Transcript Amateur Extra Licensing Class
Amateur Extra Licensing Class Feedlines & Safety
Lake Area Radio Klub Spring 2012
Amateur Radio Extra Class Element 4 Course Presentation
ELEMENT 4 Groupings
• • • • • • • •
Rules & Regs Skywaves & Contesting Outer Space Comms Visuals & Video Modes Digital Excitement with Computers & Radios Modulate Your Transmitters Amps & Power Supplies Receivers with Great Filters
Amateur Radio Extra Class Element 4 Course Presentation
ELEMENT 4 Groupings
• • •
Oscillate & Synthesize This!
Circuits & Resonance for All!
Components in Your New Rig
• •
Logically Speaking of Counters Optos & OpAmps Plus Solar
•
Test Gear, Testing, Testing 1,2,3
•
Antennas
• Feedlines & Safety
Amateur Radio Extra Class
Feedlines & Safety
•
E9E01…
The delta matching system matches a high-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.
Amateur Radio Extra Class
Feedlines & Safety
•
E9E02…
The gamma match is a 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.
•
E9E03…
The stub match uses a section of transmission line shorted at the end and connected to the feed line near the antenna.
Amateur Radio Extra Class
Feedlines & Safety
Impedance Matching Stubs (1) Since a short at end makes the diagram look like a long wire, this indicates the impedance is an inductive reactance.
(2) Since an open at end makes the diagram look like two parallel plates, this indicates the impedance is a capacitive reactance.
Amateur Radio Extra Class
Feedlines & Safety
Impedance Matching Stubs (1) Since a short at the extreme end implies an open a quarter-wave away, this makes the diagram look like two parallel plates, which indicates the impedance is a capacitive reactance.
(2) Since an open at the extreme end implies a short a quarter-wave away, this makes the diagram look like a long wire, which indicates the impedance is a inductive reactance.
Amateur Radio Extra Class
Feedlines & Safety
•
E9E04…
The purpose of the series capacitor in a gamma-type antenna matching network is to compensate for the inductive reactance of the matching network.
•
E9E05…
The driven element reactance must be capacitive in a 3-element Yagi to be tuned using a hairpin matching system.
Amateur Radio Extra Class
Feedlines & Safety
•
E9E06…
The equivalent lumped-constant network for a hairpin matching system on a 3-element Yagi is an L network.
•
E9E07…
Reflection coefficient best describes the interactions at the load end of a mismatched transmission line.
The terms - VSWR, Return Loss, Reflected Power are all ways to describe match or mismatch between a transmitter and antenna system With a VSWR of 1.4 to 1 only 2.8 % of the transmitter power is reflected back.
Impedance Mismatch Causes Reflected Wave
Amateur Radio Extra Class
Feedlines & Safety
•
E9E08…
An SWR greater than 1:1 measurement describes a mismatched transmission line.
SWR is the ratio of the maximum voltage (resulting from the interaction of Incident and reflected voltages along a transmission line) to the minimum voltage.
SWR Bridges
Amateur Radio Extra Class
Feedlines & Safety
•
E9E09…
Using a Gamma match 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.
•
E9E10…
Inserting a 1/4-wavelength piece of 75-ohm coaxial cable transmission line in series between the antenna terminals and the 50 ohm feed cable is an effective way to match an antenna with 100-ohm terminal impedance to a 50-ohm coaxial cable feed-line.
•
E9E11…
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 is to use the "universal stub" matching technique.
Amateur Radio Extra Class
Feedlines & Safety
•
E9E12…
The primary purpose of a "phasing line" when used with an antenna having multiple driven elements is to ensure that each driven element operates in concert with the others to create the desired antenna pattern.
Coaxial Cable
Amateur Radio Extra Class
Feedlines & Safety
……….Phasing line cont.
Dual Transmission Line
Amateur Radio Extra Class
Feedlines & Safety
•
E9E13…
The purpose of a "Wilkinson divider” is to divide power equally among multiple loads while preventing changes in one load from disturbing power flow to the others.
•
E9F08…
Velocity factor 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.
Amateur Radio Extra Class
Feedlines & Safety
•
E9F01…
The velocity factor of a transmission line is the velocity of the wave in the transmission line divided by the velocity of light in a vacuum.
