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please help me pointing my dish

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Sep 15th, 2006 at 1:53pm  
I hope some body help me to point my dish
I used the calculator and got these mesuerment
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dish azimuth relative to true north 234.28 deg
dish azimuth relative to magnetic north 233.34 deg
dish elevation 56.8 deg
slant range 36682.08 km
polarisation tilt 50.73 deg
polar mount main axis angle 17.99 deg
polar mount dish offset tilt 2.63 deg
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but i couldn't apply them on the dish
this is a cut view of the dish
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you can see that the red lines are not parallel
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please show me how can i use the (elevation) here

thanks
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« Last Edit: Sep 15th, 2006 at 3:54pm by Admin1 »  
 
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Reply #1 - Sep 15th, 2006 at 4:09pm  
If your mount bracket is an azimuth/elevation type and is intended for fixed pointing at one satellite see the image below, where I have added the rays followed by the radio signals.  All the rays are parallel as they come from the satellite and the elevation angle is marked EL.
...

Without any scale markings or documentation you may just have to guess that the beam approximately goes from the bottom edge of the dish to just over the top of the feed, since most offset dishes are designed this way so that the feed is just not blocking the beam.  A thin strip of wood placed across the top of the feed and under the lower edge may therefore give you the beam elevation angle.

If you have a polar mount with a motor we need to start again with close up photos of the mount bracket, from several directions and also exactly from the side for the whole dish.  Please drive the motor central before taking any pictures.

Best regards, Eric.
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Reply #2 - Sep 16th, 2006 at 12:27pm  
thank you Eric.

these are some pics of the dish

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...

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for azimuth I understand that I should move the dish to the angle as in this top view drawing (for mag. north):

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but i don't know what i should do to get the right elevation.

where should i use these numbers:

dish elevation 56.8 deg
slant range 36682.08 km
polarisation tilt 50.73 deg
polar mount main axis angle 17.99 deg
polar mount dish offset tilt 2.63 deg


if the dish stand on a right angle like in this pic:

...


please Eric, explane on the pic the measuerment I should use like in this example :

http://www.satsig.net/pol_ex1.htm
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Eric Johnston
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Reply #3 - Sep 16th, 2006 at 1:53pm  
Looking at the side view of the dish I would estimate that it is pointed at 55 deg elevation.
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The offset angle appears to be about 27 deg.   Place a strip or plank of wood across the front face of the dish.

It should lean backwards 56.8 - 27 = 30 deg.

It is presently leaning backwards by 55 - 27 =  28 deg.

Add the feed and LNB and increase the elevation a couple of degreees.  Then sweep sideways.  If no good try again with small up/down adjustments.

Best regards, Eric.
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Reply #4 - Sep 16th, 2006 at 10:23pm  
Thanks Eric.

now I understand what is the elevation and I think I can get it right.

but can you explain what is the offset angle?

and how can I get it exactly ?

I suggest that you should put a glossary page because there are many terms that new people to these things cannot understand.

thank you again for this very useful site.

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Reply #5 - Sep 16th, 2006 at 11:10pm  
Offset angle is the beam elevation angle when the front face of the dish is vertical.

To easiest way determine the offset angle is to point the dish at a known satellite, calculate the beam elevation angle, measure the slope of the front face of the dish then:
Offset angle = Beam elevation angle - slope of the front.

Best regards, Eric.
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Reply #6 - Sep 17th, 2006 at 10:30am  
thank you very much


I'll try to point it and if there is any question I'll ask you
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