Need help with a radio transmitter 27 MHz - AM


Thank you very much!
Some Spice simulators have problems to start an oscillation when using a crystal model, or the equivalent circuit of a crystal.
Replace the entire equivalent crystal circuit with a simple shunt LC circuit (1uH and 33pF, and keep C9 in place) and you will get the 27MHz oscillation, just to see how the rest of the circuit works.
I've done what you said and i obtained this

My concern is that i have quite a lot of amplification, but i'm thinking is because of the soft
The "amplification" is most likely provided by the output LC filter without an effective load.
The screenshot schematic is hard to read, I can't recognize the modulation source settings. Similarly the waveform doesn't give much information with the presently selected time scale.
You intend to AM but you're using C-Class amplifier for that..It's wrong because C-Class amplifiers need relatively high input driving levels.
You have to use A-Class amplifier to amplify the modulated signal.Simulators can sometimes not provide start-up conditions for oscillators as you can see that your oscilaltion is damped and it is dying down.( I guess the oscillator is heavily loaded by the amplifier).
Thake these points into account..
I reworked the bias values and relaxed the Q of the crystal equivalent circuit a bit. After that the circuit simulated quite quickly and reached a steady state under 250 uS. I agree with BigBoss that you need some buffer stage to prevent loading on the LC tank circuit.
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