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Discussion Starter · #1 ·
I just have to share this because I've never heard of anything like it. I've had Directv for about 5 years now in 3 different locations. I've always had a problem with a tree within the line-of-site of my dish. I've recently moved near some serious wooded area on Fort Rucker, AL and after surveying the land I determined my dish would be pointing directly at a HUGE cluster of trees. Since I upgraded to HDTV, the installer came out with a new oval dish and after he determined the azimuth he had the same worried look on his face that I did. He aligned the dish anyway and hooked up his portable strength meter and it read 97% on all LNB's. It was the tail end of winter and the trees were still bare. You could see the sky through the trees. Maybe 50% sky, 50% tree branches where the dish was pointed. Anyway, the installer had never seen anything like it. He tightened everything up and before he left he said that when the leaves start growing in spring I'll have a problem with reception. Well here it is, almost May and you cannot see the sky AT ALL through the trees. Yet I still have 97% signal strength! My dish is mounted on a 4 foot pole and I even stood directly in front of it but it still kept pumping out a picture. Only when I cuffed my hand over the LNB did the signal terminate. We had a real bad storm last night. Tornado watch, hail, flooding, lightning, but I still kept pulling in a signal on all LNB's. Maybe there is some devine intervention. Maybe it's just my destiny to receive HDTV. Either way, I'm not complaining. But I just have to ask, is there anyone out there that is or isn't having problems with trees? I can't be the only one.
 

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I'd hazard a guess that you've got a bit of an optical illusion going on. That, or very thin leaves . Because of the design of DSS dishes, the signal path is not perpendicular to the dish. While it may LOOK like you're pointing directly at a tree, the satellite is actually several degrees higher. The signal takes a "banking shot" to the LNB.


If you turn your dish upside down, a line parallel to the LNB's feedhorn would come close to intersecting the satellite. If you envision that, you'll probably notice you're actually shooting through the very top of the trees, if at all.


The leaves do have an affect. My 101 dish does shoot through the top of a nearby tree. The receiver's signal strength meter can't react fast enough to show the effects, but on a windy day a scope will show the fluctuations. Fortunately, unless there's a LARGE storm cloud in the way, the signal loss isn't enough of an issue to compromise the picture.


Doc
 

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Discussion Starter · #3 ·
Interesting. I see what your talking about now. I remember when I was surveying the site my sat receiver stated the azimuth and the degrees (46 degrees). When I look up at a 46 degree angle, I just clear the top of the trees. I thought I was good to go but when the installer came out, the dish was pointed much lower, directly at the trees. I'm assuming that when you input your zip code in a sat receiver to determine where to point your dish, it's telling you the angle of the sat in relation to your position. But in fact, you'll aim your dish slightly lower to get a banking shot. Thanks for clearing that up for me.
 

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I just completed improving a customers signal on 119. Working with a tree trimming company I sat behind the dish with my sat-site from Gourmet Entertainment,this device allows you to look at the fairly exact location of the satellite in the sky. I was able to point out the branches to the trimmer in the tree(not my cup of tea!) a couple quick cuts and the signal jumped from 40 to 75 on the Sony HD200 inside.Here in Minnesota the angle to the satellites (especially 119) is low compared to Alabama. You can look over some pretty tall trees down there. Good luck
 

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Discussion Starter · #5 ·
When I was stationed in Dayton, OH I had to fight fight with a few tree branches. After moving to Alabama I did notice the angle was much steeper. Luckily, just steep enough to clear a monstrosity of trees in my backyard.
 

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Quote:
Originally posted by wjlane
... I thought I was good to go but when the installer came out, the dish was pointed much lower, directly at the trees.
The dish may be pointing toward the trees, but the satellite signal actually hits the dish at a much higher angle. See angle diagram.
 

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Discussion Starter · #7 ·
It all makes sense to me now. Before I always thought to myself why D* didn't locate the sats at a higher orbit. Now I realize they actually did. That's what I get for trying to figure out how everything works, just shut up and watch HDTV!
 

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Actually there is only one orbit possible if the satellite is to be geostationary. It must be over the equator at an altitude of 23,400 miles (from memory) and orbiting in the direction of the Earth's rotation. This results in an orbit that takes 24 hours to complete so the satellite always appears stationary from the ground. Anything else and it won't be stationary with respect to the ground which means antenna tracking and not always visible etc. I can rather imagine this orbit is getting crowded.


The only way one geostationary satellite can be higher then another is the azimuth selected for the orbit. If it's due South of you, 180 degrees azimuth, it will be the highest possible. The further East or West you go from that the closer to the horizon the satellite gets as you follow the orbital arc downward.
 
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