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Being Beaten By Dish Alignment

Discussion in 'DIRECTV Installation/MDU Discussion' started by pjschwartz, Jul 16, 2012.

  1. pjschwartz

    pjschwartz AllStar

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    Jul 13, 2007
    I am having a heck of a time obtaining peak signal strengths. My set up is a HR20-700 and HR22-100, with a chimney mounted WNC Model BAU slimline dish.

    I had originally installed the slimline dish in 2008. My signal strengths on 110 and 119 are in the mid nineties, and also have have applicable spot beam transducers readings on 99 and 101 in the mid to high nineties. However, my conus beam readings for 101 are only in the mid eighties and, and for 99 and 103, in the high seventies to mid eighties.

    I thought these lower strengths were typical for this area of the country (south of Minneapolis, MN in Zip Code 55378), but I was recently at a friend's house and his new Directv installation is showing everything in the mid to high nineties.

    Using an Acutrac 22 Pro, I have attempted to improve my signal strength, using the dithering process, without success. I have also done the following without achieving increases in signal strength.

    * Replaced all coax line between the receiver and disk (RG6 rated up to 3 Ghz)

    * Replaced and used DirecTV approved F connectors.

    * Replaced the LNB (now a 5 LNB SWM)

    * Bypassed the sat line surge protector (and there is only 1 four way splitter between the dish and receivers).

    * Re-plumbed the EZAlign mast (dead center in the built in bullseye level and level placed on mast)

    * Although there are taller trees 100 or so feet from the dish, I have confirmed that they are not in the line of sight, both via compass/inclinometer and the Dishpointer AR app on my iPhone.

    The dithering process isn't really that hard, so I am not sure why I can't peak my 99, 101 and 103 signals (conus) into the 90s?

    1) Although I am not seeing any visible damage to my dish, could it be defective [I did notice that when placed a level on either the top or the bottom of the base of the back assembly, it was not showing level (even thought the EZALign mast was spot on level)]?

    2) How far below the line of sight elevation of the dish can trees have an impact on signal strength?

    Help ! ! ! Any tips or suggestions would be appreciated.
     
  2. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Two things come to mind:

    1. a bent reflector, even if you can't see it can do this.
    2. SWiM has shown to drop my receiver "numbers" by almost 10 points. I've repeated checking this out over the years as I first noticed it when testing the first SWM8, which was mounted a good 50' form the dish, so the dish didn't change at all. I've tried several dishes, alignments, and always get the same results. Recently I moved to a SWiM-16, so had to swap my SWiMLNB to a legacy. Tweaked the dish to the new LNB, looked at the numbers and then watched them drop again as I ran through the -16.
     
  3. pjschwartz

    pjschwartz AllStar

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    Jul 13, 2007
    Does anyone know, if my dish elevation is at 38 degrees, how many degrees above and below that setting my LOS needs to be clear of obstructions in order for signal strength not to be impacted?
     
  4. djrobx

    djrobx Godfather

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    As others have noted, it's probably a warped reflector.

    I had one that looked fine, but it just wasn't possible to peak most 99/103 transponders over 30. New reflector, same LNB & pole, and it worked fine.
     
  5. harsh

    harsh Beware the Attack Basset

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    It isn't a matter of angle at all. It is safe to think of the satellites as being infinitely far away so you need to make sure that the obstructions don't come within half the height (or width if the obstruction is to the side) of the dish from any and all satellite beams.

    Don't lose sight of the fact that the singular elevation for the dish only applies to 101W. The elevations for the other satellites are necessarily higher or lower so you should run 99W and 119W through dishpointer.com (as individual satellites) so see what the lowest elevation is.
     
  6. pjschwartz

    pjschwartz AllStar

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    Jul 13, 2007
    I have never heard of the half height rule.

    Using both compass/inclinometer and Dishpointer AR on my iPhone (confirmed via at least a 1/2 dozen checks), the 99W through 119W are all definetly above obstructions (in this case mature trees). However, I don't believe by half.
     
  7. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    I'm not sure what was meant by that statement.

    I used to live in a very wooded area and had to move my dish several times to get the LOS back.
    My last was to lower the dish just a foot or so to be able to get an LOS from under some tree branches that had grown.

    "Maybe" the half height was meant as half of the dish diameter, so it could be as little as a foot with a slimline, :confused:
     
  8. pjschwartz

    pjschwartz AllStar

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    Jul 13, 2007
    Good point. I was thinking he meant 1/2 the height going from a zero degree angle out from the dish to the obstruction . . with the height then being measured from that point on the obstruction up to the angle of the satellite coming into the dish. However, if am doing my math correctly, in the case of a 38 degree elevation, that would require an open line of site from 19 degrees through 57 degrees elevation.

    Considering though the size of the dish, that doesn't make sense.

    Maybe another way to present my question is, should I assumme that I do not currently have an LOS issue if Dishpointer AR is showing that the 99 through 119 birds are appearing in the sky, and not behind a tree?
     
  9. pjschwartz

    pjschwartz AllStar

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    When the Directv installers do a LOS survey, how much unobstructed view are they requiring between the satellite and structures underneath the beam?
     
