AM
Technology Overview
Amplitude modulation (AM) is the simplest and one of the earliest technologies for broadcasting radio programs. The baseband signal is merely multiplied by the wanted carrier frequency. A receiver can be implemented just as easily: An envelope modulator requires only a bandpass, a detector diode and a smoothing lowpass filter.
The frequency range that is used consists of long, medium and short wavelengths. It is exposed to highly fluctuating propagation conditions. In this frequency range, the waves are affected by the ionosphere. The extent to which they are reflected depends on the time of day, season and the relative number of sunspots.
Deployment Scenario
In the first 80 years of the 20th century, the most common radio broadcasting technology was AM. However, its poor efficiency and high susceptibility to interference when exposed to electrical signals, impulses and noise have made FM and digital transmission standards the technologies of choice.
Key Parameters
| AM | |
|---|---|
| Frequency | Long wave: 48.5 kHz
- 283.5
kHz
Medium Wave: 520 kHz - 1610 kHz Short wave: 2.3 MHz - 26.1 MHz |
| Modulation | AM |
| Sub-carrier Modulation | Single carrier |
| Bandwidth |
Long wave: primarily 9 kHz Medium wave: 10 kHz (ITU region 2), otherwise 9 kHz Short wave: primarily 5 kHz |
