OTA viewing: do I need to add .1?

So I've never had digital OTA service before. I'm considering it.

If I want to switch to channel 8.1, does it really require 3 button presses; ie., would simply typing 8 make TiVo tune to analog channel 8 that no longer exists? Or will Tivo automatically tack on the .1?

And does the answer differ whether one uses a Roamio OTA, an original Roamio, or a Premiere?

Thanks!

OTA viewing: do I need to add .1?