Amateur Extra Licensing Class Lake Area Radio Klub Spring 2012 Feedlines & Safety.

Amateur Extra Licensing Class

Lake Area Radio KlubSpring 2012

Feedlines & Safety

Amateur Radio Extra ClassElement 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 ClassElement 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 ClassFeedlines & 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.


• 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.


Impedance Matching Stubs

(2) Since an open at end makes the diagram look like two parallel plates, this indicates the impedance is a capacitive reactance.

(1) Since a short at end makes the diagram look like a long wire, this indicates the impedance is an inductive reactance.


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.


• 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.


• 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


• 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


• 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.


• 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


Dual Transmission Line

……….Phasing line cont.


• 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.


• 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.

• 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.

Velocity Factor = Velocity of wave in Transmission line / Velocity of light


• 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.

• 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

3.51 meters14.04/4

¼ Wavelength (in Transmission line) =(300/14.1 x .66) / 4

¼ Wavelength (in Transmission line) = (300/F(MHz)) / 4 x Velocity Factor


• 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


• E9F10… A 1/8 wavelength transmission line presents an inductive reactance to a generator when the line is shorted at the far end.

• E9F11… A 1/8 wavelength transmission line presents a capacitive reactance to a generator when the line is open at the far end.

Impedance of coaxial stubs

Wavelength Open Stub Shorted Stub

1/8 Capacitive Inductive

1/4 Low Imp. High Imp.

1/2 High Imp. Low Imp.

Short Circuit at Antenna – ZA = 0

Open Circuit at Antenna – ZA = ∞


• E9F12… A ¼ wavelength transmission line presents a very low impedance to a generator when the line is open at the far end.

• E9F13… A ¼ wavelength transmission line presents a very high impedance to a generator when the line is shorted at the far end.









• E9F14… A ½ wavelength transmission line presents a very low impedance to a generator when the line is shorted at the far end.

• E9F15… A ½ wavelength transmission line presents very high impedance to a generator when the line is open at the far end.









• 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 Size Loss/100MHz Loss/400MHz

RG-6 Large 2.3 dB 4.7 dB

RG-59 Medium 2.9 dB 5.9 dB

RG-58U Small 4.3 dB 9.4 dB

RG-8X Medium 3.7 dB 8.0 dB

RG-8U Large 1.9 dB 4.1 dB

RG-213 Large 1.9 dB 4.5 dB

Hardliner Large, Rigid 0.5 dB 1.5 dB


• 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.

http://www.seed-solutions.com/gregordy/images/AnalMeters.JPG


• E9G01… Impedance along transmission lines can be calculated using a Smith chart.

Finding Antenna Impedance, ZA, when Fed with Known Length of Transmission Line ( in Wavelengths) of Given Impedance, ZO.

Smith Chart


• E4A08… An antenna analyzer would be best for measuring the SWR of a beam antenna.

AntennaSmith…automatic antenna impedance analyzer


• E9G02… The coordinate system is used in a Smith chart is resistance circles and reactance arcs.

Circles Arcs


• 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


• 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.


• 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.


• 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.

• E9C05… The main advantages of a terminated rhombic antenna are wide frequency range, high gain and high front-to-back ratio (gain).

Open ended

Terminated


• 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.

• E9C07… A terminating resistor on a rhombic antenna changes the radiation pattern from bidirectional to unidirectional.

bidirectional

unidirectional


• 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.

• 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= 150 watts + (7 dB) – (2 dB + 2.2 dB) 150 watts + 2.8 dB

Gain/loss ratio = 10^(dB/10)or 10^(2.8/10) or 10^.28 or 1.905 ERP = 150 watts x 1.905 (the overall db gain/loss ratio)

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

285.8 watts


• 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.

• 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.

ERP = Power + gain(s) – Loss(es) ERP= 200 watts + (7 dB) – (2 dB + 2.8 dB

+1.2 dB)Gain/loss ratio = 10^(dB/10) or 10^(1/10) or 10^.1 or 1.258 ERP = 200 watts x 1.258 (the overall db

gain/loss ratio) 251.7 watts

ERP = 200 watts + 1 dB


• E9D03… The beamwidth of an antenna decreases as the gain is increased.

• 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 (RF) leaks that exceed the MPE limits are considered a significant hazard when operating a klystron or cavity magnetron transmitter.

• E0A10… PCB’s (Polychlorinated biphenyls) are found in some electronic components, such as high-voltage capacitors and transformers, are considered toxic.

• 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.

The antenna becomes more directional


• 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.


• 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.


• 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.

• E9H12… An advantage of using a shielded loop antenna for direction finding is that it is electro-statically balanced against ground, giving better nulls.

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.


• 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.


• 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.

• E9H06… The triangulation method of direction finding is when antenna headings from several different receiving stations are used to locate the signal source.

Ferrite-core bar antenna and vertical rod sense antenna.

Element 4 Extra Class Question Pool

Valid July 1, 2008

Through

June 30, 2012

Feedlines and Safety

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. The gamma matching systemB. The delta matching systemC. The omega matching systemD. 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 matchB. The delta matchC. The omega matchD. 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 matchB. The delta matchC. The omega matchD. 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 compensate for the inductive reactance of the matching network

C. To provide a rejection notch to prevent 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 capacitiveB. The driven element reactance must be inductiveC. The driven element resonance must be lower

than the operating frequencyD. 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. Pi networkB. Pi-L networkC. L networkD. Parallel-resonant tank

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

A. Characteristic impedanceB. Reflection coefficientC. Velocity factorD. Dielectric Constant

E9E08 Which of the following measurements describes a mismatched transmission line?

