Extra Class License Exam Questions

Subelement E9

Antennas and Transmission Lines

Groups

E9A - Basic Antenna parameters: radiation resistance, gain, beamwidth, efficiency, beamwidth; effective radiated power, polarization
E9B - Antenna patterns: E and H plane patterns; gain as a function of pattern; antenna design
E9C - Wire and phased array antennas: rhombic antennas; effects of ground reflections; e-off angles; Practical wire antennas: Zepps, OCFD, loops
E9D - Directional antennas: gain; Yagi Antennas; losses; SWR bandwidth; antenna efficiency; shortened and mobile antennas; RF Grounding
E9E - Matching: matching antennas to feed lines; phasing lines; power dividers
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
E9G - The Smith chart
E9H - Receiving Antennas: radio direction finding antennas; Beverage Antennas; specialized receiving antennas; longwire receiving antennas

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

E9A01 What describes an isotropic antenna?

A grounded antenna used to measure earth conductivity
A horizontally polarized antenna used to compare Yagi antennas
A theoretical antenna used as a reference for antenna gain
A spacecraft antenna used to direct signals toward the earth

E9A02 What antenna has no gain in any direction?

Quarter-wave vertical
Yagi
Half-wave dipole
Isotropic antenna

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

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

Transmission-line length
Antenna height, conductor length/diameter ratio and location of nearby conductive objects
The settings of an antenna tuner at the transmitter
Sunspot activity and time of day

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

Radiation resistance plus space impedance
Radiation resistance plus transmission resistance
Transmission-line resistance plus radiation resistance
Radiation resistance plus ohmic resistance

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

It increases geometrically
It increases arithmetically
It is essentially unaffected
It decreases

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

E9A08 What is meant by antenna bandwidth?

Antenna length divided by the number of elements
The frequency range over which an antenna satisfies a performance requirement
The angle between the half-power radiation points
The angle formed between two imaginary lines drawn through the element ends

E9A09 How is antenna efficiency calculated?

(radiation resistance / transmission resistance) x 100 per cent
(radiation resistance / total resistance) x 100 per cent
(total resistance / radiation resistance) x 100 per cent
(effective radiated power / transmitter output) x 100 percent

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

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

The standing wave ratio
Distance from the transmitter
Soil conductivity
Take-off angle

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

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?

6.17 dB
9.85 dB
12.5 dB
14.15 dB

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

The combined losses of the antenna elements and feed line
The specific impedance of the antenna
The value of a resistance that would dissipate the same amount of power as that radiated from an antenna
The resistance in the atmosphere that an antenna must overcome to be able to radiate a signal

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?

1977 watts
78.7 watts
420 watts
286 watts

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

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?

159 watts
252 watts
632 watts
63.2 watts

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

Power factor
Half-power bandwidth
Effective radiated power
Apparent power

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

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

75 degrees
50 degrees
25 degrees
30 degrees

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

36 dB
18 dB
24 dB
14 dB

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

12 dB
14 dB
18 dB
24 dB

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

Feed point impedance may become negative
The E-field and H-field patterns may reverse
Element spacing limits could be exceeded
The gain may change depending on frequency

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

Elevation
Azimuth
Radiation resistance
Polarization

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

45 degrees
75 degrees
7.5 degrees
25 degrees

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?

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

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

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

Graphical analysis
Method of Moments
Mutual impedance analysis
Calculus differentiation with respect to physical properties

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

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?

Ground conductivity will not be accurately modeled
The resulting design will favor radiation of harmonic energy
The computed feed point impedance may be incorrect
The antenna will become mechanically unstable

E9B12 What is the far field of an antenna?

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

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

Next Element Comparison
Numerical Electromagnetic Code
National Electrical Code
Numeric Electrical Computation

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

SWR vs frequency charts
Polar plots of the far field elevation and azimuth patterns
Antenna gain
All of these choices are correct

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

15 dB
28 dB
3 dB
24 dB

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

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

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?

Cardioid
Omni-directional
A figure-8 broadside to the axis of the array
A figure-8 oriented along the axis of the array

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

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

Omni-directional
Cardioid
A Figure-8 broadside to the axis of the array
A Figure-8 end-fire along the axis of the array

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

The lobes become more perpendicular to the wire
The lobes align more in the direction of the wire
The vertical angle increases
The front-to-back ratio decreases

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

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

It reflects the standing waves on the antenna elements back to the transmitter
It changes the radiation pattern from bidirectional to unidirectional
It changes the radiation pattern from horizontal to vertical polarization
It decreases the ground loss

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

E9C08 What is a folded dipole antenna?

A dipole one-quarter wavelength long
A type of ground-plane antenna
A dipole consisting of one wavelength of wire forming a very thin loop
A dipole configured to provide forward gain

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

E9C10 Which of the following describes a Zepp antenna?

A dipole constructed from zip cord
An end fed dipole antenna
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

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 decreases
The high-angle radiation increases
Both the high-angle and low-angle radiation decrease
The low-angle radiation increases

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

A wideband vertical antenna constructed from precisely tapered aluminum tubing
A portable antenna erected using two push support poles
A center fed 1.25 wavelength antenna (two 5/8 wave elements in phase)
An end fed folded dipole antenna

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

It causes increased SWR
It changes the impedance angle of the matching network
It reduces low-angle radiation
It reduces losses in the radiating portion of the antenna

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 increases in the downhill direction
The main lobe takeoff angle decreases in the downhill direction
The horizontal beam width decreases in the downhill direction
The horizontal beam width increases in the uphill direction

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 increases with increasing height
The main lobe takeoff angle decreases with increasing height
The horizontal beam width increases with height
The horizontal beam width decreases with height

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

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

Gain does not change
Gain is multiplied by 0.707
Gain increases by 6 dB
Gain increases by 3 dB

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

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 perpendicular to each other with the driven elements at the same point on the boom fed 90 degrees out of phase
Arrange two Yagis collinear to each other with the driven elements fed 180 degrees out of phase

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

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

To swamp out harmonics
To maximize losses
To minimize losses
To minimize the Q

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

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

It is increased
It is decreased
No change occurs
It becomes flat

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

Lower Q
Greater structural strength
Higher losses
Improved radiation efficiency

E9D08 What happens as the Q of an antenna increases?

