This oscillator circuit (schematic) has a low phase noise and the elliptic low pass filter found at its output helps to mitigate the harmonics. It was inspired by ideas published by U. Rohde.
Its output power is 0 dBm and harmonic 2 level lower than -70 dBm.
When using 2 oscillators of this type in a common enclosure it is important to build each circuit in a well shielded box with good power supply decoupling (see picture) .
