Thanks for all these posts.
Learned and realized a lot but before I get to that let me say that I _was_ missing something when I sent the post that started this thread. With the way I originally connected the Mag, as recommended on this forum, it does pick up the channels that go with Comcast's basic service here. No expanded basic (ESPN, CNN, and many more). But those basic channels show up not, for the most part, with the numbers Comcast assigns to them, but with what I believe are their actual DTV channel numbers. For example, the NPR over-the-air channel here is number 23. For many years if you've had Comcast cable you punch in channel 4 in the Comcast remote. Since digital, that NPR channel has two additional channels, Create and World (only available, I believe, to Comcast subscribers).
Members of that channel get a monthly program guide that lists the original channel as number 23.1, Create as 23.3, and World as 23.4. I never understood what that was about since Comcast provided Create on its channel 27 and World on its channel 28. But the mag tuner does show those channels respectively as 23.1, 23.3, and 23.4, as they are listed in the channel's program guide.
As far as making the connections so that, as probably Wajo put it, the Mag is a slave to the box, as far as the family room where that Mag will be located, it will never work in a three-person household like mine. Could never program it a week in advance and expect that it would be on the channel I want when it's time to record.
HOWEVER, as I thought about what's going on when you keep the DVD recorder on channel 3 I realized that you're not using the built-in tuner at all so I wondered whether I could even use my old analog DVD recorder in that way. And yes, it works, even to get programs on the expanded basic channels..
As I said in the original post, the tuner in my analog recorder stopped getting Comcast's expanded basic channels in July 2010 and even the basic channels in June 2012. It wasn't really that much of a problem between those two dates because I very rarely want to record anything on any channel other than the NPR channel, which that tuner could get until July 2012.
So my current thought is to set up the Mag the way I originally had it set up, which will let me record programs from the NPR channel. And I can hook up the analog DVD recorder to the, rarely used, TV in the basement, and IF there's anything I want to record on any of those Comcast expanded basic channels that the Mag tuner can't get, I can get them downstairs where I don't have to worry about someone else changing the channel between the time I program it and the time for recording.
If you've followed me all the way through this, thanks a bunch for the posts that led me to try and succeed at these various approaches.