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Thread: AudioSDR - A single Audio block SDR (software defined radio) processor/demodulator

  1. #26
    Senior Member
    Join Date
    May 2016
    Posts
    226
    @robjohn...
    Nice looking unit. I really like the simplicity of your panel and display!! My unit(s) are still being built on protoboards with hand wiring underneath.

    I'll be delighted to share my control/display software with you. However, it's continually being updated, and is not quite as clean as I would like before being released. For example, I've (just this week) added a menu sytem for adjusting operating mode/band/adjusting operating parameters etc. It's working well but the code is still a bit untidy. It's a work-in-progress and always will be.
    The other thing is that the code is closely tied to my hardware. For example, I use an I2C port expander to communicate with the tactile switches on the front panel, and I have a home-brew RF front-end with an "SDR Cube" (which has 0/6/10/16 dB atten, and 4 octave-wide BPFs) and I use another port expander to control that. I am also using direct quadrature generation from the SI5351 (without the "divide by 4"). So you may have to make quite a few adjustments.

    How should we proceed? I'll start by uploading the SI5351 libraries to GitHub tomorrow. Maybe we should continue by PM? It'll take me a day or so to package up all my libraries...

    The things I'm working on right now are:
    1) Improving the panadapter display (graphics, smoothing, and algorithm). I had to compromise with the T3.6, but the extra speed of the T4 opens up new possibilities.
    2) As you say, the AM demod is not as clean as it might be, although I get a 120 Hz hum on the audio. It should be the simplest demodulator - it is just a quadrature envelope detector - but it has given me the most problems. Also, I'm not happy with the capture range in the PLL used in the SAM detector, and am looking at that.
    3) A bigger project is the design of a proper adaptive audio noise reduction filter. At the moment it simply uses the notch filter in an enhancement mode.

    BTW - what display are you currently using? Is it the PJRC ILI9341 2.8". I ask because I'm planning to move up to a 3.5", which will mean yet another bunch of software changes. It just never ends...

    Derek

  2. #27
    Junior Member
    Join Date
    Mar 2019
    Posts
    14
    Hi Derek
    The unit is only tidy on the outside using the ILI9341 3.5" with adafruit lib, has lots of nice fonts to choose. The serial interface does generate RFI though.

    Interest is mainly your audioSDR functions. My first coding attempt with PJRC audio library was a simple DC IF SSB demod phasing method but image reject was poor and never got round to figuring out AM. Then found yours to try and was fairly straightforward to implement. I have buttons to scroll through the detectors and BW. Should I be able to compile code for the panadapter? I took code from the doc but there's nothing in the lib header files for panadapter.

    I will definitely try out any updates you post, especially AM, panadater, AGC bar-graph and library for the SI5351 tuning.

    Cheers Rob

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