Old inductor

Discussion in 'General Electronics Chat' started by ceidas, Jan 13, 2012.

  1. ceidas

    Thread Starter Member

    Dec 26, 2011
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    ANY working schematics of AM receivers with 2N3904 or without (crystal radios) would be highly appreciated. Thanx in advance.

    Edit: And please, I want stable circuits. Not extremely accurate components circuits and so on...
     
    Last edited: Jan 14, 2012
  2. Adjuster

    Late Member

    Dec 26, 2010
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    I seem to have overlooked getting back to this thread - sorry! Anyway here is a go at a bias arrangement for a crystal radio using a silicon diode.

    Note that the "reversed" use of the antenna coil coupling winding assumes that a really long aerial is used. A somewhat shorter aerial might be fed in to the top of the main inductor, perhaps via a series capacitor of 100pF or so.

    In any case, as an absolute minimum the antenna must comprise several tens of feet / at least 10 metres of wire, preferably 100 feet / 30 metres plus. A ground connection is also essential.

    Here is a link to a web site on crystal radios. Some are basic designs designed for children, others are more advanced. http://www.crystalradio.net/

    I first got a simple radio of this kind to work when I was about 11 years old. The circuit I used was very much like the one I have shown you, but in those days germanium diodes were much easier to buy, so my radio did not need any DC bias.
     
  3. Adjuster

    Late Member

    Dec 26, 2010
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  4. ceidas

    Thread Starter Member

    Dec 26, 2011
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    Well, first of all thanx for your care. Now, I bought a ta7642, this inductor and this capacitor. I made the circuit in the ta7642 datasheet with the fat inductor and with an lm386 output but nothing! Seriously, i dont know what is going on here. Even typical things dont work if I made them.
     
  5. Adjuster

    Late Member

    Dec 26, 2010
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    Your experience is not that unusual for a beginner. Electronics is not something anyone can expect to become profcient in overnight.

    One point to note is that your difficulty with a particular type of circuit does not necessarily mean that such circuits never work. It is true that some circuits you come across may have errors, something that may be more of an issue on the Internet, where material can be copied easily but might not always be verified.

    Another stumbling-block can be a repeated mistake of your own, or even a defective part re-used from one project to another. For instance, as a youngster, I got was given a pair of headphones for use with a crystal set, but I could not hear anything with them. Later I found out that although working, they had very poor sensitivity.

    Some time later I got a much better earphone which was much more sensitive, and I was finally able to get results. That was quite some moment in my life! Moral: don't give up, but be willing to re-examine what you are doing and try again.
     
  6. ceidas

    Thread Starter Member

    Dec 26, 2011
    50
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    In overnight? Seriously? I have read a lot of books about electronics (I can tell you a few if you want) but 99% when I am trying to implement something complicated in real life ALWAYS something goes wrong. Something that my precious books ALWAYS ignore for the sake of an easier explanation and an easier exercise but in the end they forget to proceed in the real life implementation of the theory.
     
  7. Adjuster

    Late Member

    Dec 26, 2010
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    I'm sorry to hear that you are finding this so frustrating. Perhaps it might help to think about some of the reasons that might be behind the difficulty. I can think of several possibilities:

    1. The books you have are less suitable for somebody trying to learn electronics as a practical hobby, as opposed to studying the subject as part of an academic course. Alternatively, the books simply may not be particularly good ones. In this case, the answer may be to get some better / more suitable books. Other forum members may may be better placed than me to advise you on that, as the books I know about are probably out of date.
    2. All books and all theory are bunkum, and it is impossible to have success with electronics. This may be what you are tempted to believe, but it is clearly wrong: other people have succeeded, including some quite young children, at least with adult supervision. The crystal radio has been quite a popular project with scouting groups.
    3. You may be in need of some instruction from somebody who knows the subject, as opposed to trying to read it up for yourself. This would be my guess, particularly in the areas of the practical skills required to build a project successfully, and also in the application of theory, as opposed to being able to repeat it parrot-fashion as a set of disconnected facts. This seems to come fairly easily to some people* but others seem to need to work at it more.
    *Or maybe they have built up related experience early in life, as may some children who grow up with a strong interest in things mechanical and electrical. Perhaps sorting out the nature/nurture argument is best left to the psychologists.
     
  8. opa627bm

    New Member

    Nov 26, 2011
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    OMG I LIKE DAT KAT!!!!!!!!!!!!!! I USED TO HAVE THE SAME LOOKING KAT IN MY LASER LAB.:p
     
  9. ceidas

    Thread Starter Member

    Dec 26, 2011
    50
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    1) The thing is I am a computer engineering student and, yes, I am studying electronics for the sake of an academic future. As you can easily guess, all the books I have read were from my university's library.

    2) I know that eventually everything will work out but things just dont go as they suppose to be by the books. At least, not in big projects when, for example, even the physical position of two inductors in a circuit matters for its function.

    3) I wish I had people helping me in what I do but you dont find people who know electronics so easily. That's why I am in this forum.
     
  10. atferrari

    AAC Fanatic!

    Jan 6, 2004
    3,241
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    Yes. I agree with that!

    And one day I started to build things that worked.... Oh yes!
     
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