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State three merits of modulation in radio transmission. (3 marks)June/July 2020
Modulation allows multiple signals to be transmitted simultaneously over the same frequency band by using different carrier frequencies or different types of modulation. This makes radio transmission more efficient, as it allows more information to be transmitted in a given frequency band. ModulatioRead more
- Modulation allows multiple signals to be transmitted simultaneously over the same frequency band by using different carrier frequencies or different types of modulation. This makes radio transmission more efficient, as it allows more information to be transmitted in a given frequency band.
- Modulation allows the transmitted signal to be tailored to the characteristics of the communication channel. Different types of modulation can be used to optimize the signal for different channel conditions, such as noise, interference, or fading.
- Modulation allows the transmitted signal to be adapted to the needs of the receiver. Different types of modulation can be used to provide different levels of signal quality, bandwidth, or data rate, depending on the requirements of the receiver.
- Modulation allows the transmitted signal to be encrypted for security purposes. Encryption can be used to protect the transmitted information from being intercepted and understood by unauthorized parties.
See lessDefine each of the following as applied to antennas: (i) front-to-back ratio; (ii) gain.(4 marks)June/July 2020
(i) Front-to-back ratio: The front-to-back ratio is a measure of the directivity of an antenna. It is defined as the ratio of the power received by the antenna when it is facing the signal source, to the power received by the antenna when it is facing away from the signal source. The front-to-back rRead more
(i) Front-to-back ratio: The front-to-back ratio is a measure of the directivity of an antenna. It is defined as the ratio of the power received by the antenna when it is facing the signal source, to the power received by the antenna when it is facing away from the signal source. The front-to-back ratio is expressed in decibels (dB).
(ii) Gain: Gain is a measure of the increase in signal strength that an antenna provides compared to a reference antenna. It is defined as the ratio of the power received by the antenna to the power received by the reference antenna, and is expressed in decibels (dB). The gain of an antenna is determined by its shape and size, and is a measure of its ability to focus the transmitted or received signal in a particular direction.
See lessmerits of FM systems.(3 marks)June/July 2020
FM signals have a higher signal-to-noise ratio compared to amplitude modulation (AM) signals, which means that they are less affected by noise and interference. This makes FM systems more reliable and provides a clearer, more stable signal. FM signals are less susceptible to fading than AM signals,Read more
- FM signals have a higher signal-to-noise ratio compared to amplitude modulation (AM) signals, which means that they are less affected by noise and interference. This makes FM systems more reliable and provides a clearer, more stable signal.
- FM signals are less susceptible to fading than AM signals, which makes them more suitable for use in mobile and portable applications where the signal may be subject to fading due to changes in the transmission path.
- FM signals have a wider bandwidth than AM signals, which allows them to transmit more information in a given frequency band. This makes FM systems more efficient and allows them to transmit higher quality audio and video signals.
- FM systems are less prone to nonlinear distortion than AM systems, which means that the transmitted signal is less distorted and more faithful to the original input signal.
- FM systems are more resistant to interference from other signals, which makes them more reliable in crowded frequency bands.
See lessDefine modulation index as used in frequency modulation (FM);(2 marks)June/July 2020
In frequency modulation (FM), the frequency of a carrier wave is varied in proportion to the amplitude of the input signal. The modulation index is a measure of the degree of frequency deviation of the carrier wave, and is defined as the ratio of the frequency deviation to the frequency of the modulRead more
In frequency modulation (FM), the frequency of a carrier wave is varied in proportion to the amplitude of the input signal. The modulation index is a measure of the degree of frequency deviation of the carrier wave, and is defined as the ratio of the frequency deviation to the frequency of the modulating signal.
Mathematically, the modulation index is given by:
Modulation index = (Frequency deviation / Frequency of modulating signal)
For example, if the frequency deviation of a carrier wave is 50 kHz and the frequency of the modulating signal is 1 kHz, the modulation index would be 50. This means that the carrier wave’s frequency is being varied by 50 kHz in response to a 1 kHz modulating signal.
The modulation index is an important parameter in FM systems, as it determines the bandwidth of the transmitted signal and the clarity of the recovered signal. A higher modulation index results in a wider bandwidth and improved signal-to-noise ratio, but may also result in increased distortion.
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