Velocity Factor = Velocity of wave in Transmission line / Velocity of light
•
E9F02…
The transmission line dielectric materials used determine the velocity factor in a transmission line.
•
E9F04…
The typical velocity factor for a coaxial cable with solid polyethylene dielectric is 0.66.
•
E9F03…
Because electrical signals move more slowly in a coaxial cable than in air, the physical length of a coaxial cable transmission line is shorter than its electrical length.
Amateur Radio Extra Class
Feedlines & Safety
•
E9F05…
The physical length of a coaxial transmission line that is electrically one-quarter wavelength long at 14.1 MHz is (
Assuming a velocity factor of 0.66
) 3.5 Meters.
¼ Wavelength (in Transmission line) = (300/F(MHz)) / 4 x Velocity Factor ¼ Wavelength (in Transmission line) =(300/14.1 x .66) / 4 14.04/4
3.51 meters
•
E9F06…
The physical length of a parallel conductor feed line that is electrically one-half wavelength long at 14.10 MHz ( Assuming a velocity factor of 0.95
) is 10 meters.
½ Wavelength (in Transmission line) = (300/F(MHz))/2 x Velocity Factor ½ Wavelength (in Transmission line) = (300/14.1 x .95)/2 20.21/2
10.10 meters
Amateur Radio Extra Class
Feedlines & Safety
•
E9F07…
450-ohm ladder line, at 50 MHz, will have a lower loss when compared to 0.195-inch-diameter coaxial cable (such as RG-58).
•
E9F09…
The physical length of a typical coaxial transmission line that is electrically one-quarter wavelength long at 7.2 MHz (Assume a velocity factor of 0.66) would be 6.9 meters. ¼ Wavelength in Transmission line) = (300/F(MHz))/4 x Velocity Factor ¼ Wavelength in Transmission line) =(300/7.2 x..66)/4 27.50/4
6.87 meters
Amateur Radio Extra Class
Feedlines & Safety
•
E9F10…
A 1 / 8 wavelength transmission line presents an inductive reactance to a generator when the line is shorted at the far end.
Short Circuit at Antenna – Z A = 0
Impedance of coaxial stubs Wavelength Open Stub Shorted Stub 1/8 1/4 1/2 Capacitive Low Imp.
High Imp.
Inductive High Imp.
Low Imp.
•
E9F11…
A 1 / 8 wavelength transmission line presents a capacitive reactance to a generator when the line is open at the far end.
Open Circuit at Antenna – Z A = ∞
Amateur Radio Extra Class
Feedlines & Safety
•
E9F12…
A ¼ wavelength transmission line presents a very low impedance to a generator when the line is open at the far end.
Open Circuit at Antenna – Z A = ∞
Impedance of coaxial stubs Wavelength Open Stub Shorted Stub 1/8 1/4 1/2 Capacitive Low Imp.
High Imp.
Inductive High Imp.
Low Imp.
•
E9F13…
A ¼ wavelength transmission line presents a very high impedance to a generator when the line is shorted at the far end.
Short Circuit at Antenna – Z A = 0
Amateur Radio Extra Class
Feedlines & Safety
•
E9F14…
A ½ wavelength transmission line presents a very low impedance to a generator when the line is shorted at the far end.
Short Circuit at Antenna – Z A = 0
Impedance of coaxial stubs Wavelength Open Stub Shorted Stub 1/8 1/4 1/2 Capacitive Low Imp.
High Imp.
Inductive High Imp.
Low Imp.
•
E9F15…
A ½ wavelength transmission line presents very high impedance to a generator when the line is open at the far end.
Open Circuit at Antenna – Z A = ∞
Amateur Radio Extra Class
Feedlines & Safety
•
E9F16…
The primary differences between foam-dielectric coaxial cable as opposed to solid-dielectric cable, assuming all other parameters are the same are reduced safe operating voltage limits, reduced losses per unit of length and higher velocity factor.
