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Extra Class Exam Question Pool

effective 7/01/2016 thru 6/29/2020

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Topic 2016-E9: Antennas and Transmission Lines


2016-E9A: Basic Antenna parameters: radiation resistance, gain, beamwidth, efficiency, beamwidth; effective radiated power, polarization

2016-E9A01: What describes an isotropic antenna?

A theoretical antenna used as a reference for antenna gain

A grounded antenna used to measure earth conductivity

A horizontally polarized antenna used to compare Yagi antennas

A spacecraft antenna used to direct signals toward the earth



2016-E9A02: What antenna has no gain in any direction?

Isotropic antenna

Quarter-wave vertical

Yagi

Half-wave dipole



2016-E9A03: Why would one need to know the feed point impedance of an antenna?

To match impedances in order to minimize standing wave ratio on the transmission line

To measure the near-field radiation density from a transmitting antenna

To calculate the front-to-side ratio of the antenna

To calculate the front-to-back ratio of the antenna



2016-E9A04: Which of the following factors may affect the feed point impedance of an antenna?

Antenna height, conductor length/diameter ratio and location of nearby conductive objects

Transmission-line length

The settings of an antenna tuner at the transmitter

Sunspot activity and time of day



2016-E9A05: What is included in the total resistance of an antenna system?

Radiation resistance plus ohmic resistance

Radiation resistance plus space impedance

Radiation resistance plus transmission resistance

Transmission-line resistance plus radiation resistance



2016-E9A06: How does the beamwidth of an antenna vary as the gain is increased?

It decreases

It increases geometrically

It increases arithmetically

It is essentially unaffected



2016-E9A07: What is meant by antenna gain?

The ratio of the radiated signal strength of an antenna in the direction of maximum radiation to that of a reference antenna

The ratio of the signal in the forward direction to that in the opposite direction

The ratio of the amount of power radiated by an antenna compared to the transmitter output power

The final amplifier gain minus the transmission line losses



2016-E9A08: What is meant by antenna bandwidth?

The frequency range over which an antenna satisfies a performance requirement

Antenna length divided by the number of elements

The angle between the half-power radiation points

The angle formed between two imaginary lines drawn through the element ends



2016-E9A09: How is antenna efficiency calculated?

(radiation resistance / total resistance) x 100 per cent

(radiation resistance / transmission resistance) x 100 per cent

(total resistance / radiation resistance) x 100 per cent

(effective radiated power / transmitter output) x 100 percent



2016-E9A10: Which of the following choices is a way to improve the efficiency of a ground-mounted quarter-wave vertical antenna?

Install a good radial system

Isolate the coax shield from ground

Shorten the radiating element

Reduce the diameter of the radiating element



2016-E9A11: Which of the following factors determines ground losses for a ground-mounted vertical antenna operating in the 3 MHz to 30 MHz range?

Soil conductivity

The standing wave ratio

Distance from the transmitter

Take-off angle



2016-E9A12: How much gain does an antenna have compared to a 1/2-wavelength dipole when it has 6 dB gain over an isotropic antenna?

3.85 dB

6.0 dB

8.15 dB

2.79 dB



2016-E9A13: How much gain does an antenna have compared to a 1/2-wavelength dipole when it has 12 dB gain over an isotropic antenna?

9.85 dB

6.17 dB

12.5 dB

14.15 dB



2016-E9A14: What is meant by the radiation resistance of an antenna?

The value of a resistance that would dissipate the same amount of power as that radiated from an antenna

The combined losses of the antenna elements and feed line

The specific impedance of the antenna

The resistance in the atmosphere that an antenna must overcome to be able to radiate a signal



2016-E9A15: What is the effective radiated power relative to a dipole of a repeater station with 150 watts transmitter power output, 2 dB feed line loss, 2.2 dB duplexer loss, and 7 dBd antenna gain?

286 watts

1977 watts

78.7 watts

420 watts



2016-E9A16: What is the effective radiated power relative to a dipole of a repeater station with 200 watts transmitter power output, 4 dB feed line loss, 3.2 dB duplexer loss, 0.8 dB circulator loss, and 10 dBd antenna gain?

