# at what angle does sat signals hit the face of the dish?



## bigtiii (Sep 5, 2007)

Friend of mine who's in the know said they don't hit straight on the face but from a high angle.....

anyone know that approximate angle? Knowing this will help me keep that part of my dish (that is mounted low in my bushes/shrubs) free of blockage.

Southeast in Alabama


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## LameLefty (Sep 29, 2006)

bigtiii said:


> Friend of mine who's in the know said they don't hit straight on the face but from a high angle.....
> 
> anyone know that approximate angle? Knowing this will help me keep that part of my dish (that is mounted low in my bushes/shrubs) free of blockage.
> 
> Southeast in Alabama


Your dish is a concave surface, a conic section - an ellipse actually, with the LNB(s) mounted at the focus (or foci, sincer there is more than one). Do you remember any high school algebra?  Then angle is not completely constant. Just point your dish at the azimuth, elevation and title angles recommended by your receiver's setup screens and you'll get SOME signal. Fine tuning is tougher.


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## bigtiii (Sep 5, 2007)

LameLefty said:


> Your dish is a concave surface, a conic section actually. Do you remember any high school algebra?  Then angle is not completely constant. Just point your dish at the azimuth, elevation and title angles recommended by your receiver's setup screens and you'll get SOME signal. Fine tuning is tougher.


My tuning is fine.....I get very strong signals and only have one periodic obstruction via a crape myrtle tree limbs.

I simply want to know the angle, or range of angles I need to keep clear....don't want to prune unnecessarily. Right now my signals are all high 90s on almost every transponder on every sat.....

and no I don't remember much of my high school algebra


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## Lord Vader (Sep 20, 2004)

I don't know about the angle--much is determined by your dish's elevation relative to the birds themselves--but the signals hit your dish toward the top of its surface. I've seen pictures of this somewhere but don't exactly recall.


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## LameLefty (Sep 29, 2006)

bigtiii said:


> My tuning is fine.....I get very strong signals and only have one periodic obstruction via a crape myrtle tree limbs.
> 
> I simply want to know the angle, or range of angles I need to keep clear....don't want to prune unnecessarily. Right now my signals are all high 90s on almost every transponder on every sat.....
> 
> and no I don't remember much of my high school algebra


Keep the entire periphery of the dish clear in a straight line in the direction the dish is pointing. Prune that sucker waaaaaay back - they grow quickly. Make sure you add plenty of clearance for winds bending the branches during weather as well. At the time of my 5 LNB upgrade, I moved the location of my dish because a crepe myrtle had grown too big to keep trimmed back enough in only a couple of seasons.


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## obxterra (Jun 22, 2007)

I believe the old rule of thumb was 20 degrees above the LNB (center). That is above where it seems to be facing.

But, with these new "skewed" dishes I'm not certain.

I understand your predicament. I wouldn't have D* if I hadn't learned to do my own installs and alignment. The pro's always back out of my driveway shakin' their heads.


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## rirwin1983 (Dec 11, 2005)

obxterra said:


> I believe the old rule of thumb was 20 degrees above the LNB (center). That is above where it seems to be facing.
> 
> But, with these new "skewed" dishes I'm not certain.
> 
> I understand your predicament. I wouldn't have D* if I hadn't learned to do my own installs and alignment. The pro's always back out of my driveway shakin' their heads.


rule of thumb is 40 degrees of clear skys in the direction of line of sight, so if ur elevation is 40, maintain 80 degrees of clear sky.


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## bigtiii (Sep 5, 2007)

obxterra said:


> I believe the old rule of thumb was 20 degrees above the LNB (center). That is above where it seems to be facing.
> 
> But, with these new "skewed" dishes I'm not certain.
> 
> I understand your predicament. I wouldn't have D* if I hadn't learned to do my own installs and alignment. The pro's always back out of my driveway shakin' their heads.


Yeah I've always done my own installs and when not *allowed* by D* I tweaked and fixed what the so called pros did half arsed.

If your angles are even close to correct then I'm in good shape.....and probably have pruned one or two more small limbs than necessary....don't tell the wife eh?:grin:


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## AntAltMike (Nov 21, 2004)

When I looked into this previously, the offset feeds of single LNB, round dishes were 20 to 22 degrees below the centerline or boresight of the dish, so if you are targeting a satellite due south, the plane of the dish perimeter is 20 to 22 degrees steeper than the plane perpendicular to the boresight.

But with multisat dishes, in which the multiple LNB axis is tilted to match the row or "skew" of the targeted satellites, while the offset is still 20 to 22 degrees, that angle is rotated and would measure as less than 20 to 22 degrees in the vertical plane.

If you need to estimate whether a signal will clear a tree or other obstruction, you need to use a compass or map to determine the the azimuth, then measure or estimate the distance to nad height of the obstruction at that azimuth, then use an elecvation table and trig to determine whether you clear it. A confusing as that sounds, anyone who passed, or even failed, his Algebra II class should be able to do it.

You can't estimate clearances by eyeballing from the back side of an offset feed antenna, and it is even extremely difficult to eyeball from the back of a mesh, prime focus dish with a center feedhorn.