Coax Cable Type, Size and Loss per 100 Feet Coax Type
RG-6 RG-59 RG-58U RG-8X RG-8U RG-213 Hardliner
Size
Large Medium Small Medium Large Large Large, Rigid
Loss/100MHz
2.3 dB 2.9 dB 4.3 dB 3.7 dB 1.9 dB 1.9 dB 0.5 dB
Loss/400MHz
4.7 dB 5.9 dB 9.4 dB 8.0 dB 4.1 dB 4.5 dB 1.5 dB
Amateur Radio Extra Class
Feedlines & Safety
•
E4A07…
The advantage of using an antenna analyzer vs. a SWR bridge to measure antenna SWR is that antenna analyzers typically do not need an external RF source.
•
E4B12…
When using a portable SWR analyzer to measure antenna resonance and feed-point impedance, connect the antenna feed line directly to the analyzer's test connector.
Amateur Radio Extra Class
Feedlines & Safety
•
E9G01…
Impedance along transmission lines can be calculated using a Smith chart.
Finding Antenna Impedance, Z A , when Fed with Known Length of Transmission Line ( in Wavelengths) of Given Impedance, Z O .
Smith Chart
Amateur Radio Extra Class
Feedlines & Safety
•
E4A08…
An antenna analyzer would be best for measuring the SWR of a beam antenna.
AntennaSmith…automatic antenna impedance analyzer
Amateur Radio Extra Class
Feedlines & Safety
•
E9G02…
The coordinate system is used in a Smith chart is resistance circles and reactance arcs.
Circles Arcs
Amateur Radio Extra Class
Feedlines & Safety
•
E9G03…
Impedance and SWR values in transmission lines are often determined using a Smith chart.
•
E9G04…
Resistance and reactance are the two families of circles and arcs that make up a Smith chart.
•
E9G05…
The type of chart shown in Figure E9-3 is a Smith chart.
Figure E9-3
Amateur Radio Extra Class
Feedlines & Safety
•
E9G06…
On the Smith chart shown in Figure E9-3, the name of the large outer circle on which the reactance arcs terminate is the reactance axis.
•
E9G07…
On the Smith chart shown in Figure E9-3, the only straight line shown is the resistance axis.
Figure E9-3 Smith Charts save hours of work.
Amateur Radio Extra Class
Feedlines & Safety
•
E9G08…
The process of normalization with regard to a Smith chart is reassigning impedance values with regard to the prime center.
•
E9G09…
Standing-wave ratio circles are a third family of circles that are often added to a Smith chart during the process of solving problems.
•
E9F10…
The arcs on a Smith chart represent points with constant reactance.
•
E9G11…
The wavelength scales on a Smith chart are calibrated in fractions of transmission line electrical wavelength.
Amateur Radio Extra Class
Feedlines & Safety
•
E9C04…
A basic rhombic antenna is a bidirectional. It is four-sided. Each side is one or more wavelengths long and is open at the end opposite the transmission line connection.
Open ended •
E9C05…
The main advantages of a terminated rhombic antenna are wide frequency range, high gain and high front-to-back ratio (
gain
).
Terminated
Amateur Radio Extra Class
Feedlines & Safety
•
E9C06…
The disadvantages of a terminated rhombic antenna for the HF bands are that the antenna requires a large physical area and 4 separate supports.
unidirectional bidirectional •
E9C07…
A terminating resistor on a rhombic antenna changes the radiation pattern from bidirectional to unidirectional.
Amateur Radio Extra Class
Feedlines & Safety
• • •
E9H04…
Effective radiated power is the term that describes station output ( including the transmitter, antenna and everything in between ), when considering transmitter power and system gains and losses.
E9H01…
The effective radiated power 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 is 286 watts.
ERP = Power + gain(s) – Loss(es) ERP= 150 watts + (7 dB) – (2 dB + 2.2 dB) Gain/loss ratio = 10^(dB/10)or 10^(2.8/10) or 10^.28 or 1.905
ERP = 150 watts x 1.905 ( 150 watts + 2.8 dB the overall db gain/loss ratio )
285.8 watts
E9H02…
The effective radiated power 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 is 317 watts.
