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Communication is the process of A. keeping in touch B. broadcasting C. exchanging information D. entertainment by electronics ANSWER: C Two key barriers to human communication are A. distance B. cost C. ignorance D. language ANSWER: A and C Electronic communications was discovered in which century? A. sixteenth B. eighteenth C. nineteenth D. twentieth ANSWER: C Which of the following is not a major communications medium? A. free space B. water C. wires D. fiber optic cable ANSWER: B Random interference to transmitted signals is called A. adjacent channel overlap B. cross talk C. garbage-in-garbage-out D. noise ANSWER: D The communications medium causes the signal to be A. amplified B. modulated C. attenuated D. interfered with
ANSWER: C
Which of the following is not a source of noise? A. another communications signal B. atmospheric effects C. manufactured electrical systems D. thermal agitation in electronic components ANSWER: A One-way communications is called A. half duplex B. full duplex C. monocomm D. simplex ANSWER: D Simultaneous two-way communications is called A. half duplex B. full duplex C. bicomm D. simplex ANSWER: B The original electrical information signal to be transmitted is called the A. modulating signal B. carrier C. baseband signal D. source signal ANSWER: C The process of modifying a high- frequency carrier with the information to be transmitted is called A. multiplexing B. telemetry C. mixing D. modulation ANSWER: D The process of transmitting two or more information signals simultaneously over the same channel is called A. multiplexing B. telemetry C. mixing D. modulation ANSWER: A Continuous voice or video signals are referred to as being A. baseband B. analog C. digital D. continuous waves ANSWER: A Recovering information from a carrier is known as A. demultiplexing B. modulation C. detection D. carrier recovery ANSWER: C Transmission of graphical information over the telephone network is accomplished by A. television B. CATV C. videotext D. facsimile ANSWER: D Measuring physical conditions at some remote location and transmitting this data for analysis is the process of A. telemetry B. instrumentation C. modulation D. multiplexing ANSWER: A Receiving electromagnetic emissions from stars is called A. astrology B. optical astronomy C. radio astronomy D. space surveillance ANSWER: C A personal communications hobby for individuals is A. ham radio B. electronic bulletin board C. CB radio D. cellular radio ANSWER: A Radar is based upon A. microwaves B. a water medium C. the directional nature of radio signals D. reflected radio signals ANSWER: D A frequency of 27 MHz has a wavelength of approximately A. 11 m B. 27 m C. 30 m D. 81 m ANSWER: A Radio signals are made up of A. voltages and currents B. electric and magnetic fields C. electrons and protons D. noise and data ANSWER: B The voice frequency range is A. 30 to 300 Hz B. 300 to 3000 Hz
C. 20 Hz to 20 kHz D. 0 Hz to 15 kHz ANSWER: B Another name for signals in the HF range is A. microwaves B. RF waves C. shortwaves D. millimeter waves ANSWER: C Television broadcasting occurs in which ranges? A. HF B. EHF C. VHF D. UHF ANSWER: C Electromagnetic waves produced primarily by heat are called A. infrared rays B. microwaves C. shortwaves D. x-rays ANSWER: A A micron is A. one-millionth of a foot B. one-millionth of a meter C. one-thousandth of a meter D. one ten-thousandth of an inch ANSWER: B The frequency range of infrared rays is approximately A. 30 to 300 GHz B. 4000 to 8000 A C. 1000 to 10,000 A D. 0.7 to 100 um ANSWER: D The approximate wavelength of red light is A. 1000 um B. 7000 A C. 3500 A D. 4000 A ANSWER: B Which of the following is not used for communications? A. x-rays B. millimeter waves C. infrared D. microwaves ANSWER: A A signal occupies the spectrum space from 1.115 to 1.122 GHz. The bandwidth is A. 0.007 MHz B. 7 MHz C. 237 MHz D. 700 MHz ANSWER: B In the United States, the electromagnetic spectrum is regulated and managed by A. business and industry B. ITU C. FCC D. The United Nations ANSWER: C For a given bandwidth signal, more channel space is available for signals in the range of A. VHF B. UHF C. SHF D. EHF ANSWER: D Having an information signal change some characteristic of a carrier signal is called A. multiplexing B. modulation C. duplexing D. linear mixing ANSWER: B Which of the following is not true about AM? A. The carrier amplitude varies. B. The carrier frequency remains constant. C. The carrier frequency changes. D. The information signal amplitude changes the carrier amplitude. ANSWER: C The opposite of modulation is A. reverse modulation B. downward modulation C. unmodulation D. demodulation ANSWER: D The circuit used to produce modulation is called a A. modulator B. demodulator C. variable gain amplifier D. multiplexer ANSWER: A A modulator circuit performs what mathematical operation on its two inputs? A. addition B. multiplication C. division D. square root ANSWER: