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Hello, can somebody help wich transistor is like bfg520

Discussion in 'Radio and Wireless' started by michael1978, Jul 27, 2018.

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  1. Audioguru

    Audioguru

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    Sep 24, 2016
    The frequency range is wrong. In a superheterodyne FM radio that has a 10.7MHz IF the local oscillator must tune from 77.3MHz to 97.3MHz or tune from 98.7MHz to 118.7MHz except a little lower in Japan where I think FM station frequencies go down to 76MHz.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,401
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    Jan 21, 2010
    I thought the FM band was 88 to 108 MHz?
     
  3. Audioguru

    Audioguru

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    Sep 24, 2016
    In most countries.
     

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  4. michael1978

    michael1978

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    Mar 17, 2012
    May i ask you something else, how can i couple mutuli nductance, can you help me please, you know good this simulator,
     
  5. WHONOES

    WHONOES

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    May 20, 2017
    Hi, I'm back after a few days in the lake district.
    Why do you want to connect multiple inductances?
    Thanks. Yes the Simetrix simulator is very good, been using it for years.
     
  6. michael1978

    michael1978

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    Mar 17, 2012
    Sorry for late, i was no in internet, what is dat multiple inductance? wha they do,

    I will like to ask you do you know something radio to design, i make rf amplifier, local oscillator, if amplifier, only i dont know so much how to demulate
     
  7. WHONOES

    WHONOES

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    May 20, 2017
    It was you who asked about multiple inductances in post #124.

    Try the link below for an introduction to FM receivers.
    http://www.arrl.org/files/file/Technology/tis/info/pdf/8506025.pdf
     
  8. michael1978

    michael1978

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    Mar 17, 2012
    THANKS MAN, yes that was true for mutual inductance coupling but i solved, thank you,
    but i dont know how to make transformer COUPLING, can you please (when you have time) to make it, i making one but is not working, i have trouble to make transformer i send you the schematic rf amp and detector.png
    can you please help with transformer from that file,
     
    Last edited: Aug 15, 2018
  9. Audioguru

    Audioguru

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    Sep 24, 2016
    It looks like you copied the Foster Seeley discriminator wrong:
     

    Attached Files:

  10. michael1978

    michael1978

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    Mar 17, 2012
    No i take from the site "whonos", this http://www.arrl.org/files/file/Technology/tis/info/pdf/8506025.pdf, but man i make some changes, i dont know how to make a transformer, the 2 capacitor connected in parallel with transformer, i read somewhere in internet, they make center frequency, to be tuned, do you know something to make working this circuits
    look and the file FMDETECTOR.png
     

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  11. michael1978

    michael1978

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    Mar 17, 2012
    Last edited: Aug 16, 2018
  12. michael1978

    michael1978

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    Mar 17, 2012
    Sorry AudioGuro, with wich capacitor you see that is 5.1Mhz, with wich capacitor you calculate tuned circuits
    foster seeley discriminator very good.png
     
  13. WHONOES

    WHONOES

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    May 20, 2017
    I don't know enough about IF amplifiers to comment which is why I directed you to that web site. I am sure there are others if only you take the trouble to search for them.
     
  14. michael1978

    michael1978

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    Mar 17, 2012
    no no i am loking to build one receiver just that, nothing else and i am almost finish
     
  15. michael1978

    michael1978

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    Mar 17, 2012
    Hi sir, do you know this circuit with Jfet, do you know, wich form tuned circuits inductor and capacitor, do you see the circuit is inductor with 470p tuned of wich capacitor ??:(
     
  16. Audioguru

    Audioguru

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    Sep 24, 2016
    Michael, it looks like you are trying to simulate a circuit, not build the circuit.

    You make many errors when you copy a schematic. Here are my attachments:
    1) This discriminator from the book has no strong DC bias on the diodes like your circuit has.
    2) Your ratio detector is completely different than the book and has a crazy RC at its output.
    3) Your inductors do not have tuning capacitors.
     

    Attached Files:

  17. michael1978

    michael1978

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    Mar 17, 2012
    But you say i miss the capacitor to be tuned perfect(i will solve), now i know, but can you tell me, wich capacitor and inductore create 5.1Mhz, can you tell me please so i can change the resonance please thanks
     
  18. michael1978

    michael1978

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    Mar 17, 2012
    DISCRIMINATOR circuit,
    and why they can pass audio signal what wrong with ratiod detector
     
  19. Audioguru

    Audioguru

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    644
    Sep 24, 2016
    The IF for an FM radio is 10.7MHz but your simulation has a generator frequency of 5.1MHz. It is easy to calculate the inductance and capacitance for an LC to resonate at a selected frequency.

    The discriminator circuit you posted has a low power Jfet with a fairly high output impedance trying to drive an 8 ohm speaker through a 2.2uF capacitor that has a value much too low for audio into an 8 ohm speaker. The Jfet and 2.2uF capacitor will be able to feed audio into the input of an audio power amplifier that can drive the speaker.

    The ratio detector you posted has a 0.1pF capacitor which is an extremely low value feeding an 8 ohm speaker which is impossible. The 0.1pF capacitor can be calculated as 0.1μF (100nF) to feed wideband audio into the input of an audio power amplifier that has a 100k input resistance. The amplifier can drive the speaker.
     
  20. michael1978

    michael1978

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    Mar 17, 2012
    No Audioguru like example I make 0.1P(it was 0.1 AND resistor OF 500K)(i change to self experiments i did it,)

    Yes is easy i know, but wich are the capacitor(i dont know wich capacitor, tell me please wich capacitor and i gonna change self, wich inductor with capacitor and gonna make 10.7? i am trying to calculate is 470p of in parallel 2 capactor from 470p i make experment but i cant find the solution (and also i make experiment i put the 8OHM resistor it was 27K with capacitor) so i remove is working transformer, just stay to change to make 10.7MHZ this how to do it?, thanks man
     
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