Modulated waves!

*Warning, alot of science stuff.Read first line first. Skip if you're not interested to find out*

Ever wondered what does "FM" and "AM" means at the back of radio stations, like Hitz.fm? FM stands for frequency modulation and AM stands for amplitude modulation. But before I go on, what is modulation? Modulation is the process of varying one waveform in relation to another waveform. Through modulation, a low-frequency information signal is conveyed by a high-frequency sinusoidal carrier wave(needed because the original information signal will suffer from too much damping and interference to reach a far distance). In telecommunications, frequency modulation (FM) conveys information over a carrier wave by varying its frequency. Amplitude modulation (AM) does the same except this time it's the amplitude of the carrier that is varied while its frequency remains constant.

For radio stations, both AM and FM are used. "But why it's always FM that we usually listen to, and not AM?" you ask? Well, for once, AM is not very suitable due to multiple reasons. AM radio signals can be severely disrupted in large urban centres by metal structures, tall buildings and sources of radio frequency interference (RFI) and electrical noise, such as electrical motors, fluorescent lights, or lightning. As a result, AM radio in many countries has lost its dominance as a music broadcasting service, and in many cities is now relegated to news, sports, religious and talk radio stations. Some musical genres – particularly country, oldies, nostalgia and ethnic/world music – survive on AM, especially in areas where FM frequencies are in short supply or in thinly populated or mountainous areas where FM coverage is poor.

On the other hand, FM is much more favoured by local radio stations. As the name implies, wide band FM (W-FM) requires a wider signal bandwidth than amplitude modulation by an equivalent modulating signal, but this also makes the signal more robust against noise and interference. Frequency modulation is also more robust against simple signal amplitude fading phenomena. As a result, FM was chosen as the modulation standard for high frequency, high fidelity radio transmission: hence the term "FM radio". A high-efficiency radio-frequency switching amplifier can be used to transmit FM signals (and other constant-amplitude signals). For a given signal strength (measured at the receiver antenna), switching amplifiers use less battery power and typically cost less than a linear amplifier. This gives FM another advantage over other modulation schemes that require linear amplifiers, such as AM

Then why don't all stations convert to FM? There are certain limitations to FM as well. One of it's main reason is that it's very expensive to make and maintain FM modulators. This problem worsens as the coverage area of FM waves is considerably shorter than AM waves, meaning many stations are needed to cover all the areas that probably 1 AM station is enough. You'll also probably realise sometimes the signals received by your radio is not clear, or produce "fuzzy" noise. This is due to the fact that strong FM signals can bleed over into neighboring frequencies making the frequencies unusable with the transmitter. Combined with the relatively low power output of FM transmitters, FM can sometimes be unsuitable for use in some large urban areas because of the number of other radio signals.

Now you know more about the meaning behind FM and AM. Yes you, the one reading this. Hope that doesn't disrupt your taste for radio music. Now if we can only make them stop replaying the same song for 10 times in an hour.

Sources: Wikipedia! But dun worry, it's all correct facts. I have my own notes but just lazy to take haha! Trust me. Trust A-Levels.