I'll bite

Have only a Roamio OTA. Generally love it. But in line with a lot of recent confusion I ask: What exactly does channel scan mean to TiVo? When I do a channel scan on my other atsc enabled devices they return channels that actually have a signal -- that doesn't seem to be the case with my Roamio. In fairness if I did a factory reset maybe that's what would happen, but I'm not real anxious to loose everything I've recorded. Also not too anxious to spend a few days transferring them all to my PC. Although that's more than D* allows me to do.