Many stations are currently broadcasting analog at full strength on their original VHF frequencies, and digital on temporary UHF frequencies at significantly reduced power. Come cutover time, the digital may be switched over to the VHF frequency that is freed up when the analog currently there goes away. Or the digital on that temp UHF frequency may go higher power and be made permanent.

All this channel switching is made transparent to the end user by something called PSIP ("Program and System Information Protocol"). That's a way that frequencies can be mapped into channel numbers. For example, analog channel 9 is broadcast on the 187.25MHz frequency. "Digital channel 9" is often referred to as "channel 9.1", but this designation does not imply any particular broadcast frequency. It could be, for example, UHF channel 42 (639.25MHz) that is "mapped" to channel 9.1 via PSIP. What your digital tv does when it scans for channels (or you tune one manually) is it reads the PSIP data that is broadcast on that frequency. That PSIP data in effect says something like "I know you found me on channel 42, but instead of calling me 42, call me 9". Your TV remembers this.

That's probably lots more than you ever wanted to know. Bottom line: What you see today in terms of "fragile signal" is not necessarily what you'll see come switchover time. Actually, the digital signal is much more robust than the analog signal. The "fragility" that has been mentioned does not have to do with digital vs. analog (analog is the more fragile). It has to do with low power temporary transmitters and antennas. Or it could have to do with you having your over-the-air antenna pointed in the wrong direction. The digital transmission may well be broadcast from a different compass direction than the analog. If your antenna is pointed in the wrong direction for what you are trying to receive, you may still be able to pick up something if you're lucky (off axis), but you may also experience "fragility" because you're pointed incorrectly.