Aiming at true south

Discussion in 'C-BAND Satellite Discussion' started by Andyboy90, Sep 20, 2019.

  1. Andyboy90

    Andyboy90 Topic Starter SatelliteGuys Guru Pub Member / Supporter

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    I installed a new 10 footer a few days ago. I can get good signal from 87W-133W. The only satellite with any footprint here below 87W is 58W. Last year I tried the NHK tp on my 1.2m dish and was able to successfully lock it but with my 10 foot dish I cannot seem to lock onto 58W. I think the problem here might be that my true south calculation is off. My true satellite is 113W but I am not in the footprint for these sats and my closest sat is 107W which is 6 degrees off. Need a better idea to overcome this issue.
     
  2. Magic Static

    Magic Static FTA Geek Staff Member HERE TO HELP YOU! Lifetime Supporter

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    The hard part of this hobby, getting the dish tweaked the best it can. This is where a good meter with a spectrum analyzer and constellation display become very useful. Of course you also need the know-how and experience to use it properly. I have an advantage by using H~H motors. They provide a consistent number of counts per degree. My due south bird is also 113W but I'm at 114.0W. I move my dish to the top center of the arc using a square to measure it. I then move it one degree east (20 counts on my setup) and tweak the dish on 113W. I then verify with other sat locations. If I couldn't get 113W, I would move the 7 degrees (140 counts) to 107W and use that.
     
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  3. a33

    a33 SatelliteGuys Pro

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    Wenn you know the exact time at a certain date that the sun is at exactly south (i use Satellite Look Angle Calculator for that, with chosen "aimed satellite" exactly my longitude), then you can aim at exactly south.
    Put some tape or a string from top middle of dish to middle of LNB, and the shadow of that should be exactly in the middle of the dish at due south time. If the sun is shining, of course...
    After that, you can check if you follow the arc properly.

    When the sun doesn't shine, or you're not at your dish at the sun-at-due-south time:
    A.) with USALS motor:
    - set the motor and /dish angles, and align everything exactly.
    - then move the motor with USALS (with correct coordinates) to the satellite longitude of your choice.
    - rotate the whole mount till you find your satellite.
    This way your setup's south will be at due south, using a not-due-south satellite.

    B.) with diseqc 1.2:
    - set the motor and /dish angles, and align everything exactly.
    - let some calculator calculate the "(modified) hour angle" from due south to the satellite of your choice.
    - using the width measure of the dish: calculate how much movement forwards/backwards of the sides of the dish corresponds to that hour angle rotation (simple goniometry).
    - move your dish to that position with your motor or actuator.
    - then rotate the whole mount till you find your satellite.
    This way your setup's south will be at due south, using a not-due-south satellite.
    (I have an approximate calculator for the modified hour angle calculation (will try to make a precise calculator someday?), so I maybe can help with steps two and three above.)

    Does this help?

    BTW: Are you indeed using MODIFIED motor angles?

    BTW2: There seem to be people that use the polar star for finding the due north/south axis.
    As the polar star is not EXACTLY above the north pole, I would think this method might be not exactly accurate. But I've no experience with that.
    And it doesn't take into account the modified motor axis angle, so that's not good also!


    greetz,
    A33
     
    #3 a33, Sep 20, 2019
    Last edited: Sep 20, 2019
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  4. Andyboy90

    Andyboy90 Topic Starter SatelliteGuys Guru Pub Member / Supporter

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    Thanks for the inputs guys. I did find my true south (most likely inaccurate) today and tried the modified inclination and declination but it has made arc tracking worse. I searched up an the arc tracking diagram posted on this site a few years ago. Here is what I did. I aimed the dish to true south and then started moving the actuator east to locate 91W. To get good strength here I had to increase the elevation angle and when I went to 101W I had to decrease the elevation angle to get the best signal. It makes me come to the conclusion that I need to decrease declination angle to better track the arc and move the mount to west. Attaching a picture for reference.
    [​IMG]
     
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  5. a33

    a33 SatelliteGuys Pro

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    If this picture is your situation now, then true south is off, AND elevation/declination is off.

