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  • DD4WH's Avatar
    04-17-2019, 01:51 PM
    https://framagit.org/PiBatRecorderPojects/TeensyRecorders/blob/master/PassiveRecorder/Fabrication/Souder%20c'est%20facile%20-%20Voici%20comment%20faire.pdf
    1 replies | 55 view(s)
  • DD4WH's Avatar
    04-14-2019, 10:43 AM
    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 eliminated some bugs...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    04-13-2019, 01:41 PM
    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: * some variables that...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    04-12-2019, 08:51 PM
    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 atan2f and...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    04-12-2019, 08:13 PM
    Hi Walter, hi Frank, yes, I can confirm: SGTL5000 overclocking with 234ksps and 281ksps works nicely . However, the processor load is about 79% when using stereo FM radio reception and 234ksps. With 281ksps, only...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    04-11-2019, 05:26 PM
    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!) * sample rates up to...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    04-11-2019, 08:07 AM
    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 change this in function
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    04-10-2019, 06:51 AM
    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 code. --> the Si5351...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    04-05-2019, 10:44 AM
    DD4WH replied to a thread Bat detector in Audio Projects
    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 of the sensitivity...
    223 replies | 22034 view(s)
  • DD4WH's Avatar
    04-05-2019, 08:32 AM
    DD4WH replied to a thread Bat detector in Audio Projects
    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 response higher than...
    223 replies | 22034 view(s)
  • DD4WH's Avatar
    04-05-2019, 07:58 AM
    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 does seem to be used...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    03-29-2019, 10:28 PM
    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 Convolution Filtering by...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    03-29-2019, 04:17 PM
    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 math . . . Why do...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    03-27-2019, 07:54 PM
    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 the SGTL5000 is so...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    03-26-2019, 03:28 PM
    DD4WH replied to a thread Change SampleRate in Audio Projects
    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 Discussions on changing...
    11 replies | 241 view(s)
  • DD4WH's Avatar
    03-24-2019, 01:17 PM
    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 translation!? And...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    03-24-2019, 12:54 PM
    DD4WH replied to a thread biquad output noise in Audio Projects
    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 states: So, I...
    10 replies | 265 view(s)
  • DD4WH's Avatar
    03-24-2019, 10:38 AM
    DD4WH replied to a thread biquad output noise in Audio Projects
    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 (Understanding Digital...
    10 replies | 265 view(s)
  • DD4WH's Avatar
    03-23-2019, 05:28 PM
    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: ...
    2 replies | 66 view(s)
  • DD4WH's Avatar
    03-23-2019, 09:40 AM
    @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 you can directly...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    03-22-2019, 09:39 PM
    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 of sample rate / 4,...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    03-22-2019, 09:02 PM
    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 been running in...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    03-22-2019, 03:39 PM
    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 only 125MHz -as far...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    03-21-2019, 03:22 PM
    DD4WH replied to a thread Bat detector in Audio Projects
    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 resolution (internal ADC) and...
    223 replies | 22034 view(s)
  • DD4WH's Avatar
    03-21-2019, 12:24 PM
    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 nice in the context of...
    38 replies | 794 view(s)
  • DD4WH's Avatar
    03-20-2019, 12:50 PM
    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 the filter order....
    2 replies | 132 view(s)
  • DD4WH's Avatar
    03-17-2019, 01:20 PM
    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
    9 replies | 211 view(s)
  • DD4WH's Avatar
    03-17-2019, 08:55 AM
    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 output caps (in the...
    9 replies | 211 view(s)
  • DD4WH's Avatar
    03-15-2019, 09:11 AM
    DD4WH replied to a thread Bat detector in Audio Projects
    Hi Cor, yes, very nice! Maybe you would like to contact him on the thread mentioned above? All the best, Frank
    223 replies | 22034 view(s)
  • DD4WH's Avatar
    03-15-2019, 08:51 AM
    DD4WH replied to a thread Bat detector in Audio Projects
    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. ...
    223 replies | 22034 view(s)
  • DD4WH's Avatar
    02-19-2019, 11:05 PM
    Hi Paul! You probably already know this WIKI site on binaural listening with the Teensy Convolution SDR: https://github.com/DD4WH/Teensy-ConvolutionSDR/wiki/Binaural-audio-=-pseudo-Stereo-demodulation At the...
    187 replies | 44894 view(s)
  • DD4WH's Avatar
    02-19-2019, 10:33 AM
    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): ...
    34 replies | 5367 view(s)
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About DD4WH

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About DD4WH
Location:
Central Europe
Interests:
Software Defined Radio, Digital Signal Processing, Bat detection & bioacoustics

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Audio Adaptor Board with headers soldered on in the EU? 04-17-2019 01:51 PM
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Join Date
10-25-2015