Re: How to print a list of the frequencies that are in the spectrum?

[Marcus Müller]

Hi Dor,

Re: 2. : That's … the input items! The actual samples that your block's signal processing works on. I think I couldn't explain this better in an email than our GNU Radio tutorials on https://tutorials.gnuradio.org already do. There's not much magic here. If you understand what a discrete-time signal is: a compact sub-sequence of the discrete-time signal flowing through your block!

> I try to understand what input carries the power vs frequency information in 
a list?  Is
> there anything like that?


To explain


Best regards,
Marcus

On 17.05.22 21:19, Dor Ratz wrote:

There's no such input. But: you can "package" your discrete-time signal into vectors of some length N, and then feed that into GNU Radio's FFT block. The output then is vectors of discrete-frequency samples. Put these vectors through a "complex to mag²" block, to convert them to power. The frequency information in the output of the FFT is implicit, as the DFT (which is what an FFT computes) simply maps N samples to N equally spaced subcarriers that divide the sample rate evenly. So, the position within the vector *is* giving you exactly the frequency. The Power is the magnitude square of the complex samples!

Hey,

Thanks a lot.


First of all, I use GNURADIO version 3.8.2 , this is the picture of the setup :
image.png

For example here the frequency of the signal source is 10khz and it can be seen 
here:

image.png

*_My questions are:_*

*1.How can I find the frequencies with relative gain higher than some threshold 
?*
*
*


image.png




I try to solve it without scipy, just with lists or numpy.




This is my code:

image.png

Thanks a lot

Dor

*2. What is exactly the input "input_items"? is it a list of gain vs what? What are the indexes? * I try to understand what input carries the power vs frequency information in a list?  Is there anything like that? <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Virus-free. www.avg.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail>

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‫בתאריך יום ג׳, 17 במאי 2022 ב-19:28 מאת ‪Marcus Müller‬‏ <‪muel...@kit.edu <mailto:muel...@kit.edu>‬‏>:‬

    Hi Dor,

    just a quick reminder: you're still using WX gui, which has been
    deprecated for roughly a decade, and GNU Radio 3.7, which is end of life.
    This could be relatively easily be solved using a Python block of your
    own design. Sadly, GNU Radio 3.7's support for these is relatively
    limited. It would be, on very many levels, be a good idea to use a more
    modern version of GNU Radio (e.g., 3.10).

    Best regards,
    Marcus

    On 16/05/2022 09.11, Dor Ratz wrote:
     > Hey,
     >
     > How can I print a list of the maximal frequencies that are in the 
spectrum?
     >
     > For example, I connect this signal source with frequency of 1KHz, so I
     > want to print 1KHz:
     >
     > image.png
     > There is the input_items[0], but if I try to print (max.input_items[0])
     > I get the power of incoming signal and not the frequency, so I'm not how
     > to do it.
     >
     >
     > Thanks,
     >
     > Dor

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