317 watts

2000 watts

126 watts

300 watts



2016-E9A17: What is the effective radiated power of a repeater station with 200 watts transmitter power output, 2 dB feed line loss, 2.8 dB duplexer loss, 1.2 dB circulator loss, and 7 dBi antenna gain?

252 watts

159 watts

632 watts

63.2 watts



2016-E9A18: What term describes station output, taking into account all gains and losses?

Effective radiated power

Power factor

Half-power bandwidth

Apparent power






2016-E9B: Antenna patterns: E and H plane patterns; gain as a function of pattern; antenna design

2016-E9B01: In the antenna radiation pattern shown in Figure E9-1, what is the 3 dB beam-width?

50 degrees

75 degrees

25 degrees

30 degrees



2016-E9B02: In the antenna radiation pattern shown in Figure E9-1, what is the front-to-back ratio?

18 dB

36 dB

24 dB

14 dB



2016-E9B03: In the antenna radiation pattern shown in Figure E9-1, what is the front-to-side ratio?

14 dB

12 dB

18 dB

24 dB



2016-E9B04: What may occur when a directional antenna is operated at different frequencies within the band for which it was designed?

The gain may change depending on frequency

Feed point impedance may become negative

The E-field and H-field patterns may reverse

Element spacing limits could be exceeded



2016-E9B05: What type of antenna pattern over real ground is shown in Figure E9-2?

Elevation

Azimuth

Radiation resistance

Polarization



2016-E9B06: What is the elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2?

7.5 degrees

45 degrees

75 degrees

25 degrees



2016-E9B07: How does the total amount of radiation emitted by a directional gain antenna compare with the total amount of radiation emitted from an isotropic antenna, assuming each is driven by the same amount of power?

They are the same

The total amount of radiation from the directional antenna is increased by the gain of the antenna

The total amount of radiation from the directional antenna is stronger by its front-to-back ratio

The radiation from the isotropic antenna is 2.15 dB stronger than that from the directional antenna



2016-E9B08: How can the approximate beam-width in a given plane of a directional antenna be determined?

Note the two points where the signal strength of the antenna is 3 dB less than maximum and compute the angular difference

Measure the ratio of the signal strengths of the radiated power lobes from the front and rear of the antenna

Draw two imaginary lines through the ends of the elements and measure the angle between the lines

Measure the ratio of the signal strengths of the radiated power lobes from the front and side of the antenna



2016-E9B09: What type of computer program technique is commonly used for modeling antennas?

Method of Moments

Graphical analysis

Mutual impedance analysis

Calculus differentiation with respect to physical properties



2016-E9B10: What is the principle of a Method of Moments analysis?

A wire is modeled as a series of segments, each having a uniform value of current

A wire is modeled as a single sine-wave current generator

A wire is modeled as a series of points, each having a distinct location in space

A wire is modeled as a series of segments, each having a distinct value of voltage across it



2016-E9B11: What is a disadvantage of decreasing the number of wire segments in an antenna model below the guideline of 10 segments per half-wavelength?

The computed feed point impedance may be incorrect

Ground conductivity will not be accurately modeled

The resulting design will favor radiation of harmonic energy

The antenna will become mechanically unstable



2016-E9B12: What is the far field of an antenna?

The region where the shape of the antenna pattern is independent of distance

The region of the ionosphere where radiated power is not refracted

The region where radiated power dissipates over a specified time period

The region where radiated field strengths are obstructed by objects of reflection



2016-E9B13: What does the abbreviation NEC stand for when applied to antenna modeling programs?

Numerical Electromagnetic Code

Next Element Comparison

National Electrical Code

Numeric Electrical Computation



2016-E9B14: What type of information can be obtained by submitting the details of a proposed new antenna to a modeling program?

All of these choices are correct

SWR vs frequency charts

Polar plots of the far field elevation and azimuth patterns

Antenna gain



2016-E9B15: What is the front-to-back ratio of the radiation pattern shown in Figure E9-2?

