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Signal Booster circuit for cell phone

Discussion in 'Radio and Communications' started by roltex_rohit123, Feb 23, 2012.

  1. unclejed613

    unclejed613 Well-Known Member

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    looks like you're stuck with a passive system, which actually is good, because you won't need a duplexer (ir diplexer.... the differnce between the two is a minor one)...
    if you build a high gain antenna, and place it in a spot where signal is good, then locate another high gain omnidirectional antenna in your house, and connect the two with low loss coax (look at the specs for loss per 100m at 1Ghz, choose the one with the lowest loss, that you can afford to buy). the loss of the coax run should be less than the signal loss at your location. if you lose 20db of signal going from where you want to place the outside antenna, to inside your home, then the cable loss should be much lower than that. let's say the cable length will be 50m, and the cable loss is 20db/100m (that's a ridiculously high number for good cable, but it will illustrate what i'm talking about), so that's a 10db loss for 50m. that's a net gain of 10db though, because inside your house was a 20db loss to begin with. with 9 or 18db gain antennas, the margin gets even better.
     
  2. trash

    trash Member

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    you can find duplexers in old mobile phones already tuned to the correct bands.

    I can't help but think there is enough parts in two old phones to accomplish the task, amplifiers and all.

    If those old phones are old nokias with external antenna sockets then you can enable the nemo, nokia engineering mode
    which you can use to test your antenna system.
     
    Last edited: May 20, 2012
  3. roltex_rohit123

    roltex_rohit123 New Member

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    i have an old nokia but how can i enter engineering mode?
     
  4. dave

    Dave New Member

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  5. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Look it up on line.
     
  6. trash

    trash Member

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    nokia logo manager and a programming cable.
    As pyro said, the information is online.
     
  7. roltex_rohit123

    roltex_rohit123 New Member

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    Guys, I think I've got an easy solution.. RFMD has come to my rescue. They have suggested me a product. RFPA2126. It seems to be the correct one... what do you say?
     
    Last edited: Aug 29, 2012
  8. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    OK that may help you boost your transmit but how are you going to boost the recever?
    See post #2 of the thread.
     
  9. roltex_rohit123

    roltex_rohit123 New Member

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    View attachment 66898 the commercial circuits use two modules of same kind but in reverse order. Some one at another forum posted me a picture of the booster commercially available booster to demonstrate the circuit. they said you have to maintain the antenna distance, otherwise it creates an oscillator. I am thinking of the same. the picture shows a module of repeater booster. I am trying to reduce the circuit by the component of RFMD
     
    Last edited: Sep 2, 2012
  10. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    The RFPA2126 is a liner power amp for transmitting.
    This is just one part you will need much more for a complete system.
    You will need a preamp to amplify the receved signal.
    Its a two way radio and you need to amplify both the input and output.
     
  11. unclejed613

    unclejed613 Well-Known Member

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    and it's a 2 way radio that does automatic T/R switching many times per second, so a booster has to do such switching very quickly, and automatically to avoid losing portions of data packets...

    theres a 50Mhz separation between the transmit and receive channels in the cell phone bands, so it would be possible to have an active amp and preamp simultaneously operating as long as the filters that route the signals through the booster have a sharp enough slope
     
    Last edited: Oct 23, 2012

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