In the GRC Frequency mod block the doc says
analog_frequency_modulator_fc
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.
Args:
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 https://wiki.gnuradio.org/index.php/Frequency_Mod 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?
This would give full scale deviation with 4x oversampling, I think. So, this might be set by default for a digital mode.
best regards