Parameters of NBFM block in GNU Radio companion

GNU Radio
1

Can anybody explain to me the following parameters of NBFM block in GRC:
Audio rate
Quadrature rate
Tau

2

‘Quadrature Rate’ is the rate that samples come into the block.

‘Audio Rate’ is the rate that samples are sent to your sound card.

‘Tau’ is described in the following link:

http://gnuradio.4.n7.nabble.com/preemph-time-constant-td26659.html

Mike

–
Mike J. M0MIK BSc MIET
Email: [email protected]
Web: http://scanoo.com

3

The ‘NBFM receive’ block’s ‘audio rate’ must be stated as it is the
value
for the output sample rate of the block. Yes, this can be the same as
‘quadrature rate’, which is the value for the input sample rate of the
block, or what sample rate it expects to receive, however the ‘audio
rate’
must be the result of dividing ‘quadrature rate’ by an integer (also
known
as audio decimation in the next paragraph), in the latter case this
would
be '96000/1=96000.

Note that when using the ‘NBFM receive’ block for example, if the
‘quadrature rate’ was ‘96000’ and the ‘audio rate’ was ‘48000’ then the
‘AM
demod’ block would have the equivalent values of ‘channel rate’ =
‘96000’
and ‘audio decimation’ of 2.

Mike

–
Mike J. M0MIK BSc MIET
Email: [email protected]
Web: http://scanoo.com

4

Thank you Mike