GNU Radio, One Step at a Time: [Discuss-gnuradio] SDR question

I have a question about software defined radio

I saw a pass band the other day on a screen which prompted me to ask

The Software defined radio has a specific bandwidth ?

Does it "scan" across the band very quickly to form the passband, or is the
bandwidth already that large it just appears as a chunk of MHz ?

I am trying to make the connection between how a Software Defined Radio
would be different from an analogue system.

For example decoding packet radio using an SDR, is there any performance
degradation due to the way it works ?

Would the SDR "sweep" and miss some of the signal ?

- Andrew VK4TEC -

GNU Radio, One Step at a Time