B The ratio of the peak modulating signal voltage to the peak carrier voltage is referred to as A. the voltage ratio B. decibels C. the modulation index D. the mix factor ANSWER: C If m is greater than 1, what happens? A. normal operation B. carrier drops to zero C. carrier frequency shifts D. information signal is distorted ANSWER: D For ideal AM, which of the following is true? A. m = 0 B. m = 1 C. m < 1 D. m > 1 ANSWER: B The outline of the peaks of a carrier has the shape of the modulating signal and is called the A. trace B. waveshape C. envelope D. carrier variation ANSWER: C Overmodulation occurs when A. Vm > Vc B. Vm < Vc C. Vm = Vc D. Vm = Vc = 0 ANSWER: A The values of Vmax and Vmin as read from an AM wave on an oscilloscope are 2.8 and 0.3. The percentage of modulation is A. 10.7 percent B. 41.4 percent C. 80.6 percent
D. 6.8 MHz ANSWER: B The output of an SSB transmitter with a 3.85 MHz carrier and a 1. kHz sine wave modulating tone is A. a 3.8485-MHz sine wave B. a 3.85-MHz sine wave C. 3.85-, 3.845-, and 3.8515- MHz sine waves D. 3848.5- and 3851.5 MHz sine waves ANSWER: C An SSB transmitter produces a 400 V peak-to-peak signal across a 52 ohm antenna load. The PEP output is A. 192.2 W B. 384.5 W C. 769.2 W D. 3077 W ANSWER: B The output power of an SSB transmitter is usually expressed in terms of A. average power B. RMS power C. peak-to-peak power D. peak envelope power ANSWER: D An SSB transmitter has a PEP ratIng of 1 kW. The average output power is in the range of A. 150 to 450 W B. 100 to 300 W C. 250 to 333 W D. 3 to 4 kW ANSWER: C Amplitude modulation is the same as A. Linear mixing B. Analog multiplication C. Signal summation D. Multiplexing ANSWER: B In a diode modulator, the negative half of the AM wave is supplied by a(n) A. Tuned circuit B. Transformer C. Capacitor D. Inductor ANSWER: A Amplitude modulation can be produced by A. having the carrier vary a resistance B. having the modulating signal vary a capacitance C. varying the carrier frequency D. varying the gain of an amplifier ANSWER: A Amplitude modulators that vary the carrier amplitude with the modulating signal by passing it through an attenuator work on the principle of A. rectification B. resonance C. variable resistance D. absorption ANSWER: C The component used to produce AM at very high frequencies is a A. varactor B. thermistor C. cavity resonator D. PIN diode ANSWER: A Amplitude modulation generated at a very low voltage or power amplitude is known as A. high-level modulation B. low-level modulation C. collector modulation D. minimum modulation ANSWER: B A collector modulator has a supply voltage of 48 V. The peak-to-peak amplitude of the modulating signal for 100 percent modulation is A. 24 V B. 48 V C. 96 V D. 120 V ANSWER: C A collector-modulated transmitter has a supply voltage of 24 V and a collector current of 0.5 A. The modulator power for 100 percent modulation is A. 6 W B. 12 W C. 18 W D. 24 W ANSWER: A The circuit that recovers the original modulating information from an AM signal is known as a A. modulator B. demodulator C. mixer D. crystal set ANSWER: B The most commonly used amplitude demodulator is the A. diode mixer B. balanced modulator C. envelope detector D. crystal filter ANSWER: C A circuit that generates the upper and lower sidebands but no carrier is called a(n) A. amplitude modulator B. diode detector C. class C amplifier D. balanced modulator ANSWER: D The inputs to a balanced modulator are 1 MHz and a carrier of 1.5 MHz. The outputs are A. 500 kHz B. 2.5 MHz C. 1.5 MHz D. all of the above E. a and b ANSWER: E A widely used balanced modulator is called the A. diode bridge circuit B. full-wave bridge rectifier C. lattice modulator D. balanced bridge modulator ANSWER: C In a diode ring modulator, the diodes act like A. variable resistors B. switches C. rectifiers D. variable capacitors ANSWER: B The output of a balanced modulator is A. AM B. FM C. SSB D. DSB
ANSWER: D
The principal circuit in the popular 1496/1596 IC balanced modulator is a A. differential amplifier B. rectifier C. bridge D. constant current source ANSWER: A The most commonly used filter in SSB generators uses A. LC networks B. mechanical resonators C. crystals D. RC networks and op amps ANSWER: C The equivalent circuit of a quartz crystal is a A. series resonant circuit B. parallel resonant circuit C. neither a nor b D. both a and b ANSWER: D A crystal lattice filter has crystal frequencies of 27.5 and 27. MHz. The bandwidth is approximately A. 2 kHz B. 3 kHz C. 27.501 MHz D. 55.502 MHz ANSWER: A An SSB generator has a sideband filter centered at 3. MHz. The modulating signal is 3 kHz. To produce both upper and lower sidebands, the following carrier frequencies must be produced: A. 2.7 and 3.3 MHz B. 3.3 and 3.6 MHz C. 2997 and 3003 kHz D. 3000 and 3003 kHz ANSWER: C In the phasing method of SSB generation, one sideband is canceled out due to A. phase shift B. sharp selectivity C. carrier suppression D. phase inversion ANSWER: A A balanced