[USRP-users] Maintaining USRP Carrier Frequency Lock

Marcus D. Leech patchvonbraun at gmail.com
Thu Jan 30 14:57:09 EST 2020


On 01/30/2020 01:35 PM, Richard Bell via USRP-users wrote:
> Hello,
>
> I am trying to collect serveral data sets through USRP X300's. Assume 
> each collection is 1000 samples long and is initiated by a user typing 
> a button on the keyboard. Each time the user hits a key 1000 samples 
> are collected and stored to a file. The time between each collect is 
> defined by the user hitting the key.
>
> I need to make sure the USRPs are not loosing carrier lock between 
> these collections. I want the USRPs to stay locked to whatever center 
> frequency is set and sit there for the length of the time the user 
> wants to collect data sets. What is the best way to ensure this?
>
> For example, if I use GNU Radio and head blocks feeding into file 
> sinks with calls to tb.start and tb.stop, does the call to tb.stop 
> cause the USRP to forget the carrier it was locked to and start over 
> again on the next call to tb.start? Can I call tb.start multiple times 
> without a call to tb.stop?
>
> Thank for any help you can provide.
>
I think this will likely work, although I think it depends on how much 
"device init" is done on flow-graph start.  I think a lot of it is done when
   the device is instantiated, and whatever happens at FG start is 
device-dependent.

You'll have to test this in your environment.

You might also chose another architecture for your software to remove 
the possibility of device re-init.

You can for example just stream forever, and only pay attention to the 
samples you want to pay attention to.





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