In the GRC Frequency mod block  the doc says

make(float sensitivity) -> frequency_modulator_fc_sptr
        Frequency modulator block.
        float input; complex baseband output
        Takes a real, baseband signal (x_m[n]) and output a frequency modulated signal (y[n]) according to:

        Where x[n] is the input sample at time n and  is the frequency deviation. Common values for  are 5 kHz for narrowband FM channels such as for voice systems and 75 KHz for wideband FM, like audio broadcast FM stations.         In this block, the input argument is , not the frequency deviation. The sensitivity specifies how much the phase changes based on the new input sample. Given a maximum deviation, , and sample rate , the sensitivity is defined as:
        Constructor Specific Documentation:
        Build a frequency modulator block.
            sensitivity : radians/sample = amplitude * sensitivity

There is somejhing missing at:   " Where x[n] is the input sample at time n and  ____________  is the frequency deviation"

Here the same is missing too.

I guess it refers to  sensitivity = K = (2*pi*freq_deviation)/samp_rate    correct?

Second question related to this one.

If I the use Quadrature_demod for demodulation of the signal, the gain parameter will be the inverso of this one isnt it?

gain=samp_rate/((2*pi*freq_deviation)   but when I insert the quadrature demod block it is autofilled with

samp_rate/(2*math.pi*fsk_deviation_hz/8.0)   where does the 8.0 come from?

best regards

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