28 dB

15 dB

3 dB

24 dB



2016-E9B16: How many elevation lobes appear in the forward direction of the antenna radiation pattern shown in Figure E9-2?

4

3

1

7






2016-E9C: Wire and phased array antennas: rhombic antennas; effects of ground reflections; e-off angles; Practical wire antennas: Zepps, OCFD, loops

2016-E9C01: What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase?

A figure-8 oriented along the axis of the array

Cardioid

Omni-directional

A figure-8 broadside to the axis of the array



2016-E9C02: What is the radiation pattern of two 1/4 wavelength vertical antennas spaced 1/4 wavelength apart and fed 90 degrees out of phase?

Cardioid

A figure-8 end-fire along the axis of the array

A figure-8 broadside to the axis of the array

Omni-directional



2016-E9C03: What is the radiation pattern of two 1/4 wavelength vertical antennas spaced a 1/2 wavelength apart and fed in phase?

A Figure-8 broadside to the axis of the array

Omni-directional

Cardioid

A Figure-8 end-fire along the axis of the array



2016-E9C04: What happens to the radiation pattern of an unterminated long wire antenna as the wire length is increased?

The lobes align more in the direction of the wire

The lobes become more perpendicular to the wire

The vertical angle increases

The front-to-back ratio decreases



2016-E9C05: What is an OCFD antenna?

A dipole feed approximately 1/3 the way from one end with a 4:1 balun to provide multiband operation

A remotely tunable dipole antenna using orthogonally controlled frequency diversity

An eight band dipole antenna using octophase filters

A multiband dipole antenna using one-way circular polarization for frequency diversity



2016-E9C06: What is the effect of a terminating resistor on a rhombic antenna?

It changes the radiation pattern from bidirectional to unidirectional

It reflects the standing waves on the antenna elements back to the transmitter

It changes the radiation pattern from horizontal to vertical polarization

It decreases the ground loss



2016-E9C07: What is the approximate feed point impedance at the center of a two-wire folded dipole antenna?

300 ohms

72 ohms

50 ohms

450 ohms



2016-E9C08: What is a folded dipole antenna?

A dipole consisting of one wavelength of wire forming a very thin loop

A dipole one-quarter wavelength long

A type of ground-plane antenna

A dipole configured to provide forward gain



2016-E9C09: What is a G5RV antenna?

A multi-band dipole antenna fed with coax and a balun through a selected length of open wire transmission line

A multi-band trap antenna

A phased array antenna consisting of multiple loops

A wide band dipole using shorted coaxial cable for the radiating elements and fed with a 4:1 balun



2016-E9C10: Which of the following describes a Zepp antenna?

An end fed dipole antenna

A dipole constructed from zip cord

An omni-directional antenna commonly used for satellite communications

A vertical array capable of quickly changing the direction of maximum radiation by changing phasing lines



2016-E9C11: How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus rocky ground?

The low-angle radiation increases

The low-angle radiation decreases

The high-angle radiation increases

Both the high-angle and low-angle radiation decrease



2016-E9C12: Which of the following describes an extended double Zepp antenna?

A center fed 1.25 wavelength antenna (two 5/8 wave elements in phase)

A wideband vertical antenna constructed from precisely tapered aluminum tubing

A portable antenna erected using two push support poles

An end fed folded dipole antenna



2016-E9C13: What is the main effect of placing a vertical antenna over an imperfect ground?

It reduces low-angle radiation

It causes increased SWR

It changes the impedance angle of the matching network

It reduces losses in the radiating portion of the antenna



2016-E9C14: How does the performance of a horizontally polarized antenna mounted on the side of a hill compare with the same antenna mounted on flat ground?

The main lobe takeoff angle decreases in the downhill direction

The main lobe takeoff angle increases in the downhill direction

The horizontal beam width decreases in the downhill direction

The horizontal beam width increases in the uphill direction



2016-E9C15: How does the radiation pattern of a horizontally polarized 3-element beam antenna vary with its height above ground?

