From 17f6d54519abc98a41ccafa9a17cb2eaf6a156c1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andr=C3=A1s=20Retzler?= Date: Sun, 8 Nov 2015 15:31:31 +0100 Subject: [PATCH] Update README.md --- README.md | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/README.md b/README.md index 0bfa756..f6ebc32 100644 --- a/README.md +++ b/README.md @@ -15,7 +15,7 @@ Note that it should be already done, if you installed *qtcsdr*. ### Modulate from raw audio file -These examples will use the raw audio file `testsound48000.raw`, which is present in this repo. You can get this file by: +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: git clone https://github.com/ha7ilm/rpitx-app-note cd rpitx-app-note; ls #There is your file. @@ -24,12 +24,25 @@ A raw audio file differs from a .wav file because it doesn't have any headers to **Generate AM modulation:** - 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 + 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 * The part `csdr gain_ff 1.0` can be changed to increase/decrease modulation. * The `-f 28400` at the end gives the transmit frequency in kHz. +**Generate USB modulation:** + 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 +**Generate LSB modulation:** + + 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 + +* It's the matter of the filter which sideband do we select: + * `csdr bandpass_fir_fft_cc -0.1 0` is the lower sideband + * `csdr bandpass_fir_fft_cc 0 0.1` is the upper sideband +* 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` + +**Generate NFM modulation:** + + cat music48000.raw | csdr convert_i16_f | csdr gain_ff 7000 | csdr convert_f_samplerf 20833 | sudo rpitx -i- -m RF -f 28400 -