No problem at all! The suggestion to use keep-one-in-N gives me a great starting place to work with, and it is helpful to know what is a good bandwidth to use, so many thanks for those suggestions! It is neat that you were into SID observing at one point, too - this is my first amateur radio project, and it has certainly been an interesting one!
Best wishes, Ellie From: Marcus D. Leech [mailto:mle...@ripnet.com] Sent: Thursday, April 20, 2017 10:05 PM To: Ellie White <orionnebul...@outlook.com> Subject: Re: [Discuss-gnuradio] File sink: file size On 04/20/2017 09:57 PM, Ellie White wrote: Hi Marcus - Apologies for the delayed response! Thanks for your helpful input and for sending the link to your SID repository. It looks like it is full of useful stuff; however when I tried to run the .grc file, it shows that a lot of blocks are missing - is there some way I can fix that? Do I need to install some blocks from a different location, or did I just do something wrong when I cloned the repository and ran the Makefile? (I'm super new to GitHub, so it could certainly be some incompetence on my part related to that). Also, based on your experience, what do you think is a good channel bandwidth? Ellie: I must apologize profusely. It turns out that SIDSuite was never converted over from Gnu Radio 3.6. I'm not sure when, if ever, I'll get to that. Channel bandwidths for the sub VLF traffic should be no more than about 200-300Hz from my recollection. Thanks again! Ellie From: Discuss-gnuradio [mailto:discuss-gnuradio-bounces+orionnebula42=outlook....@gnu.org] On Behalf Of Marcus D. Leech Sent: Friday, April 7, 2017 10:16 PM To: discuss-gnuradio@gnu.org<mailto:discuss-gnuradio@gnu.org> Subject: Re: [Discuss-gnuradio] File sink: file size On 04/07/2017 02:53 PM, Ellie White wrote: Hello, As I've mentioned in an earlier email to this list, I'm working on a small loop antenna with the purpose of monitoring solar activity. I am currently reading in the data through an RTL-SDR source, flowgraph attached. For this project, I need to be able to let my antenna run for long periods of time (upwards of an hour or more, preferably several hours) in order to get a graph of signal intensity vs. time. Right now, my setup consists of the GNU Radio flowgraph attached, that produces a file which I analyze using a Python program to get a spectral plot and a time series (for one of the 1024 channels saved in the file). I let my antenna and GNU Radio run for about 15 minutes last night collecting data, and the file size ended up at over 7 GB. I am wondering if there is any way to reduce the size of the file without tremendously reducing the quality of the data? I have a few ideas on this, but I'm hoping someone else will have better ones: -Maybe I need to reduce the sample rate. -Another option is to somehow just save the channel I need to the file, instead of all 1024. Does anyone have any advice as to how to accomplish that? If you need any more information or if I should clarify anything, please let me know. Thanks! Ellie _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org<mailto:Discuss-gnuradio@gnu.org> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio You might also take a look at my work from 6 or 7 years ago: https://github.com/patchvonbraun/SIDSuite It uses audio input. It uses a set of Gortzel transforms to pick out the channels of interest. But there are other approaches, using an FFT as you have. Since the things that you're looking for unfold over timescales of many-seconds to many-minutes, you don't need to be logging your FFT output in real-time. You could easily integrate for several seconds and dump output data at a lower rate, using keep-one-in-N. At an input rate of 2Msps, your 1024-point FFT will be producing 1953 1024-bin vectors/second. This is *much* faster than the timescale of ionospheric events, in my experience. Also, your frequency resolution will be somewhat coarse-1953Hz. This is much wider bandwidth than the naval stations you're looking at, so you'll mostly be integrating noise, rather than navy signal, in your bins.
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