Tried stub matching at 7MHz (d1=3490.4 mm, and d2=962.6mm) with unexpected results.
At 18.078MHz, V1=2.489 V, V2=3.236 V, V2delay=+5.0 nS, which gives Z=19.204+j53.537 ohm, SWR=5.8, and Zant=53.754-j103.264 ohm.
At 14.010MHz, V1=3.236 V, V2=5.014 V, V2delay=-2.0 nS, which gives Z=108.802-j90.822 ohm, SWR=3.8, and Zant=24.688-j44.895 ohm.
At 10.110MHz, V1=2.837 V, V2=3.614 V, V2delay=+1.0 nS, which gives Z=85.563+j15.044 ohm, SWR=1.8, and Zant=76.744+j24.942 ohm.
At these three bands, I can operate by using the internal antenna tuner of my rig, and I QSOed with stations in Ishikawa and Yamaguchi prefectures on 10MHz band.
However, at 7.026MHz, V1=2.656 V, V2=4.789 V, V2delay=+4.6 nS, which gives Z=75.131+j194.488 ohm, SWR=12.1, and Zant=4.118+j1.571 ohm, which I expected to be around 50+j0 ohm.