Time Machine

Time Machine is the application used for backing up, it sounds like you are talking about Time Capsule which is a router that has a hard disk enclosed in the same casing. Time Capsule can be connected wirelessly, most prefer it that way for the convenience and lack of wires.

If you are looking to use an external HD as a Time Machine backup drive they should not be connected wirelessly, they should be physically connected via USB, Firewire or Firewire 800 to your iMac. IMHO it is not wise to scrimp on backup drives, it's your backup so if when they die you've lost your backup! My recommendation is to invest a little and buy quality products that will last longer. What I normally recommend is either:

G-Tech G Series

Lacie Quadra D2 Series

OWC (www.macsales.com) Mercury Elite Pro Series

All are top quality build quality, have similar features and just work well out of the box. Personally I have Lacie's (4 of them) however I wouldn't hesitate buying any of the above.

Roger

Hello ChefEncore

Mac 101 @ http://support.apple.com/kb/HT1427

say's that

+"Setting up Time Machine is as easy as connecting an external hard drive to your Mac via FireWire or USB, or by connecting to a Time Capsule."+

There's nothing wrong with buying an External HD that is on sale, as long as it wasn't from the bottom of the barrel before it went on sale.

Dennis

although this posting is a bit old, all HDs are not alike. You should buy one with a 5-year warranty. These are enterprise quality drives and will last longer than you'll probaby want to keep it. There's a guy here at work that used to design HDs for a living and I follow his advice. He also suggested that if you want more than one drive, buy from two different mfrs so you increase odds they won't fail at the same time.