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Ham radio + PIC + audio processing

Discussion in 'Electronic Design' started by [email protected], Apr 6, 2007.

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  1. Guest

    Hello,

    I am interested in building a one-off PIC controlled portable ham
    radio receiver, specifically oriented towards a low cost direct
    conversion design optimized for CW. I have experience with PICs (and
    other MCUs) and analog and RF but very little ham experience (I am not
    a ham - or not yet - I am working on my code practice).

    I am looking at some ideas for a simple but above average quality
    (processing, technical specs) direct conversion receiver aimed at 7
    MHz and mostly CW, and later expandable to 3.5 and 14 MHz.

    While trying to solve the problem of pile-ups with a relatively
    wideband audio receiver, the following questions came up:

    - Does panorama (stereo) processing of audio in a direct conversion
    receiver help with separation, in despite of the image frequencies
    presence ?

    - Does IQ processing in a direct conversion receiver solve the image
    problem ? (i.e. two channels 90 degrees out of phase). Is anyone using
    an IQ direct conversion receiver with DC (or low frequency) output to
    amplitude and/or modulate a tone oscillator for receiving CW ? (note
    that this solves the image problem imho).

    - I think that using dynamic compression on the audio signal would
    help a lot with pileups. In a pileup there may be signals with 50 dB
    or more of relative loudness. I think that using a dynamic compressor
    can reduce that to 10-20 dB if AGC is also used. Yet, I was unable to
    find references on this. Is there a reason for not using dynamic
    compression with CW signals in a pileup (besides the difficulty
    presented by the fluctuating amplitude etc). Would a compressor not
    help in general when several signals are in the audio band, and each
    fades separately, thus confusing AGC ?

    - At least one commercial receiver (Elekraft) uses a PIC for frequency
    readout. Would a Weeder style counter create too much noise if used
    directly next to a sensitive receiver circuit ?

    thank you for any answers or pointers,
    Peter P.
     
  2. David Harmon

    David Harmon Guest

    On 6 Apr 2007 00:14:37 -0700 in sci.electronics.design,
    wrote,
    What country are you in, that still has a code requirement?
     
  3. Guest

    *I* have a code requirement, but that is not the point. The point is
    the exercise and later slow dx digital modes.

    thanks,
    Peter P.
     
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