While going back and watching an old Mr. Carlson's lab this past weekend
I suddenly had a thought. Sure enough, the Jim Williams pulser prototype I last build makes a superb TDR head that's far cheaper than a "real" one. I compared it with tape measure for various cables I have on hand and it is extremely accurate, and has excellent resolution. The extremely narrow pulse the design provides by default provides really nice performance for TDR. It can detect the reflection from an adapter installed on the tee.