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What is the reflection coefficient for a transmission line with incident voltage of 4 V and reflected voltage 0.75 V?

0.1875

Voltage and current readings are taken on a transmission line at different points. The maximum voltage reading is 30 Vrms(max) and the minimum voltage reading is 10 Vrms(min). If the maximum current reading on the line is 1.5 A, what is the lowest current reading?

0.5 A

A dipole antenna using traps is designed to transmit a 140 MHz signal and a 90 MHz signal. What is the distance between trans given a velocity factor of 0.90?

0.965

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?

1.4

A commonly used coaxial cable RG-8 A/U, has a capacitance of 29.5 pF/ft and inductance of 73.75 nH/ft, determine the amount of delay induced by a 1-ft section of this line if it will be used as a delay line

1.475 ns

Rainfaill is an important factor for fading of radio waves at frequencies above

10 GHz

Angle between an inverted V antenna is

105 degrees - 115 degrees

The number of voice channels in a basic FDM group is

12

A free space attenuation between two microwave antennas 40 km apart operating at 8 GHz is

142.55 dB

If the two towers of a 2 MHz antenna are separated by 120 electrical degrees, what is the tower separation in feet?

164 ft

The power gain of a half wave dipole with respect to an isotropic radiator

2.15 dB

A pulse requires 553 nanoseconds to travel from one end of a 111-meter coaxial cable to the other, what is the dielectric constant of the cable?

2.23

Which beamwidth represents the best antenna directivity?

20

The range of DC current that flows through a telephone is

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

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?

22,426.4 miles

What is the power gain in dB for an antenna with a directive gain of 30 dB and an efficiency of 75%?

28.75 dB

Radians per second is equal to

2pi * f

What is the frequency range of C band?

3.4 to 6.425 GHz

What frequency range do millimeter waves cover?

30 GHz - 300 GHz

At what angle is the direction of propagation in the XY plane if the E field is 180 degrees from the vertical?

45 deg

Given MUF as 7050 kHz, critical angle is 35 degrees, what is the critical frequency of this sky wave signal?

5775 MHz

What would be the physical size of a Hertz antenna operating at 97.1 MHz (k = 0.95)

58 inches

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?

6 ft

The distance between adjacent nodes of a standing wave in air dielectric is determined to be 2.406 cm. What is the frequency of the generator?

6.23 GHz

The efficiency of an antenna is 82%. Its radiation resistance is 30 ohms. What is the value of its loss resistance?

6.58 ohms

If the carrier of a 100 percent modulated AM wave is suppressed, the percentage power saving will be

66.66

Two parallel wires placed 10 inches apart make use of wires having diameter of 81 mils. What is the characteristic impedance of the line?

660 ohms

A particular cable has a capacitance of 40 pF/ft and a characteristic impedance of 70 ohms. Determine the impedance of an infinitely long section of such cable.

70

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?

73 W

What is the radiation resistance of a halfwave folded dipole in ohms?

75

What is the difference in amount of impedance between a three-wire dipole and a center-fed dipole?

9 times the feed point impedance

Indicate the correct statement regarding satellite communications

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

To separate channels in a FDM receiver, it is necessary to use

AND gates

Which polarization can be reasonably well received by a circularly polarized antenna?

All of the above (vertical, circular, horizontal)

What is a trap antenna?

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

In a half-wave antenna, where are the current nodes?

At the ends

Mathematically, the calculation of FM bandwidth requires the use of

Bessel functions

What bond does VSAT first operate?

C-band

DTMF stands for

Dual-Tone Multifrequency

What is the layer of the ionosphere that is 255 km in height?

F2

A satellite beam that covers almost 42.5% of the earth's surface

Global beam

Indicate in which of the following only one sideband is transmitted

H3E

Which of the following is a wideband omni directional HF-UHF antenna?

