Earlier this week, XBradTC linked to an interesting vid on DIY radar.
Which stirred up the ol' creative juices. I hate presentations in video format; much prefer text + drawings so's I can skip back & forth easily, and the vid is in tl;dw territory at the moment, but I downloaded a copy and skimmed through, and it reminded me of some things I'm sure I knew back in the '90s, but had somehow forgotten.
Like, the easy way to get range is with linear chirps and interference-frequency measurement, rather than trying to do direct time measurement between two detector outputs (with the attendant requirement for very short pulses, if you're trying to measure smallish distances).
Modest-range radar had crept into my mind a couple of years ago, in connection with the problem of trying to put a plane on a runway blind. (Gee, what happened a couple of years ago that would bring up such thoughts?) Augmented GPS will get X and Y close enough for a plane that's much smaller than what the runway was designed for, but accurate Z is a major headache. Integrating GPS and a short-range radar altimeter to get the last couple hundred feet with sub-foot resolution? Well, it might just work.
Not that there's much prospect of actually making a product of that (despite my having a totally cool, as well as blindingly obvious, UI concept). Between regulatory issues and potential liability, I rather suspect it's a non-starter.
Still, various ideas are now rattling around in my head (and competing with all the other ideas I haven't been having time for). Maybe next year, if I manage to relocate to a place where I'd have a proper workshop and lots of tinkering space, I'll turn some of them into products, or at least subsystems for sale.