modulator used to demodulate a SSB signal is called a(n) A. transponder B. product detector C. converter D. modulator ANSWER: B Frequency translation is done with a circuit called a A. summer B. multiplier C. filter D. mixer ANSWER: D The inputs to a mixer are fo and fm. In down conversion, which of the following mixer output signals is selected? A. fo B. fm C. fo – fm D. fo + fm ANSWER: C Mixing for frequency conversion is the same as A. rectification B. AM C. linear summing D. filtering ANSWER: C Which of the following can be used as a mixer? A. balanced modulator B. FET C. diode modulator D. all of the above ANSWER: D The desired output from a mixer is usually selected with a A. phase-shift circuit B. crystal filter C. resonant circuit D. transformer ANSWER: B The two inputs to a mixer are the signal to be translated and a signal from a(n) A. modulator B. filter C. antenna D. LO ANSWER: D An NE602 mixer IC has a difference output of 10.7 MHz. The input is 146.8 MHz. The local oscillator frequency is A. 101.9 MHz B. 125.4 MHz C. 131.6 MHz D. 157.5 MHz ANSWER: D The amount of frequency deviation from the carrier center frequency in an FM transmitter is proportional to what characteristic of the modulating signal? A. Amplitude B. Frequency C. Phase D. Shape ANSWER: A Both FM and PM are types of what kind of modulation? A. Amplitude B. Phase C. Angle D. Duty cycle ANSWER: C If the amplitude of the modulating signal decreases, the carrier deviation A. increases B. decreases C. remains constant D. goes to zero ANSWER: B On an FM signal, maximum deviation occurs at what point on the modulating signal? A. zero-crossing points B. peak positive amplitude C. peak negative amplitude D. both b and c ANSWER: D In PM, a frequency shift occurs while what characteristic of the modulating signal is changing? A. shape B. phase C. frequency D. amplitude ANSWER: D Maximum frequency deviation of a PM signal occurs at A. zero crossing points B. peak positive amplitude C. peak negative amplitude
ANSWER: C
Noise interferes mainly with modulating signals that are A. sinusoidal B. nonsinusoidal C. low frequencies D. high frequencies ANSWER: D Pre-emphasis circuits boost what modulating frequencies before modulation? A. high frequencies B. mid-range frequencies C. low frequencies D. all of the above ANSWER: A A pre-emphasis circuit is a A. low-pass filter B. high-pass filter C. phase shifter D. bandpass filter ANSWER: B Pre-emphasis is compensated for at the receiver by a A. Phase inverter B. Bandpass filter C. High-pass filter D. Low-pass filter ANSWER: D The cut-off frequency of pre- emphasis and de-emphasis circuit is A. 1 kHz B. 2.122 kHz C. 5 kHz D. 75 kHz ANSWER: B Another name for a VVC is A. PIN diode B. Varactor diode C. Snap diode D. Hot-carrier diode ANSWER: B The depletion region in a junction diode forms what part of a capacitor? A. plates B. leads C. package D. dielectric ANSWER: D Increasing the reverse bias on a varactor diode will cause its capacitance to A. decrease B. increase C. remain the same D. drop to zero ANSWER: A The capacitance of a varactor diode is in what general range? A. pF B. nF C. uF D. F ANSWER: A The frequency change of a crystal oscillator produced by a varactor diode is A. zero B. small C. medium D. large ANSWER: B A phase modulator varies the phase shift of the A. carrier B. modulating signal C. both a and b D. neither a or b ANSWER: A The widest phase variation is obtained with a(n) A. RC low-pass filter B. RC high-pass filter C. LR low-pass filter D. LC resonant circuit ANSWER: D The small frequency change produced by a phase modulator can be increased by using a(n) A. amplifier B. mixer C. frequency multiplier D. frequency divider ANSWER: C A crystal oscillator whose frequency can be changed by an input voltage is called a(n) A. VCO B. VXO C. VFO D. VHF ANSWER: B Which oscillators are preferred for carrier generators because of their god frequency stability? A. LC B. RC C. LR D. crystal ANSWER: D Which of the following frequency demodulators requires an input limiter? A. Foster-Seeley discriminator B. Pulse-averaging discriminator C. Quadrature detector D. PLL
ANSWER: A
Which discriminator averages pulses in a low-pass filter? A. Ratio detector B. PLL C. Quadrature detector D. Foster-Seeley discriminator ANSWER: C Which frequency demodulator is considered the best overall? A. Ratio detector B. PLL C. Quadrature D. Pulse-averaging discriminator ANSWER: B In a pulse-averaging discriminator, the pulses are produced by a(n) A. Astable multivibrator B. Zero-crossing detector C. One shot D. Low-pass filter ANSWER: B A reactance modulator looks like a capacitance of 35 pF in parallel with the oscillator-tuned circuit whose inductance is 50 uH and capacitance is 40 pF. What is the center frequency of the oscillator prior to FM? A. 1.43 MHz B. 2.6 MHz C. 3.56 MHz D. 3.8 MHz ANSWER: B Which of the following is true about the NE566 IC? A. It is a VCO. B. Its output is sinusoidal. C. It is an FM demodulator.
