Internet connection still dropping

My internet connection still drops at random. most irritating whenever we are online.  It could be happening whenever we are not online or on the network with our other wireless devices.  Only this time it comes back online, sometimes immediately or it can take several minutes before it comes back on its own.  I've already connected to modem directly to the main computer and it seems to work fine but I don't know if the connections are dropping whenever I'm not online.