EST TERMS FOR BOARDS PT. 2

Calculate the aperture-to-medium coupling loss for two 30-ft antennas, one at each end of the path, with a 2ᵒ scatter angle and a 900-MHz operating frequency.

3.67 dB

Copper I²R losses are reduced by what physical property of waveguides?

large surface area

What pairs of linear differential equations known to describe the voltage and current on an electrical transmission line with distance and time?

Telegraph equations

In a non-diversity microwave communication link covering 20 mi, what is the reliability when the operating frequency is 6 GHz and with 45 dB of assigned fade margin? Assume a very smooth terrain and hot humid climate.

99.999%

What is the only feasible method of modulation for recording video to and retrieving video from magnetic tape without extreme distortion?

FM

At what frequencies does the combination of the earth's surface and the D layer act as a waveguide?

VLF

A ground screen is a series of conductors buried 1 or 2 feet below the surface in a radial pattern and is usually of what length in comparison to the wavelength being used?

One-half wavelength

What is the frequency-deviation constant for a Clapp oscillator frequency-modulated for which the unmodulated frequency is 50 MHz with a fixed bias of 15 V and n = 0.1?

733 kHz/V

In collinear array antenna, where is the maximum radiation directed?

Perpendicular to the axis of the elements

What designation of ITU is the basic AM modulation scheme?

A3E

"Incoming light is partially absorbed and partially transmitted equally in all directions". This statement is known as

The Lambertian reflection

In the radio spectrum, which of the following frequencies are used for deep space radio communications?

2.29 GHz to 2.3 GHz

What is the open-circuit voltage in a λ/2 dipole when 25 W at 170 MHz is radiated from another λ/2 dipole 100 km distant? Assume an effective length of λ/π.

197 uV

In microwave radio system, determine the multipath effect for a distance of 30 km so that fade margin can be estimated for that particular link using 6 GHz of frequency and an objective of 99.999%.

44.31 dB

What is the typical duty cycle (fraction of total time during which the magnetron is actually ON) of magnetron for pulse work in radar systems?

0.1 percent

In transmission lines, the ______________ of the wave is the equivalent of the angular frequency but with respect to the distance variable.

propagation constant

In transmission lines (coaxial or two-wire), what velocity is the speed with which a point of constant phase in the wave appears to move?

Phase or group velocity

Of the possible modes of operation available for a given waveguide, the dominant mode has the ____ cutoff frequency.

lowest

In PPP connection, when one of the two nodes starts the communication, the connection goes into the:

Establish state

In CSMA/CA this is an amount of time divided into slots.

Contention Window

What is an advantage of using a trap antenna?

It may be used for multi-band operation.

VHF signals from a mobile station using a vertical whip antenna will normally be best received using a:

vertical ground-plane antenna

What is the simplest method of reducing the forbidden range of impedances?

reduce the distance between the stubs

In free space, what is the radiation characteristic of a half-wave dipole?

Minimum radiation from the ends, maximum broadside

In Bluetooth, what layer is roughly equivalent to the physical layer of the Internet model?

radio

Which statement about two-element delta loops and quad antennas is true?

They compare favorably with a three-element Yagi

For co-axial lines and waveguides, ________ is more preferred.

Short circuited stub

The size and shape of the probe determines its _____, _____, and _____.

frequency, bandwidth, power handling capability

In a frequency modulation transmitter, the ___________is located between the oscillator and the power amplifier.

frequency multiplier

The method where in the acknowledgement is being sent along with the message for two-way communication to increase efficiency:

Piggybacking

Why should you use only good quality coaxial cable and connectors for a UHF antenna system?

To keep RF loss low

The major advantage of double stub tuning is:

it uses 2 tuning stubs in fixed positions

Which of the following is not a scatter mode?

Absorption scatter

TV twin-lead transmission line can be used for a transmission line in an amateur station. The impedance of this line is approximately:

300 ohms

Propagation constant γ in terms of admittance and impedance of the transmission line is given by:

sqrt (ZY)

The permissible exposure levels of RF fields:

increases, as frequency is increased from 300 MHz to 1.5 GHz

If a single section quarter wave transformer is used for impedance matching at some frequency, then the length of the matching line is:

Is different at different frequencies

When a lossless line is terminated with an arbitrary load impedance Z_L, then it:

causes wave reflection on transmission lines

In wave propagation, when the incident wave is ______ to the surface, more of the energy is transmitted into the substance and less is reflected.

perpendicular

In sound propagation, raising the temperature of the medium (which decreases its density) has the effect of ______ the velocity of sound through the medium.

increasing

What refers to the sensation the intensity (and sometimes frequency) of sound wave produces on the ear?

Loudness

In wave propagation, if the source and the receiver are moving apart, the receiver will perceive a _____ frequency sound.

lower

Reflection of a SSB transmission from the ionosphere causes:

little or no phase-shift distortion

Which of the following Internet Protocol (IP) address classes identifies multicast addresses?

Class D

An _____ is a working document (a work in progress) with no official status and a six-month lifetime.

Internet draft

When sunspot numbers are high, how is the ionosphere affected?

Frequencies up to 40 MHz or higher are normally usable for long distance communication

If your antenna feed line gets hot when you are transmitting, what might this mean?