The main lobe takeoff angle decreases with increasing height

The main lobe takeoff angle increases with increasing height

The horizontal beam width increases with height

The horizontal beam width decreases with height






2016-E9D: Directional antennas: gain; Yagi Antennas; losses; SWR bandwidth; antenna efficiency; shortened and mobile antennas; RF Grounding

2016-E9D01: How does the gain of an ideal parabolic dish antenna change when the operating frequency is doubled?

Gain increases by 6 dB

Gain does not change

Gain is multiplied by 0.707

Gain increases by 3 dB



2016-E9D02: How can linearly polarized Yagi antennas be used to produce circular polarization?

Arrange two Yagis perpendicular to each other with the driven elements at the same point on the boom fed 90 degrees out of phase

Stack two Yagis fed 90 degrees out of phase to form an array with the respective elements in parallel planes

Stack two Yagis fed in phase to form an array with the respective elements in parallel planes

Arrange two Yagis collinear to each other with the driven elements fed 180 degrees out of phase



2016-E9D03: Where should a high Q loading coil be placed to minimize losses in a shortened vertical antenna?

Near the center of the vertical radiator

As low as possible on the vertical radiator

As close to the transmitter as possible

At a voltage node



2016-E9D04: Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance?

To minimize losses

To swamp out harmonics

To maximize losses

To minimize the Q



2016-E9D05: What is a disadvantage of using a multiband trapped antenna?

It might radiate harmonics

It radiates the harmonics and fundamental equally well

It is too sharply directional at lower frequencies

It must be neutralized



2016-E9D06: What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?

It is decreased

It is increased

No change occurs

It becomes flat



2016-E9D07: What is an advantage of using top loading in a shortened HF vertical antenna?

Improved radiation efficiency

Lower Q

Greater structural strength

Higher losses



2016-E9D08: What happens as the Q of an antenna increases?

SWR bandwidth decreases

SWR bandwidth increases

Gain is reduced

More common-mode current is present on the feed line



2016-E9D09: What is the function of a loading coil used as part of an HF mobile antenna?

To cancel capacitive reactance

To increase the SWR bandwidth

To lower the losses

To lower the Q



2016-E9D10: What happens to feed point impedance at the base of a fixed length HF mobile antenna as the frequency of operation is lowered?

The radiation resistance decreases and the capacitive reactance increases

The radiation resistance decreases and the capacitive reactance decreases

The radiation resistance increases and the capacitive reactance decreases

The radiation resistance increases and the capacitive reactance increases



2016-E9D11: Which of the following types of conductors would be best for minimizing losses in a station's RF ground system?

A wide flat copper strap

A resistive wire, such as spark plug wire

A cable with six or seven 18 gauge conductors in parallel

A single 12 gauge or 10 gauge stainless steel wire



2016-E9D12: Which of the following would provide the best RF ground for your station?

An electrically short connection to 3 or 4 interconnected ground rods driven into the Earth

A 50 ohm resistor connected to ground

An electrically short connection to a metal water pipe

An electrically short connection to 3 or 4 interconnected ground rods via a series RF choke



2016-E9D13: What usually occurs if a Yagi antenna is designed solely for maximum forward gain?

The front-to-back ratio decreases

The front-to-back ratio increases

The frequency response is widened over the whole frequency band

The SWR is reduced






2016-E9E: Matching: matching antennas to feed lines; phasing lines; power dividers

2016-E9E01: What system matches a higher impedance transmission line to a lower impedance antenna by connecting the line to the driven element in two places spaced a fraction of a wavelength each side of element center?

The delta matching system

The gamma matching system

The omega matching system

The stub matching system



2016-E9E02: What is the name of an antenna matching system that matches an unbalanced feed line to an antenna by feeding the driven element both at the center of the element and at a fraction of a wavelength to one side of center?

The gamma match

The delta match

The epsilon match

The stub match



2016-E9E03: What is the name of the matching system that uses a section of transmission line connected in parallel with the feed line at or near the feed point?