  10. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    I haven't checked what DirecTV calls out lately, but it used to be something like 5 degrees to allow for growth.
    Not sure what the Dishpointer AR is showing, but as long as it isn't "just clearing", then you're "golden" for now.
     
  11. Michael H..

    Michael H.. Member

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    May 31, 2007
    My guess is that your dish skew angle is positioned too far clockwise.
    Your reference starting point for gross positioning is the 101° sat.
    You need to point (Azimuth and Elevation) and peak these readings.
    From the 101° sat, you then orient the skew to point and peak the 119° sat (for a 5 LNB).
    This is a skew fine adjustment.
    The gross skew angle was already set at the beginning, and I believe it was slightly too CW to begin with.

    For geographic latitudes ranging from 24°N to 49°N, and longitudes nearest the middle of the range from 67°W to 125°W, the appearance of the sat "arc" tends to become "more elliptical" when viewed from the dish location.
    The dish curvature is designed to a nominal arc, the appearance of the arc at the dish geographic range center, 37°N 96°W.
    From your location, the sat arc appears to arc downwards to the west from the 99°W sat to the 119°W.
    The dish nominal arc should intersect your slightly more elliptically viewed arc at the 101°W and 119°W sats that you have peaked (two points determine a chord/line).
    The intermediate sats, 103°W and 110°W, will be offset slightly above the dish nominal arc, and the 99°W sat will be slightly below.
    This delta becomes more pronounced the further the dish location from the geometric center, but will still enable worst case 99°W and 103°W sat signal quality readings >85.

    If you were to start out your alignment by locating and peaking the 110°W (instead of 101°W) sat, and then the 119°W sat, this would result in a skew position slightly CW of the desired 101°W / 119°W alignment.
    99°W, 101°W and 103°W would all be below the dish nominal arc, and be impossible to then peak to minimum specifications.
    Not saying that you performed these steps, only that your signal numbers reflect this configuration.
    If you were to leave the CW skew configuration (not recommending you do), and adjust the azimuth and elevation (tilt down) to peak the 101°W sat, then 99°W and 103°W would be in their correct relative orientations with respect to the 101°W sat, slightly below and above the dish nominal arc respectively, however with larger displacements, but 110°W and 119°W would be substantially above, and likely out of tolerance.
    You could dither 99°W and 103°W, possibly within tolerance, but not optimally peaked for your location (in the 70's).
    This is equivalent to alignment of a 3 LNB SlimLine and why the 3 LNB is much easier to align... much more forgiving when you are concerned with 3 sats only 4° apart than 5 sats 20° apart.
     
  12. AntAltMike

    AntAltMike Hall Of Fame

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    Even when you have an "unobstructed" path from the satellite to the dish, having a solid object a few degrees off the boresight contributes "ground noise", which can calculably and measurably lower the signal to noise ratio. In another forum, back in an era when S/N margins were smaller than they are now, someone actually mathematized this for us.

    For seat of the pants calculations, you need to at least have some idea how sharply the "off boresight" rejection develops. Since DBS satellite dishes are shallow dishes, they do "see" off-boresight noise sources more severely than do the big, ugly C-band dishes.

    If I were a worrywart - which I'm not - I'd probably want to make sure that there were no building obstruction ground noise sources within 5 degrees of the transmission path.

    As far tree growth margins are concerned, the measure of that margin should be linear rather than angular.
     
  13. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Boy, has this thread gone down a path of complexity.

    "Finding 101" just shouldn't be this hard.
    Start with the "out of the box" settings for EL, AZ, and tilt.

    Move the dish slightly right/left and then repeat with a slight up/down change.
    Make sure you're not screwing up true north with magnetic north.

    Once 101 is found, "then" tilt tweaks for 119, and fine tuning [using the adjusters] for 99/103 dithering.

    It just doesn't need to be this hard.
     
  14. HoTat2

    HoTat2 Hall Of Fame

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    Their "Field Operations Training" manual pub. in 2010 states an additional 10 degrees in azimuth to either side of the end satellites for clearance. But doesn't mention anything for elevation.

    But I assume its the same.
     
  15. AntAltMike

    AntAltMike Hall Of Fame

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    "Move dish three degrees." :lol:
     
  16. harsh

    harsh Beware the Attack Basset

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    That is indeed what I meant. The beam needs to be able to hit the entirety of the reflector, not just some subset of the surface.
     
  17. pjschwartz

    pjschwartz AllStar

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    Guys, thanks. Based on your input, I believe I truly have an unobstructed LOS.

    I'm down to my last theory that my issue is due to a warped dish or defective back assembly. A new slimline is on it's way via UPS.
     
  18. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    That's the hardest to find, as it takes a swap to know, "but" it would need to be fairly seriously "hosed" to get nothing off of the 101.
     
  19. pjschwartz

    pjschwartz AllStar

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    I am able to get in the mid 80's on 101 (conus) . . . thought that was great for Minnesota until I saw a friend's new installation was getting in the 90's for 99, 101 and 103 conus . . .

    If the new dish doesnt do it, I might have to bite the bullet and ask DirecTV to have a tech come out . . .
     
  20. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    That's somewhat hopeful that it is a reflector problem.
    Do read my first post in this thread, as your friend might not be on a SWiM.
     

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