Re: [Discuss-gnuradio] phase stability of 100MHz clock in USRP2

On 02/12/11 07:10 AM, Nakajo Tomoyuki wrote:
> Dear All,
>
> Please tell me the phase stability of 100MHz clock in USRP2 when the
> 100MHz clock is locked to an external 10MHz reference signal.
>
> I have measured the temporal variation of phase difference between two
> USRP2 outputs when a 10MHz signal is fed into PPS IN ports of two
> USRP2s. The input signal of each USRP2 is fed by a same oscillator where
> the output frequency is set to 26MHz. The result indicates the phase
> difference varies from 0 to 2pi radians in about 100msec. This similar
> result is obtained in the case a 10MHz signal is not fed into PPS IN
> port. I think this observed temporal variation of phase difference is
> too rapid, therefore, suspect the 100MHz clocks are unlocked to the
> external 10MHz signal.
>
> Best regards,
> Nakajo Tomoyuki
>
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>
>
Are you configuring your UHD sink to use the extneral ref clock?

Does your external reference meet the hardware requirements:

http://files.ettus.com/uhd_docs/manual/html/usrp2.html#ref-clock-10mhz

Have you measured the phase noise of your reference?

--
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

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