Amateur Extra Class Exam Question Pool- Subelement E-9

Subelement E-1           Subelement E-2          Subelement E-3          Subbelement E-4          Subelement E-5
Subelement E-6           Subelement E-7          Subelement E-8          Subbelement E-9          Subelement E-0

SUBELEMENT E9 - ANTENNAS AND TRANSMISSION LINES [8 Exam Questions - 8 Groups]

 

 

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

 

 

E9A01 

What describes an isotropic antenna?

A. A grounded antenna used to measure earth conductivity

B. A horizontally polarized antenna used to compare Yagi antennas

C. A theoretical antenna used as a reference for antenna gain

D. A spacecraft antenna used to direct signals toward the earth

~~

 

E9A02

What antenna has no gain in any direction?

A. Quarter-wave vertical

B. Yagi

C. Half-wave dipole

D. Isotropic antenna

~~

 

E9A03 

Why would one need to know the feed point impedance of an antenna?

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

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

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

D. 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?

A. Transmission-line length

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

C. The settings of an antenna tuner at the transmitter

D. Sunspot activity and time of day

~~

 

E9A05 

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

A. Radiation resistance plus space impedance

B. Radiation resistance plus transmission resistance

C. Transmission-line resistance plus radiation resistance

D. Radiation resistance plus ohmic resistance

~~

 

E9A06 

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

A. It increases geometrically

B. It increases arithmetically

C. It is essentially unaffected

D. It decreases

~~

 

E9A07 

What is meant by antenna gain?

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

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

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

D. The final amplifier gain minus the transmission line losses

~~

 

E9A08 

What is meant by antenna bandwidth?

A. Antenna length divided by the number of elements

B. The frequency range over which an antenna satisfies a performance requirement

C. The angle between the half-power radiation points

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

~~

 

E9A09 

How is antenna efficiency calculated?

A. (radiation resistance / transmission resistance) x 100 per cent

B. (radiation resistance / total resistance) x 100 per cent

C. (total resistance / radiation resistance) x 100 per cent

D. (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?

A. Install a good radial system

B. Isolate the coax shield from ground

C. Shorten the radiating element

D. 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?

A. The standing wave ratio

B. Distance from the transmitter

C. Soil conductivity

D. 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?

A. 3.85 dB

B. 6.0 dB

C. 8.15 dB

D. 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?

A. 6.17 dB

B. 9.85 dB

C. 12.5 dB

D. 14.15 dB

~~

 

E9A14 

What is meant by the radiation resistance of an antenna?

A. The combined losses of the antenna elements and feed line

B. The specific impedance of the antenna

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

D. 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?

A. 1977 watts

B. 78.7 watts

C. 420 watts

D. 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?

A. 317 watts

B. 2000 watts

C. 126 watts

D. 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?

A. 159 watts

B. 252 watts

C. 632 watts

D. 63.2 watts

~~

 

E9A18 

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

A. Power factor

B. Half-power bandwidth

C. Effective radiated power

D. Apparent power

~~

 

 

 

 

 

 

 

 

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?

A. 75 degrees

B. 50 degrees

C. 25 degrees

D. 30 degrees

~~

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E9B02 

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

A. 36 dB

B. 18 dB

C. 24 dB

D. 14 dB

~~

 

E9B03 

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

A. 12 dB

B. 14 dB

C. 18 dB

D. 24 dB

~~

 

E9B04 

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

A. Feed point impedance may become negative

B. The E-field and H-field patterns may reverse

C. Element spacing limits could be exceeded

D. The gain may change depending on frequency

~~

 

E9B05 

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

A. Elevation

B. Azimuth

C. Radiation resistance

D. Polarization

~~

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E9B06 

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

A. 45 degrees

B. 75 degrees

C. 7.5 degrees

D. 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?

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

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

C. They are the same

D. 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?

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

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

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

D. 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?

A. Graphical analysis

B. Method of Moments

C. Mutual impedance analysis

D. Calculus differentiation with respect to physical properties

~~

 

E9B10 

What is the principle of a Method of Moments analysis?

