EST 01/13/18

Which beamwidth represents the best antenna directivity? A. 20 B. 150 C. 100 D. 360

7 degrees

The velocity of signal in air is 140 and becomes 100 as it passes through another medium. What is the index of refraction of the second medium? A. 1.4 B. 1.33 C. 0.715 D. 1.5

A. 1.4

Rainfall is an important factor for fading of radio waves at frequencies above A. 10 GHz B. 1 GHz C. 100 GHz D. 100 MHz

A. 10 GHz

What is the power gain in dB for an antenna with directive gain of 30 dB and an efficiency of 75%? A. 28.75 dB B. 35 dB C. 31.83 dB D. 40 dB

A. 28.75 dB

Radians per second is equal to: A. 2pi x f B. f + 2pi C. the phase angle D. None of the above

A. 2pi x f

A resonant half-wave dipole in free space has feed line current of 1 A. How much power appears at the input to the feed point? A. 73 W B. 218 W C. 146 W D. 292 W

A. 73 W

Angle between an inverted V antenna is A. 90 - 100 degrees B. 60 - 80 degrees C. 45 - 50 degrees D. 105 - 115 degrees

A. 90 - 100 degrees

Indicate in which of the following only one sideband is transmitted: A. H3E B. B8E C. A3E D. C3F

A. H3E

Hartley's Law is: A. I = ktB B. C = Blog2(1+2/N) C. C = 2Blog2(M) D. SR = 2fmax

A. I = ktB

The first satellite that transmits and receives simultaneously is called __________ A. IntelSat 1 B. Syncom 1 C. Explorer D. Telstar 1

A. IntelSat 1

What is the polarity of the currents that feed the V antenna? A. Opposite B. equal C. a or b D. cannot be determined

A. Opposite

What type of polarization should be used if an antenna is mounted on a moving vehicle at frequencies below 50 MHz? A. Vertical B. Horizontal C. circular D. elliptical

A. Vertical

In a half-wave antenna, where are the current nodes? A. at the ends B. at the center C. lambda/4 from the center D. less than lambda/4 from the center

A. at the ends

An example of an unbalanced line is: A. coaxial cable B. an open-wire-line cable C. 300-ohm twin-lead TV cable D. all of the above

A. coaxial cable

Comparing the signal strength at the driven element from the desired direction to the signal strength reaching the driven element from the opposite direction. A. front to back ratio B. gain C. frequency response D. beamwidth

A. front to back ratio

As frequency increases, the resistance of a wire: A. increases B. stays the same C. decreases D. changes periodically

A. increases

The effective length of a dipole is given by the formula. A. lambda/pi B. 2lambda/pi C. pi/lambda D. 2pi/lambda

A. lambda/pi

Space waves are A. line-of-sight B. reflected off the ionosphere C. same as sky waves D. radio waves used for satellite communications

A. line-of-sight

What is the difference in amount of impedance between a three wire dipole and a center fed dipole? A. nine times the feed point impedance B. four times the fed point impedance C. same as the feed point impedance D. none of the above

A. nine times the feed point impedance

The cavity magnetron uses strapping to A. prevent mode jumping B. prevent cathode back heating C. ensure bunching D. improve the phase focusing effect

A. prevent mode jumping

Indicate the false statement. Modulation is used to A. reduce the bandwidth used B. separate the differing transmissions C. ensure that intelligence may be transmitted over long distances D. allow the use of practicable antennas

A. reduce the bandwidth used

An FM receiver switching suddenly between two stations on nearby frequencies is called: A. the capture effect B. the "two-station" effect C. the threshold effect D. none of the above

A. the capture effect

The Hartley law states that A. the maximum rate of information transmission depends on the channel bandwidth B. the maximum rate of information transmission depends on depth of modulation C. redundancy is essential D. only binary codes may be used

A. the maximum rate of information transmission depends on the channel bandwidth

The technology that made cell phones practical was: A. the microprocessor chip B. high-power microwave transmitters C. the miniature cell-site D. all of the above

A. the microprocessor chip

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

A. the sensitivity and the selectivity

What is the reflection coefficient for a transmission line with incident voltage of 4 V and reflected voltage 0.75 V? A. 20 B. 0.1875 C. 2.5 D. 0.2575

