Phase stability of 100MHz clock in USRP2

GNU Radio
1

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 T.

2

On 02/12/11 07:10 AM, Nakajo T. wrote:

result is obtained in the case a 10MHz signal is not fed into PPS IN
Discuss-gnuradio Info Page

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