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

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

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

D. 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?

A. Ground conductivity will not be accurately modeled

B. The resulting design will favor radiation of harmonic energy

C. The computed feed point impedance may be incorrect

D. The antenna will become mechanically unstable

~~

 

E9B12 

What is the far field of an antenna?

A. The region of the ionosphere where radiated power is not refracted

B. The region where radiated power dissipates over a specified time period

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

D. 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?

A. Next Element Comparison

B. Numerical Electromagnetic Code

C. National Electrical Code

D. Numeric Electrical Computation

~~

 

E9B14 

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

A. SWR vs frequency charts

B. Polar plots of the far field elevation and azimuth patterns

C. Antenna gain

D. All of these choices are correct

~~

 

E9B15 

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

A. 15 dB

B. 28 dB

C. 3 dB

D. 24 dB

~~

 

E9B16 

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

A. 4

B. 3

C. 1

D. 7

~~

 

 

 

 

 

 

 

 

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?

A. Cardioid

B. Omni-directional

C. A figure-8 broadside to the axis of the array

D. 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?

A. Cardioid

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

C. A figure-8 broadside to the axis of the array

D. 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?

A. Omni-directional

B. Cardioid

C. A Figure-8 broadside to the axis of the array

D. 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?

A. The lobes become more perpendicular to the wire

B. The lobes align more in the direction of the wire

C. The vertical angle increases

D. The front-to-back ratio decreases

~~

 

E9C05 

What is an OCFD antenna?

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

B. A remotely tunable dipole antenna using orthogonally controlled frequency diversity

C. An eight band dipole antenna using octophase filters

D. 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?

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

B. It changes the radiation pattern from bidirectional to unidirectional

C. It changes the radiation pattern from horizontal to vertical polarization

D. It decreases the ground loss

~~

 

E9C07 

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

A. 300 ohms

B. 72 ohms

C. 50 ohms

D. 450 ohms

~~

 

E9C08 

What is a folded dipole antenna?

A. A dipole one-quarter wavelength long

B. A type of ground-plane antenna

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

D. A dipole configured to provide forward gain

~~

 

E9C09 

What is a G5RV antenna?

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

B. A multi-band trap antenna

C. A phased array antenna consisting of multiple loops

D. 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. A dipole constructed from zip cord

B. An end fed dipole antenna

C. An omni-directional antenna commonly used for satellite communications

D. 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?

A. The low-angle radiation decreases

B. The high-angle radiation increases

C. Both the high-angle and low-angle radiation decrease

D. The low-angle radiation increases

~~

 

E9C12 (C)

Which of the following describes an extended double Zepp antenna?

A. A wideband vertical antenna constructed from precisely tapered aluminum tubing

B. A portable antenna erected using two push support poles

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

D. An end fed folded dipole antenna

~~

 

E9C13 (C)

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

A. It causes increased SWR

B. It changes the impedance angle of the matching network

C. It reduces low-angle radiation

D. 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?

A. The main lobe takeoff angle increases in the downhill direction

B. The main lobe takeoff angle decreases in the downhill direction

C. The horizontal beam width decreases in the downhill direction

D. 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?

A. The main lobe takeoff angle increases with increasing height

B. The main lobe takeoff angle decreases with increasing height

C. The horizontal beam width increases with height

D. The horizontal beam width decreases with height

~~

 

 

 

 

 

 

 

 

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?

A. Gain does not change

B. Gain is multiplied by 0.707

C. Gain increases by 6 dB

D. Gain increases by 3 dB

~~

 

E9D02 

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

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

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

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

D. 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?

A. Near the center of the vertical radiator

B. As low as possible on the vertical radiator

C. As close to the transmitter as possible

D. At a voltage node

~~

 

E9D04 

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

A. To swamp out harmonics

B. To maximize losses

C. To minimize losses

D. To minimize the Q

~~

 

E9D05 

What is a disadvantage of using a multiband trapped antenna?

