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Horizon obstructions

Dave Guimont wrote:

I don't know why anyone would need a computer program to compute horizon obstructions, unless his horizon moves!!
I have some trees to the east that block my "view" from 90° to about 110° AZ and about 12° EL.  I simply listened for the signal as it arose in the east, recorded when I heard it, and unless the trees are cut down or some more grow higher, I know exactly where my blind spots are....Anything in any other direction is in the clear...

Wayne replies:

I can think of two valid reasons to program horizon obstructions in a satellite tracking program:

1. So that tables predicting future satellite passes don't include passes that are actually unusable due to horizon obstructions.

2. To prevent an automated station from transmitting unnecessarily when the path is obstructed by terrestrial obstructions.  This is "good amateur practice".  It might also be necessary to conform to RF exposure rules if the obstruction is very nearby and has people in it.

My "blind spots" are all due to trees, not hills or buildings.  The attenuation varies with frequency, and varies seasonally depending on the amount of leaves on the trees.

Wayne Estes W9AE
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