Antenna Queries ?

Discussion in 'Wireless & RF Design' started by Anupam, Dec 24, 2008.

  1. Anupam

    Thread Starter New Member

    Dec 24, 2008
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    0
    I have some doubts
    1. Why Wave guide feeders are pressurized generally..???
    2.
    How Electrical length of an antenna is defined ?
    3. why
    Cassegrain feed is used with a parabolic reflector ?

    Plz help me know these answers..
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Waveguides are pressurized to keep moisture out. This reduces loss for receiving weak signals, and prevents arcing when using high powered signals, as in radar.

    The basic half-wave dipole is 5% shorter than an actual electrical half-wave in free space. This is the normal physical length. In English units, the physical length of a dipole is 468/f(Mhz)

    Cassegrain systems are designed to make the antenna physically shorter for a given focal length. They can be built mechanically stronger that way.

    eric
     
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