Est Solving

1. What is the PEP bandwidth peak to peak 200V with load resistance 75Ω?

Ans. 816.66 W 2. An FM system has a frequency deviation of 2.5khz and a modulating frequency of 5 00 hz. What is the modulation index?

ANS. 5 3. What is the noise factor of the device if the device has equivalent noise temperature of 290K? ANS. 2 4. Find the maximum dynamic range for a linear PCM system using 16-boit quantization? ANS. 98.08 dB 5. Calculate the minimum data rate needed to transmit audio with a sampling rate of 40khz and 14 bits per sample. ANS. 56Kb/s 6. Suppose an input signal to a mu-law compressor has a positive voltage and amplitude 25% of the maximum possible. Calculate the output voltage as a percentage of not output. output. ANS. 75.2% 7. Suppose a composite video signal with a baseband frequency range from dc to 4Mhz is transmitted by linear PCM, using eight bits per sample and a sampling rate of 10Mhz. Calculate the bit rate, ignoring overhead. ANS. 80Mbps

8. A radio channel has a bandwidth of 10khz and a signal-to-noise ratio of 15dB. What is the minimum data rate that can be transmitted using any system? ANS. 50.3 kb/s 9. A radio channel has a bandwidth of 10Khz and a SWR of 15dB. What is the minimum m inimum data rate that can be transmitted using a code co de with sour possible states. ANS. 40kb/s 10. A typical dial-up telephone connection has a bandwidth ratio of 30dB. Calculate the Shannon limit. ANS. 29.9kb/s 11. How much bandwidth be required to transmit a DS -1 signal using a four-level code assuming a noiseless channel? ANS. 386khz 12. How many hamming bits are required for a block length of 21 message bits? ANS. 5 13. If 5 devices are going to be connected in a mesh topology, determine the number if duplexmode links. ANS. 10 14. If 5 devices are going to be connected in a mesh topology, determine determine the number I/O ports that must be connected to every device. ANS. 4 15. What is the modulation index of an FM carrier having a carrier swing of 100khz and a modulating signal of 5khz. ANS. 10 16. A BER tester sends bits at 200 baud for for 10s. There are total of 50 errors. What is the BER?

ANS.1 in 400 bits 17. A traffic of 720 Erlang is also e qual to ___ CCS. ANS. 25,920 18. A modulator transmits symbols, each of which has sixty-four different possible states, 10,000 times per second. Calculate the baud rate and bit rate. ANS. 10kbaud, 60kb/s 19. A GSM cellular ratio system uses GMSK in 200khz channel, with a data rate of 270.833kb/s. calculate the frequency shift between work and space. ANS. 135.416kb/s 20. The North America TDMA digital cell phone standard transmits at 24.3 kilobaud using DQPSK. What is the channel data rate? ANS. 48.6kb/s

21. An optic fiber is made of glass with a refractive index of 1.55 and is clad with another glass with refractive index of 1.51. Launching takes place from air. What is the numerical aperture does t he fiber have? ANS. 0.35 22. An optic fiber is made of glass with a refractive index of 1.55 and is clad with another glass with refractive index of 1.51. Launching takes place from air. What is acceptance angle?ANS.20.6⁰ 23. For an optional fiber 10km long with a pulse-spreading constant of 5 ns/km, determine the maximum digital transmission rates for return-to-zero. ANS. 20Mbps 24. For an electronic device operating at a temperature of 17⁰C with a bandwidth of 10Khz, determine the thermal noise power in dBm. ANS. -134dBm 25. A 300Ω resistor in connected across the 300Ω antenna input of a television receiver. The bandwidth of the receiver is 6Mhz, and the resistor is at room temperature. Find the noise voltage applied to the receive input. ANS. 5.4µV 26. The signal power at the input to an amplifier is 100µW. At the output, the signal power is 1W and the noise power is 30mn. What is the amplifier noise figure as a ratio? ANS. 3 27. The noise voltage produced across a 50Ω is input resistance at a temperature of 302K with a bandwidth of 6Mhz is ANS. 2.4µV 28. A 50Ω transmission line is connected to a 30Ω resistive load. Calculate the reflection coefficient.

ANS. 0.25 29. The output power of an FM transmitter is 5kW. If the power loss in transmission line is around 10W and the antenna has a power gain of 60dB, What is the ERP of the station in KW? ANS.

19.86kW 30. Determine the visual carrier frequency of TV channel 9. ANS. 187.25 31. At NTSC standard, line frequency= 15,734.26 Hz. What is equivalent line period? ANS.

63.556µsec. 32. For a total capacity 36Mbps and 64-QAM of digital modulation, What is the ideal RF bandwidth?

ANS. 6Mhz 33. What is the wavelength of a radio signal travelling at a frequency of 220Mhz in a coaxial line having Teflon foam as its dielectric, ɛr=2? ANS. 0.96

34. What is the total radio horizon distance betwee n on 80ft transmitting station and a 20ft receiving station? ANS. 18.97mi.

35. A telephone signal takes 2ms to re ach its destination. Calculate the via net loss required for an acceptable amount of echo. ANS. 0.8dB

36. Calculate the beam width between nulls of a 2-m parabolic reflector used at 6Ghz. ANS. 3.5⁰ 37. The moon or bits the earth with a period of approximately 28 days. How far away is it? Assume circular orbit. ANS. 384mm

38. A group of filters has 1/3 octave of spacing. If the initial frequency in 25Hz. What is the next frequency available for the filter? ANS. 31.5Hz

39. Find the velocity of a satellite in a circular orbit 500km above the earth’s surface. ANS. 7.61km/s 40. Find the orbital period of a satellite in a circular orbit 36,000 km above the earth’s surface if the

earth’s radius is 64,000 km. ANS. 1440 mins or 24 hrs. 41. A signal at the input to a mu-law compressor is positive with its voltage one half the maximum value. What proportion of the max output voltage is produced? ANS. 0.81Vmax

42. An IPV4 has an address space of how many? ANS. 4294967296 43. By how much should two antennas be separated for space diversity in the 11Ghzband? ANS.5.5m 44. What is the phase velocity of a rectangular waveguide with a small separation of 3cm and a desired frequency of operation of 6Ghz? ANS. 5.43x10^8 m/s

45. How far from the transmitter could a signal be received if the transmitting and receiving antennas where 40m and 20m respectively above level terrain? ANS. 44.5km

46. The sensitivity of a radio or given in terms o f dBm. If the receiver is receiving 200mw, What is the corresponding of the signal? ANS. 23dBm

47. The modulation index of an AM radio station is 0.75. if the c arrier power is 500W, What is the total transmitted power? ANS. 641W

48. Compute the baud rate for 72000 bps 64-QAM signal. ANS. 12KBaud 49. Calculate the capacity of a telephone channel that has a S/N of 1023? ANS. 30,000b/s 50. How long does it take to dual the 784-3745 using pulse dialing with .5s inter digit time? ANS. 6.8s