# How to use gr\_clock\_recovery\_mm\_cc

**URL:** <https://www.ruby-forum.com/t/how-to-use-gr-clock-recovery-mm-cc/207976>\
**Category:** GNU Radio\
**Created:** [June 7, 2011, 3:15pm UTC](https://www.ruby-forum.com/t/how-to-use-gr-clock-recovery-mm-cc/207976 "2011-06-07T15:15:38Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![luislavena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/0ea827/32.png) [@luislavena](https://www.ruby-forum.com/u/luislavena)\
**Post date:** [June 7, 2011, 3:15pm UTC](https://www.ruby-forum.com/t/how-to-use-gr-clock-recovery-mm-cc/207976/1 "2011-06-07T15:15:38Z")

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Hi All,

In the gmsk.py, the gr.clock\_recovery\_mm\_ff is used.

I want to use gr.clock\_recovery\_mm\_cc (float omega, float gain\_omega,  
float  
mu, float gain\_mu) (which implements Mueller and Mller (M&M) based clock  
recovery block with complex input, complex output) to replace the  
gr.clock\_recovery\_mm\_ff

I have done these in two steps:

1. use the same parameters (used to init gr.clock\_recovery\_mm\_ff) to  
init  
gr.clock\_recovery\_mm\_cc.  
omege=2.000000, gain\_omega=0.000625, mu=0.050000, gain\_mu=0.050000,  
omega\_relative\_limit=0.005000

2. move the clock recovery block forward before demod block  
self.connect(self, self.clock\_recovery, self.fmdemod, self.slicer,  
self)

Before modification, if I run the benchmark program using gmsk, receive  
rate  
is almost 100%, but after my modification, receive rate drops to 0%.

Does my method have problem, any help is appreciated!

---

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**Author:** ![Shen\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c5a1d2/32.png) [@Shen\_W](https://www.ruby-forum.com/u/Shen_W)\
**Post date:** [June 7, 2011, 4:45pm UTC](https://www.ruby-forum.com/t/how-to-use-gr-clock-recovery-mm-cc/207976/2 "2011-06-07T16:45:19Z")

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On Tue, Jun 7, 2011 at 9:13 AM, Shen W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> 1. use the same parameters (used to init gr.clock\_recovery\_mm\_ff) to init  
> Does my method have problem, any help is appreciated!
> 
> –  
> Wenbo

You HAVE to use the clock recovery after the demod. Pre demodulation,  
you  
don’t have the right type of signal to lock against.

Tom