Source - http://www.circuitstoday.com/wp-content/uploads/2009/10/colpitts-oscillator.png

My aim is to find the change in the inductance coil L1. All the other values are kept constant.

I built this and got the sine wave from the collector terminal (of transistor) and the Cout terminal. With this, I can calculate the frequency.

Now, I have to arrive at a formula (with unknown variables), which can relate the frequency and the inductance. I started to break down the circuit but its a confusion for me.

Interpretation I did:

Tank circuit has C (equivalent capacitance) and L in parallel.

R1 and R2 are in series (Voltage divider). Re and Ce are in parallel. R4 and Cout are in parallel.

But I am confused as to how the combination of these circuits will happen. I require some suggestions. Thank you.