Could be a router problem. Routers have separate antennas for 2.4GHz and 5Ghz. Could be interference from other 2.4GHz devices, like cordless phones, in your house.
Some things to try first:
1. Turn Off your iPad. Then turn Off (disconnect power cord for 30 seconds or longer) the wireless router & then back On. Now boot your iPad. Hopefully it will see the WiFi.
2. Go to Settings>Wi-Fi and turn Off. Then while at Settings>Wi-Fi, turn back On and chose a Network.
3. Change the channel on your wireless router (Auto or Channel 6 is best). Instructions at http://macintoshhowto.com/advanced/how-to-get-a-good-range-on-your-wireless-netw ork.html
4. Go into your router security settings and change from WEP to WPA with AES.
5. Renew IP Address: (especially if you are droping internet connection)
• Launch Settings app
• Tap on Wi-Fi
• Tap on the blue arrow of the Wi-Fi network that you connect to from the list
• In the window that opens, tap on the Renew Lease button
iOS 6 Wifi Problems/Fixes
Fix For iOS 6 WiFi Problems?
Did iOS 6 Screw Your Wi-Fi? Here’s How to Fix It
How To Fix Wi-Fi Connectivity Issue After Upgrading To iOS 6
iOS 6 iPad 3 wi-fi "connection fix" for netgear router
Apple's iOS 6 Wi-Fi problems
Look at iOS Troubleshooting Wi-Fi networks and connections http://support.apple.com/kb/TS1398
iPad: Issues connecting to Wi-Fi networks http://support.apple.com/kb/ts3304
WiFi Connecting/Troubleshooting http://www.apple.com/support/ipad/wifi/
How to Fix: My iPad Won't Connect to WiFi
iOS: Connecting to the Internet http://support.apple.com/kb/HT1695
iOS: Recommended settings for Wi-Fi routers and access points http://support.apple.com/kb/HT4199
How to Quickly Fix iPad 3 Wi-Fi Reception Problems
iPad Wi-Fi Problems: Comprehensive List of Fixes
Fix iPad Wifi Connection and Signal Issues http://www.youtube.com/watch?v=uwWtIG5jUxE
Fix Slow WiFi Issue https://discussions.apple.com/thread/2398063?start=60&tstart=0
How To Fix iPhone, iPad, iPod Touch Wi-Fi Connectivity Issue http://tinyurl.com/7nvxbmz
Unable to Connect After iOS Update - saw this solution on another post.
Note - When troubleshooting wifi connection problems, don't hold your iPad by hand. There have been a few reports that holding the iPad by hand, seems to attenuate the wifi signal.
If any of the above solutions work, please post back what solved your problem. It will help others with the same problem.
I went through the fixes suggested. Changing security and channel on the router did not seem to have any effect. The iPad still only picks up the signal from the router when within a few feet of it. I have taken the router to places with wireless, such as the airport and hotels, and it was unable to find or connect to the network. The only places it will connect to the network are the apple store, my house (dual band router), and my friends house (dual band airport router). I guess my question is whether a damaged or defective antenna could be the cause. As I understand, the pad has 1 antenna that picks up the wifi. Could damage to it result in not being able to pick up 2.4 signals, or could it be a software issue?
I very much appreciate the help and insight.
I have the same issue with an Ipad 2 since late december, tried the trick mentioned before at this post, I restored it twice and nothing worked, the only solution was to buy an airport extreme and use the dual band to get the 5ghz signal. I was told that an internal antenna may be damaged for the 2.4 ghz band and there is no way of replacing it without ruining the front panel.