Transmitters and Receivers

Transmitters that transmit AM signals are known as AM transmitters.

These transmitters are used in medium wave (MW) and short wave (SW) frequency bands for AM broadcast.

The MW band has frequencies between 550 KHz and 1650 KHz, and the SW band has frequencies ranging from 3 MHz to 30 MHz.

The two types of AM transmitters that are used based on their transmitting powers are:

• High level transmitters use high level modulation, and low level transmitters use low level modulation.

• The choice between the two modulation schemes depends on the transmitting power of the AM transmitter.

• In broadcast transmitters, where the transmitting power may be of the order of kilowatts, high level modulation is employed.

• In low power transmitters, where only a few watts of transmitting power are required , low level modulation is used.

Lesson 19