B. 0.1875

The number of voice channels in a basic FDM group is A. 6 B. 12 C. 24 D. 60

B. 12

If the two towers of a 2 MHz antenna are separated by 120 electrical degrees. What is the tower separation in feet? A. 150 ft B. 164 ft C. 250 ft D. 275 ft

B. 164 ft

What is the frequency range of C-band? A. 8.5 to 12.5 GHz B. 3.4 to 6.425 GHz C. 12.95 to 14.95 GHz D. 27.5 to 31 GHz

B. 3.4 to 6.425 GHz

What frequency range do millimeter waves cover? A. 10 GHz - 100 GHz B. 30 GHz - 300 GHz C. 10 GHz - 1000 GHz D. 30 GHz - 3000 GHz

B. 30 GHz - 300 GHz

To separate channels in a FDM receiver, it is necessary to use A. AND gates B. Bandpass filter C. Differentiation D. Integration

B. Bandpass filter

What band does VSAT first operate? A. L-band B. C-band C. X-band D. Ku-band

B. C-band

DTMF stands for: A. Digital Telephony Multiple Frequency B. Dual-Tone Multifrequency C. Dial Tone Master Frequency D. Digital Trunk Master Frequency

B. Dual-Tone Multifrequency

Satellite engine uses A. Jet propulsion B. Ion propulsion system C. Liquid fuel D. Solar jet

B. Ion propulsion system

Indicate which one of the following is not an advantage of FM over AM: A. better noise immunity is provided B. Lower bandwidth is required C. The transmitted power is more useful D. Less modulating power is required

B. Lower bandwidth is required

Indicate which of the following system is digital A. Pulse position modulation B. Pulse code modulation C. Pulse width modulation D. Pulse frequency modulation

B. Pulse code modulation

The antenna separation (in meters) required for optimum operation of space diversity can be calculated from: {where R is the effective earth radius (m) and L is path length (m)} A. S = 2lambdaR/L B. S = 3lambdaR/L C. S = lambdaR/3L D. S = lambdaR/L

B. S = 3lambdaR/L

Indicate the false statement regarding the advantages of SSB over double sideband, full carrier AM. A. more channel spaced available B. Transmitter circuits must be more stable, giving better reception C. The signal is more noise-resistant D. Much less power is required for the same signal strength

B. Transmitter circuits must be more stable, giving better reception

Tropospheric scatter is used with frequencies in the following range A. HF B. UHF C. VHF D. VLF

B. UHF

Indicate the false statement. The SWR on a transmission line infinity; the line is terminated in A. a short circuit B. a complex impedance C. an open circuit D. a pure resistance

B. a complex impedance

A pre-emphasis circuit provides extra noise immunity by A. boosting the bass frequency B. amplifying the high audio frequencies C. preamplifying the whole audio band D. converting the phase modulation to FM

B. amplifying the high audio frequencies

When microwave signals follow the curvature of the earth, this is known as A. the faraday effect B. ducting C. tropospheric scatter D. ionospheric reflections

B. ducting

Indicate the false statement A. HF mixers are generally noisier than HF amplifiers B. impulse noise voltage is independent of the bandwidth C. Thermal noise is independent of the frequency at which it is measured D. Industrial noise is usually of the impulse type

B. impulse noise voltage is independent of the bandwidth

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

B. increase antenna height

The Hartley Shannon theorem sets a limit on the A. Highest frequency that may be sent over a given channel B. maximum capacity of a channel with a given noise level C. maximum number of coding levels in a channel with a given noise level D. maximum number of quantizing levels in a channel of a given bandwidth

B. maximum capacity of a channel with a given noise level

Indicate which of the following reasons for using a counterpoise with antenna is false A. impossibility of a good ground connection B. protection of personnel working underneath C. provision of an earth for the antenna D. rockiness of the ground itself

B. protection of personnel working underneath

The end impedance of a half wave dipole is ________. A. resistive and low B. resistive and high C. inductive D. capacitive

B. resistive and high

In the spectrum of a frequency modulated wave A. the carrier frequency disappears when the modulation index is large B. the amplitude of any sideband depends on the modulation index C. the total number of sidebands depend on the modulation index D. the carrier frequency cannot disappear

