Current NanoVNA TDR implementation is almost useless, because it shows time with 1 nanosecond resolution.
I experimented with different FFT sizes and it looks that 65536 has the best resolution for NanoVNA. It allows to see picoseconds. But it produce a lot of data, it's better to use 32768 points. 16384 also usable, but insufficient resolution becomes noticeable.
This TDR feature just eats precious memory. F072 has too small memory. So, I think it's better to remove TDR function from firmware and replace it with more useful features
