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  1. Replies
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    As far as I can see, there is no need for such a...

    As far as I can see, there is no need for such a large (and processor-intense) FFT. Of course the T4 could help you, but I am pretty sure that by reducing the load you can do that on a T3.6

    Your...
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    Hi gohlhausen, thanks for your work! Did...

    Hi gohlhausen,

    thanks for your work!

    Did you test, how your FFT performs if applied to audio? In my experience, when used for convolution (FFT --> complex-multiply with filter mask --> inverse...
  3. We now use a total of 12 microSoundRecorders for...

    We now use a total of 12 microSoundRecorders for recording nocturnal Crex crex (corn crake). Thank you again, Walter, for providing us with this Teensy 3.6 recording tool with your software!

    Our...
  4. Thread: Bat detector

    by DD4WH
    Replies
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    28,389

    deleted due to browser error.

    deleted due to browser error.
  5. Thread: Bat detector

    by DD4WH
    Replies
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    28,389

    Hi Edwin, what an impressive amount of...

    Hi Edwin,

    what an impressive amount of microphones!!! Looks like a lot of soldering fun ;-).



    This is wrong for single ended mode and is not stated in the datasheet, that is what my posts in...
  6. Thread: Bat detector

    by DD4WH
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    28,389

    Hi Edwin, I feel that there are several people...

    Hi Edwin,

    I feel that there are several people having problems to understand how to use the ICS40730 in single ended mode for maximum performance ;-).

    Here is the <magic> with that MIC:

    GND...
  7. Thread: Bat detector

    by DD4WH
    Replies
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    I initially thought you were looking for people...

    I initially thought you were looking for people reporting about their experience with the ICS40730. Thats what I did.



    I can highly recommend the ICS40730 which has proved to be of excellent ...
  8. Thread: Bat detector

    by DD4WH
    Replies
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    Well, that is odd. How would you explain that...

    Well, that is odd.

    How would you explain that we use the ICS40730 in many devices with great sucess and in your setup the output is not clean?

    I am not sure what you mean with two outputs? The...
  9. Thread: Bat detector

    by DD4WH
    Replies
    331
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    28,389

    Hi Remis, we use the ICS40730 as a standard...

    Hi Remis,

    we use the ICS40730 as a standard ultrasound microphone for our semiprofessional bat recorders (in single ended mode !):

    * it has a sensational frequency response up to 160kHz
    * it...
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    Hi Holger, give this a try also, its a very...

    Hi Holger,

    give this a try also, its a very nice filter designer and also plots the response and gives you the coefficients. Also helpful is the possibility to test the filters with different...
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    Hi Valery, 1.) sample rate: yes, that is...

    Hi Valery,

    1.) sample rate: yes, that is already implemented in the newest version of the software!

    2.) yes, that is also possible, but you would have to alter the function setfreq according to...
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    Hi Frank, I have no experience with PIN diode...

    Hi Frank,

    I have no experience with PIN diode switching, but they are said to have low resistance against IM3, which means that high signal levels can seriously distort your reception. Could be...
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    Hi Valery, please learn how to use the Arduino...

    Hi Valery,

    please learn how to use the Arduino IDE and Teensyduino in order to compile your programs by yourself!

    That is really vital and important and will help you a lot for your own...
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    Hi Valery, nice to hear from you and thanks...

    Hi Valery,

    nice to hear from you and thanks for your report!

    However, I tested the situation with the AGC and I cannot confirm the behaviour you describe. The AGC works fine and similarly in...
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    Hi Wolfgang, I am happy to help, but not in...

    Hi Wolfgang,

    I am happy to help, but not in "second hand mode", so Valery should post his questions here directly on the forum.

    My suspicion is that he operates the Teensy Convolution SDR...
  16. https://framagit.org/PiBatRecorderPojects/TeensyRe...

    https://framagit.org/PiBatRecorderPojects/TeensyRecorders/blob/master/PassiveRecorder/Fabrication/Souder%20c'est%20facile%20-%20Voici%20comment%20faire.pdf
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    Hi Mike/bicycleguy, integrated your eePROM...

    Hi Mike/bicycleguy,

    integrated your eePROM code into the current version today. It now works properly, I think! I used a brandnew fresh T3.6 to test this and everything worked out nicely (after I...
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    Hi Mike, thanks for your pull request treating...

