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VSAT technology and installation >> Dish pointing and alignment >> Elevation of a old 10 ft dish
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Message started by frige on Jul 16th, 2006 at 2:32am

Title: Elevation of a old 10 ft dish
Post by frige on Jul 16th, 2006 at 2:32am
I have had c-band for a long time. The dish is a 10 foot alluminum mesh must be 20+ years old but works fine. I recently bought a new digital receiver put in a new lnb and ku feed horn ran new wire etc.
I am trying to get the best picture availiable can I use a magnetic protactor to determine the elevation? The dish is round and the feedhorn is centered with a button hook. Also what firgure should I use?
My latitude is: 30.118
Longitude is: 95.6036
G-5 is the strongest sat.
Thanks

Title: Re: Elevation of a old 10 ft dish
Post by USN - Retired on Jul 16th, 2006 at 4:48am
Before you expend too much effort on this project, I'd like to point out that Ku-band signal wavelength is considerably shorter than that of C-band. 3GHz for example has about a 100mm wavelength (25mm quarter wave), 12GHz only ~25 full (6.35 quarter). Depending upon the size of the mesh openings, some old C-band dishes have a mesh size that permits Ku-band signals to pass straight through - rather than being reflected into the feedhorn. Might not hurt to measure the gaps in the mesh before going much further. Note also that C-band dishes used at Ku-band wavelength also have a proportionately higher margin for pointing error.

Check http://www.satsig.net/azelhelp.htm for elevation pointers.

//greg//


Title: Re: Elevation of a old 10 ft dish
Post by frige on Jul 16th, 2006 at 2:25pm
Thanks Greg,
It appears that I can use my protractor. I am currently getting ku signals with a decent picture so while it may not be perfect the old dish seems capable of picking up ku band.
The sat alignment page shows 2 different angles for my area. First is dish elevation which is 42.5 then it also shows polar mount main axis. I assume I should use the elevation number correct? If so I am about 10 degrees off at the present.
Thanks
Reid

Title: Re: Elevation of a old 10 ft dish
Post by USN - Retired on Jul 16th, 2006 at 3:21pm

wrote on Jul 16th, 2006 at 2:25pm:
The sat alignment page shows 2 different angles for my area. First is dish elevation which is 42.5 then it also shows polar mount main axis. I assume I should use the elevation number correct? If so I am about 10 degrees off at the present.

A 10 degree shift of a 10' dish would almost certainly cause signal loss, so that suggests you've got a polar mount. Either that, or your elevation scale is off. Before any elevation angle can be considered accurate, you must make certain that the pole itself is perfectly plumb. Any deviation from zenith (true vertical) will result in elevation error

//greg//

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