Is there something similar to the zero-span of spectrum analyzers in gnuradio?

[Juan Antonio]

I must be very confused on this topic.

I understood that the zero-span function in an analyzer meant that the span was reduced to the maximum and, from there, what you saw on the screen was the baseband in the time domain.

I know I could try it with a filter with a few hertz of bandwidth but I can't really understand how filters work and that's why I was looking for a simpler method.