FM Transmitters
M.L. Anand · 2021
The FM transmitters have a very large bandwidth as compared to AM transmitters. In FM transmission, ground wave and sky wave propagation is not possible, and signals in VHF and UHF bands are propagated by line of sight propagation, which restricts the range upto 50 km. The FM signals can be generated by two methods: Direct Methods and Indirect Methods. The varactor (or capacitor) diode is a two terminal device whose capacitance varies with applied voltage. In a commercial transmitter, the oscillator on which a reactance modulator operates can not be a crystal oscillator because the latter provides stable but fixed frequency. Depending upon the method of FM generation employed, the FM transmitters may be classified as: Direct FM transmitters and Indirect FM transmitters. The FM transmitters have a very large bandwidth as compared to AM transmitters. The direct method is used in reactance modulators. The indirect method is used in phase shift modulator.