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Thread: Teensy Convolution SDR (Software Defined Radio)

  1. #101
    Senior Member DD4WH's Avatar
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    Hi Mike,

    filtering with FIR filters in the time domain is very inefficient when it comes to large filter sizes (= steep filters). It is much more efficient to filter in the frequency domain, which involves an FFT, a complex multiply with a filter mask and an inverse FFT. That process is called Fast Convolution.

    In the context of the Teensy Convolution SDR, its all explained here:

    https://github.com/DD4WH/Teensy-Conv...%20english.pdf

    Also you could have a look at the excellent paper by Borgerding referenced in Wikipedia:

    https://en.wikipedia.org/wiki/Overla...%93save_method

    Youngblood has published a nice paper in 2002:

    http://www.arrl.org/files/file/Techn...0708qex013.pdf

    One side effect of using Convolution filtering in an SDR is that you do not even have to demodulate SSB at all, because the sideband suppression is already done in the filter (of course, you have to choose your filter bandwidth in the right way for LSB/USB) :-).

    Have fun with the Teensy Convolution SDR,

    Frank
    Last edited by DD4WH; 07-14-2018 at 02:20 PM.

  2. #102
    Senior Member DD4WH's Avatar
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    sorry, here is the direct link to the excellent Borgerding paper:

    https://ieeexplore.ieee.org/iel5/79/33613/01598092.pdf

  3. #103
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    Compile error

    Hi Guy's I am trying to compile Teensy SDR code and setup as per Jans instruction but still get the error below. Help would be much appreciated. 1.8.6 Arduino IDE.

    C:\Program Files (x86)\Arduino\hardware\teensy\avr\libraries\Arduin o-Teensy-Codec-lib-master\asmpoly_thumb2.S:2:2: error: invalid preprocessing directive #.

    #.fpu softvfp

    ^

    Error compiling for board Teensy 3.6.

  4. #104
    Frank,
    Looks like an interesting project. FWIW I have successfully compiled 2018_03_24 code with Arduino 1.8.7, Teensy Loader 1.44 using https://github.com/DD4WH/Teensy-ConvolutionSDR.

    However, not sure what kind of hardware radio to get. The GitHub article suggests "QSD = quadrature sampling detector and a local oscillator that can be tuned by I2C (eg. Si5351, Si570, Si514 . . .) [should run with Softrock, Elektor SDR (https://www.elektor.de/elektor-sdr-reloaded-150515-91), Fifi SDR and many others]

    The ones mentioned on various pages are not available or don't seem to be Si5xxx.. based. Most seem to be complete SDRs not requiring your software solution. I'm not sure how to figure out where the QSD outputs would be. Any recommendations on how to select one? Will an open source for http://pa0rwe.nl/wp-content/uploads/..._schematic.gif be available?

    thanks
    Mike

  5. #105
    Senior Member DD4WH's Avatar
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    Hi Mike

    you can contact pa0rwe whether he still has his excellent PCBs available.

    or try the kit by QRP labs „Receiver module“, which has excellent Performance for its price.

    we have very good experience with the Si5351 as a local oscillator

    however, the Teensy Convolution SDR is more an educatioal project than a ready-to-use SDR.
    so I recommend to read through all the relevant literature and the Wiki before buying any hardware.
    Also have a look at the Wiki of our UHSDR software on github where you will find even more info on hardware but especially on the software and how they work.

    Also for high performance you need proper lowpass RF filtering at the antenna input, (as with all QSD SDRs).

    have fun and good luck

    Frank

  6. #106
    Frank,
    Thanks for the info. The QRP labs 'Receiver module' looks like the way to go with maybe the OCXO/Si5351A Synth kit.

    I recently built Bob Larkins awesome AVNA and a nice 3D printed case to put it in.
    http://www.janbob.com/electron/AVNA1/AVNA1.htm

    Click image for larger version. 

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    The same display, Teensy and audio board are used. Some parts of the schematic are very similar, such as the instrumentation configured op amps. Wondering if I can use the AVNA PWB almost as is and modify your software to input the I Q data into the AVNA path. I have massaged your SDR software to display on the AVNA so far. This just required changing some I/O pins and a few other details. As you noted this is an educational project. Wonder what else I could repurpose from the AVNA without ruining it for its normal use.

    Click image for larger version. 

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    Wonder what you think. Hopefully Bob will see this too.
    Last edited by bicycleguy; 12-15-2018 at 03:23 AM. Reason: spelling and more detail

  7. #107
    Senior Member+ Frank B's Avatar
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    Quote Originally Posted by bicycleguy View Post
    Click image for larger version. 

