Lowest Feasible KU Elevation

[oblio]

Reading this thread I realized I'm not sure what elevation really means in a pratical sense. Is zero elevation a perfectly horizontal dish?

My understanding is that the sat signal comes in at about a 30 degree angle or more for a due south pointing dish. Dish elevation is what we set the dish at to get the correct reflection from back of dish to the LNB on the arm. So if I am at 5 degree elevation, is the sat signal actually coming in at a higher incidence angle? This mean you can be pointed at an obstruction like trees but receive the feed that still comes over the top.

Seems like the farther east or west you go the incidence angle and elevation get closer and at dead east or dead west it would be the same. However as we are tracking the Clarke belt with a motor we will never be dead east or west unless we are bang on the equator.

So long story short, if I need an indicated 5 - 10 degrees of elevation to get a sat, do I actually physically have say 20 or more degrees of sat signal angle to clear a tree? I've trees at or just above dish height where I would need to go for 15W to 60W so may end up skewing right at them but I'm hoping not an issue at all. Other than lyngsat saying a specfic sat is below the horizon, I can find lots of elevation references but little for how far above the horizon a sat is and the link between that and elevation. So to modify the OP question, how far above the horizon does the SAT need to be in order to have a chance to receive it?

 

[Andrew K]

Reading this thread I realized I'm not sure what elevation really means in a pratical sense. Is zero elevation a perfectly horizontal dish?

My understanding is that the sat signal comes in at about a 30 degree angle or more for a due south pointing dish. Dish elevation is what we set the dish at to get the correct reflection from back of dish to the LNB on the arm. So if I am at 5 degree elevation, is the sat signal actually coming in at a higher incidence angle? This mean you can be pointed at an obstruction like trees but receive the feed that still comes over the top.

Seems like the farther east or west you go the incidence angle and elevation get closer and at dead east or dead west it would be the same. However as we are tracking the Clarke belt with a motor we will never be dead east or west unless we are bang on the equator.

So long story short, if I need an indicated 5 - 10 degrees of elevation to get a sat, do I actually physically have say 20 or more degrees of sat signal angle to clear a tree? I've trees at or just above dish height where I would need to go for 15W to 60W so may end up skewing right at them but I'm hoping not an issue at all. Other than lyngsat saying a specfic sat is below the horizon, I can find lots of elevation references but little for how far above the horizon a sat is and the link between that and elevation. So to modify the OP question, how far above the horizon does the SAT need to be in order to have a chance to receive it?

The best way to answer your questions is to check out dishpointer.com . Go there, type in your address, zoom in on your house, put the marker at where your dish is located, and it will give you the required dish elevation, azimuth, or whatever. If you're using an offset Ku dish like I am, be aware that you need to subtract the dish offset (for me it's 24 degrees) from the elevation that dishpointer gives you. If the satellite is 8 degrees above the horizon, then that would give you an 8-24 = -16 degree dish... the dish would appear to be pointing toward the ground since it's -16 degrees from the vertical. A vertical dish would be achieved if it was pointed at a satellite that's 24 degrees above the horizon... of course that would be if you had a 24 degree offset dish. Check to see what the offset is.

Also note that dishpointer has an option you can check in the map view that will give you the maximum height for obstacles in front of your dish. Move the pin over the obstacle and it will give you the maximum allowable height of that object. You will need to subtract your dish height above ground from that number that it gives you. This helped me a lot in determining where I should put my dish in my yard.

You don't need really ANY additional elevation angle for your dish to clear a tree. As long as the lowest part of the dish clears the tree and has a clear view of the satellite location, you're fine. Note that the elevation dishpointer gives you is the elevation above the horizon that the satellite appears in the sky at your location. These elevations are all different, and the viewable satellites for you would range anywhere from around 5 degrees up to 90 degrees (straight up) if you lived at the equator. For me, my latitude is 41 degrees north, so the highest satellite in the sky for me is about 42 degrees above the horizon (about half-way between the horizon and straight up).