Dear all,
I have been performing experiments of collecting GPS signals and checking
operations of GPS software defined receiver (SDR), using two USRP N210s.
I used "UHD: USRP Source" block in gnuradio-companion, and both clock and
time sources of the two N210s are set to be 'external'. The two N210s are
synchronized by 'octoclock-g' which distributes 10 MHz clock and 1 PPS
signals.
Until a few days ago, the experiments were successful and I check that the
SDR was able to acquire and track the received GPS signals.
However, from this week, after collecting data using those two N210s, the
SDR cannnot even acquire any GPS signals. Any parameters of the SDR and
blocks in gnuradio-companion were not changed. When I set the clock sources
of the N210s to be 'internal' or 'default', the SDR worked well.
I found that the LED of the octoclock-g, which indicates status of GPS-lock
by the internal GPSDO, is turned off even though a GPS antenna is connected
to the octoclock-g.
I checked the antenna and the cable using other commercial u-blox receiver
and there was no problem, but, the LED is still left turned off.
In data sheet of the octoclock-g, it says that the 10 MHZ clock and and 1
PPS signals can be still provided with lower accuracy, although the GPSDO
is not locked to the GPS signals.
Meanwhile, I measured the 10 MHz clock and 1 PPS output using oscilloscope.
In data sheet of the octoclock-g, it says that Vpp (Peak-to-peak voltage)
of the 10 MHz clock is about 1.4V and I found that the measured Vpp is
about 3.5V which is higher than the Vpp specified in the data sheet.
Is there anyone who can explain why my USRPs don't work well?
Thank you all.
--
*Kwansik Park*
School of Integrated Technology, Yonsei University
Yonsei Institute of Convergence Technology
*Tel :* +82-749-5909
*Fax :* +82-32-818-5801
*Mobile :* +81-10-2328-6469
*E-mail :* kwansikp...@yonsei.ac.kr
maxbraker6...@gmail.com
*Homepage :* http://gnss.kr/kwansik
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