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AM receiver not working

Discussion in 'General Electronics Discussion' started by Gherbi, Jun 13, 2013.

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  1. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    (1) That circuit is not designed to drive a speaker directly.
    (2) The world of RF is a different animal. You can't have things hanging out like that.
    (3) The Rotor on the cap should be the terminal committed to the 100nF and 120K node..
    (4) Anything I may have missed. :D

    Chris
     
    Last edited: Jun 17, 2013
  2. Gherbi

    Gherbi

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    Jun 13, 2013
    (1) Well, isn't the input signal the same? I don't understand...
    (2) What do you mean?
    (3) Isn't it the same? Anyway I connected the LC this way.
     
  3. davenn

    davenn Moderator

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    its only a single transistor output probably nowhere near enough output level to drive a speaker properly

    RF electronics compared to audio electronics is a who different thing ....
    the approach to constructing RF equipment means there needs to be a much more thoughtout and tidier construction and layout and that gets more and more critical as the frequency increases

    You can get away with all sorts of rough construction with audio gear that just wont work when dealing with RF signals and equip.

    The rotor (moving vanes) part of the tuning cap should be connected to the ground 0V rail, this will normally substantially lessen the effect of touching the tuning shaft.... using a plastic knob on the shaft will lessen that even more
    The stator ( fixed vanes) part connected to the top side of the coil and on to the detector etc parts of the circuit

    I cannot quite see what you have done in your pic.
    Having the wires from the coils/tuning cap going through holes in the metal case to the rest of the circuit is also a big NO-NO. It will drastically affect the operation of the tuned circuit.

    I would be mounting the whole thing in a plastic case instead. Mounting the tuning cap through a hole in the case. Fixing the ferrite rod/coils and circuit board in the case so they dont flop around

    As I said earlier in this post. RF construction is much more critical

    Dave
     
    Last edited: Jun 17, 2013
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Dave, this too funny. My initial take was ahhh, another cool Aussie colloquialism! I was going to ask you for a definition. :D

    Gherbi, I think you'll find that mounting everything on a wood base will afford you maximum latitude and ease of placement and affixing. Remember, when making interconnects think short and rigid. Capice? ;)

    Chris
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    just a typo now fixed :)
     
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