Thanks for your fast reply.
OK, I adjusted PREAMP gain on each band I'm using, and will use ATTN on low ones.
I suppose that it is better than using RF gain, further in the receiving path ?? But QRN (latitude 18°S) is so high on "low" bands that I need to use RF gain control, too, which varies along the hours, anyway.
(BTW I know that a vertical whip is not ideal regarding atmospheric noise ;-)
"To nobody, except those who will take pleasure here" (Franz Schubert, 1797-1828)