A BA1404 IC is used to generate a complete FM MPX signal. The chip contains all of the necessary circuitry. CI and R3, and R4 and C4 provide pre-emphasis. The transmitter runs on a single AA cell. L3 is 3 turns of #20 wire on a Ke drill (for a form). L3 is long. L4 is 4 turns #20 wire on `Me drill bit, spaced to %.
If monophonic operation is wanted, omit C5 and the 38-kHz oscillator components.
1W FM Amplifier Circuit (Boost Low Power Transmitters)
Frequency Modulation tutorial
RF Low Pass Filter for FM Transmitters (88-108mhz)