# OpenBTS internal clock (Ettus USRP B100)

**URL:** <https://www.ruby-forum.com/t/openbts-internal-clock-ettus-usrp-b100/240315>\
**Category:** GNU Radio\
**Created:** [April 8, 2014, 10:16am UTC](https://www.ruby-forum.com/t/openbts-internal-clock-ettus-usrp-b100/240315 "2014-04-08T10:16:44Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [April 8, 2014, 10:16am UTC](https://www.ruby-forum.com/t/openbts-internal-clock-ettus-usrp-b100/240315/1 "2014-04-08T10:16:44Z")

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Hi,

I’ve got an Ettus USRP B100 device which can be configured to use an  
internal 52MHz clock to operate. However after compiling and testing  
OpenBTS, it uses 64MHz clockrate. Can anyone explain why that’s the  
case? Is there any possibility to change the clockrate to 52MHz?

Cite from OpenBTS wiki:  
“The current release of OpenBTS supports the B100 series with a 64 MHz  
specific polyphase resampler and updated GSM receiver design. These  
changes resolve various issues previously seen with B100 and earlier  
versions of OpenBTS, which were due to sample rate issues and level  
control.”  
There’s no further information about that.

I can change the clockrate of the B100 to 52MHz by using the command  
uhd\_usrp\_probe --args=“master\_clock\_rate=52e6”  
Unfortunately OpenBTS still uses the different clockrate.

Greetings,  
Lenny