Pulse modulation involves modulating a carrier that is a train of regularly recurrent pulses. The modulation might vary the amplitude (PAM or pulse amplitude modulation), the duration (PDM or pulse duration modulation), or the presence of the pulses (PCM or pulse code modulation). PCM can be used to send digital data; audio signals on a compact disc use pulse code modulation

Frequency modulation uses the information signal, V_m(t) to vary the carrier frequency within some small range about its original value.

Advantage FM:

• Immune to AM noise riding on it`s carrier frequency. Affected much less by static caused by adverse weather.
• FM radio has a significantly larger bandwidth than AM radio

Disadvantage Fm :

Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent. For example, changes in the signal strength can be used to reflect the sounds to be reproduced by a speaker, or to specify the light intensity of television pixels.