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State the three analog colour TV transmission standards. (3 marks)June/July 2020
National Television System Committee (NTSC) standard: This standard was developed in the United States and is used in North and South America, as well as in some parts of Asia. The NTSC standard uses a frame rate of 30 frames per second and a scanning system with 525 lines per frame. Phase AlternatiRead more
For a broadcast FM radio transmission, state: (i)carrier frequency range; (ii)local oscillator frequency range. (9 marks)June/July 2020
(i) Carrier frequency range: In a broadcast FM radio transmission, the carrier frequency is the frequency of the radio waves that are used to transmit the information. The carrier frequency range for FM radio transmission is 87.5 MHz to 108 MHz. This range is divided into 100 channels, each with a bRead more
(i) Carrier frequency range: In a broadcast FM radio transmission, the carrier frequency is the frequency of the radio waves that are used to transmit the information. The carrier frequency range for FM radio transmission is 87.5 MHz to 108 MHz. This range is divided into 100 channels, each with a bandwidth of 200 kHz.
(ii) Local oscillator frequency range: In a radio receiver, the local oscillator generates a frequency that is mixed with the incoming radio signal to produce an intermediate frequency (IF). The frequency of the local oscillator is usually set to a fixed value that is slightly above or below the frequency of the incoming signal.
For FM radio reception, the local oscillator frequency range is typically set to a value that is 10.7 MHz above the carrier frequency. For example, if the carrier frequency is 87.5 MHz, the local oscillator frequency would be set to 98.2 MHz. This produces an IF of 10.7 MHz, which is the frequency that is used to demodulate the FM signal in the radio receiver.
See lessState 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
Define 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
Define 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.
See lessOutline three microprocessor system buses, citing their functions. (6 marks)June/July 2020
A bus is a communication system that allows different components of a computer to communicate with each other. In a microprocessor system, there are several different types of buses that perform different functions. The data bus is used to transfer data between the microprocessor, memory, and periphRead more
A bus is a communication system that allows different components of a computer to communicate with each other. In a microprocessor system, there are several different types of buses that perform different functions.
write an assembly language program to add 13 H and 08 H. ( 4marks)June/July 2020
Here is an example of an assembly language program to add two hexadecimal numbers, 13H and 08H: ; Program to add 13H and 08H ; Load 13H into register A MOV A, #13H ; Load 08H into register B MOV B, #08H ; Add the contents of register A and register B, and store the result in register A ADD A, B ; EnRead more
Here is an example of an assembly language program to add two hexadecimal numbers, 13H and 08H:
; Load 13H into register A
MOV A, #13H
; Load 08H into register B
MOV B, #08H
; Add the contents of register A and register B, and store the result in register A
ADD A, B
; End of program
This program would add the two hexadecimal numbers 13H and 08H, and store the result (1BH) in register A.
See lessDifferentiate between program counter and stack pointer, (3 marks)June/July 2020
The program counter (PC) and stack pointer (SP) are both special purpose registers in a computer's central processing unit (CPU). They are used to store the addresses of instructions and data in memory, and to control the flow of a program. The program counter is a register that stores the address oRead more
The program counter (PC) and stack pointer (SP) are both special purpose registers in a computer’s central processing unit (CPU). They are used to store the addresses of instructions and data in memory, and to control the flow of a program.
State two categories of 8085 microprocessor instruction sets.(3 marks)June/July 2020
Data transfer instructions: These instructions are used to transfer data between the microprocessor and external devices or memory. Examples include the MOV and MVI instructions. Arithmetic instructions: These instructions are used to perform arithmetic operations, such as addition, subtraction, andRead more