| Ellie
I’ll take a look later and get back to you
Cheers
Sent from my iPhone 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 < address@hidden> 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 < address@hidden>
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 < address@hidden>
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.
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<ettus-filesink.grc>
<ettus-test.grc>
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