random guess thread?
3000 miles up + 20% out by degree + taking into account latitude offsett, I would say it's out by only about 20 feet. Out. Parabolic dishes have tangentel alteration built into the set up meaning you can have a degree offsett of around 10% before signal clarity is effected.
Some of the above may not be true.
None of the above is true
I was simply calculating a triangle.3000 miles up + 20% out by degree + taking into account latitude offsett, I would say it's out by only about 20 feet. Out. Parabolic dishes have tangentel alteration built into the set up meaning you can have a degree offsett of around 10% before signal clarity is effected.
Some of the above may not be true.
None of the above is true
I have no idea of the actual tangental range of satellite dishes.
The calculation I made and the answer I gave was for the centre focus point. Just a triangle calculation.
You can be several degrees out before it stops working. The satellite's signal is not a straight 'beam' to your house it is more like a torch light with a footprint covering most of Europe, the dish being parabolic also focusses the received signal even if not quite aligned (left to right is the more critical, up and down less so iirc.)
Cheers
Ben
Cheers
Ben
BigBen said:
You can be several degrees out before it stops working. The satellite's signal is not a straight 'beam' to your house it is more like a torch light with a footprint covering most of Europe, the dish being parabolic also focusses the received signal even if not quite aligned (left to right is the more critical, up and down less so iirc.)
Cheers
Ben
This is what we went by when I worked as a sub contractor for sky. There was a bit of movement allowed for the dishes before signal strength and quality were affected. IIRC it was about 3 degrees each side before quality was lost and 5/6 for strength. The signal from Sky is only 80Hz after all.Cheers
Ben
Geostationary satellites orbit at an altitude of 35,786Km or 22,236miles above sea level (at the equator - pretty sure you know this).
The available real estate might seem pretty large but some satellites are only 1/10th of a degree apart, although in reality this represents 736Km or 457miles.
And although the footprint of a satellite might cover the whole of the UK (for example) at your fixed point within that footprint, you need to have your dish aligned to point at that teeny tiny satellite, not at an area the size of its footprint (does that make sense?).
The available real estate might seem pretty large but some satellites are only 1/10th of a degree apart, although in reality this represents 736Km or 457miles.
And although the footprint of a satellite might cover the whole of the UK (for example) at your fixed point within that footprint, you need to have your dish aligned to point at that teeny tiny satellite, not at an area the size of its footprint (does that make sense?).
Mars said:
Geostationary satellites orbit at an altitude of 35,786Km or 22,236miles above sea level (at the equator - pretty sure you know this).
The available real estate might seem pretty large but some satellites are only 1/10th of a degree apart, although in reality this represents 736Km or 457miles.
And although the footprint of a satellite might cover the whole of the UK (for example) at your fixed point within that footprint, you need to have your dish aligned to point at that teeny tiny satellite, not at an area the size of its footprint (does that make sense?).
Yes it does, I don't think I was clear in my explanation. You need to have it lined up but not as accurately as if the signal was a length of string from the satellite to your dish was what I was trying to say.The available real estate might seem pretty large but some satellites are only 1/10th of a degree apart, although in reality this represents 736Km or 457miles.
And although the footprint of a satellite might cover the whole of the UK (for example) at your fixed point within that footprint, you need to have your dish aligned to point at that teeny tiny satellite, not at an area the size of its footprint (does that make sense?).
Remember "SOH CAH TOA"
Sin(x)=op/hyp
Cos(x)=adj/hyp
Tan(x)=op/adj
Where there is a right angle triangle with an angle x (not 90 degrees). The side opposite angle x is the opposite (op) the one between x and the 90' corner is the adjacent (adj) and the longest side (opposite the right angle) is the hypotenuse (hyp).
In the original question:
The angle of 2 degrees is x, and this is the angle the dish deflects.
The length from earth to satellite is either adj or hyp as you can put the satellite at the 90' angle corner, or the other corner. With an angle as shallow as 2 degrees the hyp and adj are almost the same lenght.
The displacement of sattelite is op.
So we can use Sin or Tan.
Sin(2)=Disp/22,000, so Disp=22,000 * Sin(2 )= 767 miles
or
Tax(x)=Disp/22,000, so Disp=22,000 * Tan(2) = 768 miles
Sin(x)=op/hyp
Cos(x)=adj/hyp
Tan(x)=op/adj
Where there is a right angle triangle with an angle x (not 90 degrees). The side opposite angle x is the opposite (op) the one between x and the 90' corner is the adjacent (adj) and the longest side (opposite the right angle) is the hypotenuse (hyp).
In the original question:
The angle of 2 degrees is x, and this is the angle the dish deflects.
The length from earth to satellite is either adj or hyp as you can put the satellite at the 90' angle corner, or the other corner. With an angle as shallow as 2 degrees the hyp and adj are almost the same lenght.
The displacement of sattelite is op.
So we can use Sin or Tan.
Sin(2)=Disp/22,000, so Disp=22,000 * Sin(2 )= 767 miles
or
Tax(x)=Disp/22,000, so Disp=22,000 * Tan(2) = 768 miles
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