kopia lustrzana https://github.com/ha7ilm/rpitx-app-note
Update README.md
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README.md
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README.md
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@ -15,7 +15,7 @@ Note that it should be already done, if you installed *qtcsdr*.
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### Modulate from raw audio file
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### Modulate from raw audio file
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These examples will use the raw audio file `testsound48000.raw`, which is present in this repo. You can get this file by:
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These examples will use the raw audio file `music48000.raw` and `speech48000.raw`, which is present in this repo. You can get this file by:
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git clone https://github.com/ha7ilm/rpitx-app-note
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git clone https://github.com/ha7ilm/rpitx-app-note
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cd rpitx-app-note; ls #There is your file.
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cd rpitx-app-note; ls #There is your file.
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@ -24,12 +24,25 @@ A raw audio file differs from a .wav file because it doesn't have any headers to
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**Generate AM modulation:**
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**Generate AM modulation:**
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cat testsound48000.raw | csdr convert_i16_f | csdr gain_ff 1.0 | csdr dsb_fc | csdr add_dcoffset_cc | sudo rpitx -i- -m IQFLOAT -f 28400
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cat music48000.raw | csdr convert_i16_f | csdr gain_ff 1.0 | csdr dsb_fc | csdr add_dcoffset_cc | sudo rpitx -i- -m IQFLOAT -f 28400
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* The part `csdr gain_ff 1.0` can be changed to increase/decrease modulation.
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* The part `csdr gain_ff 1.0` can be changed to increase/decrease modulation.
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* The `-f 28400` at the end gives the transmit frequency in kHz.
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* The `-f 28400` at the end gives the transmit frequency in kHz.
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**Generate USB modulation:**
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cat speech48000.raw | csdr convert_i16_f | csdr dsb_fc | csdr bandpass_fir_fft_cc 0 0.1 0.01 | csdr gain_ff 2.0 | csdr shift_addition_cc 0.2 | sudo rpitx -i- -m IQFLOAT -f 28400
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**Generate LSB modulation:**
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cat speech48000.raw | csdr convert_i16_f | csdr dsb_fc | csdr bandpass_fir_fft_cc -0.1 0 0.01 | csdr gain_ff 2.0 | csdr shift_addition_cc 0.2 | sudo rpitx -i- -m IQFLOAT -f 28400
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* It's the matter of the filter which sideband do we select:
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* `csdr bandpass_fir_fft_cc -0.1 0` is the lower sideband
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* `csdr bandpass_fir_fft_cc 0 0.1` is the upper sideband
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* I have experienced that if the SSB signal is in the center of the I/Q signal, then it won't be okay, so I shift it a bit. So the exact frequency should be around: `rpitx frequency + 48000*0.2 = rpitx frequency + 9600 Hz`
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**Generate NFM modulation:**
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cat music48000.raw | csdr convert_i16_f | csdr gain_ff 7000 | csdr convert_f_samplerf 20833 | sudo rpitx -i- -m RF -f 28400
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