The stub match

The gamma match

The delta match

The omega match



2016-E9E04: What is the purpose of the series capacitor in a gamma-type antenna matching network?

To cancel the inductive reactance of the matching network

To provide DC isolation between the feed line and the antenna

To provide a rejection notch that prevents the radiation of harmonics

To transform the antenna impedance to a higher value



2016-E9E05: How must the driven element in a 3-element Yagi be tuned to use a hairpin matching system?

The driven element reactance must be capacitive

The driven element reactance must be inductive

The driven element resonance must be lower than the operating frequency

The driven element radiation resistance must be higher than the characteristic impedance of the transmission line



2016-E9E06: What is the equivalent lumped-constant network for a hairpin matching system of a 3-element Yagi?

A shunt inductor

Pi-network

Pi-L-network

A series capacitor



2016-E9E07: What term best describes the interactions at the load end of a mismatched transmission line?

Reflection coefficient

Characteristic impedance

Velocity factor

Dielectric constant



2016-E9E08: Which of the following measurements is characteristic of a mismatched transmission line?

An SWR greater than 1:1

An SWR less than 1:1

A reflection coefficient greater than 1

A dielectric constant greater than 1



2016-E9E09: Which of these matching systems is an effective method of connecting a 50 ohm coaxial cable feed line to a grounded tower so it can be used as a vertical antenna?

Gamma match

Double-bazooka match

Hairpin match

All of these choices are correct



2016-E9E10: Which of these choices is an effective way to match an antenna with a 100 ohm feed point impedance to a 50 ohm coaxial cable feed line?

Insert a 1/4-wavelength piece of 75 ohm coaxial cable transmission line in series between the antenna terminals and the 50 ohm feed cable

Connect a 1/4-wavelength open stub of 300 ohm twin-lead in parallel with the coaxial feed line where it connects to the antenna

Insert a 1/2 wavelength piece of 300 ohm twin-lead in series between the antenna terminals and the 50 ohm feed cable

Connect 1/2 wavelength shorted stub of 75 ohm cable in parallel with the 50 ohm cable where it attaches to the antenna



2016-E9E11: What is an effective way of matching a feed line to a VHF or UHF antenna when the impedances of both the antenna and feed line are unknown?

Use the universal stub matching technique

Use a 50 ohm 1:1 balun between the antenna and feed line

Connect a series-resonant LC network across the antenna feed terminals

Connect a parallel-resonant LC network across the antenna feed terminals



2016-E9E12: What is the primary purpose of a phasing line when used with an antenna having multiple driven elements?

It ensures that each driven element operates in concert with the others to create the desired antenna pattern

It prevents reflected power from traveling back down the feed line and causing harmonic radiation from the transmitter

It allows single-band antennas to operate on other bands

It makes sure the antenna has a low-angle radiation pattern



2016-E9E13: What is a use for a Wilkinson divider?

It is used to divide power equally between two 50 ohm loads while maintaining 50 ohm input impedance

It divides the operating frequency of a transmitter signal so it can be used on a lower frequency band

It is used to feed high-impedance antennas from a low-impedance source

It is used to feed low-impedance loads from a high-impedance source






2016-E9F: Transmission lines: characteristics of open and shorted feed lines; 1/8 wavelength; 1/4 wavelength; 1/2 wavelength; feed lines: coax versus open-wire; velocity factor; electrical length; coaxial cable dielectrics; velocity factor

2016-E9F01: What is the velocity factor of a transmission line?

The velocity of the wave in the transmission line divided by the velocity of light in a vacuum

The ratio of the characteristic impedance of the line to the terminating impedance

The index of shielding for coaxial cable

The velocity of the wave in the transmission line multiplied by the velocity of light in a vacuum



2016-E9F02: Which of the following determines the velocity factor of a transmission line?

Dielectric materials used in the line

The termination impedance

The line length

The center conductor resistivity



2016-E9F03: Why is the physical length of a coaxial cable transmission line shorter than its electrical length?

