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Simple FM transmitter

Discussion in 'Electronic Projects' started by ElectroMaster, Jul 19, 2002.

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  1. ElectroMaster

    ElectroMaster Administrator

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    This circuit is a simple two transistor (2N2222) FM transmitter. No license is required for this transmitter according to FCC regulations regarding wireless microphones. If powered by a 9 volt battery and used with an antenna no longer than 12 inches, the transmitter will be within the FCC limits. The microphone is amplified by Q1. Q2, C5, and L1 form an oscillator that operates in the 80 to 130 MHz range. The oscillator is voltage controlled, so it is modulated by the audio signal that is applied to the base of Q2. R6 limits the input to the RF section, and it's value can be adjusted as necessary to limit the volume of the input. L1 and C6 can be made with wire and a pencil. The inductor (L1) is made by winding two pieces of 24 gauge insulated wire, laid side by side, around a pencil six times. Remove the coil you have formed and unscrew the two coils apart from each other. One of these coils (the better looking of the two) will be used in the tank circuit, and the other can be used in the next one you build. The antenna (24 gauge wire) should be soldered to the coil you made, about 2 turns up from the bottom, on the transistor side, and should be 8-12 inches long. To make C6, take a 4 inch piece of 24 gauge insulated wire, bend it over double and, beginning 1/2" from the open end, twist the wire as if you were forming a rope. When you have about 1" of twisted wire, stop and cut the looped end off, leaving about 1/2" of twisted wire (this forms the capacitor) and 1/2" of untwisted wire for leads.

    [​IMG]
     
  2. drrogla

    drrogla New Member

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    could you transmit a stereo coded signal with this circut?
    connect it instead of the mic...
     
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    C4 in the project has such a high value of 0.1uF that it cuts frequencies above only 1.2KHz. FM stereo needs a response that is flat at 53KHz.
     
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  4. dave

    Dave New Member

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  5. finhas

    finhas New Member

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    very cool one hey create more like this one
     
  6. rovnex

    rovnex New Member

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    hey anyone done some TV transmitter yet? im eager to have one.
     
  7. dfhrace

    dfhrace New Member

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    so why not change the value of C4
     
  8. johnzie

    johnzie New Member

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    hello

    do u have a powerful fm transmitter... that can cover a wide place? more or less 500 meters?:)
     
  9. wmmullaney

    wmmullaney New Member

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    I think you have to have a radio operators licesce...
     
  10. skydemon2008

    skydemon2008 New Member

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    May i know how far the signal can be transmitted?
     
  11. mneary

    mneary New Member

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    Give or take, three to five meters. Maybe more, with an open channel and a sensitive receiver.

    (This one's a six year old thread.) :D
     
  12. ece_s2dent

    ece_s2dent New Member

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    mr.ElectroMaster
    can i put an "audio in" on that circuit?
     
  13. kian2003

    kian2003 New Member

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    Last edited: Sep 19, 2008
  14. firoz3321

    firoz3321 New Member

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    need a Circuit for Finding out a hidden RF transmitter

    Hello to every one,

    I need a Circuit for Finding out a hidden RF transmitter. Can some one sugges me any idea please ?
    A RF Transmitter of a fixed Frequency will be hidden some where around, And I'am Supposed to find the transmitter. This is a project competition held here. Please Help.

    Thank U

    i'm new here and am not able to creat a new thread !!!
     
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  15. mvs sarma

    mvs sarma Well-Known Member

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    I really hope that ElectroMaster would have seen the Mod4 of Audioguru. That that was a fine mod to optimize the entire design. I am yet to understand the idea behind old schematic being put forth again.

    This is not to offend the owner of the site please.
     
    Last edited: Oct 3, 2008
  16. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Perhaps you might try reading the dates on the posts?, the only person "putting it forth again" is YOU! - the original is six years old.
     
  17. mvs sarma

    mvs sarma Well-Known Member

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    Yes Nigel, it was a blunder, that i didn't note the date of the post. Sorry for that.
    BTW how it appears as a post and with an overall of 12 posts above it afresh Sir? It was an item with 11 or 12 replies over that at the time I saw it .
     
  18. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It re-appeared because someone (firoz3321) posted a reply in the thread.
     
  19. mvs sarma

    mvs sarma Well-Known Member

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    OK I got it.
     
  20. deathwing61

    deathwing61 New Member

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    could this be used to magnify the signal of my ipod's fm tuner? it cuts out at times.
     
  21. audioguru

    audioguru Well-Known Member Most Helpful Member

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    This thread talks about an FM transmitter.
    You have a receiver problem that should be in its own thread.

    Phone your radio station and ask them to boost their power so that your cheap or defective radio can pick them up without cutting out. Good luck.
     
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