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At present I work with 2 different USRPs.

One of this is the USRP2 and the another one a newer device is the X300.

This devices communicate each about QPSK and a test algorithm.

The USRP2 has an output frequency shift of 20 kHz and make it impossible to transmit narrow band signals. Therefore, I use the reference clock output of the X300 to the USRP2.

To do this, I did use the command in python with GNU Radio

self.uhd_usrp_source.set_clock_source("external", uhd.ALL_MBOARDS)

Thereafter, the output signal shift is vanished, but my data hasn't been received by the X300.

Then I increased the master clock of 200 MHz of the USRP2:

self.uhd_usrp_source.set_clock_rate(200e6, uhd.ALL_MBOARDS)

In my opinion, the USRP2 don't supported this change of frequency. My question would be:

  1. Why is it not enough to set the reference clock to extern?

  2. Why I don't receive data after this change to extern?

  3. Why did solve the change of the master clock the problem?

Marcus Müller
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Nils
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  • Wait, do you have one uhd_usrp_source, or two? How do you select which USRP gets used by the uhd_usrp_source? – Marcus Müller Apr 12 '16 at 17:47
  • I use one USRP(X300) as transmiter and USRP2 as source. The X300 received from the USRP2 acknowledgements, too. But the devices get fixed different IPs and different PCs. In python I use *self.uhd_usrp_source = uhd.usrp_source(* *device_addr=usrp_addr,...* – Nils Apr 13 '16 at 09:57

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