Have been testing various antennas on my NanoVNA V2 Plus4 and in all but one, the results appear roughly as expected.
The one that doesn't is a 2.4GHz helix, which shows a very poor match there and actual resonance/low SWR is at about 3.4GHz.
I know the helix is an electronically shortened antenna, and may not present an ideal 50ohm impedance, but that still doesn't make sense to me when making these measurements.
Can anyone explain what's going on here?
