I posted a number of plots of my SteppIR BigIR Mrk III /w 80m coil on my antenna site.
All plots were generated with the myVNA software. Calibration of the VNA was performed at the far end of the 100ft feedline to tune-out the transformation effects of the transmission line.
The scan was done while the antenna was tuned for minimum SWR on the 20m band.
The graphs can be seen here