Design and construction of An FM transmitter.

Abstract

In the last 30 years wireless communication has deeply changed the human lifestyle [1]; it has enhanced the exchange of information across the globe quickly and efficiently. Transmission of audio message wirelessly provides the exchange of information in real time. Wireless audio transmission involves the transfer of audio (acoustic) energy over a distance through the atmospheric medium, while maintaining or allowing minimal distortion to the characteristics of the audio signal, such that the integrity of the information being conveyed is maintained. An audio signal is a naturally occurring analogue signal with frequencies in the audio frequency range of roughly 20 to 20,000 Hz. Audio signals (Sound Waves) are mechanical waves generated from vibrations within a medium. They travel at a relatively slow speed of about 350m/s and they are also affected by attenuation caused by the medium they travel in, hence limiting the distance to which they can travel and remain intelligible. Long range audio message transmission can be achieved with the use of frequency modulation technique, which involves the process of imposing the audio signal (low frequency signal) onto a higher frequency signal (carrier signal) by varying the frequency of the carrier wave in accordance with the audio signal, in order to produce a modulated signal with the characteristics of an electromagnetic wave, which is more suitable for long range transmission. This method was pioneered by Edwin Howard Armstrong for FM broadcasting.