ERP = Power + gain(s) – Loss(es) ERP= 200 watts + (10 dB) – (4 dB + 3.2 dB +0.8 dB) 200 watts + 2 dB Gain/loss ratio = 10^(dB/10)or 10^(2.0/10) or 10^.20 or 1.584
ERP = 200 watts x 1.584 ( the overall db gain/loss ratio )
316.9 watts
Amateur Radio Extra Class
Feedlines & Safety
• • •
E9H03…
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-dBd antenna gain is 252 watts.
ERP = Power + gain(s) – Loss(es) ERP= 200 watts + (7 dB) – (2 dB + 2.8 dB +1.2 dB) ERP = 200 watts x 1.258 ( ERP = 200 watts + 1 dB Gain/loss ratio = 10^(dB/10) or 10^(1/10) or 10^.1 or 1.258
the overall db gain/loss ratio )
251.7 watts
E9H04…
Effective radiated power is the term that describes station output ( including the transmitter, antenna and everything in between ), when considering transmitter power and system gains and losses.
E9D01…
The gain of a parabolic dish antenna increases 6 dB when the operating frequency is doubled.
Amateur Radio Extra Class
Feedlines & Safety
• •
E9D03…
The beamwidth of an antenna decreases as the gain is increased.
The antenna becomes more directional
E9D04…
It desirable for a ground-mounted satellite communications antenna system to be able to move in both azimuth and elevation in order to track the satellite as it orbits the earth.
•
E0A11…
Injuries from radiation ( magnetron transmitter.
RF
) leaks that exceed the MPE limits are considered a significant hazard when operating a klystron or cavity •
E0A10…
PCB’s ( Polychlorinated biphenyls components, such as high-voltage capacitors and transformers, are considered toxic.
) are found in some electronic •
E0A05…
One of the potential hazards of using microwaves in the amateur radio bands is the high gain antennas commonly used can result in high exposure levels.
Amateur Radio Extra Class
Feedlines & Safety
• • • •
E0A03…
A practical way to estimate whether the RF fields produced by an amateur radio station are within permissible MPE limits would be to use a computer-based antenna modeling program to calculate field strength at accessible locations.
E0A08…
SAR (
Specific Absorption Rate
) is a measure of the rate at which RF energy is absorbed by the body.
E0A02…
When evaluating exposure levels from your station at a neighbor’s home, you must make sure signals from your station are less than the uncontrolled MPE limits.
E0A06…
There are separate electric (E) and magnetic (H) field MPE limits because: Ground reflections and scattering make the field impedance vary with location.
E field and H field radiation intensity peaks can occur at different locations.
Amateur Radio Extra Class
Feedlines & Safety
•
E9C13…
When constructing a Beverage antenna, to achieve good performance at the desired frequency it should be one or more wavelengths long.
•
E9H09…
A receiving loop antenna is an antenna made of one or more turns of wire wound in the shape of a large open coil.
•
E9H10…
The output voltage of a receiving loop antenna can be increased by increasing either the number of wire turns in the loop or the area of the loop structure.
Amateur Radio Extra Class
Feedlines & Safety
•
E9H11…
A cardioid pattern is desirable for a direction-finding system because response characteristics of the cardioid pattern can assist in determining the direction of the desired station. • Two ¼ wave vertical antennas fed 90-degrees out of phase will produce a cardioid radiation pattern. Deep null will be 180 degrees from signal being received.
E9H12…
An advantage of using a shielded loop antenna for direction finding is that it is electro-statically balanced against ground, giving better nulls.
Amateur Radio Extra Class
Feedlines & Safety
•
E9H05…
The main drawback of a wire-loop antenna for direction finding is that it has a bidirectional pattern.
•
E9H07…
An RF attenuator is desirable in a receiver used for direction finding because it prevents receiver overload from extremely strong signals.
Amateur Radio Extra Class
Feedlines & Safety
•
E9H08…
The function of a sense antenna is that it modifies the pattern of a DF antenna array to provide a null in one direction.
Ferrite-core bar antenna and vertical rod sense antenna.
•
E9H06…
The triangulation method of direction finding is when antenna headings from several different receiving stations are used to locate the signal source.
Element 4 Extra Class Question Pool Feedlines and Safety
Valid July 1, 2008 Through June 30, 2012
E9E01 What system matches a high-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.
B.
C.
D.
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?
A.
B.
C.
D.
