Old-timer trick: A half-wave (and multiples thereof) of feed-line will "repeat" the feed-point impedance at the other end.
Take your frequency, and the velocity factor, and determine length of a half-wave, then make the line.
Then set the nano's sweep range close to the intended frequency (maybe +- 500kHz), and do an OSL calibration at the end of the feed-line (SO239-to-SMA adapter with the supplied SMA OSL's works fine at HF).
Then connect it to antenna and raise it to operating height. The nano should show the actual feed-point impedance of the antenna, just as if there were no feed-line between them.
73, --kv5r
