Sounds like an interesting project! I have very little DSP experience
other than telling a DSP engineer what I want, and the code magically
appears. But http://www.earlevel.com/main/2013/10/13/biquad-calculator-v2/
has proved useful. I'm currently using a biquad as a CW filter for
reception by ear. Picking up signals below the noise level is interesting.
This, of course, is what FT8 and similar weak signal techniques do using
multi-frequency shift keying.

Are you also looking at machine decoding of the CW? I note that there is a
CW decoder in KiwiSDR, but it is very error prone with noise and fading.

I am, as a background project, looking at using SOMETHING for amateur
radio applications. My transceiver has an RS485 control bus along with a
balanced audio bus and PTT. I'm thinking of maybe using an old netbook to
control it, stream audio, etc., OR using a PIC32 (maybe MZ) to do the
same. I'm MUCH more familiar with PIC32 software, including streaming
audio (PCM and ADPCM) than I am familiar with linux talking to hardware
like a USB audio interface, USB RS485 interface, etc.). So, still playing
around with ideas.

I look forward to hearing other comments you get.

Harold
http://w6iwi.org

> I had posted a couple weeks ago and I guess it fell in the bit bucket.
>
> I'm looking for info on DFT or similar approaches to detect very weak CW
> signals buried in noise.
> I'm only interested in a 200Hz window, and I can control where it falls
> frequency wise, between 150Hz (center) and several kHz.
> I need as much frequency detail as possible, sub 1Hz definitely, but the
> "dot" is pretty short. At 20WPM that works out to well below.
> https://www.w8ji.com/cw_bandwidth_described.htm
>
> This will get implemented on an AVR or similar, with input from the
> on-board ADC.
>
> I expect I will need a rather long array of samples, but I am starting to
> think of a circular buffer there and sending chunks of to the DSP process=
..
>
> I have looked in Smith's DSP book, but I haven't found what I'm looking
> for.
>
> --
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> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>


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