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Thread: Open Source DSP Audio Processor for FT-817

  1. #26
    Junior Member
    Join Date
    Jan 2018
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    6
    Hi Frank...
    Yes, I had a browse through your code. It's very comprehensive for sure.
    How does the spectral NR sound? I believe that's what Yaesu use, and IMMO their NR is probably the best sounding in the industry.
    I will be ordering a 3.6 in the very near future...
    73
    Gerry Ei8DRB

  2. #27
    Senior Member DD4WH's Avatar
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    Oct 2015
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    Central Europe
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    458
    Hi Gerry,

    most transceivers use the LMS algorithm in the time domain for noise reduction, which does a good job when your signal already has high SNR.

    If your signal has a low SNR and you would like to "pull it out of the noise", LMS does not help very much. Here you need spectral NR in the frequency domain.

    Only very few transceivers (most of them in the 2k$ range) have spectral noise reduction algorithms implemented. Even the Elecraft K3 has only got LMS.

    I uploaded one short example of the software implemented noise reduction (collaboration with Michael, DL2FW) in the Teensy Convolution SDR, which is also implemented in the UHSDR software running on STM32F4 and STM32F7 processors.

    https://github.com/DD4WH/Teensy-Conv...r/example1.mp3

    However, we have a diversity of different hearing habits and preferences, so I realized that some people like the NR for its strong noise reduction, some dislike it because it changes the sound of the speech. Your ears decide :-).

    73 de Frank

  3. #28
    Junior Member
    Join Date
    May 2018
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    1
    Hello,

    I red the article just last night and bought a teensy 3.2 on ebay. Verry nice work has been done!
    But I think there has to be some improvemts :

    - Samplerate has to be reduced 44kHz ist 5 times higher than needed
    - reducing sample rate will give same extra power for noise canceling or / and auto notch or reducing CPU clockrate
    - Some manual notch filtering should be added

    Samplerate adjustment has to bee done in input_adc.cpp, I'll try my best after my teensy arrived.
    I'll fit my boards into my old rigs IC-202 and TS-790. Afterwards I'll send some pictures of the migration progress.

    73s Frank / DB5FP

  4. #29
    Junior Member
    Join Date
    May 2018
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    14
    Hi Gareth,
    Just came upon this thread. Wondering if you could contact me directly via email (w0eb [at] cox dot net) as I have some questions about the possibility of implementing your filter as a stand-alone, tunable filter using an encoder and a couple of selector push buttons with a small 1.44" Color TFT display to show the filter CF and Bandwidth graphically. A friend of mine is a super good programmer and between us it would be fun to get something like this working. Not to use commercially but as a good conversation point at ham fests.

    Jim Sheldon, W0EB

  5. #30
    Junior Member
    Join Date
    May 2018
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    14
    Hi Gareth,
    I did find some more info along with some images of how you wired things up, but the way you have the various items soldered to the pins on the Teensy 3.2 don't seem to reconcile with the pin assignments in settings.h.

    Also, there's an extra yellow wire coming off of pin 3 of the Teensy that doesn't have any correlation to either the encoder or the display.

    Could you post some more detailed info on how to actually connect the display, encoder and any other things to the Teensy 3.2 so I can match it with your code and build a stand-alone filter?

    Any help here would be much appreciated.

    Thanks in advance,

    Jim Sheldon, W0EB

  6. #31
    Junior Member
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    Oct 2018
    Location
    Bangalore
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    Quote Originally Posted by LU6PSG View Post
    Audio processing is fine, equalization is a MUST, but it would be a very nice addition for this project to also implement an RF compressor/clipper using the Hilbert transform, and a noise gate just like Voice Shaper. This means Microphone --> Equalization/noise gate ----> SSB modulation ---> SSB envelope compression/clipping ----> SSB Demodulation ----> Processed Audio sent to transmitter.

    The three stages of SSB processing can be achieved digitally using the hilbert transform, but I don't know how far can you go with the teensy.

    In my opinion, Voice Shaper is, by far, the most flexible and powerful speech processor available today for SSB. In the other hand, there is the need for a computer to run the software... so I see a lot of potential for an RF processing stage in this project. I guess this can be easily created in MATLAB.

    73 DE LU6PSG
    Is there any project that does this? Similar to Voice Shaper. I am keen on doing something on these lines so that I can learn some DSP stuff.

    Thanks,
    Bejoy VU3BOJ

  7. #32
    Junior Member
    Join Date
    Jul 2019
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    1

    Question FT-817 CW SSB filter

    Very nice project.

    I am wondering why it is impossible to modify the board and put not only fiscally on the place of the original filter in the FT-817 but connect to the connectors of the mechanical filters.
    With no modifications to the FT-817 radio. Or minimal.


    Best regards

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