Radio. - Here is Circuit Schematic Coplpitt’s Oscillator in PartSim. This is a common emitter Colpitts oscillator. R1 and R2 form a voltage divider to provide base bias. the emitter resistor R3 also provides some bias. R4 is the collector resisotr across which the any output signals appear. the output is fed into a parallel LC tank circuit. A capacitive voltage divider is used to provide feedback. The cap C3 between the LC dircuit and the base, effectively passes the AC feedback signal but block the DC on the collector. the phase shift on the LC network is 180 degrees from the top of L to the bottom of L.