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Signal Booster circuit for cell phone

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

  1. roltex_rohit123

    roltex_rohit123 New Member

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    hi All!!! I am currently in a very remote area and here cellphone signal sucks!! I am thinking of building a small 5-10 watt amplifier for myself for improving the signal. the signal is good outdoors but indoors it is worst. any helps please? i am new to the communication side. i have a fair idea of amplifier classes, basic electronics and microcontrollers.
     
  2. davenn

    davenn Active Member

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    A bi directional amplifier is a pretty serious undertaking and unless you have some excellent RF electronics building skills
    not a project you are likely to handly.

    Initially you would have to figure out which cell band your phone is using to the local cell tower.
    900MHz or 1900MHz else you are going to have to build an amp for each band
    I say bi-directional, as there's no point building a TX amp if you down also improve the receive signal level.

    Have you done any google searching for cell amplifiers ? maybe there's commercial stuff available ?

    Dave
     
  3. roltex_rohit123

    roltex_rohit123 New Member

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    I want to build for each of 900, 1900, 1800 and 850 band. may be seperate cost is no matter, but i need some help from you. commercial stuff is very costly in indian currency and not affordable. moreover I am learning communication electronics and would like to develop it as my project.
     
  4. dave

    Dave New Member

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  5. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    Since you have decent reception outdoors, but not indoors, you might consider an antenna fix.

    They sell car window antenna adapters ("Passive Antenna Receiver") that are designed to improve in-car signal strength.

    Google "Cell Phone Car Mount Passive Repeater Antenna".

    Be a WHOLE lot cheaper. And easier.
     
  6. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Look into "Cantena"s.
     
  7. unclejed613

    unclejed613 Well-Known Member

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    the "passive repeater" is probably the best approach. one antenna outdoors coupled to an antenna indoors by a piece of coax cable. simple, inexpensive and effective. the dipole antennas can even be made out of the coax cable itself by stripping 1/4 wavelength worth of insulation off the end, and folding back the shield braid over the outside of the cable. this leaves 1/4wavelength of the center conductor showing, and 1/4wavelength of the shield braid folded back over the insulated portion of the cable, and this forms a 1/2wave dipole.
     
  8. trash

    trash Member

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    Ok, first thing is that 5 to 10 watts in the cell phone band is a MASSIVE signal.
    Your in India and I'm unfamiliar with how they deal with interference there, but in Sunny and occasionally wet Australia we have ways of dealing with such trouble when it occurs.

    Don't push him Dave else we'll be importing them from India next week. You laughed at the chinese last century and now they build the base stations ! :D

    The first thing to consider is ..... damn... there's so much to consider. You're biting off a lot more than you can chew.
    Ok... as mentioned, a passive repeater system is much simpler and just as effective.

    Using high gain antennas is the best choice.
    If it's just an indoors problem, then you're much better just finding a car cradle kit for the phone and use a high gain external antenna like a yagi.

    800-960 and 1800-1950 is a better way to describe them.
    Recycling old mobile phone tower equipment is a place to start and learn. If you can find an old TMA then you're 80% of the way there if you really must attempt it.
     
  9. unclejed613

    unclejed613 Well-Known Member

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    using a power amp is not the solution anyway, since you will need a power amp and a receive preamp with a pair of diplexers. you only have one antenna connection on the phone, and the phone does transmit/receive switching internally, and many times per second (so a transmit/receive relay is out of the question). an active solution (amplifier) comes with a very complicated (and expensive at these frequencies) set of problems to be solved.
     
  10. JMW

    JMW Member

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    Try a US company named Tessco. They offer cellphone boosters. They used to be quite common, before the massive build out of towers.
     
  11. trash

    trash Member

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    Deleted Off Topic
    Moderation.
     
    Last edited by a moderator: May 10, 2012
  12. roltex_rohit123

    roltex_rohit123 New Member

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    what would drive the antennas?
     
