I made a simple FM transmitter following https://maker.pro/custom/tutorial/how-to-make-an-fm-transmitter and it worked! Now I need some help to understand how. My coil is made of 1 mm copper wire has 6 turns and 8 mm wire diameter. According to this online calculator: https://www.eeweb.com/tools/coil-inductance this means that: L = 3.9e-7 H
I did not have any 5 pF trim capacitor so I used a 3 pF capacitor instead.
Am I correct in assuming that the frequency this will transmit on can be found by looking at the L1 C2 as a LC oscillator and using the frequency formulae:
fR = 1/(2*pi*sqrt(LC))
If so I should get fR = 147 MHz. Which is strange since I received the signal on 91.5 MHz on my radio.
In a LC circuit I understand that the signal decays exponentially over time. That is hopefully not happening here. Why? Because of C4 maybe?
Also what is the purpose of C1?
If I want to increase the range of this FM transmitter somewhat can I do this by simply replacing R2 with a 470 Ohm resistor?
Are there free simulator programs that let me see the resulting spectrum at the antenna?