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Bat detector with am/fm ic

Discussion in 'General Electronics Discussion' started by Mor, Dec 19, 2013.

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  1. Mor

    Mor

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    Dec 2, 2011
    i have been looking at a number of different ways to make a heterodyne bat call detector. one that intrigues me is the use of an am reciever ic. i understand the principal of using the oscillator and the mixer on the ic, to shift the frequencies of the bat calls down to an audible (for us poor humans) level. i was looking at a particular chip, the TDA1220B (datasheet attached), but cannot work out how to use it. i have found a circuit that uses the TCA440 am reciever ic, but simply copying someone elses circuit doesn't help ,me understand how it all works.

    so if anyone can help me to configure the TDA 1220B, i would be very grateful.

    i need to control the oscillator frequency from about 10khz to 100khz, feed it into the mixer with the bat signal which will either be from a 40khz tranducer or an electret mic such as the MCE2500, and take the output to amplify and then to a small 32ohm speaker.

    the reason for this particular idea is that it requires so few parts as the oscillator and mixer are both within the single ic.
     

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  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    The datasheet you attached is corrupt. I can'topen it in Adobe reader.
    Have a look at this datasheet.
    On page 4 is a complete test circuit and starting on page 6 you will find application information.

    However, this chip is probably not designed for use with a local oscillator frequency of 10kHz...100kHz. I'm not familiar with this chip, but the AM section is characterised for a lo frequency of 1MHz. Since the oscillator is meant to be operated with an LC circuit, the components may be prohibitively large for such low frequencies.
     
  3. Mor

    Mor

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    Dec 2, 2011
    ah, thankyou.

    yes i saw the application notes, but it was while trying to weave my way through their meaning (being a self taught amateur), that i was getting stuck in understanding how the chip worked and what its limitation are when it comes to what i want to do with it.

    maybe i should just go back to using a circuit someone else designed with the TCA440.

    thanks for your clarification...:)
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    There's nothing wrong in using another one's circuit. It helps to build knowledge if you understand how the circuit works. Next time someone else may profit from your experience.
     
  5. Mor

    Mor

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    0
    Dec 2, 2011
    true, but i suppose i was hoping to gain a little from comparing one with the other, but then, maybe i was trying to hard to understand what i didn't.

    baby steps...
     
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