Follow up:
Observing waterfall in WSJT-X shows noise as well. Picture shows 20m, 18m, 15m, 12m, & 10m from bottom to top. One picture is with rig attached to dummy load and cycling through from 20m thru 10m. The other picture is on the antenna again cycling through from 20m through 10m. Each band has two cycles of FT8 data.?
I believe this would point to the noise coming before the D/A and audio amplifier sections. Although I don't think the CPU is the culprit, I don't think it can be ruled out. IC405 and IC406 are unlikely, as there would have to be a similar fault in both chips.?
I swapped both SMPS from my lo band QMX, but no change in noise. So I doubt power bus issues. Bad capacitor somewhere?
That leaves the RF sections or the PCM1804. I think, anyway. Any further suggestions to check?
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73, Dan? NM3A
