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Some More Simple FM Transmitters

Discussion in 'Electronic Projects' started by Iceman_Chris, Nov 28, 2004.

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  1. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Re: Question about "fmtransmitter3.gif"

    The headphones output level of an ipod is about 200 times higher than the level from a microphone. The entire preamp transistor stage of the transmitter must be removed.

    The simple transmitter circuit is a lousy child's toy that would sound horrible:
    1) Its RF frequency drifts all over the place if something gets near it or its antenna, and if its battery voltage drops.
    2) It is mono, not stereo.
    3) It doesn't have pre-emphasis (treble boost) like FM radio stations have, so it would sound muffled like an AM radio.
     
  2. ilektronikos

    ilektronikos New Member

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    VHF POWER METER

    can anyone please suggest a simple circuit for RF POWER METER for testing the oscillator output. i foun one in the site
    http://electronics-diy.com/tx500.php.
    i bulid the schematic below but it doesnt work.
    for the 2pF i use 1pF conected parallel. in the image of the project in the
    site he uses 1.8 conected in series and he 270 resistor for the emmiter insted of 1k that he has the shematic. any suggestions;
    The scematic below is from the site http://electronics-diy.com/tx200.php
    thanks in advance
     

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  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The power meter's circuit has the LED backwards.
    Also the transistor is not biased correctly but it might work.

    I don't know which 1.8, 270, 1k and emitter you are talking about.
     
  4. dave

    Dave New Member

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  5. Cool_buddy_57

    Cool_buddy_57 New Member

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    In 1st diagrame of FM transmitter i don,t know which value of variable inductor(L1) u used?plz check this.
     
  6. Platonas

    Platonas New Member

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    You are talking about the 2watt one? Anyway it is not even 1 watt.

    The coil could have 5 to 6 turns on a 6 mm diameter with a 0.6 to 1 mm wire.
    C1 is better to be a variable one with values up to 60 pf and C2 can be a 12 or 15 pf capacitor. The coil does not need to be a variable one but an aircore.

    Regards
    P.
     
  7. qqqq_@

    qqqq_@ New Member

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    gooood
    thank
     
  8. blaze3927

    blaze3927 New Member

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    sorry if i'm asking a stupid question. but...
    would this work if i connected a headphone jack to the transmitter and put that in my ipod instead of the microphone?
     
  9. Hero999

    Hero999 Banned

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    Yes but you need an attenuator (this is no problem a couple of resistors will do) and simple transmitter circuits like this give crap mono AM radio sound quality.
     
  10. manish jain

    manish jain New Member

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    fm transmiter

    hi
    thanks for reply
    but i have no idea plz can u send project diagram & some detail on my e mail id
    manishjainshah@yahoo.co.in
     
  11. manish jain

    manish jain New Member

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    can u send some theory related to it
     
  12. Hero999

    Hero999 Banned

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    Look up FM on Wikipedia.
     
  13. AND_ECE

    AND_ECE New Member

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    hello

    its that really working and what bout the range of that fm transmitter? an you explain the circuit to me.. so that i can understand thanks
     
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

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    My FM transmitter has an RF amplifier on its output.
    With a new 9V alkaline battery its range is more than 2km across a large river valley to my very sensitive home FM tuner and to my very sensitive car radio.
    The range is about 300m to my Sony Walkman radio.

    Hills, buildings and trees block the signal.
     
  15. HiTech

    HiTech Well-Known Member

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    I think I heard your broadcast of Gordon Lightfoot's song, The Edmund Fitzgerald. The transmission must have rode in on one of those Great Lakes gales that begin this time of year!!:rolleyes:
    BTW, sometime I want to discuss these Alberta Clippers that you folks send our way. That stuff has got to stop or we start sending you illegal Mexicans .... (and we have enough of them to cripple your economy!
     
    Last edited: Sep 20, 2007
  16. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Canada gets its share of illegal foreigners. They do the "dirty" work that local people don't want to do. Boatloads arrive from China each year.
     
  17. TinaiKevin

    TinaiKevin New Member

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    Does anyone have a circuit of a simple low power FM transmitter that uses crystal 1MHz and has a 105Mhz output? dont know how that is done but if anyone can help??
     
  18. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Trouble is it wouldn't be simple!.
     
  19. TinaiKevin

    TinaiKevin New Member

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    FM transmitter

    You are right about it being not simple! Is there any other alternative to the programmable chip, by using dividers/multipliers(that are set) or flipflops. I am not that well versed with all programmable stuff.

    Thanks
     
  20. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    No, from a 1MHz crystal you have to use a PLL system, you couldn't even use multipliers - which would be complicated anyway.
     
  21. mvs sarma

    mvs sarma Well-Known Member

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    If you can use 15MHz crystal as oscillator and derive the 7th harmonic, perhps you may end up getting the required 105MHz. Mostly a single 74HCU04 and few pf caps and an inductor are all that are needed. It could work off 5Vsupply. A sample diagram is attached , thanks to G Baars the designer of SW radio capture.
     
    Last edited: Jul 7, 2008
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