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For most people, an enjoyable part of driving their cars is listening to their favourite music while on the road. If an older car was equipped with a radio, it was very often an AM radio. FM radios were originally introduced in the early 1950s but AM remained the basic radio option well into the late 1970s. Today, it is hard to imagine your daily driver not even having a basic AM/FM radio and the connected car is becoming ubiquitous .

Chryco AM Radio, 1965 Barracuda



The audio spectrum (what frequencies the human ear can hear) is ranges from 20 Hz to 20,000 Hz with normal conversation taking place in the 85 to 180 Hz range for men and 165 to 255 Hz range for women. A woman's high--pitched scream can reach 3000 Hz while the highest note in an 88-key piano is 4186.01 Hz. In telephones, the usable voice bandwidth is in the 300-3400 Hz range.

For those of us with basic AM radios in our cars, it is becoming harder and harder for us to enjoy any music because the vast majority of music stations are on the FM band. AM radio stations are 10 kHz apart which means the maximum bandwidth is also 10 kHz. Therefore, the maximum upper upper modulating frequency is 5 kHz (see sideband). With AM's limited bandwidth of 10 kHz (compared with FM's 200 kHz), the available sound fidelity is best suited to talk radio and this genre is now very common on the AM band. The few AM music stations that remain are very often Adult Contemporary. The power output of AM stations varies from very low power Class D stations (50 W minimum) up to Class A clear-channel stations (often 50,000 W, like 740 AM CFZM) that broadcast for hundreds of miles. Highway Advisory Stations transmit up to 10 W. Many AM stations reduce power at night or even go off-air.