Trying to figure out if I can see the birds...

[madpoet]

Thanks guys. I just need to figure out how to mount about 10' of antenna mast on/off my deck. Bucket of concrete I guess

 

[Mr Tony]

the bucket o concrete works real good

 

[madpoet]

Ok gang, math time! Can someone tell me how to solve this one? At about 5' high I can clear my obstruction with a 45d angle. I need to figure out the mast height then to get to a 23d angle for the 119 bird. Can anyone give me a good idea how to figure this one out?

 

[rcwilcox]

seems like you all are doing this the hard way why not use
:
http://perso.numericable.fr/~gjullien/satellite.htm


you can use the sun or moon and just get a visual. I have used it in tight situations works great

 

[madpoet]

Um... wow did that site confuse me.

 

[carload]

Ok gang, math time! Can someone tell me how to solve this one? At about 5' high I can clear my obstruction with a 45d angle. I need to figure out the mast height then to get to a 23d angle for the 119 bird. Can anyone give me a good idea how to figure this one out?

Yes. Call the distance to the obstruction X. The formula for your mast height is:
5 + (X * 0.575)

Show Your Work: Assume for a moment (since you didn't say) that the obstruction is 100 feet from your mast and 105 feet high, giving 45-degree clearance when 5 feet up.

Considering the tangent of 23 degrees is about 0.425, then 100 feet of distance will let you clear 42.5 feet of obstruction. 105-42.5 = 62.5 (gulp) feet high, and that's how high the dish would have to be.

Plug in a 55-foot tree and a 50-foot distance to it. Now 50 feet of distance will let you clear 21.3 feet of tree. 55-21.3 = 33.7 feet high, which is still pretty high for a dish mount.

In general, the pole will need to be
(5 + X) - (X * 0.425).
Shuffle the parentheses and we get
5 + (X * 1) - (X * 0.425).
One more round gives us
5 + (X * (1 - 0.425))
which gives you the formula at the top.

 

[madpoet]

Hrm... that's depressing. Taller than I thought it would have to be. Thanks for laying it out for me.

-MP