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    The case looks great! Would you please publish the STL? I ordered a 3D printer for my son and me, and it looks like a worthwhile project.

  8. #108
    Senior Member+ Frank B's Avatar
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    @Frank: I've ordered the QRP labs „Receiver module“ and Filters just now.

  9. #109
    Frank B

    Just posted the 3D case for the AVNA here.
    https://groups.io/g/AVNA1/topic/3d_p...0,2,0,28882256

    It needs more knobs for the SDR !

  10. #110
    Senior Member+ Frank B's Avatar
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    You can't happen to make a similar version with the knobs for SDR? :-)

  11. #111
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    Hi Guys, I'm joining the party
    I've just complied the latest code and uploaded to a Teensy 3.6, serial monitor scrolling 'Unable to access the SD card', so all looking good so far....
    Display on order expecting delivery next week, now looking into I & Q hardware, have emailed Joris enquiring about his SDR front end boards....
    Has anyone designed a motherboard for the display, encoders and buttons? I'm learning a huge amount here already
    Thanks Frank for this fasinating project.
    73's
    Kevin

  12. #112
    Senior Member DD4WH's Avatar
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    Hi Kevin,

    nice to hear that you are working on your Teensy Convolution SDR!

    No, unfortunately, we have not yet produced a PCB design for such a motherboard. But you may consider Bob Larkinsī very nice approach:

    http://www.janbob.com/electron/SDR_Ctrl1/SDR_Ctrl1.html

    and he also designed nicely usable RF frontend filters:

    http://www.janbob.com/electron/FilterBP1/FiltBP1.html

    IQ hardware would be available here:

    https://qrp-labs.com/receiver.html

    https://www.elektor.de/elektor-sdr-s...dule-170515-91

    The latter one from Elektor looks highly recommendable and even already contains the Si5351 LO, although I have not used this newer version of the board, only the older one.

    However, you have to be smart to adjust some of the components for your specific needs (bandwidth of the quadrature detector)

    I'm learning a huge amount here already
    Thats essentially what this project is all about! ;-)

    Have fun with the Teensy Convolution SDR!

    Frank DD4WH

  13. #113
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    Thanks Frank for the update, I did look at Bob's project box, very nice, but as always there's something that I would do differently, so I've decided to pull something together myself. I'll post the schematics in a week or two. but basically the idea at the moment is to mount the display, 6 buttons and 3 encoders ( 2 encoders with buttons the tuning encoder an alps smooth rotation optical with no button), headers for I2C and band pass switching and probably pull out the SPI as well. So this hardware can be panel mounted in one, in a very simular manner to the Juma TRX2 DDS front panel.
    I also think I'll pull together the Si5153 / div x 4, splitter QSD and amps, copying the Juma front end on a seperate board. The band pass filters I'm still pondering over, but these can wait until I've finished the above
    Like all of us, far too many projects on the go...... I NEED to retire soon.......

  14. #114
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    Hi Frank,
    my pensioner status is some years old, so I have enough time for experiments.
    After no success with a PSoC5LP SDR project (10 dB image rejection) I found your very interesting Teensy3.6 Convolution SDR.
    I'm very impressed about your work, and I begun to solder the things together. The QSD is a little bit different from PA0RWE,
    but consists of the same circuits. I hope, that with phase and amplitude calibration I get better results than with the PSoC.
    What I miss is a complete description of the wiring, with all details. My try is attached, please, if you have the time, have a look at it.
    (The table is very redundant, but helps me to make the right connections...)

    http://wkiefer.de/x28/test/Teensy_DD4WH.xls

    http://wkiefer.de/x28/test/Teensy_DD4WH.pdf

    Thank you!
    Wolfgang
    Last edited by DH1AKF; Yesterday at 12:36 PM.

  15. #115
    Senior Member DD4WH's Avatar
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    Hi Wolfgang,

    thank you for your interest!

    Yes, you can expect 50-60dB of image rejection with the Teensy Convolution SDR, the automatic software I & Q phase & amplitude correction algorithm in realtime also eliminates the need for any hardware correction or manual calibrations or measurements :-).

    The pinout, the source code and a pdf describing the basic functioning can be found on github.

    PINOUT: https://github.com/DD4WH/Teensy-Conv...R%20pinout.txt

    GITHUB & WIKI: https://github.com/DD4WH/Teensy-ConvolutionSDR/wiki

    PDF with functional description: https://github.com/DD4WH/Teensy-Conv...%20english.pdf

    I have no detailed hardware wiring diagram, because everyone uses a bit different hardware setup and thats the whole fun of it . . . :-).

    Have fun with the Teensy Convolution SDR,

    Frank DD4WH

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