On 04/24/2018 10:37 AM, shachar J. brown via USRP-users wrote:
Hi All,
As I understand it, the B210 has maximum master clock rate of
61.44[MHz] for one channel, and 30.72 [MHz] per-channel while using
two channels.
I am receiving through two channels, and would like to use a sample
rate of 20[MHz] with central freq. of 98 [MHz]. I set the master
frequency to max by editing the following line in the python file:
* self.uhd_usrp_source_0.set_clock_rate(30.72e6, uhd.ALL_MBOARDS)*
(Which is equivalent to writing "30.72e6" under "clock rate" in the
USRP-SOURCE block in the grc).
To my utmost disappointment, I receive the following error:
*[WARNING] [MULTI_USRP] The hardware does not support the requested RX
sample rate:*
*Target sample rate: 20.000000 MSps*
*Actual sample rate: 15.360000 MSps*
Why is the master clock rate only half of what I assigned it?
(I did try to insert anything above 30.72e6 and received an error that
it exceeds the limit)
Thanks for your time,
Steve.
Because your delivered-to-host sample rate has to be an integer fraction
of the master clock rate. Since you've "locked" the hardware at a master
clock rate of 30.72e6, the sample-rate-adjuster has no choice but to
clip your sample rate to one that can actually be supported by the
hardware configuration.
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