It sounds like you are using the 'analogue' tuner. You need to switch over to the digital tuner and try scanning for channels again. I don't know where you are based, but the majority of countries have disbanded the analogue terrestrial service. This may be why you are not finding anything. Searching for digital signals does not produce 'snow' as the digital service uses a much higher frequency and has a squelch function which cuts out any unwanted static or interference. You would just get a blank screen. This is what makes me think you are trying to use the analogue service.
Hope this helps!