# Extracting and storing certain parameters from continuous IQ data **URL:** \ **Category:** GNU Radio\ **Created:** [March 11, 2015, 10:26pm UTC](https://www.ruby-forum.com/t/extracting-and-storing-certain-parameters-from-continuous-iq-data/234535 "2015-03-11T22:26:19Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [March 11, 2015, 10:26pm UTC](https://www.ruby-forum.com/t/extracting-and-storing-certain-parameters-from-continuous-iq-data/234535/1 "2015-03-11T22:26:19Z")
Hello everyone, So I was trying to capture continuous IQ data from my USRP N200, and this needs to be done for about a week, but because the amount of data is ginormous, that’s doesn’t seem feasible at all. Instead, what I’m now thinking of doing is processing the data in gnuradio companion in real time and just extracting certain parameters from the processed data, for instance, I would like to detect if there’s a signal present or not, at what time was the signal detected, what’s the maximum amplitude of the signal, how long did the signal last etc, and just store those pieces of information in a file. Are there any pre-existing blocks that I may use for this purpose? If not, can someone please guide me as to how to accomplish this task? This is what my flow graph looks like at the moment: [http://imgur.com/a/O2gXi](http://imgur.com/a/O2gXi) Thank you, Best, Ali ---
**Author:** ![alirose](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/bc79bd/32.png) [@alirose](https://www.ruby-forum.com/u/alirose)\ **Post date:** [March 11, 2015, 10:37pm UTC](https://www.ruby-forum.com/t/extracting-and-storing-certain-parameters-from-continuous-iq-data/234535/2 "2015-03-11T22:37:13Z")
Hey, I can’t tell you how you should do this. I can tell you that you will need to get comfortable with tags and probably messages to achieve these things you want. If you haven’t already, check out the gnuradio tutorial on programming topics to get started. They do a pretty good job explaining it there. [http://gnuradio.org/redmine/projects/gnuradio/wiki/Guided\_Tutorial\_Programming\_Topics](http://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorial_Programming_Topics) For example, suppose you only wanted to store a certain stream of data after a preamble was detected. You could use a ‘correlate and sync - tag’ block to adds tags at the start of your data to the stream and then feed this into a ‘tagged file sink’ block which will only put the portion after the tag into the file. You want a lot more functionality then this, but this could get you going in the right direction. Rich ---
**Author:** ![alirose](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/bc79bd/32.png) [@alirose](https://www.ruby-forum.com/u/alirose)\ **Post date:** [March 11, 2015, 10:50pm UTC](https://www.ruby-forum.com/t/extracting-and-storing-certain-parameters-from-continuous-iq-data/234535/3 "2015-03-11T22:50:41Z")
You can also use probes to bring out the data asynchronously from the flow which you can then process in Python. For example, you could probe at a 10 Hz rate, then have your Python script log those values to a file, or trigger some other event. I have an example here where it probes the signal level every second and logs it with GPS data: > **[GitHub - madengr/drive\_test: RF drive test application using Ettus USRP +...](https://github.com/madengr/drive_test)** > > RF drive test application using Ettus USRP + GPSDO, GNU Radio, and Google Maps Lou Ali R. wrote > signal, how long did the signal last etc, and just store those pieces of > Best, > Ali > > * * * > > Discuss-gnuradio mailing list > Discuss-gnuradio@ > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) – View this message in context: [http://gnuradio.4.n7.nabble.com/Extracting-and-storing-certain-parameters-from-continuous-IQ-data-tp52645p52647.html](http://gnuradio.4.n7.nabble.com/Extracting-and-storing-certain-parameters-from-continuous-IQ-data-tp52645p52647.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![alirose](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/bc79bd/32.png) [@alirose](https://www.ruby-forum.com/u/alirose)\ **Post date:** [March 11, 2015, 10:59pm UTC](https://www.ruby-forum.com/t/extracting-and-storing-certain-parameters-from-continuous-iq-data/234535/4 "2015-03-11T22:59:04Z")
Hey Rich, That’ll definitely give me a good start, thank you so much! I’ll check it out. Best, Ali On Wed, Mar 11, 2015 at 4:35 PM, Richard B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![alirose](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/bc79bd/32.png) [@alirose](https://www.ruby-forum.com/u/alirose)\ **Post date:** [March 12, 2015, 12:10am UTC](https://www.ruby-forum.com/t/extracting-and-storing-certain-parameters-from-continuous-iq-data/234535/5 "2015-03-12T00:10:12Z")
I saw from your other thread that you were channelizing and decimating, and I assume you are logging this to disk for extended periods. I’m doing a similar thing here: > **[GitHub - madengr/nbfm\_rec: Multi-channel narrow-band FM recorder for GNU...](https://github.com/madengr/nbfm_rec)** > > Multi-channel narrow-band FM recorder for GNU Radio Although I’m not using a channelizer, only because there is no band plan for what I was recording. Anyway, the blocking squelch may also be useful for you with a file sink. With the probing, you should be able to use that to dynamically name the files, amongst other things. Lou Ali R. wrote > Hey Lou, > > That’s a very interesting approach, I’ll look into your example as well. > Thank you very much! > > Best, > Ali – View this message in context: [http://gnuradio.4.n7.nabble.com/Extracting-and-storing-certain-parameters-from-continuous-IQ-data-tp52645p52651.html](http://gnuradio.4.n7.nabble.com/Extracting-and-storing-certain-parameters-from-continuous-IQ-data-tp52645p52651.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![alirose](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/bc79bd/32.png) [@alirose](https://www.ruby-forum.com/u/alirose)\ **Post date:** [March 11, 2015, 11:03pm UTC](https://www.ruby-forum.com/t/extracting-and-storing-certain-parameters-from-continuous-iq-data/234535/6 "2015-03-11T23:03:16Z")
Hey Lou, That’s a very interesting approach, I’ll look into your example as well. Thank you very much! Best, Ali