Yes, the HDHomerun is digital only and won't be able to tune in your analog channels. It can be confusing because the US cable systems have different rules that require the basic channels to be unencrypted, and the premium channels to support a decryption called CableCard.
In Canada, neither is true unfortunately. You get whatever your cable company chooses not to encrypt.
I'm not that familiar with the Mac products, but you likely need one of Elegato's hybrid tuners to encode the analog channels. http://www.elgato.com/elgato/na/main...oduct1.en.html
Depending where you live, you may be surprised how many over-the-air channels you can get with that HDHomerun. Go to tvfool.com and type in your address. It will tell you how many channels you can receive via antenna (and they'll be better quality than your analog cable).