Define Modulation Modulation process of putting information onto a high-frequency carrier for transmission. 2. What Is carrier frequency? In essence, then the transmission takes place at the high frequency (the carrier) which has been modified to “carry’ the lower-frequency Information. 3. Describe the two reasons that modulation Is used for communications transmission. The modulated stage accepts two inputs, the carrier and the information (intelligence) signal. 4. List three parameters of a high-frequency carrier that may be varied by a low-frequency intelligence signal. What are the frequency ranges include in the following frequency subdivision: MFC ,HP, VHF, UHF,SF? 300 kHz-MASH 3-MASH VHF= 30-MEZZO UHF=300 MASH-GHZ SF= 3-30 GHZ 9. Convert the following powers to their db equivalents: (d) p=OWE (30 db O (b) p- 0. 001 w (0 db) (c) p=o. 0001 w (-10 db) (d) p=owe (-16 db) 15. Define electrical noise, and explain why it is so troublesome to a communications receiver. Electrical noise may be define as any undesired voltages or currents that ultimately end up appearing in the receiver output. To the listener this electrical noise often manifests Itself as static. 6.
Explain the deference between external and internal noise. External noise in a received radio signal that has been Introduced by the transmitting medium and the Internal noise In a radio signal that has been Introduced by the receiver. 17. List and briefly explain the various types of external noise. Human-Made Noise It is often produced by spark-producing mechanisms such as engine ignition systems,fluorescent lights, and accumulators in electric motors. Atmospheric Noise Is caused by naturally occurring disturbances in the earth’s atmosphere, with lightning discharges being the most prominent intrusions. 3. Calculate the SIN ratio for a receiver output of v signal and 0. V noise both as a ratio and in decibel form. (69. 44, 18. Db) 27. A two-stage amplifier has a 3-db bandwidth of kHz determined by an LLC circuit at its input and operates at ICC. The first stage has Peg=db and NFG=2. Db. The second stage has Peg=40th and NFG=6. Db. The out-put Is driving a load of ohms. In testing this system, the noise off 100-k ohms resistor Is applied to Its Input. Calculate the Input and output noise voltage and power and the system noise figure. ( AM 0-1 owe,3. db) 32.
Calculate the minimum signal power needed for good reception for the receiver (5. XX-IOW) 37. Define information theory. Concerned with optimization of transmitted information. 38. What is Hartley law? Explain its significance. Information that can be transmitted is proportional to the product of the bandwidth times the time of transmission. 40. What is the seventh harmonic of kHz? (kHz’s) 49. Define importance and describe its use. Balanced condition between the inductive and capacitive reactant of a circuit. 50. Calculate an inductor’s Q at mezzo.
It has an inductance of 6 mm and a series resistance of 1 . K. Determine its dissipation. ( 3. Xx, 0. 318×10-3) 55. Define the quality factor (Q) of an LLC bandannas filter. Explain how it relates to the “selectivity’ of the filter. Describe the major limiting value on the Q of a filter. As Q increases, the filter becomes more selective: that is, a smaller passed (narrower bandwidth) is allowed. A major limiting factor in the highest attainable Q is the resistance factor. 65. Draw schematics for Hartley and Solicits oscillators. Briefly explain their operation and differences.