D. It uses LC tuned circuits. ANSWER: A An FM demodulator that uses a differential amplifier and tuned circuits to convert frequency variations into voltage variations is the A. Quadrature detector B. Foster-Seeley discriminator C. Differential peak detector D. Phase-locked loop ANSWER: C The output amplitude of the phase detector in a quadrature detector is proportional to A. Pulse width B. Pulse frequency C. Input amplitude D. The phase shift value at center frequency ANSWER: A The input to a PLL is 2 MHz. In order for the PLL to be locked, the VCO output must be A. 0 MHz B. 1 MHz C. 2 MHz D. 4 MHz ANSWER: C Decreasing the input frequency to a locked PLL will cause the VCO output to A. decrease B. increase C. remain constant D. jump to the free-running frequency ANSWER: D The range of frequencies over which a PLL will track input signal variations is known as the A. circuit bandwidth B. capture range C. band of acceptance D. lock range ANSWER: D The band of frequencies over which a PLL will acquire or recognize an input signal is called the A. circuit bandwidth B. capture range C. band of acceptance D. lock range ANSWER: B Over a narrow range of frequencies, the PLL acts like a A. Low-pass filter B. Bandpass filter C. Tunable oscillator D. Frequency modulator ANSWER: B The output of a PLL frequency demodulator is taken from the A. Low-pass filter B. VCO C. Phase detector D. none of the above ANSWER: A Which of the following circuits is not typically part of every radio transmitter? A. carrier oscillator B. driver amplifier C. mixer D. final power amplifier ANSWER: C Class C amplifiers are not used in which type of transmitter? A. AM B. SSB C. CW D. FM ANSWER: B A circuit that isolates the carrier oscillator from load changes is called a A. final amplifier B. driver amplifier C. linear amplifier D. buffer amplifier ANSWER: D A class B amplifier conducts for how many degrees of an input sine wave A. 90 deg to 150 deg B. 180 deg C. 180 deg to 360 deg D. 360 deg ANSWER: B Bias for a class C amplifier produced by an input RC network is known as A. signal bias B. self bias C. fixed external bias D. threshold bias ANSWER: A An FM transmitter has a 9 MHz crystal carrier oscillator and frequency multipliers of 2, 3, and
- The output frequency is A. 54 MHz B. 108 MHz C. 216 MHz D. 288 MHz ANSWER: C The most efficient RF power amplifier is which class amplifier? A. A B. AB C. B D. C ANSWER: D Collector current in a class C amplifier is a A. sine wave B. half sine wave C. pulse D. square wave ANSWER: C The maximum power of typical transistor RF power amplifiers is in what range? A. milliwatts B. watts C. hundreds of watts D. kilowatts ANSWER: C Self-oscillation in a transistor amplifier is usually caused by A. excessive gain B. stray inductance C. internal capacitance D. unmatched impedances ANSWER: C Neutralization is the process of A. canceling the effect of internal device capacitance B. by passing undesired alternating current C. reducing gain D. eliminating harmonics ANSWER: A Maximum power transfer occurs when what relationship exists between the generator
C. 19.6 MHz D. 21.2 MHz ANSWER: D The main cause of image interference is A. poor front-end selectivity B. low gain C. a high IF D. a low S/N ratio ANSWER: A For best image rejection, the IF for a 30 MHz signal would be A. 455 kHz B. 3.3 MHz C. 9 MHz D. 55 MHz ANSWER: D A tuned circuit is resonant at 4 MHz. Its Q is 100. The bandwidth is A. 400 Hz B. 4 kHz C. 40 kHz D. 400 kHz ANSWER: C A crystal filter has a 6 dB bandwidth of 2.6 kHz and a 60 dB bandwidth of 14 kHz. The shape factor is A. 0. B. 5. C. 8. D. 36. ANSWER: B Most internal noise comes from A. shot noise B. transit-time noise C. thermal agitation D. skin effect ANSWER: C Which of the following is not a source of external noise? A. thermal agitation B. auto ignitions C. the sun D. fluorescent lights ANSWER: A Noise can be reduced by A. widening the bandwidth B. narrowing the bandwidth C. increasing temperature D. increasing transistor current levels ANSWER: B Noise at the input to a receiver can be as high as several A. microvolts B. millivolts C. volts D. kilovolts ANSWER: A Which circuit contributes most to the noise in a receiver? A. IF amplifier B. AF amplifier C. demodulator D. mixer ANSWER: D Which noise figure represents the lowest noise? A. 1.6 dB B. 2.1 dB C. 2.7 dB D. 3.4 dB ANSWER: A Which filter shape factor represents the best skirt selectivity? A. 1.
