# Working with WFM sample data **URL:** \ **Category:** GNU Radio\ **Created:** [February 14, 2012, 9:03pm UTC](https://www.ruby-forum.com/t/working-with-wfm-sample-data/216813 "2012-02-14T21:03:57Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![luislavena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/0ea827/32.png) [@luislavena](https://www.ruby-forum.com/u/luislavena)\ **Post date:** [February 14, 2012, 9:03pm UTC](https://www.ruby-forum.com/t/working-with-wfm-sample-data/216813/1 "2012-02-14T21:03:57Z")
hello! i’m a new user embarking on some exploration to evaluate GNUradio and the USRP platform for some multichannel radio monitoring. i am starting with sample file processing before buying any hardware, as CPU usage is my chief concern. my problem is with using a large sample file captured from the FM broadcast-band: i can’t get it to work with the simplest of graphs in GRC. i was able to use Sharlene Katz’s handy GRC tutorials to get her AM sample file running through an FFT scope and demodulated to audio, so i know my GNUradio install is working. however, running my WFM sample file results in no activity on the FFT scope, and i get errors when mousing over the FFT window. the sample file was described to me as 32-bit complex IQ baseband, 98.0MHz center, 25Msps, gain 30 from an N200r4 + WBX. to try a very simple graph, i loaded it in to the GRC like this: [File Source (complex)] -\> [Throttle (complex, 25M)] -\> [FFT Sink (complex, 25M rate, baseband 98M)] running this graph results in an FFT scope with no activity; cutting the sample rates to 250k has no effect. if i mouse over the FFT window i get this error: * * * Traceback (most recent call last): File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/plotter\_base.py”, line 187, in \_on\_paint for fcn in self.\_draw\_fcns: fcn1 File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/plotter\_base.py”, line 59, in draw self.\_draw() File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/grid\_plotter\_base.py”, line 395, in \_draw\_point\_label label\_str = self.\_populate\_point\_label(x\_val, y\_val) File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/channel\_plotter.py”, line 150, in \_populate\_point\_label label\_str += ‘\n%s: %s’%(channel, common.eng\_format(y\_value, self.y\_units)) File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/common.py”, line 82, in eng\_format coeff, exp, prefix = get\_si\_components(num) File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/common.py”, line 48, in get\_si\_components exp = get\_exp(num) File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/common.py”, line 37, in get\_exp return int(math.floor(math.log10(abs(num)))) ValueError: cannot convert float NaN to integer * * * relevant info: GNUradio 3.3.0, Python 2.6, Mac OS 10.7.3, MacPorts install. sample data is stored on an internal hard drive. this seems like a pretty simple task, so there’s either something simple i’m missing or there’s a bug or misconfiguration in my install. any help would be appreciated - i’ve got a lot to figure out with this file, but i can’t seem to get past this step. thank you, - emilio gonzalez KI6NVO ---
**Author:** ![emilio\_gonzalez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/7ea924/32.png) [@emilio\_gonzalez](https://www.ruby-forum.com/u/emilio_gonzalez)\ **Post date:** [February 14, 2012, 9:20pm UTC](https://www.ruby-forum.com/t/working-with-wfm-sample-data/216813/2 "2012-02-14T21:20:06Z")
It’s very likely that your on-disk sample format isn’t what you’ve declared to Gnu Radio, and it’s seeing some garbage numbers. Is it possible that it’s stored as 16-bit I 16-bit Q in the file? If so, you’ll need to convert it before any of your complex-float blocks do anything with it. On Tue, 14 Feb 2012 12:02:34 -0800, emilio gonzalez wrote: > hello! > > i’m a new user embarking on some exploration to > evaluate GNUradio and > the USRP platform for some multichannel radio > monitoring. i am starting > with sample file processing before buying > any hardware, as CPU usage is > my chief concern. > > my problem is > with using a large sample file captured from the FM > broadcast-band: i > can’t get it to work with the simplest of graphs in > GRC. i was able > to use Sharlene Katz’s handy GRC tutorials to get her > AM sample file > running through an FFT scope and demodulated to audio, so > i know my > GNUradio install is working. however, running my WFM sample > file > results in no activity on the FFT scope, and i get errors when mousing over the FFT window. > the sample file was described to me as > 32-bit complex IQ baseband, > 98.0MHz center, 25Msps, gain 30 from an > N200r4 + WBX. to try a very > simple graph, i loaded it in to the GRC > like this: > [File Source (complex)] > → [ Throttle (complex, 25M) > ] > → [FFT Sink (complex, 25M rate, baseband 98M)] > > running this > graph results in an FFT scope with no activity; cutting > the sample > rates to 250k has no effect. if i mouse over the FFT window > i get > this error: > > * * * > > Traceback (most recent call last): > File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/plotter\_base.py”, > line 187, in \_on\_paint > for fcn in self.\_draw\_fcns: fcn1 > File > “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/plotter\_base.py”, > line 59, in draw > self.\_draw() > File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/grid\_plotter\_base.py”, > line 395, in \_draw\_point\_label > label\_str = > self.\_populate\_point\_label(x\_val, y\_val) > File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/channel\_plotter.py”, > line 150, in \_populate\_point\_label > label\_str += ‘n%s: > %s’%(channel, common.eng\_format(y\_value, > self.y\_units)) > File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/common.py”, > line 82, in eng\_format > coeff, exp, prefix = > get\_si\_components(num) > File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/common.py”, > line 48, in get\_si\_components > exp = get\_exp(num) > File “/opt/local/lib/python2.6/site-packages/gnuradio/wxgui/plotter/common.py”, > line 37, in get\_exp > return int(math.floor(math.log10(abs(num)))) ValueError: cannot convert float NaN to integer > * * * > > relevant > info: GNUradio 3.3.0, Python 2.6, Mac OS 10.7.3, MacPorts > install. > sample data is stored on an internal hard drive. > > this seems like a > pretty simple task, so there’s either something > simple i’m missing or > there’s a bug or misconfiguration in my install. > any help would be > appreciated - i’ve got a lot to figure out with this > file, but i > can’t seem to get past this step. > > thank you, > > - emilio gonzalez KI6NVO > * * * Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [1] [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) [2] Links: