To knfenimore and Yosemite,
Thank you for your comments. Sometimes it is helpful just knowing other folks are interested!
I was able to identify the squeal as coming from the alternator belt. I called the alternator tech support 800 number, borrowed a volt meter from AutoZone, and the tech walked me through the alternator tests. He concluded the “new” alternator was bad. AutoZone ordered a replacement, tested it on their machine, found it to be good, and I installed this second “new” alternator.
(So, knfenimore, your comment “cheap rebuilt units can always be bad” was true. For the record, I have been using rebuilt parts for years. This is the first time one was bad.)
Ok, that was a few days ago. For two days, the alternator was charging the battery as it is supposed to. Except I was also smelling a burnt smell, like burnt rubber. And, the second day, the belt squeal came back.
This morning, after a local errand, the smell was back. The squeal was intermittent. Then, on the way home, the battery light came on on the dashboard. I got the car home before it died, lifted the hood, and found the alternator belt had broken.
So, I will replace the belt. Hopefully, that will do the trick.
(But, I wonder if how I installed the alternator could have caused the belt to heat up and break. The belt was not new, at least a few years old. And, by eye, the alternator seemed straight, not crooked. I hadn’t tried the water-on-the-belt test, as you both suggested.)
Thanks again for your interest in my problem.