On 2025-07-31 10:05, gech...@gmail.com wrote:
When I run the following command:
/usr/lib/uhd/examples/tx_samples_from_file --freq 2484e6 --rate 3e6
--gain 10 --wirefmt sc16 --ref=internal --file
/home/ubuntutx/uhd/examples/tx_transmit_data.dat --repeat
UHD generates this warning:
“The requested interpolation is odd; the user should expect
CIC rolloff. Select an even interpolation to ensure that a halfband
filter is enabled.”
The transmission appears to run without errors, but I don’t see any
signal on the spectrum analyzer. Could you please clarify what this
warning means and if it might be related to why the signal isn’t
showing up?
Thanks.
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You haven't said which daughtercard(s) you have installed, so that will
factor into the answer.
But a couple of main points:
3e6 SPS doesn't divide the master-clock on the X310 precisely (defaults
to 200MHz), so UHD will find a rate that is close that DOES satisfy the
requirement that the
sample rate be an integer fraction of the master clock rate.
IN ADDITION, the resulting rate produces an interpolation *factor* that
is of odd order, so the filter arrangement in the DUC (that rate-changes
your
desired sample rate to the rate that the DACs operate at) will
produce a typical half-band roll-off. This is normal with DUC/DDC
implementations of
this type.
So, if your data are sampled at exactly 3.00MSPS, your entire TX
spectrum will be somewhat "off", but should still show up. What
daughtercard(s) are you using?
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