Just before I leave for 2 months, I measured the 3-Band
antenna for  20m-17m-15m .
Below are the measured SWR values for the antenna installed
on the car as seen in the picture below.
Values measured with MFJ-269 after 2 m coax cable.

20m:           SWR
14.000    =  1,3
14.040    =  1,2
14.070    =  1,1
14.080    =  1,0
14.260    =  1,0
14.285    =  1,1
14.310    =  1,2
14.340    =  1,3

The SWR bandwidth 1:2 is  13.805 - 14.575
 
17m           SWR
18.000   =  1,2
18.060   =  1,1
18.085   =  1,0
18.250   =  1,0
18.280   =  1,1

The SWR bandwidth 1:2 is   17.750 - 18.600


15m           SWR
21.000   =  1,5
21.060   =  1,4
21.090   =  1,3
21.120   =  1,2
21.135   =  1,1
21.156   =  1,0
21.220   =  1,0
21.240   =  1,1
21.275   =  1,2
21.315   =  1,3
21.345   =  1,4
21.390   =  1,5

The SWR bandwidth 1:2 is  20.890 - 21.515

This is the 3 band antenna in 20 m setting