The gamma match The delta match The omega match The stub match
E9E03 What is the name of the matching system that uses a short perpendicular section of transmission line connected to the feed line near the antenna?
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.
B.
C.
D.
To provide DC isolation between the feed-line and the antenna To compensate for the inductive reactance of the matching network To provide a rejection notch to prevent 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?
A.
B.
C.
D.
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 on a 3-element Yagi?
A.
B.
C.
D.
Pi network Pi-L network L network Parallel-resonant tank
E9E07 What parameter best describes the interactions at the load end of a mismatched transmission line?
A.
B.
C.
D.
Characteristic impedance Reflection coefficient Velocity factor Dielectric Constant
E9E08 Which of the following measurements describes a mismatched transmission line?
A.
B.
C.
D.
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?
A.
B.
C.
D.
Double-bazooka match Hairpin match Gamma match All of these answers are correct
E9E10 Which of these choices is an effective way to match an antenna with a 100-ohm terminal impedance to a 50-ohm coaxial cable feed-line?
A.
B.
C.
D.
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?
A.
B.
C.
D.
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?
A.
B.
C.
D.
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 the purpose of a "Wilkinson divider"?
A.
B.
C.
D.
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 divides power equally among multiple loads while preventing changes in one load from disturbing power flow to the others It is used to feed low-impedance loads from a high-impedance source
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.
B.
C.
D.
Velocity factor Characteristic impedance Surge impedance Standing wave ratio
E9F01 What is the velocity factor of a transmission line?
A.
B.
C.
D.
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 What determines the velocity factor in a transmission line?
A.
B.
C.
D.
The termination impedance The line length Dielectric materials used in the line The center conductor resistivity
E9F04 What is the typical velocity factor for a coaxial cable with solid polyethylene dielectric?
A.
B.
C.
D.
2.70
0.66
0.30
0.10
E9F03 Why is the physical length of a coaxial cable transmission line shorter than its electrical length?
A.
B.
C.
D.
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
E9F05 What is the physical length of a coaxial transmission line that is electrically one-quarter wavelength long at 14.1 MHz? (Assume a velocity factor of 0.66.) A.
B.
C.
D.
20 meters 2.3 meters 3.5 meters 0.2 meters
E9F06 What is the physical length of a parallel conductor feed line that is electrically one-half wavelength long at 14.10 MHz? (Assume a velocity factor of 0.95.) A.
B.
C.
D.
15 meters 20 meters 10 meters 71 meters
E9F07 What characteristic will 450-ohm ladder line have at 50 MHz, as compared to 0.195-inch-diameter coaxial cable (such as RG-58)?
A.
B.
C.
D.
Lower loss Higher SWR Smaller reflection coefficient Lower velocity factor
E9F09 What would be the physical length of a typical coaxial transmission line that is electrically one-quarter wavelength long at 7.2 MHz? (Assume a velocity factor of 0.66) A.
B.
C.
D.
10 meters 6.9 meters 24 meters 50 meters
E9F10 What kind of impedance does a 1/8-wavelength transmission line present to a generator when the line is shorted at the far end?
A.
B.
C.
D.
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 kind of impedance does a 1/8-wavelength transmission line present to a generator when the line is open at the far end?
A.
B.
C.
D.
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 kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is open at the far end?
A.
B.
C.
D.
A very high impedance A very low impedance The same as the characteristic impedance of the line The same as the input impedance to the final generator stage
E9F13 What kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is shorted at the far end?
A.
B.
C.
D.
A very high impedance A very low impedance The same as the characteristic impedance of the transmission line The same as the generator output impedance
E9F14 What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is shorted at the far end?
A.
B.
C.
D.
A very high impedance A very low impedance The same as the characteristic impedance of the line The same as the output impedance of the generator
E9F15 What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is open at the far end?
A.
B.
C.
D.
A very high impedance A very low impedance The same as the characteristic impedance of the line The same as the output impedance of the generator
E9F16 What is the primary difference between foam-dielectric coaxial cable as opposed to solid-dielectric cable, assuming all other parameters are the same?
A.
B.
C.
D.
Reduced safe operating voltage limits Reduced losses per unit of length Higher velocity factor All of these answers are correct
E4A07 Which of the following is an advantage of using an antenna analyzer vs. a SWR bridge to measure antenna SWR?
