A 1 dB change in loudness is about the smallest level of change which is
fairly easily perceived by the human ear. BUT ONLY WITH AN INSTANTANEOUS, X
versus Y, CHANGE IN LOUDNESS.

To attempt to judge the difference, with a precision of 1 S-unit, between
the loudnesses of a G5RV and a 1/2-wave dipole fed by an open-wire line,
with a time lag of months, a change in the number of sunspots, on different
bands, with a different receiver, is futility in the extreme.

Yet some people appear to have no difficulty in making the comparison.