Using the FFT mode with its much small resolution filters and 10k points it became possible to see the PLL shoulder
This was made with the first IF at 2.6GHz. Phase noise has somewhat improved due to a better power supply
At the left you see the resolution filter from 1kHz till about 3kHz, the PLL shoulder is at -60dB and extends till 30kHz.
Above that you see a linear drop (actually logarithmic) till below -90dB at 300kHz. Did not check yet if the angle? corresponds with ADIPLLsym output
The resolution is now good enough to see small changes in the PLL setting such as changing the loop current or setting R to a different value
Also the 10MHz XCO on the green ADF4351 modules is not the most stable and testing with a very stable external 10MHz TCXO may now have a visible impact. The more you see, the more can be improved, so much fun!
