-Can you guys help me understand this circuit?
-Is a signal converted into AC from DC and connected to a antenna to transmit electromagnetic waves in specific frequencies?
-How is the frequencies tuned?
-How to change DC to AC ? (With Inductor, capacitors...?)
-How to receive and convert back signals that can be used? (Use capacitors, diodes...?)
Simpler circuit
More Complex and better
-Is a signal converted into AC from DC and connected to a antenna to transmit electromagnetic waves in specific frequencies?
No that is not how it works.
C1, C2 & L1 form a resonant circuit and along with Q1 it forms an oscillator.
The audio signal is injected into the oscillator and changes the amplitude of oscillation. (to me this looks like an AM transmitter but I suppose that this loading could also cause some FM)
-How is the frequencies tuned?
C1 is a variable capacitor and so changes the oscillators frequency.
How to change DC to AC ? (With Inductor, capacitors...?)
No relevance to this circuit but with diodes and a capacitor.
How to receive and convert back signals that can be used?
You need a radio receiver, for FM it needs to have a discriminator circuit, it can be made in many ways but inductors is the normal method.
