Hello Ivo:
What you are dumping is the raw signal data that you are getting from your USB dongle, converted to the GNU Radio's complex number format (2x IEEE754 single precision floats), resampled by the rational resampler to a different effective sampling rate (from 250kS/s to 192kS/s) . The dongle is giving you the complex baseband representation of the signal that it is observing - from (99.1MHz - 125kHz) to (99.1MHz + 125kHz), shifted to -125kHz to 125kHz. GNU Radio receives the data, and then converts it to the format which GNU Radio can easily process - the normalized complex number format. This is passed to the resampler, which reduces the bandwidth to +- 96kHz. Then, the data is dumped into the file. The file will contain a list of 64 bit complex numbers (two 32bit float numbers, interleaved). The easiest way to open this is using GNU Radio's file sink. An alternative way using Python or Octave is described at https://wiki.gnuradio.org/index.php/FAQ#What_is_the_file_format_of_a_file_sink.3F_How_can_I_read_files_produced_by_a_file_sink.3F . And yes, the data stored by using the 'File Sink' contains more information than the data that stored by using the 'FM Demod' and the 'Wav File Sink'. That also means that you may have to do additional processings on the data to get meaningful information out, however. (But you will have to deal with that, if you want to generalize your program and process non-FM signals as well.) Regards, Kyeong Su Shin ________________________________ 보낸 사람: Ivo Carlson <[email protected]> 대신 Discuss-gnuradio <[email protected]> 보낸 날짜: 2018년 4월 25일 수요일 오전 4:31:00 받는 사람: Müller, Marcus (CEL) 참조: [email protected] 제목: Re: [Discuss-gnuradio] Read FM signal I think I wasn't clear enough. When I say the format I mean the Physical Equivalency of the output (e.g. The number x represents the point in a Time x Frequency graph). For now, I'm using the attached flowgraph to read a radio signal. I need a way open the wave or the spectrogram so I can apply a Statistical method. As I already have the .wav so use Octave is a possibility, but I wish to know if that's the better way. Looks to me that use the File Sink will provide better info than the WAV, but how can I use it for it? Should I generate the file with the File Sink in a specific extension? Where can I open it and what is the physical meaning of that information? I'm using this flowgraph to read an FM signal but I wish to expand to other kinds of electromagnetic waves in the future, is that the better way of doing this? I'm already opened to suggestions on the flowgraph and reading signal process. Best Regards On Thu, Apr 19, 2018 at 5:08 PM, Müller, Marcus (CEL) <[email protected]<mailto:[email protected]>> wrote: Nope! That's a common misconception! The file sink just writes the bits as they come in. Whether, for example, a 64 bit item is actually a complex number consisting of two 32 bit IEEE754 floats, or a double, or two 32 bit integers, or one 64bit integers, or just a vector of 8 Bytes of data (chars) is really of no difference to the sink. On Thu, 2018-04-19 at 20:04 +0000, Patrick Sathyanathan wrote: > Hi Ivo, > > The binary format depends on what you have set as the "Input Type" in the > file sink. The default is "Complex" in which case the values are 32-bit float > I followed by 32-bit float Q. The order of the 4-bytes in the float likely > depends on the endianness of your host system. > > --Patrick > From: Discuss-gnuradio > <[email protected]<mailto:[email protected]>> > on behalf of rear1019 <[email protected]<mailto:[email protected]>> > Sent: Wednesday, April 18, 2018 9:58 PM > To: [email protected]<mailto:[email protected]> > Subject: Re: [Discuss-gnuradio] Read FM signal > > On Tue, 17 Apr 2018 at 14:32:17 -0300, Ivo Carlson wrote: > > […] > > The file sink saves the data in a binary format, but I don't know what > > this data represents. How do I interpret this data? What does this data > > represent? > > This question can not be answered as we don’t know how your flowgraph > looks like. Provide your flowgraph (.grc file) or a screenshot (open the > flowgraph in GNU Radio Companion, go to File menu and select “Screen > Capture”). > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected]<mailto:[email protected]> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ > Discuss-gnuradio mailing list > [email protected]<mailto:[email protected]> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list [email protected]<mailto:[email protected]> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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