Q:

capacitor function in AM transmitter

I got a Kit for AM radio transmitter , and i understand the function for most  of the circuit except two capacitor i wonder about their functionality  is ?.  See the picture below 

I understand the AM transmitter contain 3 main parts 1th the mic circuit then amplifier then LC circuit , but what i don't understand the function of C3 and C5. 
When i tried to simulate the circuit all current except small amount  [ from the sours ]  used to flow from mic through C2 then C3 to ground .  
also C5 I would like to know what its function ?. 
i lost simulation, but if needed i will re-do it again upon request 
Thank you a lot in advance 

A:

C3  (1000 pF) is required for the transistor to oscillate at very high frequency, perhaps 100 MHz.  At this frequency, C3 is a short circuit from base-to-ground, allowing the oscillator to oscillate as a common-base Colpitts circuit.  For the audio input, C3 is high impedance, so that audio can change base voltage and base current.  C2 (100 nF) has a low impedance for audio, connecting microphone output to the oscillator's base. 
C5 (10 pF) provides radio-frequency feedback so that the transistor oscillates.  It also adds some extra capacitance to the 4-turn inductor to set the oscillating frequency.  C5 and C6 work together to feed back radio-frequency collector voltage to the transistor emitter: they provide high-impedance to low-impedance match from transistor's high collector impedance to the transistor's low emitter impedance.  Both C5 and C6 are small enough that they do not affect audio...for audio, the 220 ohm emitter resistor results in a fairly high input impedance for the microphone. 
Understand that the transistor is primarily a very-high-frequency oscillator.  By changing its bias voltage and current with audio input, frequency and amplitude of oscillations also change.  It will not provide excellent AM or FM modulation.  Simulating this circuit requires a very fine time-step so that you can see VHF oscillations.  This results in very long simulation runs if you also want to see audio modulation.