Wonder you guys try to add in inductance ( 110 uH ) and plus 7fT
Of radiator element on the top of the 40M.? for 80M.
Or try to make inductance and radiator element to suit your 80M frequencies.
I did try here and the 80M is narrow bandwidth i get 60khz.
I tune to center frequencies around 3.600 and VSWR without tuner 1:2
and at the band edge 2:0. and it does not disturb the rest of the band. 10-40M
The inductance wound on 20mm PVC and 1mm Enamel copper wire.