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another FM transmitter project

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by hannobisschoff@gmail.com, Apr 14, 2011.

  1. hannobisschoff@gmail.com

    hannobisschoff@gmail.com Member

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    Hi, sorry for not saying, but I'm based in South Africa.
     
  2. killivolt

    killivolt Well-Known Member

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    Kinda makes sense on your location and the Magazine. Do they distribute it in south africa or did you get it off the net?
     
  3. hannobisschoff@gmail.com

    hannobisschoff@gmail.com Member

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    I Got it off the net. I'm sorry to say, but SA is a bit behind when it comes to electronics as a hobby.
     
  4. dave

    Dave New Member

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  5. killivolt

    killivolt Well-Known Member

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    The net seems likely to me (Borderless) Thank, for the responses. Good luck in your pursuit. Best regards.

    kv
     
    Last edited: Feb 14, 2013
  6. nerous

    nerous New Member

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    how to get a perfect transistor for my transmitter here in ghana

    AM in need of help rite now plz am tryen to build an fm transmitter here in africa but don't kno wat type of transistor to use
     
  7. tytower

    tytower Banned

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    Errr---Use a black one

    Don't want to get caught up in a racist fiasco
     
  8. trash

    trash Member

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    Still trying to get banned from forums tytower ?

    Talking Electronics have published lots of good books which are cheap and packed with FM bug circuits and ideas. You can still mail order their books and kits
    http://talkingelectronics.com/
     
  9. tytower

    tytower Banned

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    What you on about trash?
    Thought you would be landfill long ago

    Got no humour - don't read my posts
    aannnddd isn't advertising commercial stuff agin the rules ?
    Although I do find Colin's work very easy to follow
     
    Last edited: Jul 16, 2011
  10. Ziddik

    Ziddik Member

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    u said "use a black one" and thats rude! Ppl like u must banned from these kinds of sites!

    @nerous, u may try Bc547,2n2222a,2n3904 for low power fm transmitters and 2n3866,2n2219a for higher power transmitters,
    good luck
     
    • Like Like x 1
  11. tytower

    tytower Banned

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    WOWSER in the extreme
     
    Last edited: Jul 19, 2011
  12. audioguru

    audioguru Well-Known Member Most Helpful Member

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    I am a white-skinned person. Is it rude to call me "white"?
    Is it rude to call a Chinese person "Oriental"?
     
  13. Ziddik

    Ziddik Member

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    is it possible to use any kinds of "black transistor" for an Fm transmitter? For example s8550!! I didnt mean that in a racial way nor black skin or white skin! He said "use a black one" and thats definitely rude
     
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

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    A Wing Shing S8550 PNP transistor is not black, it is Oriental.
    I have never seen one since I use American 2N3904 NPN transistors that work at a frequency that is double the max frequency of the S8550.
     
  15. Ziddik

    Ziddik Member

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    UTC S8550 is a black transistor, aint it?
     
  16. audioguru

    audioguru Well-Known Member Most Helpful Member

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    I went to China to find a UTC datasheet for their S8550 transistor. It shows no skin colour so it might be purple instead of black.
    It might not work as an FM transmitter because some of them have a gain of 1 (like a piece of wire) at 100MHz and won't oscillate at frequencies up to 108MHz.
     

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    Last edited: Jul 21, 2011
  17. Ziddik

    Ziddik Member

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    purple? I have never seen a transistor in purple colour.. have u seen one?
     
  18. Ziddik

    Ziddik Member

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    is BC547 better than 2n3904 for low power RF amplifier? And I have seen the fm transmitter you have posted using 3 or 4 2n3904 so whats the range of the transmitter?.
     
    Last edited: Jul 21, 2011
  19. audioguru

    audioguru Well-Known Member Most Helpful Member

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    My FM transmitter is fairly low power so a BC547 will work the same as my 2N3904.

    "How many long it could be reach" does not make sense in English. Maybe you are asking how far away it can be received which we call "its range"?

    I tested it across a large river valley with nothing in between. It was more than 2km to my expensive very sensitive FM stereo and my very sensitive car radio, it was about 300m to a cheap portable Sony Walkman FM stereo radio and it was across the street to a cheap FM radio from The Dollar Store (it uses a TDA7088 FM radio IC). The Dollar Store sells very cheap Chinese and Indian junk). In my neighbourhood houses and trees reduced the range a lot.

    The transmitter antenna was 80cm long and hanged vertically out an upstairs window. My FM stereo and car radio antennas were also long and arranged vertically. My Sony Walkman radio uses its earphones cord as the antenna (not good) and the radio from The Dollar Store has a whip antenna that is much too short at about only 12cm (it picks up only strong local stations but is also overloaded by many of them).

    Many cheap FM radios are overloaded by strong local stations so the range will be reduced a lot. My cheap Sony Walkman radio has a local-distant switch that attenuates the antenna input when switched to local. When overloaded a station appears at many points across the dial.
    When my transmitter is close to a cheap radio then it appears at many points across the entire dial.
     
  20. Ziddik

    Ziddik Member

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    you could make a long range transmitter if u try because u are a very experienced guy in electronics. but why u still playing with those old and cheap 2n3904 transistors? Have u ever tried to make one for a higher power or failed to?
     
  21. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Don't you know that it is illegal in most countries to make a powerful radio transmitter (more than a few mW output)? You must have a licence which shows a certain frequency (if a frequency is available) and the circuit must be certified to have excellent spec's.

    My FM transmitter that uses 2N3904 transistors is much too powerful (its output is about 20mW to 100mW) and its frequency is not very stable.
    I tested my transmitter for only one hour because it caused interference to cheap nearby radios and I was afraid that somebody might complain and send the RF cops to catch me illegally transmitting without a licence. I never used it again.

    My simple transmitter was my fix of one that somebody posted and didn't work. I biased everything properly, added the output transistor to separate the antenna from the oscillator, added a voltage regulator and added pre-emphasis.
     

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