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1. For radio transmission in free space, signal power is reduced in proportion to the square of the distance from the source, where as in wire
1. For radio transmission in free space, signal power is reduced in proportion to the square ofthe distance from the source, where as in wire transmission, the attenuation is a fixednumber of dB per kilometer. The following table is used to show the dB reduction relative tosome reference for free space radio and uniform wire. Fill in the missing numbers tocomplete the table.2 . What is the difference between QPSK and offset QPSK?3. A modified NRZ code known as enhanced-NRZ (E-NRZ) is sometimes used for highdensity magnetic tape recording. E-NRZ encoding entails separating the NRZ-L data stream into7-bit words; inverting bits 2,3, 6,and 7; and adding one parity bit to each word. The parity bit ischosen to make the total number of 1s in the 8-bit word an odd count. What are the advantages ofE-NRZ over NRZ-L? Any disadvantages?4.5.6 For the bit stream 01001110, sketch the waveforms for each of the codes of table 5.2. Assume that the signal level for the preceding bit for NRZI was high; the most recent preceding 1 bit (AMI) has a negative voltage; and the most recent preceeding 0 bit (pseudoternary) has a negative voltage.5. the voice signal must be used to modulate a higher (carrier) frequency for which the naturalantenna size is smaller/a. What is the length of an antenna one-half wavelength long for sending radio at 300Hz?b. An alternative is to use a modulation scheme for transmitting the voice signal bymodulating a carrier frequency, so that the bandwidth of the signal is a narrow bandcentered on the carrier frequency. Suppose we would like a half-wave antenna tohave a length of 1 m. What carrier frequency would we use?6. For radio transmission in free space, signal power is reduced in proportion to the square of the distance from the source, where as in wire transmission, the attenuation is a fixed number of dB per kilometer. The following table is used to show the dB reduction relative to some reference for free space radio and uniform wire. Fill in the missing numbers to complete the table.7. Suppose a ray of visible light passes from the atmosphere into water at an angle to the horizontal of 30o. What is the angle of the ray in the water? Note: At standard atmospheric conditions at the earth's surface, a reasonable value for the refractive index is 1.0003. typical value of refractive index is 4/3
