Hi Marcus, I've attached the two flowgraphs I am using to record data from the Ettus SDR; the TCP server (ettus-test.grc) which reads in the data samples, and the TCP client (ettus-filesink.grc). I am not sure how to determine how the sampling is terminated -- perhaps you can advise me on this? Would the TCP block be an example of a termination, or am I misunderstanding this concept? And if we establish that the sampling is "interrupted", from there how do I calculate the decimation needed for my desired integration time?
Thanks so much for your help on this! Cheers, Ellie On Sun, Aug 11, 2019 at 1:51 AM Marcus D. Leech <patchvonbr...@gmail.com> wrote: > On 08/10/2019 11:43 PM, Ellie White wrote: > > Hi Marcus, > > Thanks for the advice. So, I just tried an experiment to test out your > suggestion, and came up with a puzzling result. I set the sample rate to 4 > MHz, and the decimation in the integrate block to 4 MHz, and recorded data > for about 5 seconds. Instead of getting about 5 samples out, I tried to > read the file and was told that there were "no samples" in the file. I then > tried setting the decimation to samp_rate / fft_size, and the result there > was the same. Any thoughts on why this might be? > > Thanks, > Ellie > > Probably buffering in Gnu Radio. How did you terminate the sampling? > > If you just interrupted it, there would have been samples "in flight" that > never made it "home". > > > > On Sat, Aug 10, 2019 at 11:17 PM Marcus D. Leech <patchvonbr...@gmail.com> > wrote: > >> On 08/10/2019 10:48 PM, Ellie White wrote: >> >> Hi Marcus, >> >> Thanks for your reply. I am not sure how the integration works, but if >> you know how the Integrate block does the integration, then that is how my >> flowgraph does it. I suspect it is "sum /reduce /dump" as you mentioned, >> though perhaps we would need to investigate the Integrate block's source >> code to be sure? Thanks in advance for any additional suggestions you might >> have on this! >> >> Cheers, >> Ellie >> >> Here's the documentation on the integrate block: >> >> https://wiki.gnuradio.org/index.php/Integrate >> >> So, if your samples are coming in at 1kHz, and you want 1 second of >> integration time (and an output rate of 1Hz), you'd set the >> "decimation" parameter to 1000. >> >> This is one of the reasons I prefer single-pole-IIR filters--since I can >> do sample-rate reduction as a separate process, via keep-one-in-N. >> >> >> >> On Sat, Aug 10, 2019 at 7:37 PM Marcus D. Leech <patchvonbr...@gmail.com> >> wrote: >> >>> On 08/10/2019 03:40 PM, Ellie White wrote: >>> > Hi all, >>> > >>> > I hope you're doing well! Thanks again for your help with my questions >>> > earlier this summer. I've got another thing to ask now; I am in the >>> > process of configuring a system to record integrated spectra using the >>> > attached flowgraph, and I am trying to determine how to integrate for, >>> > say, 60 seconds -- if I want to do this, what should my decimation be, >>> > and how do I calculate that? I have been able to approximate this by >>> > trial and error, but I would like to know the calculation behind it. >>> > >>> > Thanks in advance for any advice you can provide, much appreciated. >>> > Have a good afternoon! >>> > >>> > Cheers, >>> > Ellie >>> > >>> It kind of depends on how you're doing integration. >>> >>> An approach that strictly does sum/reduce/dump then you need as many >>> samples as would occur over your desired integration time. >>> >>> For a single pole IIR filter, it's a bit trickier, and you'd set the >>> "Alpha" parameter to: >>> >>> e^sqrt(sample-rate*integraton-time) >>> >>> Which will approximate an R-C integrator with the given integration >>> time. >>> >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >> >> >
ettus-filesink.grc
Description: application/gnuradio-grc
ettus-test.grc
Description: application/gnuradio-grc
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