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Thread: Teensy Convolution SDR (Software Defined Radio)

  1. #501
    Hello together,

    here is a small update on the status of my MSi001 Teensy convolution project.
    After doing some additional shielding of the board and putting everything together in the metal box and as planned supplyng it from Li ion battery, I succeeded to drop the noise floor slightly lower than before (see the table below). But the main task was to check the actual dynamic range with current hardware (SGTL5000 - VDDA=3.3V claims SNR-90dB).
    Basically used the algorithm proposed from Frank.
    Quote Originally Posted by DD4WH View Post
    ......
    Concerning the "bit resolution", I personally think it would be better to measure the "dynamic range" of the whole system:
    * use 50 Ohm resistor instead of an antenna
    * "measure" the noise level in 500Hz bandwidth
    * insert a signal of defined (high) signal level into the antenna input
    * measure the largest signal level without compression / desensibilization in 500Hz bandwidth
    * and the difference between the two measurements is the dynamic range of the whole SDR system
    * if you can achieve 16 bit == 96dB, your system will be high end quality, I think :-)
    .........
    The settings are also included in the picture

    Click image for larger version. 

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    The dynamic range that I succeeded to measure is roughly around 82dB, equivalent of around 14 bit resolution.

    Second topic is more for fun
    Last days I got a bit more time and I add some kind of "Menu Assistant"
    Click image for larger version. 

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    Now it is possible with long press of the encoder to call the "Menu Assistant" and it is possible to scroll up and down, change the selected position and as well is indicated small block diagram to to give you hint what you change at the moment.
    As an advantage it is possible to scroll with the encoder directly (much faster) and also 7 positions of the menu are visible at a time.

    The actual code lies here:
    https://www.dropbox.com/s/64i77appz8...07_24.rar?dl=0

  2. #502
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    Nice work Tisho! Sounds like your radio is working well. I like the menu - it looks great.

  3. #503
    Hi Bill, did you have time to measure the dynamic range of you one? I am curious to see how the TI ADC is performing.

  4. #504
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    Quote Originally Posted by tisho View Post
    Hi Bill, did you have time to measure the dynamic range of you one? I am curious to see how the TI ADC is performing.
    I didn't measure it yet. I need to get some more attenuators. I used to have a whole bunch of them but now I only have a few.

  5. #505
    Senior Member DD4WH's Avatar
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    Fantastic developments! I am really impressed!
    @tisho: the menu looks excellent! I would really like to include it into the main code. Is it possible that you submit a pull request to my github? it would be very laborious to take the code from your repo and merge it by hand . . .
    Also the figures look very good! We should not expect miracles from a 3$-chip ;-). But the figures look very satisfying and could possibly be improved by adding an attenuator at the antenna input or simply by switching off the preamp
    @Bill: your MATLAB experiments look very good! I am a total newbie to MATLAB, so I am very impressed. Also, I am not so good in the DSP-associated math, my approach to the DSP-subject is more like thinking in graphical blocks :-).
    we had some discussion here in the forum on the minimum phase FIR filters and there is also a nice video of a talk by Warren Pratt during the HAM RADIO fair in Friedrichshafen in 2018, which is very informative.

    I will not have the opportunity to do much on the subject in the next three weeks, so I will remain silent and come back to the forum in a few weeks.

  6. #506
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    Quote Originally Posted by WH7U View Post
    ...
    I agree that the 74LVC4066 is a great chip. According to the data sheet, the typical t-on time is 2.5 ns and the t-off time is 3.4 ns which is very fast.

    Here is what I have been thinking about when I should have been sleeping... In this mixer circuit, if I have my receiver set to my maximum (non-multiplied) frequency of 50 MHz, the clock period is 20 ns (1/50 MHz). So the quadrature switches are each on for 1/4 of each 20 ns period. This means that each switch is on for 5 ns and off for 15 ns (I'm ignoring the second set of four switches but they are doing exactly the same thing). But when I consider the delays in the 74LVC4066, my switches turn on faster than they it turn off (typical of FETs due to their gate capacitance). Say we start a timer when the first switch turns on at t=0 ns. The first switch should turn off at t=5 ns and at the same time, the second switch should turn on. But the first switch actually turns on at t=2.5 ns and turns off at t=8.4 ns (5 ns + 3.4 ns). The second switch turns on at 7.5 ns (5 ns + 2.5 ns). So during the time between 7.5 ns and 8.4 ns both switches are on! This happens four times each period so we have two switches on for a total time of 0.9*4 ns = 3.6 ns during the period. This is 18% of the period.
    ...
    Your calculation is only right for the 3253 with the internal 1:4 decoder. A QSD with a 4066 switch IC each switch of the four switches are a half RF period on and of!

  7. #507
    Hi Frank,
    Would like to start with that I am a newbie with the GitHib.
    I made a "pull request" but have a feeling it didn't work as expected (somehow it is showing to many changes in the main "ino" file, but the file it is correct). Nonetheless when you have time you can take a look, you can see that the whole "Menu Assistant" it is in a separate "ino" file so the merge will be not that hard.
    Meanwhile I will read a bit more in the GitHub documentation to see if I really did everything correct.

  8. #508
    Senior Member DD4WH's Avatar
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    Quote Originally Posted by tisho View Post
    Hi Frank,
    Would like to start with that I am a newbie with the GitHib.
    I made a "pull request" but have a feeling it didn't work as expected (somehow it is showing to many changes in the main "ino" file, but the file it is correct). Nonetheless when you have time you can take a look, you can see that the whole "Menu Assistant" it is in a separate "ino" file so the merge will be not that hard.
    Meanwhile I will read a bit more in the GitHub documentation to see if I really did everything correct.
    Thanks a Lot! Will Take a Look in August, sorry, that its Not possible earlier!

  9. #509
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    Hello,

    I have seen that in addition to the menus, you have incorporated the AFC into the original teensy msi001 support, good work.

    My two cents: It would be interesting if Frank and the others think about adopting a reference hardware for the github master, to facilitate code maintenance in the near future.

    Greetings, Esteban EA8DGL.


    Quote Originally Posted by tisho View Post
    Hello together,

    here is a small update on the status of my MSi001 Teensy convolution project.
    After doing some additional shielding of the board and putting everything together in the metal box and as planned supplyng it from Li ion battery, I succeeded to drop the noise floor slightly lower than before (see the table below). But the main task was to check the actual dynamic range with current hardware (SGTL5000 - VDDA=3.3V claims SNR-90dB).
    Basically used the algorithm proposed from Frank.


    The settings are also included in the picture

    Click image for larger version. 

Name:	Dynamic_Range_Measurement.png 
Views:	27 
Size:	15.6 KB 
ID:	21112
    The dynamic range that I succeeded to measure is roughly around 82dB, equivalent of around 14 bit resolution.

    Second topic is more for fun
    Last days I got a bit more time and I add some kind of "Menu Assistant"
    Click image for larger version. 

Name:	20200724_213256_T.jpg 
Views:	51 
Size:	89.2 KB 
ID:	21113Click image for larger version. 

Name:	20200724_213340_T.jpg 
Views:	46 
Size:	108.6 KB 
ID:	21114
    Now it is possible with long press of the encoder to call the "Menu Assistant" and it is possible to scroll up and down, change the selected position and as well is indicated small block diagram to to give you hint what you change at the moment.
    As an advantage it is possible to scroll with the encoder directly (much faster) and also 7 positions of the menu are visible at a time.

    The actual code lies here:
    https://www.dropbox.com/s/64i77appz8...07_24.rar?dl=0

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