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B Can orbiting lcds replace radio towers?

  1. Jun 24, 2017 #1
    Couldnt we put lcd type filters into orbit and modulate sun/moon light to produce high definition radio/tv? Obviously it would need to be large but it seems like it wpuld be much more efficient.
     
  2. jcsd
  3. Jun 24, 2017 #2

    Drakkith

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    What is an LCD-type filter and what does it have to do with television or radio when placed in orbit?
     
  4. Jun 24, 2017 #3
    Liquid crystal modulation, the type on lcd tvs. Modulating sunlight and using photodetectors to convert it into a digital signal.

    Im assuming it takes less energy to twist the liquid crystal molecules than the electromagnetic energy it could modulate.
     
  5. Jun 24, 2017 #4

    berkeman

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    Okay, after re-reading your thread title and your posts a few times, I think I understand what you are asking. Whew!

    So maybe you are asking if we could use transmission modulation of sunlight with a large LCD panel to repeat radio signals (like satellite radio) for receivers on Earth. Is that close?

    problems I see..
    • Would work only for the mid-day hours
    • Would be very limited in bandwidth -- do you know about what bandwidth a typical communication satellite deals with?
    • Would require receivers to be outside and be able to track very accurately the position of the optical repeater satellite
     
  6. Jun 24, 2017 #5
    I apologize. I thought it made sense. That "whew" made me laugh though.

    Im talking about replacing a radio transmitter with these sunlight modulators. Shouldnt the amount of solar energy be high enough that detectors dont have to be outside?
     
  7. Jun 24, 2017 #6

    Drakkith

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    Okay. I know what an LCD is, I just didn't know what an LCD-type filter is in this context. What are you filtering? Obviously sunlight, but what parts of the spectrum? The whole visible spectrum?

    Sure. This is trivial. But I don't yet see the connection to a TV/radio in orbit.

    I have no idea what this means. What detectors and what are they no longer outside of?

    You need to develop your idea or at least your explanation more. I don't even know the scale of what you're proposing, let alone any of the details of what this is even supposed to do.
     
  8. Jun 24, 2017 #7
    I know what he's talking about. I think reflection would be better than filtering. But I don't see how it could be better than what we already have.

    Two problems that come to mind right off are:
    1. Would only work when there is no cloud cover.
    2. Switching speed of LCDs would need to be improved by many orders of magnitude.

    The up-link signal would still need to transmitted using conventional methods. No savings there. And our current satellites are not that inefficient. They use sunlight for power.
     
  9. Jun 24, 2017 #8
    How would you use reflection?
    1. No idea how to address this problem. I don't even know how far outside the filter's "shadow" you could detect the transmission.
    2. It could be done with other types of electro optic modulators. I only proposed liquid crystal because they are cheap to make and light.

    I said radio specifically because you don't need an uplink signal. I'm not sure about T.V though.

    This is only a fun little thought experiment. I'm not planning on making this a reality. I would just like to know how feasible it is.
     
  10. Jun 24, 2017 #9
  11. Jun 24, 2017 #10

    berkeman

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  12. Jun 24, 2017 #11

    berkeman

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  13. Jun 24, 2017 #12

    Drakkith

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    Ah, now I understand what you're trying to do. Instead of sending out a microwave signal from a satellite that carries the information, you're re-directing sunlight and using a liquid crystal panel (or some other device) to switch the outgoing light on or off to modulate it with the information. Receiving stations would be "looking" at the satellite and receiving the modulated sunlight.
     
  14. Jun 24, 2017 #13
  15. Jun 24, 2017 #14

    berkeman

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    Glad you liked the humorous response. :smile:

    Why would the uplink be any different? You still need to get the information up to the satellite at 24,000 miles to be downlinked...
     
  16. Jun 24, 2017 #15

    Drakkith

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    Why not?
     
  17. Jun 24, 2017 #16
    Yes sir. I know it's not perfect.
     
  18. Jun 24, 2017 #17

    berkeman

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  19. Jun 24, 2017 #18
    The uplink could be amplified on the panel. It would be amplified again while modulating solar energy.
     
  20. Jun 24, 2017 #19

    Drakkith

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    It's already amplified on current satellites when it is received prior to processing/re-transmitting.
     
  21. Jun 24, 2017 #20
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