REPORT ON AM TRANSMISSION AND RECEPTION - Essay Example

The following laboratory experiment is a practical demonstration of AM technique with the application of a balanced modulator. First the message signal will be modulated with carrier signal using balanced modulator. The modulated signal is then amplified sufficiently and transmitted through antenna. The transmitted signal is then received through a receiver. Before mixing the signal to local tune, the received signal efficiency is enhanced through a RF amplifier and then shifted to pre-define IF frequency, normally at 455 KHz in AM broadcasting systems.

The desired signal is boosted by using an IF filter. It discards the undesired portion of signals. Finally, the original message is recovered using a envelop detector. For modulation of carrier we first we will generate the carrier wave through the application of VCO-LO while the message signal will be generated through signal generator. The whole process involves following steps; After adjusting everything and setting the oscilloscope vertical mode to ALT and trigger on channel 1 as shown in figure (5) bellow, the message signal (M) is connected the oscilloscope channel 1 and channel 2 probe is to be connected to output of the modulator.

Now if we vary the frequency of message signal while keeping the amplitude constant the frequency of the Amplitude modulated signal also changes while its “amplitude” will remain constant as shown in figure (6) on next page. Also the output signal with modulating index 1 and when it over-modulated is shown in figures (8) and (9) respectively below. In case of over-modulation the modulation index will have greater than unity value. Since the condition for envelope detector in terms of modulation is defined as; Now as further step the two-post connector at the output of balanced modulator is connected to “SSB” and “AM” terminals while another two two-post