PERCDC REFRESHER – EST 1 1. “Pink” noise has: A. Equal power per Hertz B. Equal power per octave C. Constant power D. None of the above 2. The Miller Effect can be avoided by: A. Using a common-emitter amplifier B. Using a common-base amplifier C. Increasing the Q of the tuned circuit D. It cannot be avoided 3. Indicate the true statement. Most receivers conforms to the A. Amplitude-modulated group B. Frequency-modulated group C. Superheterodyne group D. Tuned radio frequency receiver group 4. Indicate the false statement. The need for modulation can best be exemplified by the following. A. Antenna lengths will be approximately λ/4 long
B. An antenna in the standard broadcast AM band is 16,000 ft C. All sound is concentrated from 20 Hz to 20kHz D. A message is composed of unpredictable variations in both amplitude and frequency 5. Space noise generally covers a wide frequency spectrum, but the strongest interference occurs A. Between 8 MHz and 1.43 GHz B. Below 20 MHz C. Between 20 to 120 MHz D. Above 1.5 GHz 6. Infrared frequencies range from ___ to ___: A. 0.3 THz – 300 THz B. 0.3 PHz – 3 PHz C. 0.03 THz – 3000 THz D. 0.03 PHz – 3000 PHz
7. At frequencies above ____, atmospheric noise is relatively insignificant A. 30 Hz B. 30 kHz C. 30 MHz D. 30 GHz 8. The ideal noise factor is A. 0 B. 1 C. Infinity D. A negative value 9. Determine the modulation index of a standard FM broadcast having a hypothetical maximum carrier frequency deviation of +/-12 kHz and a maximum modulating frequency of 4 kHz. A. 9 B. 6 C. 3 D. 4 10. One way to derive FM from PM is: A. Integrate the modulating signal before applying to the PM oscillator B. Integrate the signal out of the PM oscillator C. Differentiate the modulating signal before applying to the PM oscillator D. Differentiate the signal out of the PM oscillator 11. A pre-emphasis of 75 ms refers to: A. The time it takes for the circuit to work B. The “dead time” before deemphasis occurs C. The time delay between the L and R channels D. The time-constant of the filter circuits used 12. Practical transmitters are usually designed to drive a load impedance of: A. 50 ohms resistive B. 75 ohms resistive C. 300 ohms resistive D. 600 ohms resistive
13. What is the frequency of an electromagnetic wave whose maximum peaks are separated by a distance of 8 in? A. 1.4778 GHz B. 37.5 MHz C. 14.778 GHz D. 3.75 MHz 14. Determine the equivalent noise temperature of a receiver with a noise figure of 4 dB at 300 K environment temperature. A. 900 K B. 453.6 K C. 635.4 K D. 90 K 15. These are active filters made of op-amps, capacitors, and transistor switches. A. Bandpass filters B. Smoothing filter C. Commutating filters D. Audio filter 16. This is used to keep the receiver audio tuned off until an RF signal appears at the receiver input. A. Limiter B. Squelch C. Bleeder D. Filter 17. It is the process of converting a frequency or band of frequencies to another location in the total frequency spectrum. A. Modulation B. Frequency conversion C. Frequency modulation D. Heterodyning 18. The current of an AM transmitter is 12 A when unmodulated but increases to 13 A when modulated. Calculate %m. A. 59% B. 95% C. 46% D. 64%
19. An RG-11/U foam coaxial cable has a maximum voltage standing wave of 52 V and a minimum voltage of 17 V. Find the value of a resistive load in the given situation. A. 37.54 ohms B. 24.59 ohms C. 59.42 ohms D. 73.45 ohms 20. A polar diagram or graph representing field strengths or power densities at various angular positions relative to an antenna. A. Footprint B. Absolute radiation pattern C. Radiation pattern D. Relative radiation pattern 21. Common mode rejection ratios for common balanced transmission lines. A. 10 dB to 30 dB B. 100 dB to 300 dB C. 40 dB to 70 dB D. 4 dB to 7 dB 22. Indicate the false statement. The SWR on a transmission line is infinity; the line is terminated in A. A short circuit B. A complex impedance C. An open circuit D. A pure reactance 23. Indicate the true statement below. The directional coupler is A. A device used to connect a transmitter to a directional antenna B. A coupling device for matching impedance C. A device used to measure transmission line power D. An SWR measuring instrument 24. The two basic specifications for a receiver are: A. The sensitivity and the selectivity B. The number of converters and the number of Ifs
