Lou, thanks for your interest. Yes the entire thing was made purely with GRC and there was no modification to the generated Python. All that is required to run the scanoo_rx GRC file unmodified is a UHD compatible device and an installation done with "./pybombs install uhd gnuradio". Johnathan's GNURadio Live DVD should work too - http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioLiveDVD .
For reference, here is a screenshot of the scanoo_rx GRC flowgraph - https://raw.githubusercontent.com/m0mik/scanoo/master/apps/scanoo.com_rx.grc.png Starting at the top left, the 'UHD USRP Source' block receives complex time domain samples from your UHD compatible SDR hardware and sends these complex time domain samples to the 'Stream to Vector' block and the three 'WX GUI' display blocks. The 'Stream to Vector' block sends the complex time domain samples in vector chunks of size 'fft_len' to the 'FFT' block which outputs the vector chunks of complex samples in frequency domain format. FYI, the 'WX GUI FFT Sink' blocks (aka 'FFT Rough Tune'/'FFT Fine Tune') do this internally in order to display the signals in the frequency domain. The output of the 'FFT' block is sent to a 'Selector' block which is the pathway to the 'Probe Signal Vector' block used for spectrum sensing. The 'FFT' block also sends samples to a 'Vector to Stream' block which puts the vector chunks back into a single stream of samples in frequency domain format. The 'Vector to Stream' block sends the stream of frequency domain samples to the 'Keep M in N' block which is responsible for picking out the channel we want and at the same time it decimates the signal to 'channel_samp_rate' in order to reduce the amount of data processing required for blocks further down the chain. The channel is chosen by either a mouse click on the 'FFT Fine Tune' / 'FFT Zoom' displays or by enabling 'Spectrum Sense' mode. When 'Spectrum Sense' mode is enabled, the maximum signal found is selected as determined by the 'Probe Signal Vector' block. The 'Keep M in N' block sends the selected complex frequency domain samples to the 'Stream to Vector' block in order for the samples to be converted back into complex time domain format by the 'FFT' block which is set to 'Reverse' (IFFT). The 'FFT' block outputs a vector of complex time domain samples of the chosen channel and sends these via a 'Vector to Stream' block to an 'FFT Filter' block. The 'FFT Filter' block is responsible for decimating and filtering the time domain sample stream. The bandwidth of the filter is adjustable in the 'Main' section of the GUI controls and can be seen when viewing with the 'FFT Zoom' display. In the 'FFT Filter' block there is logic to change the filter automatically when the modulation is changed. AM/NBFM/WBFM use a lowpass filter and LSB/USB use a complex bandpass filter. >From the 'FFT Filter' block the sample stream is sent at a rate of 'quad_samp_rate' to the 'Power Squelch' block. This squelch block is responsible for determining whether the chosen signal is powerful enough to lock on to. If so, the samples are passed through a 'Feed Forward AGC' for signal level normalisation and then on to the audio demodulation blocks via the modulation 'Selector' block. The 'Probe Avg Mag^2' block after the 'Power Squelch' block is used to halt the spectrum sensing and center frequency hopping in order to lock onto the selected channel. This 'Probe Avg Mag^2' block is also the reason for the signal holding on channel for a few seconds after the squelch cuts out. This delay is adjustable with the block's alpha setting. If there are any queries as to the use of raw FFT bin indexes then I'll be happy to explain that too, such as in the frequency lockout feature. Mike -- Mike Jameson M0MIK BSc MIET Email: [email protected] Web: http://scanoo.com On Tue, Jun 10, 2014 at 5:49 PM, madengr <[email protected]> wrote: > Mike, > > Can you give a general overview of how the program works, and maybe what > you > are doing with the FFT and IFFT, and how you accomplish the tuning via > mouse > click in GRC? I assume this is entirely done in GRC and there was no > modification of the generated Python? > > Thanks, > Lou > KD4HSO > > > > Mike Jameson-2 wrote > > Hi all, > > > > The latest version of my scanoo_rx GRC SDR scanning application is now > > available via GitHub. Please star the project if you like it and report > > bugs by creating an issue on the GitHub page. > > > > > > https://github.com/m0mik/scanoo > > > > Mike > > > > -- > > Mike Jameson M0MIK BSc MIET > > Email: > > > mike@ > > > Web: http://scanoo.com > > > > > > -- > View this message in context: > http://gnuradio.4.n7.nabble.com/Scanoo-rx-New-GUI-Center-Freq-Hopping-SSB-Modulation-tp48866p48882.html > Sent from the GnuRadio mailing list archive at Nabble.com. > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >
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