Question

Frequency modulation is best achieved at what stage in a transmitter?

Answer 1

At an oscillator (first RF stage).

Explanation:

FM transmitters generally modulate an RF oscillator by pulling its frequency slightly above and below its center (unmodulated) frequency, in correspondence with the modulating signal.

This is often done using a varicap (variable capacitance) diode connected to a crystal oscillator, or a VCO (voltage controlled oscillator).

The frequency modulated output from the oscillator is then either amplified for transmission, or 'mixed' to the required transmitter output frequency and then amplified for transmission.