Hi, Jose -
I might suggest lowering the Park frequency. With my U3S unit (on 20m and 30m), I found it was initially drifting downward in
frequency. When I set Park to 150,00,000, it was then drifting upward in frequency. I experimented with
different settings of Park, and ended up at something like 141,300,00 ... that worked well for my setup
(I also put a heat sink on the crystal on the synthesizer board and put some foam around the whole
synthesizer assembly ... have a look at Hans' Application Note on this topic.