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Using a Compass

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Ex Member
Ex Member


Oct 30th, 2006 at 11:35am  
Hi,

I see that it is helpfull to use a compass when setting up a sat system. How do you obtain a correct reading from the compass, when so many of the parts used to support the satellite dish / motor are metal?

Is there a special type of compass to use (By the way, I have never used a compass before, so not sure if the readings are correct).

Thanks,
UKCamaroSS
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Eric Johnston
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Reply #1 - Oct 30th, 2006 at 4:58pm  
To find a satellite set the elevation accurately first, then swing the dish boldly in the general azimuth direction and you should find the satellite on the first sweep.  Azimuth accuracy need only be approximate.

My calculator, e.g. http://www.satsig.net/maps/satellite-tv-dish-pointing-uk-ireland.htm
will tell you the requires azimuth to an accuracy of about +/-2 deg magnetic bearing, which is good enough.  Just swing the dish 30 deg either side of the general direction.   On a sunny day you don't even need a compass, just consider the time of day and the sun. East is 90, South 180 and west 270 deg.

Compass error due to steel objects and buildings may be 10 deg or more.   For an accurate true bearing use a GPS and walk 50m in an arbitary direction.  The true bearing of that walk direction is then given to an accuracy of about 2 deg.  Try walking each way several times and average the result if you want greater accuracy.  On a sunny day or at night you may be able to align the GPS display with the sun or moon and that will provide you with a bearing without having to move about.  You need a GPS with a compass / sky style display that shows the position of the sun, moon and the visible satellites.

For true bearings use the calculator at http://www.satsig.net/ssazelm.htm
wxw

See also: Using a magnetic compass

Best regards, Eric.
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« Last Edit: Oct 14th, 2007 at 4:52pm by Admin1 »  
 
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Ex Member
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Reply #2 - Nov 21st, 2006 at 11:30am  
good explaination eric

compass is used as basic refrence line only, its acuracy depend on condition where u use it
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