B. 2.
C. 5.
D. 8
ANSWER: A
Which input signal below represents the best receiver sensitivity? A. 0.5 uV B. 1 uV C. 1.8 uV D. 2 uV ANSWER: A The transistor with the lowest noise figure in the microwave region is a(n) A. MOSFET B. Dual-gate MOSFET C. JFET D. MESFET ANSWER: D The AGC circuits usually control the gain of the A. mixer B. detector C. IF amplifiers D. audio amplifiers ANSWER: C Selectivity is obtained in most receivers from A. crystal filters B. mechanical filters C. double-tuned circuits D. audio filters ANSWER: A Widest bandwidth in a double- tuned circuit is obtained with A. undercoupling B. critical coupling C. optimum coupling D. overcoupling
ANSWER: D
Automatic gain control permits a wide range of signal amplitudes to be accommodated by controlling the gain of the A. RF amplifier B. IF amplifier C. mixer D. AF amplifier ANSWER: B In an IF amplifier with reverse AGC, a strong signal will cause the collector current to A. increase B. decrease C. remain the same D. drop to zero ANSWER: B Usually AGC voltage is derived by the A. RF amplifier B. IF amplifier C. demodulator D. AF amplifier ANSWER: C An AFC circuit is used to correct for A. audio distortion B. strong input signals C. instability in the IF amplifier D. frequency drift in the LO ANSWER: D A circuit that keeps the audio cut off until a signal is received is known as A. a squelch B. AFC C. AGC D. a noise blanker ANSWER: A
A BFO is used in the demodulation of which types of signals? A. AM B. FM C. SSB or CW D. QPSK ANSWER: C Which of the following circuits are not typically shared in an SSB transceiver? A. crystal filter B. mixers C. power supply D. LO ANSWER: B The basic frequency synthesizer circuit is a(n) A. mixer B. frequency multiplier C. frequency divider D. PLL ANSWER: D The output frequency increment of a frequency synthesizer is determined by the A. frequency division ratio B. reference input to the phase detector C. percentage of output frequency D. frequency multiplication factor ANSWER: B The output frequency of a synthesizer is changed by varying the A. reference input to the phase detector B. frequency division ratio C. frequency multiplication factor D. mixer LO frequency ANSWER: B The bandwidth of a parallel LC circuit can be increased by A. increasing XC B. decreasing XL C. decreasing coil resistance D. a resistor connected in parallel ANSWER: B The upper and lower cutoff frequencies of a tuned circuit are 1.7 and 1.5 MHz respectively. The circuit Q is A. 8 B. 10 C. 16 D. 24 ANSWER: A The noise voltage across a 300 ohm input resistance to a TV set with a 6 MHz bandwidth and a temperature of 30 deg C is A. 2.3 uV B. 3.8 uV C. 5.5 uV D. 6.4 uV ANSWER: C The stage gains in a superheterodyne are as follows: RF amplifier, 10 dB; mixer, 6 dB; two IF amplifiers, each 33 dB; detector, -4 dB; AF amplifier, 28 dB. The total gain is A. 73 dB B. 82 dB C. 106 dB D. 139 dB ANSWER: C A tuned circuit resonates at 12 MHz with an inductance of 5 uH whose resistance is 6 ohm. The circuit bandwidth is A. 98 kHz B. 191 kHz C. 754 kHz D. 1.91 MHz ANSWER: B In a receiver with noise-derived squelch, the presence of an audio signal causes the audio amplifier to be A. enabled B. disabled ANSWER: A Multiplexing is the process of A. several signal sources transmitting simultaneously to a receiver on a common frequency B. sending the same signal over multiple channels to multiple destinations C. transmitting multiple signals over multiple channels D. sending multiple signals simultaneously over a single channel ANSWER: D In FDM, multiple, signals A. transmit at different time B. share a common bandwidth C. use multiple channels D. modulate one another ANSWER: B Each signal in an FDM system A. modulates a subcarrier B. modulates the final carrier C. is mixed with all the others before modulation D. serves as a subcarrier ANSWER: B Frequency modulation in FDM systems is usually accomplished with a A. reactance modulator B. varactor C. VCO D. PLL ANSWER: C Which of the following is not a typical FDM application? A. telemetry B. stereo broadcasting C. telephone D. secure communications ANSWER: D The circuit that performs demultiplexing in an FDM system is a(n) A. op amp B. bandpass filter C. discriminator D. subcarrier oscillator ANSWER: B Most FDM telemetry systems use A. AM B. FM C. SSB D. PSK ANSWER: B The best frequency demodulator is the A. PLL discriminator B. pulse-averaging discriminator C. Foster-Seeley discriminator D. ratio detector ANSWER: A The modulation used in FDM telephone systems is A. AM B. FM
D. none of the above ANSWER: D Which of the following is not a common transmission line impedance? A. 50 ohm B. 75 ohm C. 120 ohm D. 300 ohm ANSWER: C For maximum absorption of power at the antenna, the relationship between the characteristic impedance of the line Zo and the load impedance Zl should be A. Zo = Zl B. Zo > Zl C. Zo < Zl D. Zo = 0 ANSWER: A The mismatch between antenna and transmission line impedances cannot be corrected for by A. using an LC matching network B. adjusting antenna length C. using a balun D. adjusting the length of transmission line ANSWER: D A pattern of voltage and current variations along a transmission line not terminated in its characteristic impedance is called A. an electric field B. radio waves C. standing waves D. a magnetic field ANSWER: C The desirable SWR on a transmission line is A. 0 B. 1 C. 2 D. infinity ANSWER: B A 50 ohm coax is connected to a 73 ohm antenna. The SWR is A. 0. B. 1 C. 1. D. 2. ANSWER: C The most desirable reflection coefficient is A. 0 B. 0. C. 1 D. infinity ANSWER: A A ratio expressing the percentage of incident voltage reflected on a transmission line is known as the A. velocity factor B. standing wave ratio C. reflection coefficient D. line efficiency ANSWER: C The minimum voltage along a transmission line is 260 V, while the maximum is 390 V. The SWR is A. 0. B. 1. C. 1. D. 1. ANSWER: D Three feet is one wavelength at a frequency of A. 100 MHz B. 164 MHz C. 300 MHz D. 328 MHz ANSWER: D At very high frequencies, transmission lines are used as A. tuned circuits B. antennas C. insulators D. resistors ANSWER: A 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 ANSWER: B A shorted half-wave line at the operating frequency acts like a(n) A. capacitor B. inductor C. series resonant circuit D. parallel resonant circuit ANSWER: C A popular half-wavelength antenna is the A. ground plane B. end-fire C. collinear D. dipole ANSWER: D The length of a doublet at 27 MHz is A. 8.67 ft. B. 17.3 ft. C. 18.2 ft. D. 34.67 ft.