C. The spurious response and the tracking D. The signal and the noise 25. When comparing values for shape factor: A. A value of 1.414 dB is ideal B. A value of 0.707 is ideal C. A value of 1.0 is ideal D. There is no ideal value 26. Compared to a 300-ohm line, the loss of a 50-ohm cable carrying the same power: A. Would be less B. Would be more C. Would be the same D. Cannot be compared 27. The typical antenna in an AM radio is a: A. Dipole B. Folded dipole C. Ferrite “loop-stick” D. None of the above 28. The radiated beam from a parabolic “dish” transmitting
antenna is: A. Collimated B. Phased C. Dispersed D. None of the above 29. A balanced format transmission line used at low frequencies. Applications include 4-wire telephony and microphone circuits. A. Twisted pair B. Twin lead C. Coaxial cable D. Star quad 30. Twisted pair was invented by: A. Alexander Graham Bell B. Oliver Heaviside C. Joseph John “J. J.” Thomson D. None of the above 31. A type of cable used in electronics to carry alternating current, designed to reduce the skin effect and proximity effect
losses in conductors used at frequencies up to about 1 MHz. A. Feeder cable B. Twisted pairs C. Litz wire D. Solid wire 32. CAT-3 cable must have at least _____ turns per inch. A. One B. Two C. Three D. Four 33. The characteristic impedance of LMR-900 is A. 75 ohms B. 73 ohms C. 53 ohms D. 50 ohms 34. It is a coaxial cable constructed using round copper, silver or gold tubing or a combination of such metals as a shield. It used in broadcasting as well as many other forms of radio communication. A. Leaky cable B. Hard line C. Triaxial cable D. Biaxial cable 35. Determine the power saving in percent when the carrier is suppressed in an AM signal modulated to 80%. A. 75.8% B. 80% C. 66.7% D. 100% 36. To couple a coaxial line to a parallel-wire line, it is best to use a A. Slotted line B. Balun C. Directional coupler D. Quarter-wave transformer 37. A phase-locked loop has a VCO with a free-running frequency of 12 MHz. As the frequency of the reference input is gradually raised from zero, the loop locks
at 16 A. B. C. D.
10 MHz and comes out again at MHz. Find the lock range. 16 kHz 15 kHz 4 kHz 8MHz
38. A folded dipole has a typical impedance equal to: A. 73 B. 75 C. 50 D. 300 39. A shorted quarter-wave line at the operating frequency acts like a(n) A. Series resonant circuit B. Parallel resonant circuit C. Capacitor D. Inductor 40. Calculate the thickness of a crystal in inches if its natural frequency is 75 MHz. A. 873 x 10^-9 in B. 175 x 10^-9 in C. 436 x 10^-9 in D. 345 x 10^-9 in 41. Level or Category of UTP cable which was developed for IEEE 802.5 token ring local area networks operating at a transmission rates of 4 Mbps: A. Level 1 or Cat 1 B. Cat 3 C. Level 2 or Cat 2 D. Cat 4 42. A quarter wave vertical antenna with drooping radials typically has an impedance equal to: A. 73 B. 75 C. 50 D. 300 43. A transducer that transmits or receives electromagnetic waves. A. Transmitting antenna B. Receiving antenna C. Parabolic dish D. Aerial
44. The axis through the main lobe is called the ___: A. Secondary axis B. Boresight axis C. Minor axis D. Line of nodes 45. A positive voltage pulse sent down a transmission line terminated with its characteristic impedance: A. Would reflect as a positive pulse B. Would reflect as a negative pulse C. Would reflect as a positive pulse followed by a negative pulse D. Would not reflect at all 46. The “attenuation of free space” is due to: A. Losses in the characteristic impedance of free space B. Losses due to absorption in the upper atmosphere C. The decrease in energy per square meter due to expansion of the wavefront D. The decrease in energy per square meter due to absorption of the wavefront 47. The first complete system of wireless communications was provided by: A. Samuel Morse B. Guglielmo Marconi C. James Maxwell D. Heinrich Hertz 48. It is defined as the difference in decibels between the minimum input level necessary to discern the signal and the input level that will overdrive the receiver and produce distortion. A. Dynamic range B. Noise figure C. Bandwidth efficiency D. Bandwidth improvement 49. Which of the following is the simplest form of tuned-circuit frequency discriminator?
