I recently made a video showing how to measure impedance 3 ways with a VNA including the s11, series sw1, and the shunt s21 methods.
See if interested.
Larry. W0QE
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On 3/14/2020 5:58 PM, Roger Need via Groups.Io wrote:
On Sat, Mar 14, 2020 at 04:36 PM, WB2UAQ wrote:
I also measured the feed point impedance of a 67 ft wire at 7 MHz using the
Nanovna and found it to be 3600 to 3900 ohms shunted by about 8 pF. This Z
is about 1250-j1820...way out of the range of the Nanovna (S11)
Yes the S11 bridge method starts to get quite inaccurate after the impedance gets higher than a few hundred ohms. Fortunately the NanoVNA can do S21 measurements and we can determine complex impedance at several thousand ohms using the "Series Method" shown below. The equations are not that complicated and I was hoping Rune could add them to NanoVNA Saver. Presently I do them in a spreadsheet after an import of a S21 Touchstone file.
Roger