ANSWER: B
A popular vertical antenna is the A. collinear B. dipole C. ground plane D. broadside ANSWER: C The magnetic field of an antenna is perpendicular to the earth. The antenna’s polarization A. is vertical B. is horizontal C. is circular D. cannot be determined from the information given ANSWER: B An antenna that transmits or receives equally well in all directions is said to be A. omnidirectional B. bidirectional C. unidirectional D. quasidirectional ANSWER: A The horizontal radiation pattern of a dipole is a A. circle B. figure eight C. clover leaf D. narrow beam ANSWER: B The length of a ground plane vertical at 146 MHz is A. 1.6 ft. B. 1.68 ft. C. 2.05 ft. D. 3.37 ft. ANSWER: A
The impedance of a dipole is about A. 50 ohm B. 73 ohm C. 93 ohm D. 300 ohm ANSWER: B A directional antenna with two or more elements is known as a(n) A. Folded dipole B. ground plane C. loop D. array ANSWER: D The horizontal radiation pattern of a vertical dipole is a A. figure eight B. circle C. narrow beam D. clover leaf ANSWER: B In an Yagi antenna, maximum direction of radiation is toward the A. director B. driven element C. reflector D. sky ANSWER: A Conductors in mutlielement antennas that do not receive energy directly from the transmission line are known as A. parasitic elements B. drives elements C. the boom D. receptors ANSWER: A A coax has an attenuation of 2. dB per 100 ft. The attenuation for 275 ft is A. 2.4 dB B. 3.3 dB C. 4.8 dB D. 6.6 dB ANSWER: D An antenna has a power gain of
- The power applied to the antenna is 32 W. The effective radiated power is A. 15 W B. 32 W C. 120 W D. 480 W ANSWER: D Which beam width represents the best antenna directivity? A. 7ohm B. 12ohm C. 19ohm D. 28ohm ANSWER: A The radiation pattern of collinear and broadside antennas is A. omnidirectional B. bidirectional C. unidirectional D. clover-leaf shaped ANSWER: B Which antenna has a unidirectional radiation pattern and gain? A. dipole B. ground plane C. Yagi D. collinear ANSWER: C A wide-bandwidth multielement driven array is the A. end-fire B. log-periodic C. Yagi D. collinear ANSWER: B Ground-wave communications is most effective in what frequency range? A. 300 kHz to 3 MHz B. 3 to 30 MHz C. 30 to 300 MHz D. above 300 MHz ANSWER: A The ionosphere causes radio signals to be A. diffused B. absorbed C. refracted D. reflected ANSWER: C The ionosphere has its greatest effect on signals in what frequency range? A. 300 kHz to 3 MHz B. 3 to 30 MHz C. 30 to 300 MHz D. above 300 MHz ANSWER: B The type of radio wave responsible for long distance communications by multiple skips is the A. ground wave B. direct wave C. surface wave D. sky wave ANSWER: D Microwave signals propagate by way of the A. direct wave B. sky wave C. surface wave D. standing wave ANSWER: A Line-of-sight communications is not a factor in which frequency range? A. VHF B. UHF C. HF D. Microwave ANSWER: C A microwave-transmitting antenna is 550 ft high. The receiving antenna is 200 ft high. The maximum transmission distance is A. 20 mi. B. 33.2 mi. C. 38.7 mi. D. 53.2 mi. ANSWER: D To increase the transmission distance of a UHF signal, which of the following should be done? A. increase antenna gain B. increase antenna height C. increase transmitter power D. increase receiver sensitivity ANSWER: B A coax has a velocity factor of 0.68. What is the length of a half wave at 30 MHz? A. 11.2 ft B. 12.9 ft C. 15.6 ft D. 16.4 ft ANSWER: A Which transmission line has the lowest attenuation? A. twin lead B. RG-11/U
C. Varactor D. Schottky ANSWER: B Which type of diodes does not ordinarily operate with reverse bias? A. Varactor B. IMPATT C. Snap-off D. Tunnel ANSWER: D Low-power Gunn diodes are replacing A. Reflex klystrons B. TWTs C. Magnetrons D. Varactor diodes ANSWER: A Which of the following is not a microwave tube? A. Traveling-wave tube B. Cathode-ray tube C. Klystron D. Magnetron ANSWER: B In a klystron amplifier, velocity modulation of the electron beam is produced by the A. Collector B. Catcher cavity C. Cathode D. Buncher cavity ANSWER: D A reflex klystron is used as a(n) A. amplifier B. oscillator C. mixer D. frequency multiplier ANSWER: B For proper operation, a magnetron must be accompanied by a A. cavity resonator B. strong electric field C. permanent magnet D. high dc voltage ANSWER: C The operating frequency of klystrons and magnetrons is set by the A. cavity resonators B. DC supply voltage C. input signal frequency D. number of cavities ANSWER: A A magnetron is used only as a(n) A. amplifier B. oscillator C. mixer D. frequency multiplier ANSWER: B A common application for magnetrons is in A. radar B. satellites C. two-way radio D. TV sets ANSWER: A In a TWT, the electron beam is density-modulated by a A. permanent magnet B. modulation transformer C. Helix D. cavity resonator ANSWER: C The main advantage of a TWT over a klystron for microwave amplification is A. lower cost B. smaller size C. higher power D. wider bandwidth ANSWER: D High-power TWTs are replacing what in microwave amplifiers? A. MESFETs B. magnetrons C. klystrons D. IMPATT diodes ANSWER: C The most widely used microwave antenna is a A. half-wave dipole B. quarter-wave probe C. single loop D. horn ANSWER: D What happens when a horn antenna is made longer? A. Gain increases B. beam width decreases C. both a and b D. neither a nor b ANSWER: A A pyramidal horn used at 5 GHz has an aperture that is 7 by 9 cm. The gain is about A. 10.5 dB B. 11.1 dB C. 22.6 dB D. 35.8 dB ANSWER: A Given the frequency and dimensions in Question 34 above, the beam width is about A. 27ohm B. 53ohm C. 60ohm D. 80ohm
