You can!
If you're using GRC to design your GNU Radio system, it's the "Clock
Rate" property of the UHD USRP Source / Sink blocks; if you're directly
coding, you want to call set_clock_rate() before doing anything else,
or supplying "master_clock_rate=184.32e6" with your device address.
Best rega
Dear Paul,
I'd recommend taking this to the USRP-users mailing list (in CC), since
it's not really GNU Radio-related.
Since that clock rate setting doesn't really "exist" until the device
is operating, you can't query that from any program than the program
currently using the USRP (but that progr