Folding back does work in antenna element before loading coils as well!

Earlier, during tuning of 20/80m loaded coil dipole antenna of VU2XTO design, I used to trim the elements meant for 20m. Finally I ended up with very short elements for 20m, before the loading coils and it was difficult to reverse the process. Usually while tuning simple dipole antennas, we fold back and twist the antenna elements when we want to reduce the length to increase the resonant frequency. This time I tried the same process with elements before the loading coil as well. Folded back 12cm x 2 before the loading coil on one side, as an experiment. In effect there were three layers of wire in that segment. It did shift the point of dip in SWR noted on NanoVNA, both on 20m and the 80m segment which is yet to resonate. In the bargain, I lost resonance on 30m amateur radio band.

This was the antenna configuration before folding back. Folding back reduced 24cm of length in the 5m segment.

On 30m band, SWR dip was at 10.2 MHz before the folding back experiment.

SWR dip shifted to 10.3 MHz after folding back. It went beyond the tuning range of FT-710 radio so that I lost access to 30m amateur radio band, which I had for the past two days.

The SWR dip at 6.9 MHz near the 40m amateur radio band was not much affected, with only a minor increase in SWR from 1.813 to 1.927. That was tunable in the FT-710 radio.

SWR dip at 13.750 MHz shifted to 14.000 MHz after folding back so that 20m band became tunable on my FT-710 radio. So I am back on 20m band. Folding back and reducing length of 20m element before the loading coil by 24cm, causing a segment with three layers of 12 cm each, has shifted up the SWR dip by 250 kHz.