B. the amplitude of any sideband depends on the modulation index

Equalizing pulses in TV are sent during A. horizontal blanking B. vertical blanking C. the serrations D. the horizontal retrace

B. vertical blanking

A positive voltage pulse sent down a transmission line terminated in a short-circuit: 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

B. would reflect as a negative pulse

A free space attenuation between two microwave antennas 40 km apart operating at 8 GHz is A. 146.7 dB B. 82.5 dB C. 142.55 dB D. 86.7 db

C. 142.55 dB

What is the radiation resistance of a half-wave folded dipole in ohms? A. 75 B. 292 C. 176 D. 216

C. 176

Given MUF as 7050 kHz, critical angle is 35 degrees, what is the critical frequency of this sky wave signal? A. 7.43 MHz B. 6.5 MHz C. 5.775 MHz D. 7.05 MHz

C. 5.775 MHz

What would be the physical size pf a Hertz antenna operating at 97.1 MHz? (k=0.95) A. 50 in B. 65 in C. 58 in D. 115 in

C. 58 in

A paraboloid is to have power gain of 41.55 dB. If the frequency of operation is to be 8 GHz, what is the diameter of the parabolic reflector? A. 10 ft B. 2.3 ft C. 6 ft D. 18 ft

C. 6 ft

What is a trap antenna? A. An antenna for rejecting interfering signals B. A highly sensitive antenna with maximum gain in all directions C. An antenna capable of being used on more than one band because of the presence of parallel LC networks D. An antenna with large capture area

C. An antenna capable of being used on more than one band because of the presence of parallel LC networks

Mathematically, the calculation of FM bandwidth requires the use of A. ordinary trigonometry and algebra B. Taylor series C. Bessel functions D. fractals

C. Bessel functions

Collects very weak signal from a broadcast satellite? A. Helical antenna B. LNA C. Satellite dish D. TWT

C. Satellite dish

If k-factor is greater than 1, the array beam is bent A. Away from the earth B. Towards the ionosphere C. Towards the earth D. Towards the outer space

C. Towards the earth

For QAM, the two dimensions of its symbol space are: A. amplitude and frequency B. frequency and phase angle C. amplitude and phase angle D. I-bits and Q-bits

C. amplitude and phase angle

Microwave link repeaters are typically 50km apart A. because of atmospheric attenuation B. because of output power limitations C. because of earth's curvature D. to ensure that the applied dc voltage is not excessive

C. because of earth's curvature

Image frequencies occur when two signals: A. are transmitted on the same frequency B. enter the mixer, with one being a reflected signal equal to the IF frequency C. enter the mixer, one below and one above the local oscillator by a difference equal to the IF D. enter the mixer, and the difference between the two signals is equal to twice the IF

C. enter the mixer, one below and one above the local oscillator by a difference equal to the IF

For best matching, the load on a cable should be: A. lower than Zo B. higher than Zo C. equal to Zo D. 50 ohms

C. equal to Zo

How does the gain of a parabolic dish type antenna change when the operating frequency is doubled? A. gain does not change B. gain is multiplied by 0.707 C. gain increases 6 dB D. gain increases 3 dB

C. gain increases 6 dB

The carrier is simultaneously modulated by two sine wave with the modulation indices of 0.3 and 0.4; the total modulation index A. is 1 B. cannot be calculated unless the phase relations are known C. is 0.5 D. is 0.7

C. is 0.5

Short circuited stubs are preferred to open circuited stub because the latter are A. more difficult to make and connect B. made of transmission line with a different characteristic impedance C. liable to radiate D. incapable of giving a full range of reactances

C. liable to radiate

The optimum value for SWR is: A. zero B. as large as possible C. one D. there is no optimum value

C. one

Which of the following is not an omni directional antenna? A. vertical folded dipole B. discone C. rhombic D. turnstile

C. rhombic

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

C. the decrease in energy per square meter due to expansion of the wavefront

The wavelength of a radio signal is: A. equal to f/c B. equal to c/lambda C. the distance a wave travels in one period D. how far the signal can travel without distortion

C. the distance a wave travels in one period

"Skin effect" refers to: A. the way radio signals travel across a flat surface B. the tissue-burning effect of a strong RF signal C. the increase of wire resistance with frequency D. none of the above

