Well noted, I will rethink the assembly in the box, particularly for the grounding of all the circuits. In fact all of them are fasten on a plastic sheet and consequently not aground at all

Secondly, I will filter the 7808 with 100 and 200µ condensators instead of 100 and 200nF

At least, I will shielded the wires between various circuits and GPIO card. I already connected 3.3v from RPI to ADF4351 circuit seems better.....
So I have an important work but assume that result will be at rendez vous.
As soon every things are in order I will keep the team informed.
For info, the power supply is 74G8490 IBM and suppose is well filtered. Out 5v.05 and on RPI GPIO 4.94v using a low loss USB cable.
73'
Bernars F1NST