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Question about an FM Transmitter

Discussion in 'General Electronics Discussion' started by jdouglasusn, Aug 8, 2012.

  1. jdouglasusn

    jdouglasusn

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    May 29, 2012
    How exactly do we test this circuit to see if it's working properly?

    Do I plug in a audio device (let's say my MP3 player) to the audio input.
    Set my radio for like 103MHz, and adjust R1 until i hear something, or am I way off track?
     

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    With no input signal, adjust the tuning of your radio to a space between stations. You should hear static (a hiss).

    No adjust the tuning on the transmitter (with no signal input) until it goes very quiet.

    Then add signal and you *should* be able to hear it.
     
  3. jdouglasusn

    jdouglasusn

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    May 29, 2012
    Never went quiet.

    But everything checks good for voltage, and continuity.
    longer antenna maybe?

    I'm also on a Naval Air base right now, I'm sure that can mess with it.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I'd be getting an oscilloscope and looking at the output.

    Within a metre or so I doubt you'd need an antenna. A short length of wire would be more than adequate.
     
  5. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Is this a kit? Do you have a Voltmeter?
     
    Last edited: Aug 9, 2012
  6. jdouglasusn

    jdouglasusn

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    May 29, 2012
    yes I do

    But anyways problem solved, the radio's antenna sucks.
    Different radio clear as crystal.

    Thanks to everyone trying to help :)
     
  7. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    That's odd. To paraphrase Steve; If the transmitter & receiver are in close proximity you shouldn't need an antenna at all. I wouldn't think the receiver wouldn't need one either.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    It's possible that the bad receiver has some sort of squelch to hide the sound of static, and that makes it harder to find the silent part of the band where the transmitter is working.

    It is also possible that it is digital and steps 100kHz at a time and this too make is hard to tune one to the other.

    It's even possible that the signal is overloading the input of one receiver.
     
  9. jdouglasusn

    jdouglasusn

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    May 29, 2012
    The radio just doesn't get good reception. It doesn't hide the sound of static. It's not digital. I just use the one at work, it's perfectly fine, from across the room even.
     
  10. jdouglasusn

    jdouglasusn

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    May 29, 2012
    Unless the receiver is a piece of junk, which it is.
    Used a different one and now it's fine. But thanks anyways.
     
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