At 14.05MHz, my swr-power meter, Comet CMX-200, says that when I set
the forward power to be 6W, the reflected power becomes 2W, which means abs(gamma)=sqrt(2/6)=0.577 and swr=(1+abs(gamma))/(1-abs(gamma))=3.73.
These values are in good agreement with the ones obtained by an impedance bridge.
gnuplot> load "gnuplot1.g"
Freq [MHz]=14.05
V1=3.232
V2=4.973
Cursor 1=2.2e-009
Cursor 2=6e-009
vratio=1.53867574257426
phase1 [deg]=11.1276
phase2 [deg]=30.348
abs(gamma)=0.589937579394383
swr=3.87730623314914
cz={99.2259973692051, 90.3894587505872}
Note that the measured impedance of 99.22+i90.38 means that the impedance of the antenna at its feed point is 106.58-i90.41, considering the coax cable length of 20m.
At 18.1MHz, CMX-200 tells the forward power of 6W and the reflected power of 2.8W, which means abs(gamma)=sqrt(2.8/6)=0.683 and swr=5.31, while they are 0.688 and 5.41, respectively, by an impedance bridge.