Ive noticed a pattern I dont understand. Multiple occasions. Different times of day. Sitting on my couch. Tablet in hand, connected to wireless router on cable modem, surfing the web. Sprint phone sitting on couch next to me, connected over 3G cell network, streaming internet radio. Restating the obvious, these two devices are connected to teh intarwebz in completely different ways, not on the same network. Both connections are kinda weak, as in one bar on each. The phenomenon goes like this: When the phone's audio stream pauses because cell data connection hiccups, and I'm clicking a link on the tablet browser to load a page like FChat, which is usually an instant page load... i stare at the tablet for 5-10secs in silence and as soon as the audio stream starts again, the page loads immediately. Is that like a widespread momentary local internet outage? Maybe sprint buys their bandwidth from suddenlink, the same ISP as the wireless? A glitch in The Matrix?
Most likely not an Internet outage because it takes time for NOC to react to outages. Usually they don't do anything till people start ringing up to complain You did mention a lack of signal, it sounds like local interference. Did you try changing the wireless channel on the modem? The best way of trouble shooting these type of problems is having all bars for both devices, which could mean moving devices(including the modem) around so that both of them are full.
Are you certain that the tablet isn't using the phone for a connection, perhaps via bluetooth or shared wifi? Alternatively, are you certain the phone's not using the wifi? If they are truly separate, then there's a common upstream somewhere that's glitching.
My wifes phone automatically uses the wifi if it is available and only uses the cell connection when no wifi is available. This cuts down on minute usage.
Wireless router typically on 2.4GHz band. Susceptible to interference (as noted). Try changing the channel and if your devices support it, try going to 5GHz. May be helpful - http://www.cyberwalker.com/article/316 BR/Brian.