Cessna,
I can't tell you why your signal is "junk" (could be your location, could be your laptop, could be lots of things). To use the 5g signal you need a computer/phone/game console/whatever that can operate on that frequency. Many draft N cards and devices (probably including the iPhone) will only use the 2.4ghz band.
Bottom line, you presumably purchased the 825 for its dual band capability but it sort of sounds like you don't have anything that can connect at 5ghz or, if your computer is using that frequency, you're too far from the router or have too many walls between devices.
Cheers