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2 audio signals to a single fm transmitter

Discussion in 'Audio' started by Nicholas bray, Nov 24, 2016.

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  1. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Would it be possible to connect two different audio signals via their respective 3.5 inch headphone outputs to a single fm transmitter at the same time ?

    The two audio outputs would mostly be off and just come on now and again
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    not a problem
    as long as they were both not on at the same time ... else it will be a garbled mess of transmitted audio
     
  3. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Could this be achieved with a y splitter cable.?
     
  4. Alec_t

    Alec_t

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    Jul 7, 2015
    Depends if the headphone output signals have a DC component. If they do, you may need to couple the two outputs to the Tx via respective capacitors.
     
    davenn likes this.
  5. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    The outputs are actually from fishing bite alarms not mp3 players but they still use 3.5" jacks.
    How would I know if they have a dc component I thought the signals would be purely ac ?

    A capacitor could be used to allow the ac signal but block dc ?
     
  6. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    I want to use a cheap fm transmitter and plug it into my bite alarm and use a pocket radio as my receiver in the bivvy I would use separate transmitters for each bite alarm but I think that would mean also using two radios as it wouldn't be able to pick up the two signals at the same time
     
  7. BobK

    BobK

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    Jan 5, 2010
    Just put them each through a 1K resistor connected together to the XMTR input.

    Bob
     
  8. Audioguru

    Audioguru

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    Sep 24, 2016
    A 3.5" plug would be ENORMOUS! A modern headphones jack and plug are fairly small 3.5mm.
    A Y splitter would short the two outputs together which might damage them.
    The two added 1k resistors form an audio mixer.
     
  9. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Yep sorry 3.5mm my mistake.
    Thanks for all you input I've had it working with the splitter cable I bought unfortunatley it was intended for a microphone and a headphone and it only works if I half pull out the transmitter from the 3.5mm socket.

    I tested it first with a pair of headphones and one side of the audio was coming though the left speaker and the other audio through the right speaker at this point I had a brainwave.

    The alarms have mono outputs if I connect two mono jack plugs to each individual alarm and run them to a stereo 3.5mm socket link the commons together and use the positive of the one alarm as the left audio and the positive of the other alarm as the right audio they will be electrically isolated

    I can then plug in the 3.5mm stereo jack found on the transmitter and it will transmitter which ever channel there is audio my little pocket radio is mono anyway
     
  10. Audioguru

    Audioguru

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    Sep 24, 2016
    Your transmitter is mono with a mono input? Then it has only one "hot" audio input that would short the left and right stereo channels together. If there is a signal on one channel and no signal on the other channel then there will probably be no signal to the transmitter.
    You need an audio mixer which is simple two resistors, one from each channel and the other ends are joined and feed the transmitter input.
     
  11. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Hi audio guru the fm transmitter has a stereo input but the two devices I'm connecting to it are mono.
    The transmitter may be broadcasting in mono I'm no sure but not bothered about that
     
  12. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    14801001561440-1.jpg
     
  13. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Right so that transmitter has two "hot" audios and one common
     
  14. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    14801003115521.jpg
     
  15. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    And the two devices I will be connecting to take mono jacks as shown above

    Hope this makes sense hard to explain in words
     
  16. Audioguru

    Audioguru

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    Sep 24, 2016
    Yes the stereo transmitter has two audio inputs, each one from a bite alarm.

    Why the radio system? All fishermen I have seen are very close to their poles and when a fish bites the pole wakes them up.
     
  17. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    It's for night fishing you have the receiver close to your bed to alert you sometimes you even turn the volume down on the alarms for less disturbance.

    Theres not much choice for standalone transmitters and receivers and the one most people buy retails at around £170
     
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