A.
B.
C.
D.
Antenna analyzers automatically tune your antenna for resonance Antenna analyzers typically do not need an external RF source Antenna analyzers typically display a time-varying representation of the modulation envelope All of these answers are correct
E4B12 How should a portable SWR analyzer be connected when measuring antenna resonance and feedpoint impedance?
A.
B.
C.
D.
Loosely couple the analyzer near the antenna base Connect the analyzer via a high impedance transformer to the antenna Connect the antenna and a dummy load to the analyzer Connect the antenna feed line directly to the analyzer's connector
E9G01 Which of the following can be calculated using a Smith chart?
A.
B.
C.
D.
Impedance along transmission lines Radiation resistance Antenna radiation pattern Radio propagation
E4A08 Which of the following instruments would be best for measuring the SWR of a beam antenna?
A.
B.
C.
D.
A spectrum analyzer A Q meter An ohmmeter An antenna analyzer
E9G02 What type of coordinate system is used in a Smith chart?
A.
B.
C.
D.
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?
A.
B.
C.
D.
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?
A.
B.
C.
D.
Resistance and voltage Reactance and voltage Resistance and reactance Voltage and impedance
E9G05 What type of chart is shown in Figure E9-3?
A.
B.
C.
D.
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?
A.
B.
C.
D.
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?
A.
B.
C.
D.
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?
A.
B.
C.
D.
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?
A.
B.
C.
D.
Standing-wave ratio circles Antenna-length circles Coaxial-length circles Radiation-pattern circles
E9G10 What do the arcs on a Smith chart represent?
A.
B.
C.
D.
Frequency SWR Points with constant resistance Points with constant reactance
E9G11 How are the wavelength scales on a Smith chart calibrated?
A.
B.
C.
D.
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
E9C04 Which of the following describes a basic rhombic antenna?
A.
B.
C.
D.
Unidirectional; four-sided, each side one quarter-wavelength long; terminated in a resistance equal to its characteristic impedance Bidirectional; four-sided, each side one or more wavelengths long; open at the end opposite the transmission line connection Four-sided; an LC network at each corner except for the transmission connection Four-sided, each side of a different physical length
E9C05 What are the main advantages of a terminated rhombic antenna?
A.
B.
C.
D.
Wide frequency range, high gain and high front-to-back ratio High front-to-back ratio, compact size and high gain Unidirectional radiation pattern, high gain and compact size Bidirectional radiation pattern, high gain and wide frequency range
E9C06 What are the disadvantages of a terminated rhombic antenna for the HF bands?
A.
B.
C.
D.
The antenna has a very narrow operating bandwidth The antenna produces a circularly polarized signal The antenna requires a large physical area and 4 separate supports The antenna is more sensitive to man made static than any other type
E9C07 What is the effect of a terminating resistor on a rhombic antenna?
A.
B.
C.
D.
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
E9H04 What term describes station output (including the transmitter, antenna and everything in between), when considering transmitter power and system gains and losses?
A.
B.
C.
D.
Power factor Half-power bandwidth Effective radiated power Apparent power
E9H01 What is the effective radiated power 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.
B.
C.
D.
1977 watts 78.7 watts 420 watts 286 watts
E9H02 What is the effective radiated power 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.
B.
C.
D.
317 watts 2000 watts 126 watts 300 watts
E9H03 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-dBd antenna gain?
A.
B.
C.
D.
159 watts 252 watts 632 watts 63.2 watts
E0A04 When evaluating a site with multiple transmitters operating at the same time, the operators and licensees of which transmitters are responsible for mitigating over-exposure situations?
A.
B.
C.
D.
Only the most powerful transmitter Only commercial transmitters Each transmitter that produces 5% or more of its maximum permissible exposure limit at accessible locations Each transmitter operating with a duty cycle greater than 50%
E9D01 How does the gain of a parabolic dish antenna change when the operating frequency is doubled?
A.
B.
C.
D.
Gain does not change Gain is multiplied by 0.707
Gain increases 6 dB Gain increases 3 dB
E9D03 How does the beamwidth of an antenna vary as the gain is increased?
A.
B.
