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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
    0.1μF feeding 500k ohms has a cutoff frequency (-3dB) calculated to be extremely low at 3.2Hz. We cannot hear below 20Hz and many speakers cannot produce frequencies below 35Hz.

    I do not know the inductance values you have. 470pF might not be a good value for them.
    Look in Google for an LC Resonance Calculator.

    I cannot understand your broken English. Is there a forum in your country in your own language?
     
  2. michael1978

    michael1978

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    Mar 17, 2012
    One simple question
    Do you understand this circuits(i think yes, you know) foster seeley discriminator very good.png
    So you said it resonate at 5.1mhz, wich one are those LC circuits in schematics?(wich make lc at 5.1Mhz) wich capacitor and inductance, can you look in circuits and you can tell me, and problem is solved i think those are better forum
     
  3. Audioguru

    Audioguru

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    Sep 24, 2016
    I did not say anything resonates at 5.1MHz. I said your signal generator in the simulation wrongly produces 5.1MHz instead of the correct 10.7MHz. Your schematic has more errors.

    The black and white schematic I posted is correct and widely used. It clearly shows the tuning capacitors parallel with the transformer coils.
     
  4. michael1978

    michael1978

    388
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    Mar 17, 2012
    yes that right, i correct it but it has no correct wave,

    about the second circuit is so design for 5.1Mhz, not for 10.7 MHZ, but i draw it in ltspice i thought he gonna explain how to change in the book , but i did not explain:(
     
  5. michael1978

    michael1978

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    Mar 17, 2012
    But did you run it, the file is working perfect
     
  6. michael1978

    michael1978

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    Mar 17, 2012
    I go to change, but one more time i with no ask you anymore, is rely this circuit wrong, you know man i dont understand how he can do such big mistake
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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  8. michael1978

    michael1978

    388
    2
    Mar 17, 2012
    I change the audioguru, but i did not know wich value to put in R and C, can you told me please
     

    Attached Files:

  9. michael1978

    michael1978

    388
    2
    Mar 17, 2012
    I dont know Steve, to make mistake in book...
     
  10. michael1978

    michael1978

    388
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    Mar 17, 2012
    HI, Audioguru, can you please help for values of RC, for tank circuit i gona take it to make, i have this site and here is for lc formula etc....http://www.zen22142.zen.co.uk/Theory/tunedcct.htm please :(
     
  11. Audioguru

    Audioguru

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    Sep 24, 2016
    Will you buy 10.7MHz transformers and a discriminator? They were sold 40 years ago but not today. Today an FM radio uses crystal filters instead of transformers. Digikey has 10.7MHz IF bandpass crystal filters and crystal filter discriminators.
     
  12. michael1978

    michael1978

    388
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    Mar 17, 2012
    Hi, Audioguro please try to understand me , my intention is to make a fm tuner from ZERO and i get enough help from you and other peopels, and when i finish (after is easy i buy complete chip radio,), because after i know how is working, that is, ( and i rad also from here, they dont show the value of components for detector http://www.rfcafe.com/references/electrical/NEETS-Modules/NEETS-Module-12-3-11-3-20.htm) please try to understand me, you have just to tell wich value for rc and after i think i almost ready to complete all parts, thnx
     
  13. Audioguru

    Audioguru

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    Sep 24, 2016
    Today, where will you buy 10.7MHz IF transformers and a 10.7MHz discriminator transformer or a 10.7MHz ratio detector transformer? They might have the tuning capacitor inside. Crystal filters replaced IF transformers years ago.

    You want to know the values of WHICH rc? You posted a txt file where I cannot see the schematic. Please post the schematic (a print screen).
     
  14. michael1978

    michael1978

    388
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    Mar 17, 2012
    Ok Here, the value of R4, R5, and C3, C4, please 1.png
     
  15. Audioguru

    Audioguru

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    Sep 24, 2016
    I am glad to see that you turned around the diodes so that are not conducting all the time.
    Now you have the anodes of the diodes not connected to the transformer.
    Also you have coil L4 and C10 shorted to the positive supply with C5.
    The schematic does not have a positive supply so it will not work and will not simulate.
     
  16. michael1978

    michael1978

    388
    2
    Mar 17, 2012
    You right look what i have forget most importing things, i i go to change thanks but what about values?
     
  17. michael1978

    michael1978

    388
    2
    Mar 17, 2012

    I dont know is good working, what do you think, again i have probem with frequency,
    2.png 22.png
     
  18. Audioguru

    Audioguru

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    Sep 24, 2016
    You made your schematic with the parts too far apart then the text is too small to see.
    Also you did not right click on the schematic part of the simulation then select "View" then select "Zoom to Fit".
    The large sinewave that is slowly reducing its level is 667kHz. Why?
    You still have some mistakes I showed before. Why?
     

    Attached Files:

  19. michael1978

    michael1978

    388
    2
    Mar 17, 2012
    I Realy dont know, where to connected, this i change diode
    look now 2.png 22.png
     
  20. Audioguru

    Audioguru

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    644
    Sep 24, 2016
    Michael, you do not know what you are doing. I am ready to quit trying to help you.
     

    Attached Files:

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