Electrical signals move more slowly in a coaxial cable than in air

Skin effect is less pronounced in the coaxial cable

The characteristic impedance is higher in a parallel feed line

The surge impedance is higher in a parallel feed line



2016-E9F04: What is the typical velocity factor for a coaxial cable with solid polyethylene dielectric?

0.66

2.70

0.30

0.10



2016-E9F05: What is the approximate physical length of a solid polyethylene dielectric coaxial transmission line that is electrically one-quarter wavelength long at 14.1 MHz?

3.5 meters

20 meters

2.3 meters

0.2 meters



2016-E9F06: What is the approximate physical length of an air-insulated, parallel conductor transmission line that is electrically one-half wavelength long at 14.10 MHz?

10 meters

15 meters

20 meters

71 meters



2016-E9F07: How does ladder line compare to small-diameter coaxial cable such as RG-58 at 50 MHz?

Lower loss

Higher SWR

Smaller reflection coefficient

Lower velocity factor



2016-E9F08: What is the term for the ratio of the actual speed at which a signal travels through a transmission line to the speed of light in a vacuum?

Velocity factor

Characteristic impedance

Surge impedance

Standing wave ratio



2016-E9F09: What is the approximate physical length of a solid polyethylene dielectric coaxial transmission line that is electrically one-quarter wavelength long at 7.2 MHz?

6.9 meters

10 meters

24 meters

50 meters



2016-E9F10: What impedance does a 1/8 wavelength transmission line present to a generator when the line is shorted at the far end?

An inductive reactance

A capacitive reactance

The same as the characteristic impedance of the line

The same as the input impedance to the final generator stage



2016-E9F11: What impedance does a 1/8 wavelength transmission line present to a generator when the line is open at the far end?

A capacitive reactance

The same as the characteristic impedance of the line

An inductive reactance

The same as the input impedance of the final generator stage



2016-E9F12: What impedance does a 1/4 wavelength transmission line present to a generator when the line is open at the far end?

Very low impedance

The same as the characteristic impedance of the line

The same as the input impedance to the generator

Very high impedance



2016-E9F13: What impedance does a 1/4 wavelength transmission line present to a generator when the line is shorted at the far end?

Very high impedance

Very low impedance

The same as the characteristic impedance of the transmission line

The same as the generator output impedance



2016-E9F14: What impedance does a 1/2 wavelength transmission line present to a generator when the line is shorted at the far end?

Very low impedance

Very high impedance

The same as the characteristic impedance of the line

The same as the output impedance of the generator



2016-E9F15: What impedance does a 1/2 wavelength transmission line present to a generator when the line is open at the far end?

Very high impedance

Very low impedance

The same as the characteristic impedance of the line

The same as the output impedance of the generator



2016-E9F16: Which of the following is a significant difference between foam dielectric coaxial cable and solid dielectric cable, assuming all other parameters are the same?

All of these choices are correct

Foam dielectric has lower safe operating voltage limits

Foam dielectric has lower loss per unit of length

Foam dielectric has higher velocity factor






2016-E9G: The Smith chart

2016-E9G01: Which of the following can be calculated using a Smith chart?

Impedance along transmission lines

Radiation resistance

Antenna radiation pattern

Radio propagation



2016-E9G02: What type of coordinate system is used in a Smith chart?

Resistance circles and reactance arcs

Voltage circles and current arcs

Voltage lines and current chords

Resistance lines and reactance chords



2016-E9G03: Which of the following is often determined using a Smith chart?

Impedance and SWR values in transmission lines

Beam headings and radiation patterns

Satellite azimuth and elevation bearings

Trigonometric functions



2016-E9G04: What are the two families of circles and arcs that make up a Smith chart?

Resistance and reactance

Resistance and voltage

Reactance and voltage

Voltage and impedance



2016-E9G05: What type of chart is shown in Figure E9-3?

Smith chart

Free space radiation directivity chart

Elevation angle radiation pattern chart

Azimuth angle radiation pattern chart



2016-E9G06: On the Smith chart shown in Figure E9-3, what is the name for the large outer circle on which the reactance arcs terminate?

