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Duplexer for my GSM active Repeater

Discussion in 'General Electronics Discussion' started by roltex_rohit123, May 20, 2012.

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  1. roltex_rohit123

    roltex_rohit123

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    Oct 12, 2009
    I am currently working to finish my project. I need to construct a duplexer for of 100db isolation at 900MHz frequency range. any suggestions/ help?
     
  2. davenn

    davenn Moderator

    13,671
    1,892
    Sep 5, 2009
    you are probably never going to get 100dB isolation

    the best you could expect even for something commercial would be around the 40 - 60 dB
    and the 60dB would be an extreme limit. 40 - 50 dB would be an excellent expected result

    Dave
     
  3. roltex_rohit123

    roltex_rohit123

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    0
    Oct 12, 2009
    the gain in the antenna would be around 50db so is it ok with 40-50db isolation?
     
  4. davenn

    davenn Moderator

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    1,892
    Sep 5, 2009
    50dB gain? what sort of antenna are you using a very large greater than 20 metre diameter dish ? :)

    Dave
     
    Last edited: May 21, 2012
  5. roltex_rohit123

    roltex_rohit123

    92
    0
    Oct 12, 2009
    the gain is from the module. I have an old dish antenna from my satellite TV diameter 1meter
     
  6. davenn

    davenn Moderator

    13,671
    1,892
    Sep 5, 2009
    a module is that the receive module ? transmit module ?
    what is your intended transmitter output ?


    a 1 metre dish will have a ~ 14 - 15 dBi gain at 900MHz

    you need to be more accurate in you descriptions so that misunderstandings dont happen :)


    a 20 element yagi will give ~ 17dBi gain at 900 MHz
    2 of them in phase will add another 3 dB of gain

    cheers
    Dave
     
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