Dick,
The Nano-F has different firmware that is not compatible with the smaller NanoVNA. You can still perform TDR measurements from the PC side using NanoVNA-Saver or NanoVNA-Sharp. You can also make a request to BH5HNU on the NanoVNA-F group forum (
/g/nanovna-f) to add TDR to a future firmware release.
- Herb
