Dish Antenna

Discussion in 'Homework Help' started by extremeads1, Apr 1, 2008.

  1. extremeads1

    Thread Starter Active Member

    Feb 10, 2007
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    Why the surface of the dish antenna is meshy & parabolic?....................its my homework question pls help me out ! thnx in advance
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
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  3. Dave

    Retired Moderator

    Nov 17, 2003
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    Why parabolic?

    Since the the EM waves have travelled a considerable distance (assuming they have come from a satellite) they are approaching being parallel. thingmaker3's link should explain the rest as a parabolic dish would focus in coming waves to a single point (typically the receiver).

    Why mesh?

    The mesh holes are small enough not to allow penetration of certain frequencies of EM waves. At the operational frequencies of sat comms this is certainly true. Mesh holes makes for less material, which makes the dish a) lighter, and b) cheaper.

    Dave
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
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    Lighter and cheaper are booth good. Lowered wind resistance is even better. When I was in the Navy, we had an old solid dish as part of a tertiary backup system. We had to re-align the old thing after every storm. The dishes with holes almost always weathered the storms without misalignment.
     
  5. Dave

    Retired Moderator

    Nov 17, 2003
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    How could I miss that one - it is probably the most important particularly in days gone by when the dishes where quite sizeable. Nowadays commercial dishes (like you Sky dish) are pretty small but it is still a consideration.

    Dave
     
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