Re: FFT Size and Signal & Vector Sources Amplitude Unit

[Marcus D. Leech]

On 08/03/2023 15:43, DİREN ERDEM AYDIN via GNU Radio, the Free & Open-Source Toolkit for Software Radio wrote:

Dear All,

Changing only FFT size of the freq sink block during simulation drops signal power drastically, screenshots are given in the attachments. I am providing the pulse burst from the vector source as 6144 points (6 ones and the rest of the points are zero). Since FFT sink blocks show the average power of the points on freq domain, increasing FFT size would increase the number of zeros in the buffer so power is reduced. 

What do you think about this approach, is it ok? and there are fluctuations in the 32k example, that's why it is thicker than 4k plot, what is the reason for this?

Moreover, no unit is written in vector or signal sources amplitude sections. Are units assumed as volts?

Regards,

dea

 

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    Units are *UTTERLY UNSCALED*, but Gnu Radio normally operates within
    {-1.0,+1.0} for floating-point values.
    
    Most hardware drivers honor this system and scale their (complex,
    usually) samples appropriately--so those samples will
      be *linearly related* to the instantaneous *voltage* as seen at
    the antenna, but turning that into real-world values
      is up to the user, typically.    Gnu Radio itself has no idea what
    these samples *mean* in terms of the real world.
      Any actual hardware device will perform considerable analog (and
    then digital) signal processing on the antenna signals.
      So all that you know when you get those samples into Gnu Radio is
    that they're (mostly) linearly-related to an antenna voltage.