  13. roltex_rohit123

    roltex_rohit123 New Member

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    I have searched for a few components
    BFG410W
    BGA416
    MAX2235
    BFP650
    MAX2056
    MAX2057( both these 56 and 57 products for all band amplification)

    Thank you.

    sorry for the 5-10 watt!! I now realise i dont have to help the whole locality. 1 watt is too good.

    the products say it is a 20-30db gain. it is good for me
     
    Last edited: May 18, 2012
  14. trash

    trash Member

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    Start simple, work out where you can get any signal first.

    If you can get a weak signal at your location or house etc, then half the work is already done.
    All it will require is something simple like a good antenna on a pole and some coax.

    Find out where the base station is in relation to where you are. This may help work out a solution too if you have a hill or a building in the way.
    Something as simple as a beam bender may be all you need.

    More power just isn't going to work, cellular phone systems don't work like that.
    If you present a stronger signal to a base station it will consider that you are in a good reception area and it will reduce it's power to compensate.
    By transmitting more power you will be making things worse, not better.

    Do you know what sort of mobile phone system is being used ? AMPS, GSM, CDMA, WCDMA ?
    Do you know where the nearest or most accessible mobile phone tower is and how far away it is ?
    And do you have more details on where you are in relation to that tower and any obstructions?

    I've just had a look at Nagpur on google earth and the city appears to be relatively flat with a few surrounding hills on the edge of town.
     
  15. roltex_rohit123

    roltex_rohit123 New Member

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    The tower is not known but I can find it out from the cellular company. the obstruction are mainly buildings. My apartment is on the back side in a concrete jungle. and to place an antenna is just running the cable 40 feet down from the top floor. My phone is GSM 900 MHz. I am trying to make this for my final year project. I am currently in midphase of third year. Sufficient time means good chances for improvement. so it is quite imp to make this a good one.
     
  16. trash

    trash Member

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    It sounds like the best solution and quickest is to put an omni antenna on the roof of the building. The same as a car kit antenna or a high gain base station antenna. If it's a project, then I would consider putting the effort into designing a high gain ~9dBi base station antenna.

    Use a good coax and connect it directly to the phone with the proper MMCX connector or use a car cradle kit.

    If you were to build an amplifier you would need to consider that it is full duplex, and requires filtering and isolation in each direction and still you need to go to the effort of constructing a reasonable antenna system for it's use.
    The simplest solution is often the best. The effort is better spent designing and building a good antenna and sourcing low loss coax.
    For the 10 to 15dB you seek in an amplifier, this is much simpler to build into a high gain loop yagi or phased array.
     
  17. roltex_rohit123

    roltex_rohit123 New Member

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    i cannot connect anything to my phone. my whole family has to use the resultant. the base station antenna I don't think are allowed to be used in india by general public. I have designed a good yagi antenna but I have one question that what would drive the antenna? coz the signal from the tower would be transmitted by the antenna to the other end of the cable. but how would it radiate the signal? so I thought of building an amplifier to drive the antenna. it would also drive more than 2-3 phones.
     
    Last edited: May 20, 2012
  18. trash

    trash Member

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    What model phone are you using ? Most phones have an antenna interface. A lot have an MMCX socket, others have pin connections on the interface cable which are used for external antennas. Some phones do not have an interface of any kind. In that case you can use an inductive loop.
    It's not really user friendly and only one phone can be used.
    It is possible to use another small omni antenna somewhere inside close to where you intend to use the phone.
    Multiple phones can use it all at the same time, there is no limit to how many phones you can use.

    There is more loss when the phone is not directly connected to the coax, but this can be made up with more gain in the yagi and better quality coax.
    Something like LDF1-50 would be my choice.
     
    Last edited: May 20, 2012
  19. roltex_rohit123

    roltex_rohit123 New Member

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    its an Indian brand. Micromax X560. it oes not have external antenna support.
     
  20. trash

    trash Member

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    How did you hope to attach an amplifier to it ?

    It looks like you're stuck with a passive antenna beam bender.
    At least then if you attempt to build an active repeater system, you can build it into your passive system as an improvement.
     
  21. roltex_rohit123

    roltex_rohit123 New Member

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    I would not attach the amplifier to the phone. i would amplify the antenna signal and the mobile signal seperately if possible. someone also sugested me to use a duplexer for this purpose.
     

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