¿i need help with my simple electronic radio proyect?

Discussion in 'General Electronics Chat' started by leonheard, Jan 8, 2013.

  1. leonheard

    Thread Starter Member

    Jan 8, 2013
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    0
    hi!

    i started to do electronic stuff few month ago, i study in internet, i made many proyects
    succesfully, ( i do really love electronic, its my passion these days ) well... now i have a problem with my new proyect.... i want to make a radio controller with 4 mhz 4 legs crystall oscillator , so when i press on switch in the emisor, then the receptor switchs on, and then led turns on, but it didnt work...

    what am doing wrong? i need help, i will appreciating a lot.

    the 2 crystalls i use are:
    - 4 legs crystall oscillator MURATA ERIE m 7160 83 28 4,0000 ( i didnt find its datasheet, but i saw 1 in google that looked like this model...)

    here is my circuit schematics:

    http://s8.postimage.org/63z2zop6t/my_circuit_help.png


    Información adicional
    when i touch the base of the transistor the led turns ON, so i dont think i puted the transitors wrong...
     
  2. SPQR

    Member

    Nov 4, 2011
    379
    48
    Hi and welcome to the forum.

    Well, I wonder where you got the schematics from?

    Usually you need things like transistors and resistors to go along with the crystal on the transmitter side.
    Something like THIS.
     
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  3. leonheard

    Thread Starter Member

    Jan 8, 2013
    48
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    well its my own schematics :p ( i thought this was gonna works by pure logic :p) i have also a 2 legs crystal, but they said that a 4 legs crystal would be better because its a complete circuit ( thats why my transmitter rf circuit doesnt have any added transistors, just vcc, ground and antenna ) dunno maybe they lie to me or something xD


    i bought a crystall oscillator ( so i dont need to build a lc circuit ) i thought this crystall was gonna make some ac, sign wave to make some radio waves...
     
  4. SPQR

    Member

    Nov 4, 2011
    379
    48
    I think THIS page will help you get started.
     
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  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    A "crystal" with 4 legs is a crystal oscillator. If the antenna is the correct length and is connected to its output then it is a very crude radio transmitter.

    But we don't know what the "receiver circuit" is since it is hidden inside a box.
    The oscillator is not modulated so the "receiver" will simply saturate when it receives the signal.

    Oh yeah. The LED is connected backwards and does not have a current-limiting resistor so it will not light if the receiver receives the signal but it might burn out immediately when the base of the darlington is touched.

    The darlington-connected transistors need a very high signal level to turn them on since they are followers. A follower has a voltage loss and has no voltage gain.
     
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  6. leonheard

    Thread Starter Member

    Jan 8, 2013
    48
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    crude radio transmitter? how can i make it a good radio transmitter?

    okei i suppose that i will have to make a LC circuit as a receiver, it have to be 4 mhz also isnt it? :)

    mmm yea sorry i forgot to put the MINUS/line sign behind the triangle xD

    thanks for ur time :)
     
  7. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    A transmitter has a sine-wave output that has no harmonics that cause interference to othew radio systems. But the oscillator has a square-wave output full of harmonics.
    The harmonics are reduced with an LC filter that your circuit is missing.

    A radio receiver has many LC tuned circuits but yours has none.
    A radio receiver also has an amplifier with a high voltage gain but your darlington transistor follower has a voltage gain of only almost 1.

    What triangle? We are talking about an electronic circuit not about triangles.
    The symbol for the LED is almost a triangle but it is shown connected backwards.
     
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  8. leonheard

    Thread Starter Member

    Jan 8, 2013
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  9. Audioguru

    New Member

    Dec 20, 2007
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    The LC tuned circuit is a fairly good filter if it is in the correct circuit.
    The circuit you found of an "FM receiver" is garbage that probably will not work.
     
  10. leonheard

    Thread Starter Member

    Jan 8, 2013
    48
    0
    okei, thanks for the advice.... well yesterday i builted a new circuit, just improvising, and i made it actually work! :D this is somehow strange cuz i didnt use a lc circuit, or crystall oscillator for transimmer first... i only used 3 transitors, 5v power supply, and many resistors not even any antenna.....


    then i switched my radio from fm to MW ( it think its same as am ) and put a long antenna to it, and finally tunet to... about 500 Khz... and i could heard my mp3 song that was in my other room.... ( a friend called me and i heard also his voice in my radio :D )
    it was not clear voice(noise) but still could heard 70% well...

    what was that? why it works? did i actually made some radio waves? or was my radio soooo sensitive that it could detect my simple circuit inductions without antenna or something?

    then i made this circuit also, and it worked, not so good as my early circuit but it was okei

    http://postimage.org/image/cn3wzwoup/



    damn, am comfused but want to learn :)

    thanks ;)
     
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