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My project is to monitor the power and the deviation of 3 radio FM stations, sending this values into a MySQL database. I can't stream directly the audio of the station, due to limited bandwidth.

So I ask you if there is a method, command or Python script to get power level and deviation of an FM signal from an RTL SDR.

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  • $\begingroup$ what do you mean with "deviation"? Because for an FM radio station, the frequency deviation is actually what transports the audio data (hence, the name "FM", frequency modulation), and a SQL database isn't meant to store samples of audio... $\endgroup$ – Marcus Müller Feb 28 at 13:33
  • $\begingroup$ I think he means the maximum deviation which would be some number in kHz, which is to be sampled periodically, then written to a database. $\endgroup$ – Phil Frost - W8II Mar 1 at 0:34
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You may wish to look into GNU Radio as the basic platform from which to develop your specific application. GNU Radio is based on the Python and C programming languages using SWIG for the interface between the two. In GNU Radio you are essentially connecting various blocks (a functional processing unit with inputs and outputs) in a graphical form into "flowgraphs" to build your application. You can do a great deal of customization of blocks.

You can also add your own "private" extensions to GNU Radio using Out of Tree modules. You can do this by authoring in C or C++, for example. This perhaps would be a good approach for meeting your database interface requirements. You may find some ready made code on the Internet that you can use for this purpose.

You may also be able to use the File Sink block to output binary data to a file for post processing into your database. The use of meta data headers may also prove helpful to your application. See the file_meta_sink Class Reference.

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RE: My project is to monitor the power ...

The power present in a received e-m wave is highly dependent on the frequency, propagation path, the receive antenna pattern characteristics when installed, and other factors.

Accurate measurement of such received power over most open-area propagation paths is difficult to achieve, requiring expensive receive equipment assembled as a system having known characteristics at each frequency tested.

The SDR output likely will produce only relative indications of received field/power, which due to the unknowns that are present can be deceptive as a basis to compare the performances of several radiating sources.

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