No data are dropped, but there will *always* be a disturbance in the
analog domain when you're changing the synthesizer frequency. PLLs
require a non-zero time to "lock", which means they converge to the
correct frequency over some small time interval (a few msec, typically).
Along with this, the filters in the DDC will take <group-delay> time
for the analog disturbance to propagate through the filter.
What underlying USRP device are you using?
On 2016-12-20 10:14, Tom Golden wrote:
> Hi All,
>
> I am connecting my flowgraph to a doppler prediction tool. My block
> currently modifies a variable that is used to specify the center frequency of
> the USRP Source block. The variable is updated every second.
>
> When the variable updates, I see blank data (looks like all zeros) for a
> short blip when this occurs. My QT FFT and Scope sinks flatline for a short
> period (subsecond). Has anyone else seen this?
>
> I've changed my flowgraph to leave the USRP Source alone and shift the
> frequency using a signal generator and multiply block. I'm concerned about
> doing this for TX. My concern is reduced performance because I'm not
> transmitting at the center frequency for the USRP Sink. Is my concern
> unfounded? Does anyone know if the same discontinuity for USRP Source is
> present for USRP Sink?
>
> Thanks in advance,
> -Tom
>
> _______________________________________________
> Discuss-gnuradio mailing list
> [email protected]
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
_______________________________________________
Discuss-gnuradio mailing list
[email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
