DSP/SDR on a microcontroller

Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by KC6ETE, Dec 7, 2018.

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  1. KC6ETE

    KC6ETE Ham Member QRZ Page

    It seems to me that it should be feasible to do a DSP receiver using a microcontroller, directly from the antenna on these bands. Is there anyone already working on this?
  2. N0UU

    N0UU Ham Member QRZ Page

    Using one of the NVIDIA sound cards, if you can program them!, should be a slam dunk. not sure if anyone has done that with a fast AD, etc on a microcontroller. Anxious to see what you come up with. N0UU
  3. VA3VF

    VA3VF Ham Member QRZ Page

    Try Microchip's DSPic series of microcontrollers.
  4. KC6ETE

    KC6ETE Ham Member QRZ Page

    The PC route is exactly what I don't want. The various available SDRs are very wideband and likely pretty noisy, and none of them seem to be capable of working in small bandwidths.
    I'm just looking to implement CW for now.

    I was hoping someone had a project that I could look at as a starting point, on Pic, AVR, ARM or something similar.
  5. KF5FEI

    KF5FEI Ham Member QRZ Page

    IIRC, one of the more recent interviews on The Amp Hour Podcast was a guy who made FPGA demo boards that could be used for DSP.
  6. KC6ETE

    KC6ETE Ham Member QRZ Page

    FPGAs eat lots of power. At these low frequencies, I think it should be doable with a simple microcontroller. Possibly requiring a faster ADC than you usually see, or by aliasing the carrier down, but definitely without the power hogs.
  7. N0UU

    N0UU Ham Member QRZ Page

    WAAAAY back I met Ray Petit at a HamFest in Wash State doing a really early demo of CCW, Coherent CW, on a picnic table in the woods. Was in the Navy I think and was early active in digital modes. I'm pretty sure he passed away quite young. I got involved and somewhere have a box of CCW equipment, deCarle's boards, etc. This article explains why CCW went away, but would be fun to try with new chips, etc. Cheap and effective. Remember that you are exchanging needed freq stability and timing to listen to your own oscillator, but relatively simple now. https://midnightdesignsolutions.com/ccw/n2apb-wb9flw/n2apb-wb9flw.pdf
  8. N0UU

    N0UU Ham Member QRZ Page

  9. KC6ETE

    KC6ETE Ham Member QRZ Page

    Ok, that's closer to what I'm thinking. The 475 khz band is pretty narrow, and I think it should be possible to create a receiver that looks only at that band.
    I wouldn't expect it to fall into CCW exactly.
    I would expect some drift on my part and theirs. I can control my end to 10ppm, maybe better. As long as I can follow the signal over time, that would be fine.
    Last edited: Dec 7, 2018

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