Helical antenna

Hartley's Law is

I = ktB

Indicate the false statement

Impulse noised voltage is independent of the bandwidth

To increase the transmission distance of a UHF signal, which of the following should be done?

Increase antenna height

Indicate which one of the following is not an advantage of FM over AM

Lower bandwidth is required

What is the polarity of the currents that feed the V antenna?

Opposite

Indicate which of the following system is digital

Pulse Code Modulation

Which of the following is not an omnidirectional antenna?

Rhombic

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))

S = 3*(lambda)*R / L

Collects very weak signals from broadcast satellite?

Satellite dish

Which of the reception problems below is not due to multipath?

Slow fading

The first satellite that transmits and receives simultaneously is called

Telstar 1

Indicate the false statement regarding the advantages of SSB over double sideband, full carrier AM

Transmitter circuits must be more stable. Giving better reception

Tropospheric scatter is used with frequencies in the following range

UHF

The equation for full-carrier AM is:

V(t) = (Ec+Em*sin(wmt))*sin(wct)

What type of polarization should be used if an antenna is mounted on a moving vehicle at frequencies below 50 MHz?

Vertical

Indicate the false statement. The SWR on a transmission line is infinity; the line is terminated in

a complex impedance

A pre-emphasis circuit provides extra noise immunity by

amplifying the high audio frequencies

For QAM, the two dimensions of its symbol space are

amplitude and phase angle

Interlacing is used in television to

avoid flicker

Microwave link repeaters are typically 50km apart

because of the earth's curvature

An example of an unbalanced line is

coaxial cable

When microwave signals follow the curvature of the earth, this is known as

ducting

Image frequencies occur when two signals:

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

equal to Zo

Comparing the signal strength at the driven element from the desired direction to the signal strength reaching the driven element from the opposite direction

front to back ratio

How does the gain of a parabolic dish type antenna change when the operating frequency is doubled?

gain increases 6 dB

One of the main functions of the RF amplifier in a super heterodyne receiver is to

improve the rejection of the image frequency

As frequency increases, the resistance of a wire

increases

Time division multiplex

interleaves pulses belonging to different transmissions

Satellite engines use

ion propulsion system

The carrier is simultaneously modulated by two sine wave with the modulation indices of 0.3 and 0.4; the total modulation index

is 0.5

The effective length of a dipole is given by the formula

lambda / pi

Short circuited stubs are preferred to open circuited stub because the latter are

liable to radiate

Space waves are

line-of-sight

The Hartley Shannon theorems set a limit on the

maximum capacity of a channel with a given noise level

When two or more signals share a common channel, it is called

multiplexing

The radius of the circle you draw on a Smith Chart represents

none of the above (voltage, current, impedance)

The optimum value for SWR is

one

The cavity magnetron uses strapping to

prevent mode jumping

. Indicate which of the following reasons for using a counterpoise with antennas is false

protection of personnel working underneath

Indicate the false statement. Modulation is used to

reduce the bandwidth used

The end impedance of a half wave dipole is

resistive and high

The wavelength of a radio signal is

the distance a wave travels in one period

The Hartley law states that

the maximum rate of information transmission depends on the channel bandwidth

In the spectrum of a frequency modulated wave

the amplitude of any sideband depends on the modulation index

An FM receiver switching suddenly between two stations on nearby frequencies is called

the capture effect

The "attenuation of free space" is due to

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

"Skin effect" refers to

the increase of wire resistance with frequency

The technology that made cellphones practical was

the microprocessor chip

The two basic specifications for a receiver are

the sensitivity and the selectivity

A directional coupler with three or more holes is sometimes used in preference to the two-hole coupler

to increase the bandwidth of the system

If k-factor is greater than 1, the array beam is bent

towards the earth

The main difference between the operation of transmission lines and wave guides is that

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

Equalizing pulses in TV are sent during

vertical blanking

A positive voltage pulse sent down a transmission line terminated in a shortcircuit

would reflect as a negative pulse


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