SWR bandwidth increases
SWR bandwidth decreases
Gain is reduced
More common-mode current is present on the feed line

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

To increase the SWR bandwidth
To lower the losses
To lower the Q
To cancel capacitive reactance

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 decreases
The radiation resistance decreases and the capacitive reactance increases
The radiation resistance increases and the capacitive reactance decreases
The radiation resistance increases and the capacitive reactance increases

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

A resistive wire, such as spark plug wire
A wide flat copper strap
A cable with six or seven 18 gauge conductors in parallel
A single 12 gauge or 10 gauge stainless steel wire

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

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

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

The front-to-back ratio increases
The front-to-back ratio decreases
The frequency response is widened over the whole frequency band
The SWR is reduced

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

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 gamma matching system
The delta matching system
The omega matching system
The stub matching system

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

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 gamma match
The delta match
The omega match
The stub match

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

To provide DC isolation between the feed line and the antenna
To cancel the inductive reactance of the matching network
To provide a rejection notch that prevents the radiation of harmonics
To transform the antenna impedance to a higher value

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

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

Pi-network
Pi-L-network
A shunt inductor
A series capacitor

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

Characteristic impedance
Reflection coefficient
Velocity factor
Dielectric constant

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

An SWR less than 1:1
A reflection coefficient greater than 1
A dielectric constant greater than 1
An SWR greater than 1:1

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?

Double-bazooka match
Hairpin match
Gamma match
All of these choices are correct

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?

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

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 a 50 ohm 1:1 balun between the antenna and feed line
Use the universal stub matching technique
Connect a series-resonant LC network across the antenna feed terminals
Connect a parallel-resonant LC network across the antenna feed terminals

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

E9E13 What is a use for a Wilkinson divider?

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 divide power equally between two 50 ohm loads while maintaining 50 ohm input impedance
It is used to feed low-impedance loads from a high-impedance source

Group 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

E9F01 What is the velocity factor of a transmission line?

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

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

The termination impedance
The line length
Dielectric materials used in the line
The center conductor resistivity

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

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

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

2.70
0.66
0.30
0.10

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?

20 meters
2.3 meters
3.5 meters
0.2 meters

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?

15 meters
20 meters
10 meters
71 meters

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

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

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?

10 meters
6.9 meters
24 meters
50 meters

E9F10 What impedance does a 1/8 wavelength transmission line present to a generator when the line is shorted 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 to the final generator stage

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

The same as the characteristic impedance of the line
An inductive reactance
A capacitive reactance
The same as the input impedance of the final generator stage

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

The same as the characteristic impedance of the line
The same as the input impedance to the generator
Very high impedance
Very low impedance

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

E9F14 What impedance does a 1/2 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 line
The same as the output impedance of the generator

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

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?

Foam dielectric has lower safe operating voltage limits
Foam dielectric has lower loss per unit of length
Foam dielectric has higher velocity factor
All of these choices are correct

Group E9G The Smith chart

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

Impedance along transmission lines
Radiation resistance
Antenna radiation pattern
Radio propagation

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

Voltage circles and current arcs
Resistance circles and reactance arcs
Voltage lines and current chords
Resistance lines and reactance chords

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

Beam headings and radiation patterns
Satellite azimuth and elevation bearings
Impedance and SWR values in transmission lines
Trigonometric functions

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

Resistance and voltage
Reactance and voltage
Resistance and reactance
Voltage and impedance

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

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?

Prime axis
Reactance axis
Impedance axis
Polar axis

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

The reactance axis
The current axis
The voltage axis
The resistance axis

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

Reassigning resistance values with regard to the reactance axis
Reassigning reactance values with regard to the resistance axis
Reassigning impedance values with regard to the prime center
Reassigning prime center with regard to the reactance axis

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

E9G10 What do the arcs on a Smith chart represent?

Frequency
SWR
Points with constant resistance
Points with constant reactance

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

In fractions of transmission line electrical frequency
In fractions of transmission line electrical wavelength
In fractions of antenna electrical wavelength
In fractions of antenna electrical frequency

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

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?

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
It should be one or more wavelengths long

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

E9H03 This question was deleted by the Question Pool Committee on February 1, 2016

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

It automatically cancels ignition noise in mobile installations
It is electro statically balanced against ground, giving better nulls
It eliminates tracking errors caused by strong out-of-band signals
It allows stations to communicate without giving away their position

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

E9H06 What is the triangulation method of direction finding?

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
Antenna headings from several different receiving locations are used to locate the signal source
A fixed receiving station uses three different antennas to plot the location of the signal source

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

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

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

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

A large circularly polarized antenna
A small coil of wire tightly wound around a toroidal ferrite core
One or more turns of wire wound in the shape of a large open coil
A vertical antenna coupled to a feed line through an inductive loop of wire

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

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

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

A very sharp peak
A very sharp single null
Broad band response
High-radiation angle