    Hi Mike,

    thanks for your pull request treating EEPROM.

    Sorry, I messed up the github (github is not one of my strengths, I must admit . . .).

    There seem to be problems with your code:

    *...
  19. Replies
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    Awesome!!!! That specific atan2 approximation...

    Awesome!!!!

    That specific atan2 approximation lowers the processor load in FM demodulation from 40.6% to 28.15% (234ksps sample rate) and in the first tests I cannot hear the difference between...
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    Hi Walter, hi Frank, yes, I can confirm: ...

    Hi Walter, hi Frank,

    yes, I can confirm:

    SGTL5000 overclocking with 234ksps and 281ksps works nicely [I use those sample rates frequently for receiving wide band FM stereo broadcast stations...
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    new version of Teensy Convolution SDR is on...

    new version of Teensy Convolution SDR is on github

    https://github.com/DD4WH/Teensy-ConvolutionSDR

    new:

    * new excellent SDR hardware by DO7JBH supported
    * bugfixes (thanks bicycleguy!)
    *...
  22. Replies
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    bicycleguy, thanks for your very good and...

    bicycleguy,

    thanks for your very good and precise observation!

    Probably my fault, sorry!

    It could be that this odd behaviour is caused by a buffer overflow (that is my fault!):

    please...
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    Hi bicycleguy, sounds good, would like to try...

    Hi bicycleguy,

    sounds good, would like to try to integrate your code into the script, if you allow!

    However, calibration_factor has to be type unsigned long long, please change that in your...
  24. Thread: Bat detector

    by DD4WH
    Replies
    331
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    28,389

    Hi Alain, the datasheet of the ICS40730 states...

    Hi Alain,

    the datasheet of the ICS40730 states that the mic has a sensitivity that is 6dB lower in single-ended mode vs. differential mode. However, the high SNR of 74dBA is the same irrespective...
  25. Thread: Bat detector

    by DD4WH
    Replies
    331
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    28,389

    Salut Alain, Edwin, Cor, Jean-Do. and all others...

    Salut Alain, Edwin, Cor, Jean-Do. and all others interested,

    Darras et al. (2018) in their paper use the ICS40720, which is an older version of the MEMS. Also they do not describe any frequency...
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    Hi bicycleguy, thanks for the suggestion! I...

    Hi bicycleguy,

    thanks for the suggestion!

    I do not understand the code fully yet, so I will take some more time to digest it. However, a couple of things to comment on:

    - calibration factor...
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    Hi Derek, thanks for your clarifying reply! ...

    Hi Derek,

    thanks for your clarifying reply!

    I had to read over that again in my favourite book (Rick Lyons "Understanding Digital Processing") and one of my favourite papers on Fast...
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    Hi Derek, sounds very interesting, looking...

    Hi Derek,

    sounds very interesting, looking forward to it!

    Sorry for my potentially silly question, my approach to DSP is more a way of trial and error than really having available any formal...
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    Martin, yes, we thought about this. I am not...

    Martin,
    yes, we thought about this. I am not sure whether the actual 12bit resolution of the ADCs (even if you set them to 16bit) will be sufficient for a high quality radio, but who knows whether...
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    hi Martin, what Thierry probably meant was this...

    hi Martin, what Thierry probably meant was this method by Frank B:

    https://forum.pjrc.com/threads/38753-Discussion-about-a-simple-way-to-change-the-sample-rate?highlight=change+sample+rate
    ...
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    Derek, thanks a lot for the detailed...

    Derek, thanks a lot for the detailed explanations!



    excellent! Thats totally new to me, I thought you had to rotate the frequency bins of the FFT output (and not the coefficients) for frequency...
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    Sorry, my mistake, I thought "int" was 16bit. So...

    Sorry, my mistake, I thought "int" was 16bit. So the coeffs have 32bit precision, I agree.

    So, we boiled the problem down to the internal precision of the calculations:

    The link you mentioned...
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    Summarizing the main points from the links given...

    Summarizing the main points from the links given above and summing this up with my own experience with IIR filters on the Teensy and having read pages 280ff in the excellent book by Rick Lyons...
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    Hi Martin, not sure if this is the same...

