A short wire of length 30cm is added at each far end of the element.
gnuplot> load "gnuplot1.txt"
Freq [MHz]=7.026
V1=3.653
V2=6.169
Cursor 1=1e-009
Cursor 2=2e-009
vratio=1.68874897344648
phase1 [deg]=2.52936
phase2 [deg]=5.05872
abs(gamma)=0.69113364433374
swr=5.47529251182366
cz={252.437028893358, 72.0354980323906}
The VSWR is now estimated to be 5.475, which coincides well with the measurement by CMX-200 SWR meter.
Considering the coax cable length of 20m, Zant is estimated to be 9.491+9.744j [ohm].
