How To Calculate Clearance for Vertical Obstacles (trees, buildings, etc..), when installing a Satellite Dish.

Credit to Michael Kilgore at FTAList.com. An old friend of mine. He wrote this in his 2007 FTA Pocket Guide. I just found it digging through old stuff.

How much can you clear?

With a little trigonometry you can determine how far back you need to be from any vertical obstacles (trees, buildings, etc) in your dish's line of sight.

It all depends on the elevation angle.

For every 10 feet of horizintal distance, you can clear this much vertical height:

15 degrees - 2.6 feet

20 degrees - 3.6 feet

25 degrees - 4.6 feet

30 degrees - 5.7 feet

35 degrees - 7.0 feet

40 degrees - 8.3 feet

45 degrees - 10 feet

50 degrees - 11.9 feet

55 degrees - 14.2 feet

60 degrees - 17.3 feet

Example:

If your elevation angle is 35 degrees and the base of a tree thats in the way is 60 feet away, you can clear the tree until it is (6 x 7.0) or 42 feet high.

If you mount your dish high, as when on a roof, you can add that height. Using the previous example, if your dish is mounted 15 feet off the ground, you can clear the tree until it is (42 + 15) 57 feet high.