Export to 16 bit signed WAV (don’t forget to also change the Project Rate otherwise it will export in 48kHz) Audacity: trim and resample to 11.025kHz.GNU Radio receiver records 44.1 kHz WAV.I have then transcoded tha WAV file to 16 bit signed, 11.025 kHz using VLC and Audacity, which then was decoded using wxtoimg. The audio output from the demodulator is also dumped to a WAV file. If you want to use the cool sound of NOAA satellites in your next music composition or video let me know 🙂 The video below shows the playback of the recorded IQ data from a NOAA-15 pass. The latter is necessary to maintain a constant sample rate that was used to record the data. The playback program is a simple WFM receiver where the USRP source is replaced with a file source and a throttle block. Being able to hear the APT signal during recording helped me point the antenna in the right direction 😉 The only required function of the data recorder is to dump the USRP data directly to a binary file however, I also included a WFM receiver. I wasn’t attempting real-time decoding of the images - I only wanted to test the IQ data recording and playback I have described here and here. On the software side I used simple WFM receiver implemented in GNU Radio Companion and a free version of WXtoImg for decoding the images. I used my Arrow II 3 element handheld yagi for 145 MHz and of course the USRP with the WBX daughterboard. I only wanted to explore IQ data recording and playback with GNU Radio but when I first used NOAA 15 as test signal and saw what I could receive I got slightly distracted from my original plan. This weekend I ended up receiving APT signals from NOAA polar orbiting weather satellites.
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