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## saryon (Aug 12, 2007)

Mine were having LOS issues for the 5lnb off my roof and were surprised the 3lnb that was there was even working due to pine trees in the path. After some discussion we decided it couldn't be worse than it was, so installed the 5lnb anyway. I've got high 90s on all 5 sats. Go figure.


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## Juppers (Oct 26, 2006)

You may want to check out this thread http://www.dbstalk.com/showthread.php?t=63277
And let the sun tell you which branches need to go.


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## RobertE (Jun 10, 2006)

You can use this link to locate the azimuth and look angle for just about any sat position in North America.

http://www.emantechnology.com/lookangle.asp


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## bigtiii (Sep 5, 2007)

RobertE said:


> You can use this link to locate the azimuth and look angle for just about any sat position in North America.
> 
> http://www.emantechnology.com/lookangle.asp


is that look angle from the center of dish or vertical post?


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## Rakul (Sep 3, 2007)

RobertE said:


> You can use this link to locate the azimuth and look angle for just about any sat position in North America.
> 
> http://www.emantechnology.com/lookangle.asp


Now that is a cool site for azimuth of a satalite, thanks RobertE!!!


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## carl6 (Nov 16, 2005)

bigtiii said:


> is that look angle from the center of dish or vertical post?


The look angle is relative to a flat horizontal reference. Look straight ahead = zero degrees elevation. Look straight up = 90 degrees elevation. If the satellite has an elevation of 38 degrees, that is 38 degrees up from horizontal. So from approximately the vertical center line of your dish, look up the indicated amount. That's where the dish is "looking" to see the satellite.

Carl


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## bigtiii (Sep 5, 2007)

carl6 said:


> The look angle is relative to a flat horizontal reference. Look straight ahead = zero degrees elevation. Look straight up = 90 degrees elevation. If the satellite has an elevation of 38 degrees, that is 38 degrees up from horizontal. So from approximately the vertical center line of your dish, look up the indicated amount. That's where the dish is "looking" to see the satellite.
> 
> Carl


Then I am back to have pruned too much. Thanks....that made the most sense on line of sight.

I'm at 37-48 degrees and I'm 100% clear sky. No wonder my signals are so strong.


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## vollmey (Mar 23, 2007)

carl6 said:


> The look angle is relative to a flat horizontal reference. Look straight ahead = zero degrees elevation. Look straight up = 90 degrees elevation. If the satellite has an elevation of 38 degrees, that is 38 degrees up from horizontal. So from approximately the vertical center line of your dish, look up the indicated amount. That's where the dish is "looking" to see the satellite.
> 
> Carl


Hey Carl,

I've done my own installs until this new slimline back in March. D* for the 101 Sat shows an elevation of 48 deg. here in Tulsa. Looking at my dish today after watching the video and reading the paper work is at roughly 38-39 deg to the center of the elevation nuts on the dish (Slimline). My 101 sat reading are from mid 80's to mid 90's with the 110 and 119 all in the upper to mid 90's. If I'm understanding this Sat. stuff the lower elevation and the right tilt is peaking the 119 sat. But the lower elevation is hurting the 101 sat. which in turn is lowering my 99 (local sat) and the 103B. My 99 readings are all in the mid 80's for the transponders that serve my HD locals. My 103B readings are mid to low 70's with a few mid 60's. Tell me if I'm wrong in thinking this but tiliting my dish back just a 2-3deg. should get that 101 sat and help with the 103B and 99??.

If D* recommends 48 deg. here in Tulsa and everything is plumb the elevation marks at the side of the dish from the center of the nut should at least be pretty close to 48 deg. right?? Not below 40 which it's set at now.


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## azarby (Dec 15, 2006)

vollmey said:


> Hey Carl,
> 
> I've done my own installs until this new slimline back in March. D* for the 101 Sat shows an elevation of 48 deg. here in Tulsa. Looking at my dish today after watching the video and reading the paper work is at roughly 38-39 deg to the center of the elevation nuts on the dish (Slimline). My 101 sat reading are from mid 80's to mid 90's with the 110 and 119 all in the upper to mid 90's. If I'm understanding this Sat. stuff the lower elevation and the right tilt is peaking the 119 sat. But the lower elevation is hurting the 101 sat. which in turn is lowering my 99 (local sat) and the 103B. My 99 readings are all in the mid 80's for the transponders that serve my HD locals. My 103B readings are mid to low 70's with a few mid 60's. Tell me if I'm wrong in thinking this but tiliting my dish back just a 2-3deg. should get that 101 sat and help with the 103B and 99??.
> 
> If D* recommends 48 deg. here in Tulsa and everything is plumb the elevation marks at the side of the dish from the center of the nut should at least be pretty close to 48 deg. right?? Not below 40 which it's set at now.


If the dish is set up correctly the rotation of the dish from horizontal should not matter as the dish is centered on 101. The only affect on 101 should come from azimuth and elevation. Rotation about the axis that is centered about 101 will have the most effect on 110 and 119 and minimal effect on 99 and 103.

bob


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