qrp.ddc,
Thanks for taking the time to reply. Ham's such as myself are generally looking to purchase specific types of 50 ohm cable such as RG-58, RG-223, RG-6 etc. The cables are all marked by the manufacturer according to type and we pretty much know the velocity factors by heart, so entering that info into the nanoVNA is a no-brainer. I don't really use the nanoVNA's TDR function for purchasing specific lengths, but rather to ensure for instance that a 10 meter length of cable being offered for sell doesn't have damage at say 4 meters to its inner conductor. One cable I measured before purchasing had very strange peaks and valleys on the nanoVNA's TDR function (wish I could have saved the screenshot), when I examined it more closely I could see slight equally spaced pits on its outer insulation. I'm guessing the cable was used in a mismatched power transmitting application and the spacing of the insulation pit marks was associated with the transmit frequency. So I use the TDR function as more of a sanity check to help sort the chaff from the wheat.
Sorry, I mistakenly assumed you had access to a professional level TDR to not appreciate how, even with its limits, the TDR function on the nanoVNA is a godsend to hobbyists, students, and radio amateurs as essentially a throw-in to its vector network analyzer capabilities. Let's hope in nanoVNA V2 that Hugen increases the number of measurement points and gives you some of the other things on your wish list.
Herb
