# Parameters of NBFM block in GNU Radio companion

**URL:** <https://www.ruby-forum.com/t/parameters-of-nbfm-block-in-gnu-radio-companion/240734>\
**Category:** GNU Radio\
**Created:** [April 28, 2014, 11:11am UTC](https://www.ruby-forum.com/t/parameters-of-nbfm-block-in-gnu-radio-companion/240734 "2014-04-28T11:11:42Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\
**Post date:** [April 28, 2014, 11:11am UTC](https://www.ruby-forum.com/t/parameters-of-nbfm-block-in-gnu-radio-companion/240734/1 "2014-04-28T11:11:42Z")

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

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**Author:** ![ali\_hanif](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ac91a4/32.png) [@ali\_hanif](https://www.ruby-forum.com/u/ali_hanif)\
**Post date:** [April 28, 2014, 6:18pm UTC](https://www.ruby-forum.com/t/parameters-of-nbfm-block-in-gnu-radio-companion/240734/2 "2014-04-28T18:18:14Z")

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‘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](http://gnuradio.4.n7.nabble.com/preemph-time-constant-td26659.html)

Mike

–  
Mike J. M0MIK BSc MIET  
Email: removed\_email\_address@domain.invalid  
Web: [http://scanoo.com](http://scanoo.com)

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**Author:** ![ali\_hanif](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ac91a4/32.png) [@ali\_hanif](https://www.ruby-forum.com/u/ali_hanif)\
**Post date:** [April 30, 2014, 4:04am UTC](https://www.ruby-forum.com/t/parameters-of-nbfm-block-in-gnu-radio-companion/240734/3 "2014-04-30T04:04:43Z")

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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: removed\_email\_address@domain.invalid  
Web: [http://scanoo.com](http://scanoo.com)

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**Author:** ![ali\_hanif](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ac91a4/32.png) [@ali\_hanif](https://www.ruby-forum.com/u/ali_hanif)\
**Post date:** [April 30, 2014, 4:11am UTC](https://www.ruby-forum.com/t/parameters-of-nbfm-block-in-gnu-radio-companion/240734/4 "2014-04-30T04:11:52Z")

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Thank you Mike