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why noise from phone

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  • 26-01-2012 1:39pm
    #1
    berrypendel
    Closed Accounts Posts: 365 ✭✭


    When i leave my phone beside the clock radio at night every so often there is a short burst of radiation like a call is coming through. you can hear it from the radio. i am curious to know why this is, does the phone 'check in' with the tower every so often?


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    #2
    TBi
    Registered Users Posts: 1,784 ✭✭✭TBi


    This has happened with mobile phones for years. The phone is just 'checking in' with the mast.


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    #3
    Intouch9
    Registered Users Posts: 209 ✭✭Intouch9


    I have the same thing with my radio alarm clock and my iPhone. Is coverage a bit dodge in your house by any chance?


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    #4
    Spanner16
    Closed Accounts Posts: 3 ✭Spanner16


    Nothing to do with the phone checking in with the mast.
    Its something called EMI (eletromagnetic interference) Any object the runs on electricty will emit some form of EMI and because the speaker of the phone is so sensitive it will pick up on the radio waves coming from the clock radio and vica versa


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    #5
    Sponge Bob
    Banned (with Prison Access) Posts: 25,234 ✭✭✭✭Sponge Bob


    Normally the noise comes from the radio speaker not the phone speaker.


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    #6
    TBi
    Registered Users Posts: 1,784 ✭✭✭TBi


    Spanner16 wrote: »
    Nothing to do with the phone checking in with the mast.
    Its something called EMI (eletromagnetic interference) Any object the runs on electricty will emit some form of EMI and because the speaker of the phone is so sensitive it will pick up on the radio waves coming from the clock radio and vica versa

    Do you even know what you are talking about?

    The noise is from the GSM signal. The signal is in the 900MHz/1800MHz range but uses time division multiple access (TDMA) to allow more than one phone conversation on the same frequency. This TDMA creates a low frequency beat (217Hz) which is picked up and amplified by the radio's on board amplifier.

    "A disadvantage of TDMA systems is that they create interference at a frequency which is directly connected to the time slot length. This is the buzz which can sometimes be heard if a TDMA phone is left next to a radio or speakers."

    From WikiPedia

    Texas Instruments Paper on this


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    #7
    Spanner16
    Closed Accounts Posts: 3 ✭Spanner16


    TBi- You are the reason why I don't post on Forums, One tries to give a bit of friendly information in laymans terms you respond with "Do you even know what you are talking about?" I do not have to produce evidence of my qualifications or knowlegde to answer a question.
    Obviously cut and paste and Wikipedia are a close friend of yours:D


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    #8
    TBi
    Registered Users Posts: 1,784 ✭✭✭TBi


    Spanner16 wrote: »
    TBi- You are the reason why I don't post on Forums, One tries to give a bit of friendly information in laymans terms you respond with "Do you even know what you are talking about?" I do not have to produce evidence of my qualifications or knowlegde to answer a question.
    Obviously cut and paste and Wikipedia are a close friend of yours:D

    Thank you for the compliment.

    However you gave wrong information. You inferred that the speaker of the phone was picking up interference from the radio, this is wrong. The speaker on the phone would be shielded from this, or else it would amplify it's own TDMA interference signal.

    In laymans terms you would just (truthfully) say that the phone is interfering with the radio while it talks to the mast. (Which is what it is doing)


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