What are amplitude modulation,frequency modulation and phase modulation?Do they have anything to do with radio?
Modulation means to change ( modulate ) a particular characteristic of a carrier wave , based on the message you are trying to superimpose on the carrier wave. Modulation is compulsory due to, amongst various other reasons, primarily due to the fact that the normal message frequencies/bandwidth is low which would necessitate insanely huge antenna size. To overcome this practical constraint, modulation enables shifting the message to a higher frequency range, by employing a carrier of far higher frequency when compared to the message bandwidth. Based on which characteristic of the carrier wave is controlled by the message signal, the different modulation schemes are defined and the names are self explanatory. AM – Message controls amplitude of the carrier wave – Pros – very low bandwidth requirement, Easy demodulation – Cons – Very low Noise Immunity FM – Message controls frequency of the CW – Pros- Improved noise immunity – Cons – Increased bandwidth requirement, Demodulation circuitry