C. the increase of wire resistance with frequency

The main difference between the operation of transmission lines and waveguides is that A. the latter are not distributed, like transmission lines B. the former can use stubs and quarter wave transformers, unlike the latter C. transmission lines is use the principal mode of propagation, and therefore do not suffer from low frequency cut off D. terms such as impedance matching and standing wave ratio cannot be applied to waveguides

C. transmission lines is use the principal mode of propagation, and therefore do not suffer from low frequency cut off

The power gain of a half wave dipole with respect to an isotropic radiator. A. 3 dB B. 5 dB C. 6 dB D. 2.15 dB

D. 2.15 dB

The range of DC current that flows through a telephone is: A. 20 uA to 80 uA B. 2 mA to 8 mA C. 200 uA to 800 uA D. 20 mA to 80 mA

D. 20 mA to 80 mA

A super heterodyne receiver with an IF of 450 kHz is tuned to a signal at 1200 kHz. The image frequency is A. 750 kHz B. 1650 kHz C. 900 kHz D. 2100 kHz

D. 2100 kHz

At what height must a satellite be placed above the surface of the earth in order for its rotation to be equal to the earth's rotation? A. 26,426.4 miles B. 27,426.4 miles C. 23,426.4 miles D. 22,426.4 miles

D. 22,426.4 miles

The efficiency of an antenna is 82%. Its radiation resistance is 30 ohms. What is the value of its loss resistance? A. 75 ohms B. 12 ohms C. 15 ohms D. 6.58 ohms

D. 6.58 ohms

If the carrier of a 100 percent modulated AM wave is suppressed, the percentage power saving will be A. 50 B. 100 C. 150 D. 66.66

D. 66.66

Indicate the correct statement regarding satellite communications. A. If two earth stations do not face a common satellite, they should communicate via double-satellite hop B. satellites are allocated so that it is impossible for two earth stations not to face the same satellite C. collocated earth station are used for frequency diversity D. A satellite earth station must have as many receiver chains as there are carriers transmitted to it

D. A satellite earth station must have as many receiver chains as there are carriers transmitted to it

What is the layer in the ionosphere that is 255 mi in height? A. D B. F1 C. E D. F2

D. F2

A satellite beam that covers almost 42.5% of the earth's surface A. Zone beam B. Hemispherical beam C. Spot beam D. Global beam

D. Global beam

The radius of the circle you draw on a Smith Chart represents: A. the voltage B. the current C. the impedance D. None of the above

D. None of the above

Which of the reception problems below is not due to multipath? A. Delayed spreading B. Rayleigh fading C. Random Doppler shift D. Slow fading

D. Slow fading

Which polarization can be reasonably well received by a circularly polarized antenna: A. vertical B. circular C. horizontal D. all of the above

D. all of the above

Interlacing is used in television to A. produce the illusion of motion B. ensure that all the lines on the screen are scanned, not merely the alternate ones C. simplify the vertical sync pulse train D. avoid flicker

D. avoid flicker

Which of the following is a wideband omni directional HF-UHF antenna? A. log periodic B. parabolic dish C. discone D. helical antenna

D. helical antenna

One of the main functions of the RF amplifier in a super heterodyne receiver is to A. provide improved tracking B. permit better adjacent-channel rejection C. increase the tuning range of the receiver D. improve the rejection of the image frequency

D. improve the rejection of the image frequency

Time division multiplex A. can be used with PCM only B. combines five groups into a super group C. stacks 24 channels in adjacent frequency slots D. interleaves pulses belonging to different transmissions

D. interleaves pulses belonging to different transmissions

When two or more signals share a common channel, it is called: A. sub-channeling B. signal switching C. SINAD D. multiplexing

D. multiplexing

A directional coupler with three or more holes is sometimes used in preference to the two hole coupler A. because it is more efficient B. to increase coupling of the signal C. to reduce spurious mode generation D. to increase the bandwidth of the system

D. to increase the bandwidth of the system

The equation for full-carrier AM is: A. v(t) = (Ec + Em) x sin(wct) B. v(t) = (Ec x Em) x sin(wmt) x sin(wct) C. v(t) = (Ec + Em) x sin(wmt) + sin(wct) D. v(t) = (Ec + Emsin(wmt)) x sin(wct)

D. v(t) = (Ec + Emsin(wmt)) x sin(wct)