    Hi Martin,

    not sure if this is the same problem (that we have called "twin peak problem", because in an SDR spectrum display you see twin peaks from one carrier), but you could have a look here:
    ...
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    @Frank: OK, did not know that, I thought the FPU...

    @Frank: OK, did not know that, I thought the FPU of the new T4 would handle double as fast as float ;-)

    @Rob: if you use the Si5351 directly, your need for 4x higher LO frequency is avoided, so...
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    Ah, OK, now I understood! For AM & SSB...

    Ah, OK, now I understood!

    For AM & SSB reception up to 30MHz I use sample rates of 96k or 100k, that seems quite clean of spurs in the range that the SDR uses (as we use an intermediate frequency...
  37. Replies
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    Thanks Frank for the Si5351 link. Yes, confirmed,...

    Thanks Frank for the Si5351 link. Yes, confirmed, I have never experienced problems with phase noise in the Si5351 and also never had problems with slow lock of the Si5351 or Si570 which I have both...
  38. Replies
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    Hi Rob, thanks for your comments! As a...

    Hi Rob,

    thanks for your comments!

    As a biologist, I may not be up to the latest developments in the RF engineering field.

    Why would you think the DDS AD9850 is "much faster" ? It goes up to...
  39. Thread: Bat detector

    by DD4WH
    Replies
    331
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    28,389

    Hi Polly, I do not think that it is possible...

    Hi Polly,

    I do not think that it is possible to record ultrasound files to SD with a sample rate of 1.8MHz with the Teensy 3.6 . . .

    We use a maximum sample rate of 500kHz with 12bit...
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    Hi Derek, unfortunately I can confirm that the...

    Hi Derek,

    unfortunately I can confirm that the WM8731 (together with an STM32F4 / STM32F7) has exactly the same problem of an occasional random one sample delay. You are right, that is not very...
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    Try the Iowa Hills IIR Filter designer ...

    Try the Iowa Hills IIR Filter designer

    http://iowahills.com/8DownloadPage.html

    For each filter stage you need a 2nd order filter and you need to specify the sample rate, cutoff frequency and...
  42. Frank, have a look at the TPA6011 and the...

    Frank, have a look at the TPA6011 and the schematic on page 16 of the datasheet

    http://www.ti.com/lit/ds/symlink/tpa6011a4.pdf
  43. Hi Frank, not quite sure what you want . . . ...

    Hi Frank,

    not quite sure what you want . . .

    Maybe this:

    https://www.maximintegrated.com/en/products/analog/audio/MAX9879.html

    The problem with class A/B amps is that you need quite big...
  44. Thread: Bat detector

    by DD4WH
    Replies
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    28,389

    Hi Cor, yes, very nice! Maybe you would...

    Hi Cor,

    yes, very nice!

    Maybe you would like to contact him on the thread mentioned above?

    All the best,

    Frank
  45. Thread: Bat detector

    by DD4WH
    Replies
    331
    Views
    28,389

    Brandnew and very promising, another alternative...

    Brandnew and very promising, another alternative for the (semi-)professional bat worker:

    The bat recorder (Passive Recorder) and bat detector (Active Recorder) approach by Jean-Do.
    ...
  46. Replies
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    Hi Paul! You probably already know this WIKI...

    Hi Paul!
    You probably already know this WIKI site on binaural listening with the Teensy Convolution SDR:
    ...
  47. A lot of people have done that. You will find...

    A lot of people have done that. You will find links to several threads with different approaches here (all in the context of audio logging to SD card, with or without the audio lib):
    ...
  48. Replies
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    Sorry, I made a mistake: the Carson formula for...

    Sorry, I made a mistake: the Carson formula for the approximate bandwidth of an FM-modulated signal is the following:

    Bandwidth = 2 * (frequency deviation + baseband bandwidth of the audio signal)...
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    Hi Wolfgang, for wideband FM reception, the...

    Hi Wolfgang,

    for wideband FM reception, the SDR is in 3x undersampling mode, so your math is approximately right, if you divide the real receive frequency by 3 :-)

    However, in all demodulation...
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    I added some info on how to use the menu buttons,...

    I added some info on how to use the menu buttons, encoders and encoder push buttons in the Teensy Convolution SDR here:

    https://github.com/DD4WH/Teensy-ConvolutionSDR/wiki/Menu

    Have fun!
    ...
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