ANSWER: B
The diameter of a parabolic reflector should be at least how many wavelengths at the operating frequency? A. 1 B. 2 C. 5 D. 10 ANSWER: D The point where the antenna is mounted with respect to the parabolic reflector is called the A. Focal point B. center C. locus D. tangent ANSWER: A Using a small reflector to beam waves to the larger parabolic reflector is known as A. Focal feed B. Horn feed C. Cassegrain feed D. Coax feed ANSWER: C Increasing the diameter of a parabolic reflector causes which of the following: A. decreased beam width B. increased gain C. increased beam width D. a and b E. b and c F. none of the above ANSWER: D A helical antenna is made up of a coil and a A. director B. reflector
C. dipole D. horn ANSWER: B The output of a helical antenna is A. vertically polarized B. horizontally polarized C. circularly polarized D. both a and b ANSWER: C A common omnidirectional microwave antenna is the A. horn B. parabolic reflector C. helical D. bicone ANSWER: D As the height of a satellite orbit gets lower, the speed of the satellite A. increase B. decreases C. remains the same D. none of the above ANSWER: A The main function of a communications satellite is as a(n) A. Repeater B. Reflector C. Beacon D. Observation platform ANSWER: A The key electronic component in a communications satellite is the A. Telemetry B. On-board computer C. Command and control system D. Transponder ANSWER: D A circular orbit around the equator with a 24-h period is called a(n) A. Elliptical orbit B. Geostationary orbit C. Polar orbit D. Transfer orbit ANSWER: B A satellite stays in orbit because the following two factors are balanced. A. satellite weight and speed B. gravitational pull and inertia C. centripetal force and speed D. satellite weight and the pull of the moon and sun ANSWER: B The height of a satellite in a synchronous equatorial orbit is A. 100 mi. B. 6800 mi. C. 22,300 mi. D. 35,860 mi. ANSWER: C Most satellites operate in which frequency band? A. 30 to 300 MHz B. 300 MHz to 3 GHz C. 3 GHz to 30 GHz D. above 300 GHz ANSWER: C The main power sources for a satellite are A. batteries B. solar cells C. fuel cells D. thermoelectric generators ANSWER: B The maximum height of an elliptical orbit is called the A. perigee B. apex C. zenith D. apogee ANSWER: D Batteries are used to power all satellite subsystems A. at all times B. only during emergencies C. during eclipse periods D. to give the solar arrays a rest ANSWER: C The satellite subsystem that monitors and controls the satellite is the A. propulsion subsystem B. power subsystem C. communications subsystem D. telemetry, tracking, and command subsystem ANSWER: D The basic technique used to stabilize a satellite is A. gravity-forward motion balance B. spin C. thruster control D. solar panel orientation ANSWER: B The jet thrusters are usually fired to A. maintain attitude B. put the satellite into the transfer orbit C. inject the satellite into the geosynchronous orbit D. bring the satellite back to earth ANSWER: A Most commercial satellite activity occurs in which band(s)? A. L B. C and Ku C. X D. S and P ANSWER: B How can multiple earth stations share a satellite on the same frequencies? A. frequency reuse B. multiplexing C. mixing D. they can’t ANSWER: A The typical bandwidth of a satellite band is A. 36 MHz B. 40 MHz C. 70 MHz D. 500 MHz ANSWER: D Which of the following is not usually a part of a transponder? A. LNA B. mixer C. modulator D. HPA ANSWER: C The satellite communications channels in a transponder are defined by the A. LNA B. bandpass filter C. mixer D. input signals ANSWER: B The HPAs in most satellites are A. TSTs B. klystrons C. vacuum tubes D. magnetrons ANSWER: B
ANSWER: A
