only 2.4ghz found, 5.0ghz not in range

I have the WNDR3300 on Windows7 computer. With the mode setting at Up to 270Mbps at 5GHz & 54Mbps at 2.4GHz. I have named the N connection 'blue. and the G connection 'green'.

While sitting at the desk where the modem is my asus transformer prime tf201 tablet only sees the green/G signal. If I change the mode to Up to 270Mbps at 2.4GHz then it will find and connect to the blue/N signal.

My question is why is the blue/N signal not in range when the mode is set to 'Up to 270Mbps at 5GHz & 54Mbps at 2.4GHz?