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RF problem caused display to blank

Discussion in 'Electronic Basics' started by Dummy, Mar 9, 2005.

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  1. Dummy

    Dummy Guest

    I have one radio (330Mhz-400MHz), equipped with antenna and remote
    speaker mic.
    When the radio is transmitting at 4W over a groundplane with LCD
    display facing down, display blank problem could be seen occasionally.
    The display was totally blank and not functioning. Of course, radio
    was still working well. Turning the radio OFF and ON again would have
    the display recovered.

    A copper tape that applied at the LCD flex solved the problem. But no
    display blank issue was not seen at other bands of radios such as from
    100MHz-200MHz and 400MHz-500MHz. All radios are using same LCD, same
    circuitry and similar platform design. Even though the problem has
    been solved, the behaviour of the display blank problem was not
    properly understood, especially when it's frequency dependent, and it
    happened when display was facing downwards the big groundplane, and it
    didn't happen at other bands of radio. Can somebody shed some light on
    this?
     
  2. Leon Heller

    Leon Heller Guest

    http://www.geocities.com/leon_heller
    One or more of the connections to the LCD was probably acting as an antenna
    at that particular frequency or a harmonic of it.

    Leon
     
  3. Typical EMC mystery problem. Of course it can be explained. Start with
    Maxwell's Equations and go on from there. (;-)

    Alternatively, just remember that things like that can happen.
     
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