is the time capsule a dual band and if so how do i use it as a single band

If your Time Capsule is less than 3-4 years old, then you have a simultaneous dual band Time Capsule.

Both bands are always on. It is not possible to turn one band on and turn the other off, and vice versa. However, if needed, you can also turn both bands off and use another router.

The best that you can do with the Time Capsule is assign a different name to the 2.4 GHz and 5 GHz bands, which will in effect result in 2 different networks.

Connect devices to the network that you want to use......either 2.4 GHz or 5 GHz.

Need to know what operating system that you are using on your Mac or PC.

If you have a Mac and do not know, click on the Apple icon in the upper left corner of the screen, then click on About This Mac and post back with the OS X Version that you see there.

You have to have Airport Utility for Windows installed on the PC. Is it?

AirPort Utility 5.6.1 for Windows - Apple

Open up AirPort Utility

Click or select the Time Capsule

Click Manual Setup

Click the Wireless tab located below the icons at the top of the window

Click the Wireless Options button near the bottom of the window

Enter a check mark in the box next to 5 GHz name

Click Done

Click Update at the lower right

Now the 2.4 GHz network has the same name as before

The 5 GHz network has "5 GHz" added to the name

Connect devices to the network that you want.

What were the results when you named the networks separately?