Reactance axis

Prime axis

Impedance axis

Polar axis



2016-E9G07: On the Smith chart shown in Figure E9-3, what is the only straight line shown?

The resistance axis

The reactance axis

The current axis

The voltage axis



2016-E9G08: What is the process of normalization with regard to a Smith chart?

Reassigning impedance values with regard to the prime center

Reassigning resistance values with regard to the reactance axis

Reassigning reactance values with regard to the resistance axis

Reassigning prime center with regard to the reactance axis



2016-E9G09: What third family of circles is often added to a Smith chart during the process of solving problems?

Standing wave ratio circles

Antenna-length circles

Coaxial-length circles

Radiation-pattern circles



2016-E9G10: What do the arcs on a Smith chart represent?

Points with constant reactance

Frequency

SWR

Points with constant resistance



2016-E9G11: How are the wavelength scales on a Smith chart calibrated?

In fractions of transmission line electrical wavelength

In fractions of transmission line electrical frequency

In fractions of antenna electrical wavelength

In fractions of antenna electrical frequency






2016-E9H: Receiving Antennas: radio direction finding antennas; Beverage Antennas; specialized receiving antennas; longwire receiving antennas

2016-E9H01: When constructing a Beverage antenna, which of the following factors should be included in the design to achieve good performance at the desired frequency?

It should be one or more wavelengths long

Its overall length must not exceed 1/4 wavelength

It must be mounted more than 1 wavelength above ground

It should be configured as a four-sided loop



2016-E9H02: Which is generally true for low band (160 meter and 80 meter) receiving antennas?

Atmospheric noise is so high that gain over a dipole is not important

They must be erected at least 1/2 wavelength above the ground to attain good directivity

Low loss coax transmission line is essential for good performance

All of these choices are correct



2016-E9H04: What is an advantage of using a shielded loop antenna for direction finding?

It is electro statically balanced against ground, giving better nulls

It automatically cancels ignition noise in mobile installations

It eliminates tracking errors caused by strong out-of-band signals

It allows stations to communicate without giving away their position



2016-E9H05: What is the main drawback of a wire-loop antenna for direction finding?

It has a bidirectional pattern

It is non-rotatable

It receives equally well in all directions

It is practical for use only on VHF bands



2016-E9H06: What is the triangulation method of direction finding?

Antenna headings from several different receiving locations are used to locate the signal source

The geometric angles of sky waves from the source are used to determine its position

A fixed receiving station plots three headings to the signal source

A fixed receiving station uses three different antennas to plot the location of the signal source



2016-E9H07: Why is it advisable to use an RF attenuator on a receiver being used for direction finding?

It prevents receiver overload which could make it difficult to determine peaks or nulls

It narrows the bandwidth of the received signal to improve signal to noise ratio

It compensates for the effects of an isotropic antenna, thereby improving directivity

It reduces loss of received signals caused by antenna pattern nulls, thereby increasing sensitivity



2016-E9H08: What is the function of a sense antenna?

It modifies the pattern of a DF antenna array to provide a null in one direction

It increases the sensitivity of a DF antenna array

It allows DF antennas to receive signals at different vertical angles

It provides diversity reception that cancels multipath signals



2016-E9H09: Which of the following describes the construction of a receiving loop antenna?

One or more turns of wire wound in the shape of a large open coil

A large circularly polarized antenna

A small coil of wire tightly wound around a toroidal ferrite core

A vertical antenna coupled to a feed line through an inductive loop of wire



2016-E9H10: How can the output voltage of a multiple turn receiving loop antenna be increased?

By increasing either the number of wire turns in the loop or the area of the loop structure or both

By reducing the permeability of the loop shield

By increasing the number of wire turns in the loop and reducing the area of the loop structure

By winding adjacent turns in opposing directions



2016-E9H11: What characteristic of a cardioid pattern antenna is useful for direction finding?

A very sharp single null

A very sharp peak

Broad band response

High-radiation angle





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