Re: Questions On GNU Radio FFT Data logging

[Martin Luelf]

Dear Zen Chen,

to subscribe to the mailing list you need to follow this link: 
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
I think the account on the GNURadio website is for editing the Wiki etc.

You are sampling your signal at 10 MSamples per second. Since you use a 
complex signal (blue input to the file sink) that means each sample is 
two 32 bit floating point numbers). Thus your generated binary file has 
a size of 80 MByte per second of recording.

If you convert that into a CSV file the default formater for 
numpy.savetxt() is .18e, meaning that each real and imaginary part will 
be written as 24 characters (one place before the decimal, the decimal 
point, the 18 places after the decimal and 4 chars for the exponential). 
These need to be delimited by a comma and finally a new line character. 
That makes 50 characters per measurement. For a regular ASCII file each 
char is 1 Byte so you are writing 50 Byte/sample * 10 MSample/s = 500 
MByte per second of recording.

That is a lot of data. For a 5 second recording for example you are 
asking Excel to import a 5GB file (!). I don't know Excel too much but 
that sounds like it might be to much. Possible remedies are: try to 
reduce the sampling rate (which will reduce the monitored bandwidth) or 
try to record very short bursts, or (my personal opinion) try to analyze 
your signal in a program that is more suitable to signal analysis than 
Excel. You most definitely want something that can work directly with 
the binary files from GNURadio's file sink rather than having to use a 
CSV file. GNURadio itself, python/numpy, Matlab/octave, C++ are all good 
choices for the analysis (and certainly many more).

Yours
Martin



On 10.12.21 09:59, Zen Chen wrote:
> Yes933_10_12_20212nd.csv 
> <https://drive.google.com/file/d/1tEaxr9bQICfDm-Uu6nIfGcLSQd6Rfb1Z/view?usp=drive_web>
> HI all,My name is Zen Chen , a GNU radio Novice and I tried to create an 
> account on the GNU Radio .org website to post my questions on the 
> mailing list however I could not . I am using GNU radio and Hack RF 1 to 
> design a power spectrum analyser and I am using the attached flowgraph 
> to and python script to give me the attached CSV file however , the 
> results (FFT connect to file sink) is to large to be contained in a 
> single excel file . Is there a problem in my GNU Radio Flowgraph?
>
> Regards,
> Chong Zhi