Radio DIY

Discussion in 'The Projects Forum' started by wirefree, Jan 2, 2015.

  1. wirefree

    Thread Starter New Member

    Jan 2, 2015
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    0
    Seasons' Greetings!

    May 2015 be good for all of you who read this, and may it realize my radio project started back in 2003, questions on which are the content of this thread:

    IMG_0252.JPG WP_20150102_001.jpg

    It will sound silly, but I took this project up when meaning and purpose of almost all components used in here were unknown to me. I was just a lost lil' boy, post the dotcom bubble, looking for some meaning on the opposite end of the planet from my home in New Delhi. So I had to make a radio...california dreamin'.

    It never worked and still doesn't. And this is what I bring to you: making this radio work will put the puzzle of my life in some perspective, even 15 years hence.

    I would greatly appreciate your assistance and guidance.

    Best regards,
    wirefree (aka Gaurav)
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Do you seriously think there is anyone on this planet that can tell you what's wrong with your radio based on the information you just provided?

    I can tell you that toilet roll tubes make very poor coil formers.
     
  3. nerdegutta

    Moderator

    Dec 15, 2009
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    Hi Wirefree, and welcome to the forum.

    A good way to start a thread is to provide as much information as you possible can. To start you off a bit: What about a schematic? What have you done to troubleshoot. What are you expecting?

    Best of luck.
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
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    many people start with a toilet paper tube with about 90 turns on it. search for crystal set radios on line, there are quite a few sites. one is makeradio.com from Dave Schmarder, he has lots of designs and explanations. yours probably needs a tuning capacitor, I dont see one in the pictures. another site is http://www.crystalradio.net/.
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    A crystal radio begins with a good aerial and a good ground. Do you have both of these?

    Then you need a germanium diode such as 1N34 and a high impedance earphone or headset, at least 5kΩ.

    Here is your simplest working crystal radio:

    [​IMG]
     
  6. DickCappels

    Moderator

    Aug 21, 2008
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    Doesn't get simpler than that!

    Some people might have trouble getting their hands on a germanium diode or even one of those small signal Schottky diodes. So one question, MrChips, is could he get started with just a small signal silicon diode such as the 1N914/916/4148?
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Only if he forward biased the Si diode using ~10meg and 1.5V battery. The advantage of a germanium diode is that its rectification effeciency is high even without external bias. The knee of a Si diode is so far out there that the rectification effeciency sucks near zero bias. The radio signal is so small that it doesn't even come close to forward biasing a Si diode.
     
  8. Dodgydave

    Distinguished Member

    Jun 22, 2012
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  9. Art

    Distinguished Member

    Sep 10, 2007
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    It can get simpler than that depending where you live.
    Right here a Human can be the diode junction and earth for one particular station on 359 kHz.

    I assume your tuning is supposed to be done by touching the coil? That doesn’t look like a stable inductor.
    It would still work here.
     
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    - You will need more turns of wire on your tube. About 90 will do (usually - assuming 455 to 1600 kHz AM radio).
    It looks like you have multiple pieces of wire connected with your terminal strip to make your coil. Don't do that, get one continuous piece of wire for the 90 turns.

    - when you re-wrap the wire on the tube, make it nice and neat and use some clear tape to keep everything nice and aligned with no overlaps.

    - make sure you have a GERMANIUM diode. Look at the little glass diode with a magnifying glass and tell us the number on it (something like 1N34 is likely). Other types of diodes do not work well.

    - make sure you have the old fashioned AM radio crystal headphones - not modern headphones. The crystal headphones have 1000 to 5000 ohms of resistance. Modern headphones only have 60 or less ohms of resistance. This is critical just like the above are critical.

    - hopefully you are within about 15km of a strong AM radio station. Use an antenna that is plenty long. Your power is coming from the antenna. Long means 3 meters or more.
     
  11. wirefree

    Thread Starter New Member

    Jan 2, 2015
    3
    0
    Greatly appreciate all responses. The encouragement is bolstering.

    I regret my sketchy first post; thinking of those years still gets me wavy.

    In the following pictures I have added as much detail as the components yielded:

    IMG_0261.JPG IMG_0262.JPG

    Could this work?

    -
    wirefree
     
  12. WBahn

    Moderator

    Mar 31, 2012
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    It's awfully hard to tell if a jumbled mess of components will work, especially when one of them is labeled "unknown component".

    You are also being very inconsistent in your nomenclature.

    Your 41e2 resistor actually appears to be a 4.7kΩ resistor.

    It would sure help if you posted a SCHEMATIC of your circuit.
     
  13. sirch2

    Well-Known Member

    Jan 21, 2013
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    The "unknown component" looks like it could be the diode. There are two transistors so it is attempting to be more than a crystal radio but I cannot see a tuning capacitor.

    Here's a circuit diagram

    [​IMG]
     
  14. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Schematic is the magic word here. The rest is just blah blah blah.
     
  15. takao21203

    Distinguished Member

    Apr 28, 2012
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    I asked my distributor, some of the parts are currently "awaiting delivery". I guess its just an excuse?
     
  16. wirefree

    Thread Starter New Member

    Jan 2, 2015
    3
    0
    Gentlemen,

    Please find attached the circuit diagram. It complements the photograph in Post #11 above.

    IMG_0380.JPG
    All guidance would be greatly appreciated.

    Regards,
    wirefree
     
  17. MrChips

    Moderator

    Oct 2, 2009
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    Why is there a capacitor in series with the battery?

    Why do you resistors have powers of e multipliers?
     
  18. wmodavis

    Well-Known Member

    Oct 23, 2010
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    Two antennas?
     
  19. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Four inductors?
     
  20. MrChips

    Moderator

    Oct 2, 2009
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    No ground?
     
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