I've decided not to pursue AFC after all. To use it, you have to drop from 320 MHz to 160 MHz, and it's tethered to your phone to "check in" once a day just to stay active. I think it’s better to use your ISP router for AFC. They already have your name and address. My ISP router broadcasts 6 GHz at 25 dBm, so if I wanted AFC range, I’d just stick with that.
320 MHz channels are available, depending on location. I do not believe the range is as long as 160 MHz, so there is a trade-off.