A carrier recovery circuit is not needed with A. BPSK B. QPSK C. DPSK D. QAM ANSWER: C The basic modulator and demodulator circuits in PSK are A. PLLs B. balanced modulator C. shift registers D. linears summers ANSWER: B The carrier used with a BPSK demodulator is A. generated by an oscillator B. the BPSK signal itself C. twice the frequency of the transmitted carrier D. recovered from the BPSK signal ANSWER: B A 9600-baud-rate signal can pass over the voice-grade telephone line if which kind of modulation is used? A. BPSK B. QPSK C. DPSK D. QAM ANSWER: D Quadrature amplitude modulation is A. amplitude modulation only B. QPSK only C. AM plus QPSK D. AM plus FSK ANSWER: C A QAM modulator does not use a(n) A. XNOR B. bit splitter C. balanced modulator D. 2-to-4 level converter ANSWER: A A rule or procedure that defines how data is to be transmitted is called a(n) A. handshake B. error-detection scheme C. data specification D. protocol ANSWER: D A popular PC protocol is A. parity B. Xmodem C. CRC D. LRC ANSWER: B A synchronous transmission usually begins with which character? A. SYN B. STX C. SOH D. ETB ANSWER: A The characters making up the message in a synchronous transmission are collectively referred to as a data A. set B. sequence C. block D. collection ANSWER: C Bit errors in data transmission are usually caused by A. equipment failures B. typing mistakes C. noise D. poor S/N ratio at the receiver ANSWER: C Which of the following is not a commonly used method of error detection? A. parity B. BCC C. CRC D. redundancy ANSWER: D Which of the following words has the correct parity bit? Assume odd parity. The last bit is the parity bit. A. 1111111 1 B. 1100110 1 C. 0011010 1 D. 0000001 0 ANSWER: B Another name for parity is A. vertical redundancy check B. block check character C. longitudinal redundancy check D. cyclical redundancy check ANSWER: A Ten bit errors occur in two million transmitted. The bit error rate is A. 2 x 10- B. 5 x 10- C. 5 x 10- D. 2 x 10- ANSWER: C The building block of a parity or BCC generator is a(n) A. shift register
B. XOR
C. 2-to-4 level converter D. UART ANSWER: B A longitudinal redundancy check produces a(n) A. block check character B. parity bit C. CRC D. error correction ANSWER: A Dividing the data block by a constant produces a remainder that is used for error detection. It is called the A. vertical redundancy check B. horizontal redundancy check C. block check character D. cyclical redundancy check ANSWER: D A CRC generator uses which components? A. balanced modulator B. shift register C. binary adder D. multiplexer ANSWER: B Which of the following is not a LAN? A. PBX system B. hospital system C. office building system D. cable TV system ANSWER: D The fastest LAN topology is the A. ring B. bus C. star D. square ANSWER: B
Which is not a common LAN medium? A. twin lead B. twisted pair C. fiber-optic cable D. coax ANSWER: A A mainframe computer connected to multiple terminals and PCs usually uses which configuration? A. bus B. ring C. star D. tree ANSWER: C A small telephone switching system that can be used as a LAN is called a A. ring B. WAN C. UART D. PBX ANSWER: D Which medium is the least susceptible to noise? A. twin lead B. twisted pair C. fiber-optic cable D. coax ANSWER: C Which medium is the most widely used in LANs? A. twin lead B. twisted pair C. fiber-optic cable D. coax ANSWER: B Transmitting the data signal directly over the medium is referred to as A. baseband B. broadband C. ring D. bus ANSWER: A The technique of using modulation and FDM to transmit multiple data channels of a common medium is known as A. baseband B. broadband C. ring D. bus ANSWER: B What is the minimum bandwidth required to transmit a 56 kbits/s binary signal with no noise? A. 14 kHz B. 28 kHz C. 56 kHz D. 112 kHz ANSWER: B Sixteen different levels (symbols) are used to encode binary data. The channel bandwidth is 36 MHz. The maximum channel capacity is A. 18 Mbits/s B. 72 Mbits/s C. 288 Mbits/s D. 2.176 Gbits/s ANSWER: C What is the bandwidth required to transmit at a rate of 10 Mbits/s in the presence of a 28-dB S/N radio? A. 1.075 MHz B. 5 MHz C. 10 MHz D. 10.75 MHz ANSWER: A Which circuit is common to both frequency-hopping and direct- sequence SS transmitters? A. correlator B. PSN code generator C. frequency synthesizer D. sweep generator ANSWER: B Spread spectrum stations sharing a band are identified by and distinguished from one another by A. PSN code B. frequency of operation C. clock rate D. modulation type ANSWER: A The type of modulation most often used with direct-sequence SS is A. QAM B. SSB C. FSK D. PSK ANSWER: D The main circuit in a PSN generator is a(n) A. X-OR B. multiplexer C. shift register D. mixer ANSWER: A To a conventional narrowband receiver, an SS signal appears to be like A. noise B. fading C. a jamming signal D. an intermittent connection ANSWER: A Which of the following is not a benefit of SS? A. jam-proof B. security C. immunity to fading D. noise proof ANSWER: D Spread spectrum is a form of multiplexing. A. true B. false ANSWER: A The most critical and difficult part of receiving a direct-sequence SS signal is A. frequency synthesis B. synchronism C. PSN code generation D. carrier recovery ANSWER: B Which of the following is not a common application of fiber-optic cable? A. computer networks B. long-distance telephone systems C. closed circuit TV D. consumer TV ANSWER: D Total internal reflection takes place if the light ray strikes the interface at an angle with what relationship to the critical angle? A. less than B. greater than C. equal to D. zero
