Hello, I recently encountered an issue while using the QT GUI Frequency Sink in GNU Radio, which caused incorrect frequency readings when the displayed bandwidth was set to a value smaller than the sampling rate (\(fs\)).
My signal source was set to generate a cosine wave at 1000 Hz, with the sampling rate 32k. The QT GUI Frequency Sink was configured with a displayed bandwidth of samp_rate / 8 = 4 kHz. The frequency of the signal was displayed incorrectly on the plot, showing around 120 Hz instead of the expected 1 kHz. After investigating, I think that this behavior was caused by how the QT GUI Frequency Sink rescales and interprets the frequency axis when the displayed bandwidth is set to a smaller range. When I increased the bandwidth in the frequency sink to match the full samp_rate, the signal frequency was displayed correctly. Is this a correct assessment and does it work like that for you too? Best regards, yabool2001
