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Guest Message by DevFuse

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Installer states no LOS. Should I pursue further?


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84 replies to this topic

#81 OFFLINE   bigglebowski

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Posted 01 August 2011 - 05:15 PM

But the issue through that gap, 160' (across the street) away there is a pretty tall tree that causes LOS issues. And that tree is pretty much smack in the middle of the gap that we would need to point to in the first place.


Go to the site dishpointer.com and put your location (even if its just somewhere in town) choose the 99, 101, and 103 sats. They have an option to figure out what distance an item that is in the LOS and how much clearance you need to overcome an obstacle at a given height. The reference will be from the ground so dont forget to compensate the height at which its mounted like 20' up on the roof of house.

You will find that at 160' out you can only clear about a 30' object, on the roof maybe you clear 50'. Do you know how tall the tree is now, not to mention how much taller it will get? Even if you go to the as far back in your yard you still may not clear it.

A simple clinometer LOS tool if you have an iphone is to get an app like the carpenter ones that show the angle at which the phone is tilted. Make sure you calibrate it for approx level like from a wall in your house that you know is level. Then add something that is straight like a ruler to the long edge of the phone, if you want put a small loop on the end of the ruler like to make like a target sight. Now take the phone around with a mirror so you can see the angle or get someone to watch it and tell you when the angle says 9-10 degrees. When you look through the sight you will see the obstacles in your LOS.

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#82 ONLINE   harsh

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Posted 01 August 2011 - 06:00 PM

Trigonometry tells us that a distant tree can be no higher than D x sine(look angle).

At 9 degrees, the sine is ~0.15643 so at 1000', a hill can be no taller than 156' above the dish elevation. At one mile, an obstruction must be less than 825' higher than the dish.

Assuming that the tree is 160' away, it can be no taller than 25' for the foreseeable future.

It seems like the local and distant trees make up something quite a bit like a peep sight aimed at 101W.

Too often we enjoy the comfort of opinion without the discomfort of thought. -- JFK


#83 OFFLINE   eakes

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Posted 01 August 2011 - 06:22 PM

To be mathematically correct the expression is D (distance) x tangent (look angle) = H (height). At small angles the error is not much but do the calculation for 45 degrees and it's a different story!

#84 OFFLINE   joe diamond

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Posted 01 August 2011 - 09:29 PM

Trigonometry tells us that a distant tree can be no higher than D x sine(look angle).

At 9 degrees, the sine is ~0.15643 so at 1000', a hill can be no taller than 156' above the dish elevation. At one mile, an obstruction must be less than 825' higher than the dish.

Assuming that the tree is 160' away, it can be no taller than 25' for the foreseeable future.

It seems like the local and distant trees make up something quite a bit like a peep sight aimed at 101W.


Ah, I love it when you talk dirty!

I couldn't remember the trig but the point is...as you correctly point out, even small stuff that would be ignored further south is a deal breaker in the land of ten degrees elevation.

This is a job for a transit or a locklevel. Clinometers are for ball bark estimates where you have plenty of room.

After taking a horizontal shot on a correctly set transit....crank up ten degrees and hope for blue sky.

Joe

#85 OFFLINE   jdspencer

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Posted 02 August 2011 - 07:32 AM

How far back can you go from the problem tree? This may help sighting over that tree. And of course you could always install a tower.
Here's a short one.
http://www.solidsign...nna Towers&sku=

Not sure how you would you align the dish.
DirecTV since '96, Waivers for ABC, CBS, NBC, & Fox, HR23-700 & HR24-500/AM21, using ethernet based MRV.




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