Re: How to display a part of the GRC spectrum?

[Marcus D. Leech]

On 03/02/2023 12:07, George Edwards wrote:

Thank you Marcus, thank you everyone!

A more fundamental question I have is: Let's assume I was working at a low sample rate, say 32 kHz. Both the QT Freq GUI and the webgui would display a spectrum between -16 kHz +16 kHz. Suppose, I would like the displays to pop-up over the range 5-12 kHz, is there a way to instruct either the QT or webgui block to plot what I consider my range of interest at a sample rate of 32 kHz?

Thanks for all your inputs.

Regards,

George

    Yeah, you can just use the UI controls to "zoom in" if that's all
    you care about.
    
    If you want it (the GUI block) to be only "seeing" that spectrum,
    then the frequency-xlating FIR/FFT filter does what you want.

On Fri, Feb 3, 2023, 9:12 AM Marcus Müller <mmueller@gnuradio.org> wrote:

First of all, that's a high sampling rate!

You would want to shift the signal (e.g using the "Rotator" block, or
just by using a signal source at the shift frequency and a (conjugate)
multiplication), then decimate it by a factor of 3 GHz / 8 MHz = 375.

 From a point of view of designing the decimator, decimation by 375 is
quite a mouthful - it requires a filter transition width of
significantly less than 1/375 of the input Nyquist rate. So, it would
seem advisable to do this decimation in a cascade of decimators – in the
extreme case, decimation by 3, by 5, by 5, by 5.

Best regards,
Marcus

On 2/3/23 16:52, George Edwards wrote:
> Dear GNURadio Community,
>
> Let's say I build a GRC flowgraph operating at a sample rate of 3 GHz
> and wish to display the spectrum over the fixed range of 1GHz +/-
> 4MHz, how do I get the QT GUI Frequency sink to plot over this range?
>
> Thank you!
>
> George