Sun outage on undersized dish

Discussion in 'Free To Air (FTA) Discussion' started by polgyver, Oct 10, 2018.

  1. polgyver

    polgyver Topic Starter Creative Tinkerer

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    Some time ago I wondered what happened to Sun outage, since I did not notice major interruption in watching programs, except reduced "Q" (quality) percentage, which lasted a few minutes( I was using 39" dishes)
    Today I tried to document the Sun outage, by setting up smaller dish and using 3 screens.
    10 annotated photos follow ;
    thumb_IMG_2013_1024.jpg thumb_IMG_2017_1024.png thumb_IMG_2018_1024.jpg thumb_IMG_2020_1024.jpg thumb_IMG_2021_1024.jpg thumb_IMG_2022_1024.jpg thumb_IMG_2024_1024.jpg thumb_IMG_2026_1024.jpg thumb_IMG_2029_1024.jpg thumb_IMG_2031_1024.jpg
     
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  2. RimaNTSS

    RimaNTSS SatelliteGuys Pro

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    I do not have time ( and maybe motivation) this year for experiment. But 3 outages before I programmed one of my Enigma2 receivers with 1.2m motorized antenna (only position 28.5*E was from bigger dish) to follow the arc and record all reception data. That was from 7AM till 17PM. From recorded data I've built this graph where 4eeffect of outage is clearly seen. ScreenHunter_207 Mar. 02 22.29.jpg
     
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  3. Cham

    Cham VE4GLS
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    Interesting spikes on 75e and 46e. Wonder what causes that?
     
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  4. RimaNTSS

    RimaNTSS SatelliteGuys Pro

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    Those spikes remind me the very middle of the hurricane were is usually calm ;)
     
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  5. polgyver

    polgyver Topic Starter Creative Tinkerer

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    Just a little speculation...
    Measured on screen, the first stretch from 90* to 75* is 22.5 mm long, it covers : 90 - 75 = 15* . 15* divided by 22.5 = 0.66 deg/mm
    Second stretch, 75* to 46* is 70.5 mm long, it covers : 75* - 46* = 29* . 29* divided by 70.5 * = 0.41 deg/mm
    Looks like the spike width is approximately 1 mm, roughly 1/2 * (degree).
    This is the width of Sun (or, Moon) we see from Earth, measured in degrees.
    Is it possible, that the data recorder was more sensitive to Sun's edges, than to its center ?
    Your comparison to calmness in the hurricane center is quite accurate...
    thumb_IMG_2034_1024.jpg
     
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  6. RimaNTSS

    RimaNTSS SatelliteGuys Pro

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    I do not know what was that about the spikes. Perhaps it is just issue of false reading from the receiver's interface. I just examined the data and see that it was just one reading per satellite among other readings. Data was taken ~8 second between readings and only one reading ubnormal. So, there were no "hurricane eye" ..... unfortunately. ScreenHunter_766 Oct. 11 20.30.jpg
     
  7. harshness

    harshness SatelliteGuys Master

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    Why would the size of the dish matter?
     
  8. RimaNTSS

    RimaNTSS SatelliteGuys Pro

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    Cuz bigger the size the narrower the beam, so bigger antenna has bigger sun-outage effect.
     
  9. harshness

    harshness SatelliteGuys Master

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    The sun is much larger than the relative speck that is the satellite. I guess it is a matter of the interval as opposed to how much.
     
  10. RimaNTSS

    RimaNTSS SatelliteGuys Pro

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    I meant the beam of the satellite system, bigger dish has narrow beam and therefore effect of the outage is more visible.
     
  11. harshness

    harshness SatelliteGuys Master

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    You're calling it "more visible" and I'm saying longer duration. When the sun passes behind the satellite, it doesn't matter how big your dish is, the satellite signal will be swamped for pretty much as long as the sun's disc is "in the beam". On a smaller dish, it picks the sun's "signal" up earlier and loses it later because its beam is wider but I doubt that the interference is any more intense as "more visible" suggests. Of course if the sun is well above or well below the satellite, that's a different story and it could be a matter of intensity as the big dish may not "see" the sun at all in it beam.

    I never thought much about it myself as I'm not usually watching (or even recording) TV when this happens.
     
  12. N5XZS

    N5XZS SatelliteGuys Pro

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    Don't you think is more notable on C-band than Ku on sun's signals since the wavelength is longer on C band and the noise floor is much higher than on Ku?:rolleyes:
     

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