A. B. C. D.
Foster-Seeley discriminator Ratio detector Slope detector PLL detector
50. For a low-power transistor modulator with a modulation coefficient of 0.4, a quiescent voltage gain of 80, and input carrier amplitude of 0.002V, what is maximum and minimum voltage gains? A. 112 and 48 B. 110 and 46 C. 100 and 40 D. 115 and 51 51. Calculate the amount of frequency deviation caused by a limited noise spike that still causes an undesired phase shift of 40 degrees when the input frequency is 15 kHz. A. 12.40 kHz B. 10.47 kHz C. 13.29 kHz D. 14.45 kHz 52. Which of the following is not a typical characteristic impedance of a coaxial cable? A. 50 ohms B. 52 ohms C. 45 ohms D. 93 ohms 53. What is emission F3F? A. Facsimile B. RTTY C. Modulated CW D. Television 54. An AM signal has the following characteristics: the carrier frequency is 150 MHz, the modulating signal frequency is 3 kHz, the carrier voltage is 60 volts, where the modulating signal (Em) is 30 volts. Find the peak voltage of the upper side frequency A. 10 V B. 15 V C. 30 V D. 7.5 V
55. Which of the following is not a basic field of FM? A. Broadcast B. TV Video C. Mobile Communication D. Amateur Radio 56. In FM Broadcasting, what is the lowest required modulating frequency? A. 50 Hz B. 30 Hz C. 10 Hz D. 5 Hz 57. For a given length of RG 8A/U coaxial cable with a distributed capacitance of 96.6 pF/m and a relative dielectric constant of 2.6, determine the velocity factor. A. 0.91 B. 0.69 C. 0.62 D. 0.71 58. If a 500-kHz transmitter of a constant power produces a field strength of 100uV/m at a distance of 100 mi from the transmitter, what would be the theoretical field strength at a distance of 50 mi from the transmitter? A. 25 uV/m B. 200 uV/m C. 50 uV/m D. 400 uV/m 59. Fixed-frequency or channel operation of a transmitter is obtained by using a ____. A. LC Oscillator B. RC Oscillator C. Crystal Oscillator D. Synthesizer 60. Calculate the required Q for a 3 MHz carrier with sideband separation of 50 Hz and 40-dB sideband suppression. A. 250000 B. 120000 C. 125000 D. 150000
61. ___ are types of noise generated by equipments that produces sparks. A. Equipment noise B. Atmospheric noise C. Space noise D. Internal noise 62. The radio wavelength known as ____ falls within the medium frequency range. A. Centimetric B. Decametric C. Hectometric D. Myriametric 63. When the power ratio of input to output is 1/100, the loss of the circuit, in dB, is A. 20 B. -20 C. 10 D. 3 64. Calculate the EIRP in dBW for a 55 W transmitter into a dipole with 85% efficiency. A. 16.65 dBW B. 13.38 dBW C. 16.83 dBW D. 18.84 dBW 65. A transistor RF power amplifier operating class C is designed to produce 50 W output with supply voltage of 90V. If the efficiency is 70%, what is the average collector current? A. 793 mA B. 952 mA C. 476 mA D. 342 mA 66. R3E modulation is sometimes used to A. Allow the receiver to have a frequency synthesizer B. Simplify the frequency stability problem in reception C. Reduce the power that must be transmitted D. Reduce the bandwidth required for transmission
67. A transmission line of unknown impedance is terminated with two different resistances, and the SWR is measured each time. With a 75-ohm termination, the SWR measures 1.5, and with a 300-ohm termination, it measures 2.65. What is the impedance of the line? A. 50 ohms B. 36 ohms C. 113 ohms D. 800 ohms 68. Indicate in which time one of the following only one sideband is transmitted: A. H3E B. A3E C. B8E D. C3F 69. It is an analog method of combining two or more analog sources that originally occupied the same frequency band in such a manner that the channels do not interfere with each other. A. ATM B. FDM C. TDM D. WDM 70. The difference between the IF and the BFO frequencies is called ___. A. Information signal B. Beat frequency C. Carrier signal D. Heterodyned signal 71. A balanced modulator is sometimes called ___. A. Balance ring modulator B. Balance resistor modulator C. Balance lattice modulator D. Any of these 72. A type of filter that receives electrical energy, converts it to mechanical vibrations and then converts the vibrations back to electrical energy at its output. A. Crystal filter