A. It might radiate harmonics

B. It radiates the harmonics and fundamental equally well

C. It is too sharply directional at lower frequencies

D. It must be neutralized

~~

 

E9D06 

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

A. It is increased

B. It is decreased

C. No change occurs

D. It becomes flat

~~

 

E9D07 

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

A. Lower Q

B. Greater structural strength

C. Higher losses

D. Improved radiation efficiency

~~

 

E9D08 

What happens as the Q of an antenna increases?

A. SWR bandwidth increases

B. SWR bandwidth decreases

C. Gain is reduced

D. 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?

A. To increase the SWR bandwidth

B. To lower the losses

C. To lower the Q

D. 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?

A. The radiation resistance decreases and the capacitive reactance decreases

B. The radiation resistance decreases and the capacitive reactance increases

C. The radiation resistance increases and the capacitive reactance decreases

D. 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. A resistive wire, such as spark plug wire

B. A wide flat copper strap

C. A cable with six or seven 18 gauge conductors in parallel

D. 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. A 50 ohm resistor connected to ground

B. An electrically short connection to a metal water pipe

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

D. 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?

A. The front-to-back ratio increases

B. The front-to-back ratio decreases

C. The frequency response is widened over the whole frequency band

D. The SWR is reduced

~~

 

 

 

 

 

 

 

 

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?

A. The gamma matching system

B. The delta matching system

C. The omega matching system

D. 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?

A. The gamma match

B. The delta match

C. The epsilon match

D. 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?

A. The gamma match

B. The delta match

C. The omega match

D. The stub match

~~

 

E9E04 

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

A. To provide DC isolation between the feed line and the antenna

B. To cancel the inductive reactance of the matching network

C. To provide a rejection notch that prevents the radiation of harmonics

D. 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?

A. The driven element reactance must be capacitive

B. The driven element reactance must be inductive

C. The driven element resonance must be lower than the operating frequency

D. 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?

A. Pi-network

B. Pi-L-network

C. A shunt inductor

D. A series capacitor

~~

 

E9E07 

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

A. Characteristic impedance

B. Reflection coefficient

C. Velocity factor

D. Dielectric constant

~~

 

E9E08 

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

A. An SWR less than 1:1

B. A reflection coefficient greater than 1

C. A dielectric constant greater than 1

D. 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?

A. Double-bazooka match

B. Hairpin match

C. Gamma match

D. 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?

A. 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

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

C. 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

D. 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?

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

B. Use the universal stub matching technique

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

D. 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?

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

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

C. It allows single-band antennas to operate on other bands

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

~~

 

E9E13 

What is a use for a Wilkinson divider?

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

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

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

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

~~

 

 

 

 

 

 

 

 

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?

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

B. The index of shielding for coaxial cable

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

D. 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?

A. The termination impedance

B. The line length

C. Dielectric materials used in the line

D. The center conductor resistivity

~~

 

E9F03 

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

A. Skin effect is less pronounced in the coaxial cable

B. The characteristic impedance is higher in a parallel feed line

C. The surge impedance is higher in a parallel feed line

D. 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?

A. 2.70

B. 0.66

C. 0.30

D. 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?

A. 20 meters

B. 2.3 meters

C. 3.5 meters

D. 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?

A. 15 meters

B. 20 meters

C. 10 meters

D. 71 meters

~~

 

E9F07 

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

A. Lower loss

B. Higher SWR

C. Smaller reflection coefficient

D. 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?

A. Velocity factor

B. Characteristic impedance

C. Surge impedance

D. 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?

A. 10 meters

B. 6.9 meters

C. 24 meters

D. 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. A capacitive reactance

B. The same as the characteristic impedance of the line

C. An inductive reactance

D. 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?

A. The same as the characteristic impedance of the line

B. An inductive reactance

C. A capacitive reactance

D. 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?

A. The same as the characteristic impedance of the line

B. The same as the input impedance to the generator

C. Very high impedance

D. 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?

A. Very high impedance

B. Very low impedance

C. The same as the characteristic impedance of the transmission line

D. 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?

A. Very high impedance

B. Very low impedance

C. The same as the characteristic impedance of the line

D. 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?

A. Very high impedance

B. Very low impedance

C. The same as the characteristic impedance of the line

D. 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?

A. Foam dielectric has lower safe operating voltage limits

B. Foam dielectric has lower loss per unit of length

C. Foam dielectric has higher velocity factor

D. All of these choices are correct

~~

 

