Hi Robbie,
RadarBox does not require the internet to function but it is helpfull :)
Without the net RadarBox will be showing flights that are picked up your antenna only. How far is the nearest airport? what is its traffic like (commerical or ga)?
RadarBox will pick up ADS-B traffic and display them on the map and also pick up Mode-S traffic but not display them on the map. Have a quick look through the FAQ section.