B. Mechanical filter C. LC filter D. SAW filter 73. The quarter-wavelength transformer line acts as a step down transformer when the load resistance is with what relationship with the characteristic impedance of the quarter-wavelength transformer? A. Equal B. Less than C. Greater than D. None of these 74. The characteristic impedance of a microstrip is equal to ___ ohms. A. 50 to 200 B. 25 to 50 C. 100 to 200 D. 50 to 75 75. A varactor has a maximum capacitance of 80 pF and is tuned circuit with 100 uH inductor. Find the tuning voltage necessary for the circuit to resonate at triple the frequency produced by the varactor. A. 7.5 V B. 40 V C. 70 V D. 80 V 76. Calculate the gain of a parabolic antenna using a 2.5-m diameter dish operating at 10 GHz. A. 57.9 B. 67.7 C. 52.2 D. 46.2 77. Which of the following is NOT a color code for Category 5 UTP? A. Blue/white stripe and blue B. Orange/white stripe and orange C. Red/white stripe and red D. Brown/white stripe and brown 78. What is the major cause of fading? A. Phase difference B. Topographic variation
C. Climate D. Ionospheric variation 79. A receiver produces a noise power of 200mW with no signal. The output level increases by 5W when a signal is applied. Calculate (S+N)/N in decibels. A. 10.14 dB B. 11.34 dB C. 13.12 dB D. 14.14 dB 80. An AM broadcast transmitter has a carrier power output of 50 kW. What is the total power would be produced with 90% modulation? A. 70.25 kW B. 88.15 kW C. 99.45 kW D. 66.98 kW 81. Scatter transmission is used at what frequencies? A. EHF and VLF B. HF and VHF C. VHF and UHF D. ELF and VLF 82. Why are verticals sometimes toploaded? A. To resonate on high frequency B. To decrease the electrical length C. To resonate on low frequency D. To look better 83. In what range of frequencies are most omnidirectional horizontally polarized antennas used? A. VHF and UHF B. HF and VHF C. UHF and HF D. LF and MF 84. A transmitter supplies 25 W to a load through a line with SWR of 4:1. Find the power absorbed by the load. A. 32 W B. 64 W C. 23 W D. 12 W
85. What is the percent total harmonic distortion for a fundamental frequency with amplitude of 9 Vrms, second harmonic amplitude of 0.3 Vrms, and the third harmonic amplitude of 0.1 Vrms? A. 2.795 % B. 1.25% C. 2.5% D. 3.5% 86. What is the 12th octave for a 1kHz repetitive wave? A. 6.012 MHz B. 4.096 MHz C. 8.89 MHz D. 5.045 MHz 87. What method can be used to determine the feed-point impedance of a vertical antenna? A. Resistance substitution B. Impedance matching C. Dissipated resistance measurement D. Grounding the antenna 88. The frequency band normally used to penetrate ocean depths and therefore used for communicating with submarine is ________. A. EHF B. MF C. HF D. ELF 89. Typical mode of radiation of helical antenna is A. End fire B. Normal C. Common mode D. Differential mode 90. A measure of mismatch in a transmission line A. Reflection coefficient B. Propagation delay C. Standing wave ratio D. All of these 91. Placing a metallic array on the antenna effects to increase the current at the base of the antenna, and also to make the
current distribution more uniform. What is this called?\ A. Stub matching B. Grounding C. Top loading D. Feeding 92. Calculate the beam width between nulls of a 2-m paraboloid reflector used at 6GHz. A. 14 deg B. 7 deg C. 3.5 deg D. 0.875 deg 93. This is often used to cure the problem of great thickness required of lenses used at lower microwave frequencies or for strong curved wavefronts. A. Splicing B. Zoning C. Curving D. Polarizing 94. Which of the following antenna types is not designed for transmitting at 10 GHz. A. Horn antenna B. Dish antenna C. Zepp antenna D. Helical antenna 95. Two antennas have gains of 5.3 dBi and 4.5 dBd, respectively. Which has a greater gain? A. The first antenna has a higher gain B. The second antenna has a higher gain C. Both antennas have the same gain D. Cannot be determined 96. Which of the following is not a reason why most half-wave antennas are mounted horizontally at low frequencies? A. Physical construction is easier B. More cost-effective C. Mounting is easier D. Support is easier
97. Which antennas usually consist of two or more half-wave dipoles mounted end to end? A. Hertz B. Marconi C. Collinear D. Yagi 98. A one-quarter wavelength of coaxial or balanced transmission line of a specific impedance connected between a load and a source in order to match impedances is A. A balun B. An autotransformer C. A Q section D. Dummy load 99. It is the ability of the oscillator in a receiver to oscillate either above or below the selected radio frequency carrier by an amount equal to the intermediate frequency throughout the entire radio frequency band. A. Heterodyning B. Ranging C. Tracking D. Conversion 100. The capacitor used which prevents a portion of the signal from radiating from their leads A. Bypass B. Feedthrough C. Coupling D. Neutralization