The SWR may be too high, or the feed line loss may be high.

Which of the following wireless networking standards is capable of supporting speeds of 54 Mbps and is also backward compatible with IEEE 802.11b?

IEEE 802.11g

Two or more parts of the radio wave follow different paths during propagation and this may result in phase differences at the receiver. This "change" at the receiver is called:

Fading

What noise is the random motion of electrons in a wire, which creates an extra signal not originally sent by the transmitter?

Thermal

When does scatter propagation on the HF bands most often occur?

When communicating on frequencies above the maximum usable frequency (MUF)

What is cross-modulation interference?

Modulation from an unwanted signal is heard in addition to the desired signal

What is a delta loop antenna?

A type of cubical quad antenna, except with triangular elements rather than square

What refers to the variation in the packet arrival time. It is also the uneven delay in the delivery of audio or video packets?

Jitter

Optical fibers use reflection to guide light through a channel. A glass or plastic core is surrounded by a cladding of ____ dense glass or plastic.

less

Datagram switching is normally done at the _____ layer.

network

The minimum bandwidth of Manchester and differential Manchester is ___ times that of NRZ.

2

What is the dominant method of digital-to-analog modulation?

QAM

The ______ in the header of a packet in a datagram network remains the same during the entire journey of the packet.

Destination address

In FDM, up to five groups can be multiplexed to create a composite signal called a _____.

supergroups

Companding gives greater weight to ____ signals and less weight to ____ ones.

strong, weak

NRZ-L and NRZ-I both have a ___ component problem.

DC

Aviation services use predominantly ____ microphones.

dynamic

When a vacuum tube operates at VHF or higher frequencies as compared to lower frequencies:

Transit time of electrons becomes important.

What is the maximum range for signals using transequatorial propagation?

About 5,000 miles.

The most common twisted-pair cable used in communications is referred to as ______.

UTP

In FDM, 12 voice channels are multiplexed onto a higher-bandwidth line to create a _____.

group

An error-detecting code can detect what types of errors?

Errors for which it is designed; other types of errors may remain undetected.

How does the bandwidth of the transmitted signal affect selective fading?

It is more pronounced at wide bandwidths.

In FDM, six master groups can be combined into a _______.

jumbogroup

In digital transmission, the _____ gives us the upper limit; the _____tells us how many signal levels we need.

Shannon capacity, Nyquist formula

The controlled oscillator synthesizer is sometimes preferred to the direct one because:

It is relatively free of spurious frequencies.

In FDM, 10 supergroups are multiplexed to create a _______.

master group

When the receiver has good blocking performance, this means that:

It is unaffected by AGC derived from nearby transmission.

Vestigial sideband modulation (C3F) is normally used for

HF point to point communications

An antenna that is circularly polarized is the _____.

helical

If the composite signal is _____, the decomposition gives a combination of sine waves with continuous frequencies.

nonperiodic

According to Fourier analysis, any _____ signal is a combination of simple sine waves with different frequencies, amplitudes, and phases.

composite

Since noise phase modulates the FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude:

decreased

In order to couple two generators to a waveguide system without coupling them to each other, one could not use a:

E - plane T

The typical squelch circuit:

Cuts off an audio amplifier when the carrier is absent.

In digital transmission, _____ the levels of a signal may reduce the reliability of the system.

increasing

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

Transmitter circuits must be more stable. Giving better reception.

Indicate the antenna that is not wideband:

Marconi

_____ are sets of bit patterns have been designed to represent text symbols.

Code

In a ______ network, there is no resource reservation; resources are allocated on demand.

packet-switched

An RFC classified as _____ contains general, historical, or tutorial information related to the Internet.

informational

What layer has the ability to refract signals as high as 20 megahertz and for this reason, it is valuable for communications in ranges up to about 1500 miles?

E layer

Which of the following is true about connectionless protocol?

The frames are not connected

What should you do for safety if you put up a UHF transmitting antenna?

Make sure the antenna will be in a place where no one can get near it when you are transmitting

The radiation field _____linearly as the distance from the antenna is increased.

decreases

For an Ethernet frame, a preamble, which is used to alert the receiving system to the coming frame and enable it to synchronize its clock if it's out of synchronization, consists of how many bytes of alternating 1's and 0's?

7 bytes

An antenna changeover switch in a transmitter-receiver combination is necessary:

so that one antenna can be used for transmitter and receiver

How can an antenna system be protected from lightning damage?

Ground all antennas when they are not in use

In a frequency modulation transmitter, the _______ is located between the modulator and the frequency multiplier.

oscillator

A receiver designed for SSB reception must have a BFO (beat frequency oscillator) because:

the suppressed carrier must be replaced for detection

In _______ transmission, all stations will receive the frame, the stations that are members of the group keep and handle it; the rest discard it.

multicast

If you install a 6-meter Yagi antenna on a tower 50 meters from your transmitter, which of the following feed lines is best?

RG-213

Which of the following is not a Password Authentication Protocol (PAP) packet?

Authenticate-send

What may happen if an FM transmitter is operated with the microphone gain or deviation control set too high?

It may cause interference to other stations operating near its frequency