 

 

 

 

 

 

 

E9G -  The Smith chart

 

 

E9G01 

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

A. Impedance along transmission lines

B. Radiation resistance

C. Antenna radiation pattern

D. Radio propagation

~~

 

E9G02 

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

A. Voltage circles and current arcs

B. Resistance circles and reactance arcs

C. Voltage lines and current chords

D. Resistance lines and reactance chords

~~

 

E9G03 

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

A. Beam headings and radiation patterns

B. Satellite azimuth and elevation bearings

C. Impedance and SWR values in transmission lines

D. Trigonometric functions

~~

 

E9G04 

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

A. Resistance and voltage

B. Reactance and voltage

C. Resistance and reactance

D. Voltage and impedance

~~

 

E9G05 

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

A. Smith chart

B. Free space radiation directivity chart

C. Elevation angle radiation pattern chart

D. 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?

A. Prime axis

B. Reactance axis

C. Impedance axis

D. Polar axis

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E9G07 

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

A. The reactance axis

B. The current axis

C. The voltage axis

D. The resistance axis

~~

 

E9G08 

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

A. Reassigning resistance values with regard to the reactance axis

B. Reassigning reactance values with regard to the resistance axis

C. Reassigning impedance values with regard to the prime center

D. 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?

A. Standing wave ratio circles

B. Antenna-length circles

C. Coaxial-length circles

D. Radiation-pattern circles

~~

 

E9G10 

What do the arcs on a Smith chart represent?

A. Frequency

B. SWR

C. Points with constant resistance

D. Points with constant reactance

~~

 

E9G11 

How are the wavelength scales on a Smith chart calibrated?

A. In fractions of transmission line electrical frequency

B. In fractions of transmission line electrical wavelength

C. In fractions of antenna electrical wavelength

D. In fractions of antenna electrical frequency

~~

 

 

 

 

 

 

 

 

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?

A. Its overall length must not exceed 1/4 wavelength

B. It must be mounted more than 1 wavelength above ground

C. It should be configured as a four-sided loop

D. It should be one or more wavelengths long

~~

 

E9H02 

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

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

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

C. Low loss coax transmission line is essential for good performance

D. All of these choices are correct

~~

 

E9H03     DELETED February 1, 2016

~~

 

E9H04 

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

A. It automatically cancels ignition noise in mobile installations

B. It is electro statically balanced against ground, giving better nulls

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

D. It allows stations to communicate without giving away their position

~~

 

E9H05 

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

A. It has a bidirectional pattern

B. It is non-rotatable

C. It receives equally well in all directions

D. It is practical for use only on VHF bands

~~

 

E9H06 

What is the triangulation method of direction finding?

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

B. A fixed receiving station plots three headings to the signal source

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

D. 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?

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

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

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

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

~~

 

E9H08 

What is the function of a sense antenna?

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

B. It increases the sensitivity of a DF antenna array

C. It allows DF antennas to receive signals at different vertical angles

D. It provides diversity reception that cancels multipath signals

~~

 

E9H09 

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

A. A large circularly polarized antenna

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

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

D. 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?

A. By reducing the permeability of the loop shield

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

C. By winding adjacent turns in opposing directions

D. 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. A very sharp peak

B. A very sharp single null

C. Broad band response

D. High-radiation angle

~~

Subelement E-1           Subelement E-2          Subelement E-3          Subbelement E-4          Subelement E-5
Subelement E-6           Subelement E-7          Subelement E-8          Subbelement E-9          Subelement E-0
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