# Using WBFM block

**URL:** <https://www.ruby-forum.com/t/using-wbfm-block/230221>\
**Category:** GNU Radio\
**Created:** [June 5, 2014, 9:59am UTC](https://www.ruby-forum.com/t/using-wbfm-block/230221 "2014-06-05T09:59:27Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\
**Post date:** [June 5, 2014, 9:59am UTC](https://www.ruby-forum.com/t/using-wbfm-block/230221/1 "2014-06-05T09:59:27Z")

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Hi All,  
I am doing simple wide band FM…The flowgraph is as attached…When i  
execute it i am getting following error:

gr\_remez: insufficient extremals – cannot continue  
Traceback (most recent call last):  
File “/home/ali/Desktop/top\_block.py”, line 109, in   
tb = top\_block()  
File “/home/ali/Desktop/top\_block.py”, line 75, in **init**  
max\_dev=4000000,  
File  
“/usr/local/lib/python2.7/dist-packages/gnuradio/analog/wfm\_tx.py”,  
line 69, in **init**  
40) # stopband atten dB  
File  
“/usr/local/lib/python2.7/dist-packages/gnuradio/filter/optfir.py”,  
line 55, in low\_pass  
taps = filter.pm\_remez (n + nextra\_taps, fo, ao, w, “bandpass”)  
File  
“/usr/local/lib/python2.7/dist-packages/gnuradio/filter/filter\_swig.py”,  
line 466, in pm\_remez  
return \_filter\_swig.pm\_remez(\*args, \*\*kwargs)  
RuntimeError: gr\_remez: insufficient extremals – cannot continue

Is the quadrature rate and audio rate are high?

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<div class="post-metadata">

**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\
**Post date:** [June 5, 2014, 10:19am UTC](https://www.ruby-forum.com/t/using-wbfm-block/230221/2 "2014-06-05T10:19:31Z")

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Given your question, I think you already know the answer. 2MHz is far  
from audio. Please refer to the wbfm example in GNU Radio, which has  
sane parameters.

Greetings,  
Marcus

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<div class="post-metadata">

**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\
**Post date:** [June 5, 2014, 3:47pm UTC](https://www.ruby-forum.com/t/using-wbfm-block/230221/3 "2014-06-05T15:47:55Z")

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On Thu, Jun 5, 2014 at 4:37 AM, jason sam [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> ok.Then how can i achieve FM for greater deviation.i.e. in MHz range in  
> GRC?

What you’re seeing is a result of the Remez algorithm in the optfir  
module  
not properly converging. Why isn’t always clear; you can either tighten  
up  
or loosen the demands on the filter being built to try and fix it. You  
could also go into the code and replace the optfir call with firdes. The  
resulting filter might not be as good as you want and more taps, but it  
will at least always build.

Tom

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<div class="post-metadata">

**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\
**Post date:** [June 5, 2014, 10:38am UTC](https://www.ruby-forum.com/t/using-wbfm-block/230221/4 "2014-06-05T10:38:24Z")

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ok.Then how can i achieve FM for greater deviation.i.e. in MHz range in  
GRC?

On Thu, Jun 5, 2014 at 1:18 PM, Marcus Müller [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)