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

[George Edwards]

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 

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