I have to design VCO for frequencies from 85-108MHz using varactor(s). I checked the internet for some designs, and I think this one will be fine, although I'm not using very wide band.

Do you think this design is fine, or would something else be better?

However, the problem is that I don't know where to start. I believe that the transistor must be biased in such a way as to have around half of the Vcc voltage drop on the R2 resistor (Common Collector A-class amplifier). But I don't know what values of resistors should I use. I also don't know why R3 on the collector is needed. And I don't understand why it has R7 when it is already biased with R1 and R5 resistors.

About frequency: If my thinking is correct the frequency could be calculated with 1/(2*pi*sqroot(LC)) where C is the serial capacitance of C3, C4, D2, D1 together. Right?

I also have some trouble understanding the working of the Common Collector Colpitts oscillator. I don't understand where does the phase shift come from. The phase shift of the CC amplifier is 0 degrees, but the phase shift of the tank circuit is 180 degrees, so there must be something wrong here.

Thank you for your answers.