audio circuit needed for qrp transceiver

Discussion in 'The Projects Forum' started by DanW8KMX, Dec 2, 2018.

  1. DanW8KMX

    Thread Starter Member

    Oct 21, 2009
    25
    1
    I have just completed a QRP transceiver which works perfect however it has no AGC circuit. I would like to come up with a relative simple schematic of something I can build and insert right before the audio amp.
    I hope I am making this request on the correct forum. It seemed as though I had several choices.
    You can respond here or to my personal email, w8kmx@bellsouth.net.
    Regards,
    Dan
     
  2. LesJones

    Well-Known Member

    Jan 8, 2017
    2,072
    622
    You could build some kind of audio amplitude limiter / compressor but that would not solve the main problems that a normal AGC system solves.
    This will not prevent overloading the RF and IF stages of the receiver. You need to use the DC component from the detector stage and use it to control the gain of the RF and IF amplifier stages.

    Les.
     
  3. danadak

    Distinguished Member

    Mar 10, 2018
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  4. DanW8KMX

    Thread Starter Member

    Oct 21, 2009
    25
    1
    Hello Les and Dana. Many thanks for your post to my question. Unfortunately, I am not an engineer, my degree is in business and finance, but I am a "half-fast" technician. I can follow instructions and build and align but I am not good in design.
    I was hoping to find a somewhat simple solution to my problem and my problem is this. With headphones attached to my QRP transceiver (MMR-40) I hear stations very well and pleasant etc. but then another station comes on the frequency and it is way too loud so I turn down the volume. There doesn't seem to be any distortion or overloading, I just need a circuit that does the automatic volume control rather than the manual control I now have.
    I thought the best way to do that was to sample the audio and feed back a control voltage to the audio amp thereby adjusting the gain of that amp. Hopefully I would find such a circuit (that someone else had built) and I could just duplicate that circuit and drop it in.
    I have gone to the links you provided and I can see it's instructional value but I am not capable of using that data and designing a circuit for my purposes.
    Thanks again for your post.
    Regards, Dan
     
  5. danadak

    Distinguished Member

    Mar 10, 2018
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  6. DanW8KMX

    Thread Starter Member

    Oct 21, 2009
    25
    1
    Dana: This is great help. I see two already designed and proven (I hope) circuits that I can duplicate. Many thanks.
    Dan, W8KMX
     
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