|Subject:||Re: [Discuss-gnuradio] gr-uhd: rx_freq tag and lo_locked|
|Date:||Tue, 31 Mar 2015 22:15:53 +0200|
|User-agent:||Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0|
the rationale behind that is that these tags correspond to the stream metadata coming from the USRP, which tell the host when the tuning *operation* has taken place. Now, you're right, it's a problem to think you're tuned although your LO still hasn't settled, but since tunes could also be digital-path only, using the "earliest" time seems correct.
By the way, you might also want to try a different approach, based on timed commands: you can set a time for things like tune requests, thus making sure that the tuning happens at the exact point in time you want it to (and not influenced by the latency and load of your general purpose PC). You can then simply "take" the right samples without caring about tags at all, because you know when these should occur (i.e. which numbers these should have).
PS: try turning off the DC offset correction, if you're on the N210, for fast-tuning applications. You'll have a bigger DC offset, but less "swinging" after each tune.
PS2: I don't know whether your overall frequency range allows this, but as long as you tune within your USRP/daughterboards physical bandwidth, you might just tune digitally and avoid LO retuning:
On 03/31/2015 09:54 PM, Anderson, Douglas J. wrote:
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