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cellphone qu estion

Discussion in 'Electronic Repair' started by Mike Muderick, Mar 16, 2006.

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  1. If I leave my cell phone near my computer speakers I will hear occasional
    buzzing, clicking, etc. Before the phone begins to ring, I hear a
    dah..dah.daahhhhh. I know this is RF interference being picked up by the
    amplifier in the speaker. If one were to record this sound with a
    microphone at 11 or 22Khz, would it be possible to obtain any information
    (usable signal) from the recorded audio?
    Thanks,
     
  2. The phone is periodically querying its environment as it programmed to do.
    No, on a practical basis, the audio that you could record is not useful.
     
  3. Well this answer is similar to your question..

    I have a friend who lives close to an AM band radio station. If he turns his
    computer speakres on they will faintly pick up the radio station near by. It
    is kind of coo.. I would immagine if cell phones were still analog you could
    probably hear a conversation the same way.

    - Mike
     
  4. GregS

    GregS Guest

    I don't know how many current phones still do, but both my phones
    have both analog and digital capability. FM not AM analog.

    The basic problem with AM is AM. Amplitude modulation. Aircraft
    radio's use some AM, but most communication services
    are FM or now digital. Analog cell phones are some type of FM.

    Strong FM and television stations can easily demod into
    active devices, but not always audible.

    If you use one of those Led phone blinkers that work from
    radiation, you will see the same thing occuring before a ring
    or when the phone is communication with a tower.

    greg
     
  5. GregS

    GregS Guest


    If a cell phone is in a roaming area, and especially if its in a remote
    area, the phone needs to transmit on high power, where if it has good
    signal strength, it transmits on low power. It makes a huge difference
    in battery charge time, in standby mode. On roaming mode, it will tend
    to communicate with the tower much more often, than being in a home
    area.

    greg
     
  6. Typical example of "topic drift":

    "If one were to record this sound with a
    microphone at 11 or 22Khz, would it be possible to obtain any information
    (usable signal) from the recorded audio?"

    The basic answer is still "NO."
     
  7. Frank S.

    Frank S. Guest

    It is either a GSM (Cingular, Tmobile Suncom etc.) the amplifier if
    detecting the rf signal which is a pulsed signal. It is the phone
    "checking in" with the base station,
    There is no "usable" information being transmited (other then to the phone"
    Frank
     
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