C.
D.
It increases geometrically It increases arithmetically It is essentially unaffected It decreases
E9D04 Why is it desirable for a ground-mounted satellite communications antenna system to be able to move in both azimuth and elevation?
A.
B.
C.
D.
In order to track the satellite as it orbits the earth So the antenna can be pointed away from interfering signals So the antenna can be positioned to cancel the effects of Faraday rotation To rotate antenna polarization to match that of the satellite
E0A11 Which of these items might be a significant hazard when operating a klystron or cavity magnetron transmitter?
A.
B.
C.
D.
Hearing loss caused by high voltage corona discharge Blood clotting from the intense magnetic field Injury from radiation leaks that exceed the MPE limits Ingestion of ozone gas from the cooling system
E0A10 What material found in some electronic components such as high-voltage capacitors and transformers is considered toxic?
A.
B.
C.
D.
Polychlorinated biphenyls Polyethylene Polytetrafluroethylene Polymorphic silicon
E0A05 What is one of the potential hazards of using microwaves in the amateur radio bands?
A.
B.
C.
D.
Microwaves are ionizing radiation The high gain antennas commonly used can result in high exposure levels Microwaves often travel long distances by ionospheric reflection The extremely high frequency energy can damage the joints of antenna structures
E0A03 Which of the following would be a practical way to estimate whether the RF fields produced by an amateur radio station are within permissible MPE limits?
A.
B.
C.
D.
Use a calibrated antenna analyzer Use a hand calculator plus Smith-chart equations to calculate the fields Walk around under the antennas with a neon lamp probe to find the strongest fields Use a computer-based antenna modeling program to calculate field strength at accessible locations
E0A08
What does SAR measure?
A.
B.
C.
D.
Synthetic Aperture Ratio of the human body Signal Amplification Rating The rate at which RF energy is absorbed by the body The rate of RF energy reflected from stationary terrain
E0A02 When evaluating exposure levels from your station at a neighbor’s home, what must you do?
A.
B.
C.
D.
Make sure signals from your station are less than the controlled MPE limits Make sure signals from your station are less than the uncontrolled MPE limits Nothing; you need only evaluate exposure levels on your own property Advise your neighbors of the results of your tests
E0A06 Why are there separate electric (E) and magnetic (H) field MPE limits?
A.
B.
C.
D.
The body reacts to electromagnetic radiation from both the E and H fields Ground reflections and scattering make the field impedance vary with location E field and H field radiation intensity peaks can occur at different locations All of these answers are correct
E9C13 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.
B.
C.
D.
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
E9H09 What is a receiving loop antenna?
A.
B.
C.
D.
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 Any antenna coupled to a feed line through an inductive loop of wire
E9H10 How can the output voltage of a receiving loop antenna be increased?
A.
B.
C.
D.
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 reducing either the number of wire turns in the loop or the area of the loop structure By increasing either the number of wire turns in the loop or the area of the loop structure
E9H11 Why is an antenna with a cardioid pattern desirable for a direction-finding system?
A.
B.
C.
D.
The broad-side responses of the cardioid pattern can be aimed at the desired station The response characteristics of the cardioid pattern can assist in determining the direction of the desired station The extra side lobes in the cardioid pattern can pinpoint the direction of the desired station The high-radiation angle of the cardioid pattern is useful for short-distance direction finding
E9H12 What is an advantage of using a shielded loop antenna for direction finding?
A.
B.
C.
D.
It automatically cancels ignition noise pickup 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?
A.
B.
C.
D.
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
E9H07 Why is an RF attenuator desirable in a receiver used for direction finding?
A.
B.
C.
D.
It narrows the bandwidth of the received signal It eliminates the effects of isotropic radiation It reduces loss of received signals caused by antenna pattern nulls It prevents receiver overload from extremely strong signals
E9H08 What is the function of a sense antenna?
A.
B.
C.
D.
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
E9H06 What is the triangulation method of direction finding?
A.
B.
C.
D.
The geometric angle of sky waves from the source are used to determine its position A fixed receiving station plots three headings from the signal source on a map Antenna headings from several different receiving stations are used to locate the signal source A fixed receiving station uses three different antennas to plot the location of the signal source