    Pole is plumb, east/west-wise, I assume?
    Did you set due south with < pole - motor axis - dish > exactly aligned ("zero-position"), as needed?
    Which method did you use to find the due south?

    Modified angles: Did you set the angles with an inclinometer (app), or with hardware scales on mount/dish?
    For Edmonton: modified axis elevation about 35.81, modified declination offset about 6.99, total dish elevation 28.82 degrees. Did you use about those values?

    Greetz,
    A33
     
    #5 a33, Sep 21, 2019
    Last edited: Sep 21, 2019
  6. Andyboy90

    Andyboy90 Topic Starter SatelliteGuys Guru Pub Member / Supporter

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    I didn’t have much time yesterday to use advanced methods to find true south. I eyeballed it with my fence line as a guide. I have played with everything but my declination. I think I need to move the dish mount west and raise the dish up a bit by lowering declination angle. The pole is plumb and I am using a semi- professional digital inclinometer to measure the angles and also I am using the modified calculations. Also you are dead on about the declination angle but my inclination angle is 53.6
     
  7. Magic Static

    Magic Static FTA Geek Staff Member HERE TO HELP YOU! Lifetime Supporter

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    Don't put too much effort into adjusting declination. It is not the problem with tracking the arc. Some dishes don't have adjustable declination, like my AJAK mounts and the BirdView mounts. The AJAK has selectable bolt holes on the dish ring for declination one degree apart. No fine adjustment. The BV is set at the factory. Some guys still try and adjust it with shims on the dish attaching points. But declination doesn't change signal strength as much as you think. On a dish like yours I would measure the declination angle with the inclinometer , set it and forget it. ;)
     
  8. a33

    a33 SatelliteGuys Pro

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    So if with 'inclination angle' you mean "90 minus axis elevation angle", you would be located at about 53.0 North? (To get the total dish elevation of 29.4.)

    I agree with MagicStatic: set the declination offset angle once, and then leave it untouched after that (unless there are specific indications that something is very wrong in the declination).
    Finetune with motoraxis elevation (on 'difficult' satellites).


    Oops! That is more than the maximum correction of modified motor angles, as compared to 'traditional' motor angles!
    I would guess with a 10-footer that would be noticable?!? (I have only a 100cm Ku dish.)

    greetz,
    A33
     
  9. a33

    a33 SatelliteGuys Pro

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    Sun at true south today at 113W will be at 19:24:42 UTC.

    So subtract the hours difference of your timezone from UTCtime, and you have your local sun-at-due-south time.

    Greetz,
    A33
     
  10. Andyboy90

    Andyboy90 Topic Starter SatelliteGuys Guru Pub Member / Supporter

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    I didn’t get a chance to do anything today but I am on my days off starting tomorrow. I recently found out that Anik 111.1W has an active TP so that will greatly help me in aiming my dish
     
  11. a33

    a33 SatelliteGuys Pro

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    That's nice.
    Remember that if you can set it right from the start, you hardly have have any timeconsuming finetuning to do.

    If you need more sun-at-due-south dates for the coming days, and maybe more precise than for 113.00 West, just ask!

    BTW This time "true south today at 113W will be at 19:24:42 UTC" was for Sunday 9/22! (While I wrote my post, we in Europe were already after midnight sat/sun.)

    Greetz,
    A33
     
  12. Andyboy90

    Andyboy90 Topic Starter SatelliteGuys Guru Pub Member / Supporter

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    I used 111.1 to set true south for my dish and the signal is stronger than ever on every satellite.
     
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  13. Conway

    Conway SatelliteGuys Family

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    What kind of signal are you getting on METV on 101 West with your 10 footer?. I did my alignment myself as well using the noon day sun. I am getting 12.5 db on METV.
     

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