Hi, KD7LMO provides a binary GPS recording, presumably made with the USRP (thank you!). It is advertised as "4msps / complex GPS Snapshot (500 mS)". I use these ratios to determine what the file size should be: 500e-3 seconds 4e6 complex_samples / second 2 floats / complex_sample 32 bits / float 1/8 bytes / bit Multiply them all together and I get 16e6 bytes. However, KD7LMO's file is 32e6 bytes large. Can someone explain the discrepancy or misunderstanding? Thank you! Chris
on 2007-01-25 20:57
on 2007-01-26 18:06
Either I recorded them as 64-bit floats (double) or I did the conversion from time in seconds to samples incorrectly. The capture script I wrote is located at: http://www.kd7lmo.net/ground_gnuradio_software.html The code calls the file_sink method. I'm not sure what units/types it generates. dst = gr.file_sink (gr.sizeof_gr_complex, filename) head = gr.head(gr.sizeof_gr_complex, sample_count) fg.connect(src, head, dst) So the recording may be 1 seconds, instead of 500mS.
on 2007-01-26 20:07
firstname.lastname@example.org wrote: > Either I recorded them as 64-bit floats (double) or I did the conversion > from time in seconds to samples incorrectly. The capture script I wrote > is located at: mgray, Thanks for the response. Your script looks fine to me, but I'll try running it. Perhaps you typed one second at the command prompt. I tried to read the data as 64 bit floats, but it looked strange (typical values 1e13) and I quickly gave up on that. It appears that the first 7000 samples are bad. I attached a plot of the mag of the first 10000. The remainder look like the last chunk on the plot. I still cannot acquire a signal, but I'm working on that (could be my fault). BTW, I am working with gps_4m_complex.21Apr2005.dat Thanks, Chris PS: attachment rejected by gnu.org
on 2007-01-26 21:21
Chris S. wrote: > PS: attachment rejected by gnu.org I put it here: http://www.stankevitz.com/temp/samples.gif