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| From: | Kyeong Su Shin |
| Subject: | Re: [Discuss-gnuradio] Read FM signal |
| Date: | Wed, 25 Apr 2018 04:23:33 +0000 |
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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 <address@hidden> 대신 Discuss-gnuradio <discuss-gnuradio-bounces+address@hidden>
보낸 날짜: 2018년 4월 25일 수요일 오전 4:31:00 받는 사람: Müller, Marcus (CEL) 참조: address@hidden 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.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)
<address@hidden> wrote:
Nope! That's a common misconception! |
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