Focal point please!!!

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charroo

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Apr 17, 2008
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Hi! my name is Clifford.
I recently acquire a used Channel Master 1.8m offset dish without the feed horn, could anyone tell me how to find the focal point, or give me the measurements?
 
Anole

Anole

SatelliteGuys Master
Sep 22, 2005
11,819
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L.A., Calif.
Could you post some pictures?
Is the mounting arm or the struts in place? Or do you have just a bare dish?
Any idea what it was used for before you got it?

edit: looks like Demonlord used to have one.
 
Anole

Anole

SatelliteGuys Master
Sep 22, 2005
11,819
13
L.A., Calif.
Never mind, I found plenty of good pictures.
Have you looked through this manual for the dish?

Also, I think those calculations above are for prime focus dishes, not offset.
 
Anole

Anole

SatelliteGuys Master
Sep 22, 2005
11,819
13
L.A., Calif.
this should get you close:

Here is what I would do, based on the drawings . . .

Set the dish so the face is vertical. Use an inclinometer to make sure!
Use the side brace mount holes as the "center" of the dish.
Put a tight string across the dish, from one side brace hole to the other.
The string will obviously not be against the dish surface.
Take a broomhandle and cut/mark it to 1.10 meters
Put one end against the dish, under the center of the string.
Take an inclinometer, and set it on the broomhandle.
Tilt your broomhandle down 23º , and where the end of it is, that's where you want to put the LNB.
This should get you quite close.

From here you tune as you would on any dish, by adjusting the LNB toward and away from the dish.

edit: If you have the mount shown, check the elevation of a known satellite against the marks on the mount.
Adjust the height of the LNB to agree with the markings.
You should not be off by much if the above procedure worked and you followed it carefully. ;)

re-edit: changed procedure and distance.
 

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Tron

Tron

SatelliteGuys Master
May 6, 2005
6,599
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Metro New Orleans, LA
I know a place that has at least a couple of these (reflectors only, no feedhorn or feed support poles). They don't want to part with them, though :(

Nice pictures, Anole!
 
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