gnuradiotips
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gnuradiotips [2021/09/12 10:06] – [Using Baseband I/Q Recordings] mm3iig | gnuradiotips [2021/09/13 22:26] – [Using Baseband I/Q Recordings] mm3iig | ||
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===== Using Baseband I/Q Recordings ===== | ===== Using Baseband I/Q Recordings ===== | ||
- | Depending on the specifics of your recording you may need to change bits of this. You’ll want to use a WAV file sync, set the channels to two, and then immediately convert from float to complex to do useful things with the data. Then you’ll want a throttle block to set your desired sample rate. If you have recordings in a format other than 16-bit stereo you may need to add extra conversion steps into your flowgraph, or convert your input file first with other software. | + | Depending on the specifics of your recording you may need to change bits of this. You’ll want to use a WAV file sync, set the channels to two, and then immediately convert from float to complex to do useful things with the data. Then you’ll want a throttle block to set your desired sample rate. If you have recordings in a format other than RIFF 16-bit stereo you may need to add extra conversion steps into your flowgraph, or convert your input file first with other software. |
- | If your chosen signal is in the middle of the baseband, you’re done! If it isn’t, you will need to “tune in” to the signal with a Frequency Xlating FIR or FFT Filter first. | + | One thing you will have to look out for is the 4 GB wav file size limit in GNU Radio. |
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- | One thing you will have to look out for us the 4 GB wav file size limit in GNU Radio. | + | |
To get around this you can use a tool such as sox to chop up your file into smaller chunks. You can estimate using different times and see if you get the chunk sizes you want - the following command will continue to make chunks of the chosen mm:ss length until there’s no more data and iterate a number after the outfile name: | To get around this you can use a tool such as sox to chop up your file into smaller chunks. You can estimate using different times and see if you get the chunk sizes you want - the following command will continue to make chunks of the chosen mm:ss length until there’s no more data and iterate a number after the outfile name: | ||
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**sox --ignore-length infile.wav outfile.wav trim 0 mm:ss : newfile : restart** | **sox --ignore-length infile.wav outfile.wav trim 0 mm:ss : newfile : restart** | ||
+ | For RF64 WAV files you can use a File Source followed by an iShort to Complex to effectively skip the header and send out valid data. | ||
+ | |||
+ | If you’ve got the opposite issue - a bunch of smaller basebands that need joining together, you can try: | ||
+ | |||
+ | **sox --ignore-length infile1.wav ... infile[n].wav outfile.wav** | ||
+ | |||
+ | After all of that: if your chosen signal is in the middle of the baseband, you’re done! If it isn’t, you will need to “tune in” to the signal with a Frequency Xlating FIR or FFT Filter first. | ||
===== Adding, Subtracting, | ===== Adding, Subtracting, | ||
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===== Working with bits and bytes ===== | ===== Working with bits and bytes ===== | ||
- | To follow. Some basic advice for digital signals on how to actually convert from bytes to signals you can modulate, and how to go from a stream of demodulates | + | To follow. Some basic advice for digital signals on how to actually convert from bytes to signals you can modulate, and how to go from a stream of demodulated |
===== Useful Flowgraphs ===== | ===== Useful Flowgraphs ===== | ||
- | Add a list of useful GRCs with explanatory text here. You can build your own projects off these. | + | Add a list of useful GRCs with explanatory text here. You can build your own projects off these basic ideas. |
To be added: | To be added: | ||
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* NFM Modulation | * NFM Modulation | ||
* NFM Demodulation | * NFM Demodulation | ||
+ | * WFM Stereo Modulation | ||
+ | * WFM Stereo Demodulation | ||
* QPSK Modulation | * QPSK Modulation | ||
* QPSK Demodulation | * QPSK Demodulation | ||
* BPSK Modulation | * BPSK Modulation | ||
* BPSK Demodulation | * BPSK Demodulation |
gnuradiotips.txt · Last modified: 2021/09/13 22:27 by mm3iig