Colpitts Oscillator at Resonance

Using a circuit from the RF schematics section, and the formula from the theory section, you can estimate the resonant frequency for this oscillator:

Working out the parallel capacitance, C1 C2, (27*27)/(27+27) = 13.5pF
Assuming that the coil, L has an inductance of 0.2uH then:

 

= 96.8 MHz

This puts the frequency of oscillation in the middle of the UK FM Band (87.5 - 108 MHz). If an inductor with a core is used, then the oscillator can be tuned by moving the core. If an air spaced core is used, then tuning is achieved by physically squeezing or separating the turns.