A. An SWR less than 1:1B. A reflection coefficient greater than 1C. A dielectric constant greater than 1D. 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 matchB. Hairpin matchC. Gamma matchD. 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. 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 techniqueC. Connect a series-resonant LC network

across the antenna feed terminalsD. 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 the purpose of 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 divides power equally among multiple loads while preventing changes in one load from disturbing power flow to the others

D. 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. Velocity factor B. Characteristic impedanceC. Surge impedanceD. Standing wave ratio

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 cableC. The velocity of the wave in the transmission line

multiplied by the velocity of light in a vacuumD. 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. The termination impedanceB. The line lengthC. Dielectric materials used in the lineD. The center conductor resistivity

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

A. 2.70B. 0.66C. 0.30D. 0.10

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

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. 20 metersB. 2.3 metersC. 3.5 metersD. 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. 15 metersB. 20 metersC. 10 metersD. 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. Lower lossB. Higher SWRC. Smaller reflection coefficientD. 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. 10 metersB. 6.9 metersC. 24 metersD. 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. A capacitive reactanceB. The same as the characteristic

impedance of the lineC. An inductive reactanceD. 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. The same as the characteristic impedance of the line

B. An inductive reactanceC. A capacitive reactanceD. The same as the input impedance of



A. A very high impedanceB. A very low impedanceC. The same as the characteristic

impedance of the lineD. The same as the input impedance to




impedance of the transmission lineD. The same as the generator output

impedance



impedance of the lineD. 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. Reduced safe operating voltage limitsB. Reduced losses per unit of lengthC. Higher velocity factorD. 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. Antenna analyzers automatically tune your antenna for resonance

B. Antenna analyzers typically do not need an external RF source

C. Antenna analyzers typically display a time-varying representation of the modulation envelope

D. All of these answers are correct

E4B12 How should a portable SWR analyzer be connected when measuring antenna resonance and feedpoint impedance?

A. Loosely couple the analyzer near the antenna base

B. Connect the analyzer via a high-impedance transformer to the antenna

C. Connect the antenna and a dummy load to the analyzer

D. Connect the antenna feed line directly to the analyzer's connector

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

A. Impedance along transmission linesB. Radiation resistanceC. Antenna radiation patternD. Radio propagation

E4A08 Which of the following instruments would be best for measuring the SWR of a beam antenna?

A. A spectrum analyzerB. A Q meterC. An ohmmeterD. An antenna analyzer

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

A. Voltage circles and current arcsB. Resistance circles and reactance arcsC. Voltage lines and current chordsD. Resistance lines and reactance chords

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

A. Beam headings and radiation patternsB. Satellite azimuth and elevation

bearingsC. Impedance and SWR values in

transmission linesD. Trigonometric functions

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

A. Resistance and voltageB. Reactance and voltageC. Resistance and reactanceD. Voltage and impedance

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

A. Smith chartB. Free-space radiation directivity chartC. Elevation angle radiation pattern chartD. 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 axisB. Reactance axisC. Impedance axisD. Polar axis

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

A. The reactance axisB. The current axisC. The voltage axisD. 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 circlesB. Antenna-length circlesC. Coaxial-length circlesD. Radiation-pattern circles

E9G10 What do the arcs on a Smith chart represent?

A. FrequencyB. SWRC. Points with constant resistanceD. 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

E9C04 Which of the following describes a basic rhombic antenna?

A. Unidirectional; four-sided, each side one quarter-wavelength long; terminated in a resistance equal to its characteristic impedance

B. Bidirectional; four-sided, each side one or more wavelengths long; open at the end opposite the transmission line connection

C. Four-sided; an LC network at each corner except for the transmission connection

D. Four-sided, each side of a different physical length

E9C05 What are the main advantages of a terminated rhombic antenna?

A. Wide frequency range, high gain and high front-to-back ratio

B. High front-to-back ratio, compact size and high gain

C. Unidirectional radiation pattern, high gain and compact size

D. Bidirectional radiation pattern, high gain and wide frequency range

E9C06 What are the disadvantages of a terminated rhombic antenna for the HF bands?

A. The antenna has a very narrow operating bandwidth

B. The antenna produces a circularly polarized signal

C. The antenna requires a large physical area and 4 separate supports

D. 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. 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

E9H04 What term describes station output (including the transmitter, antenna and everything in between), when considering transmitter power and system gains and losses?

A. Power factorB. Half-power bandwidthC. Effective radiated powerD. 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. 1977 wattsB. 78.7 wattsC. 420 wattsD. 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. 317 wattsB. 2000 wattsC. 126 wattsD. 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. 159 wattsB. 252 wattsC. 632 wattsD. 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. Only the most powerful transmitterB. Only commercial transmittersC. Each transmitter that produces 5% or

more of its maximum permissible exposure limit at accessible locations

D. 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. Gain does not changeB. Gain is multiplied by 0.707C. Gain increases 6 dBD. Gain increases 3 dB

E9D03 How does the beamwidth of an antenna vary as the gain is increased?

A. It increases geometricallyB. It increases arithmeticallyC. It is essentially unaffectedD. 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. In order to track the satellite as it orbits the earth

B. So the antenna can be pointed away from interfering signals

C. So the antenna can be positioned to cancel the effects of Faraday rotation

D. 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. Hearing loss caused by high voltage corona discharge

B. Blood clotting from the intense magnetic fieldC. Injury from radiation leaks that exceed the

MPE limitsD. 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. Polychlorinated biphenylsB. Polyethylene C. PolytetrafluroethyleneD. Polymorphic silicon

E0A05 What is one of the potential hazards of using microwaves in the amateur radio bands?

A. Microwaves are ionizing radiationB. The high gain antennas commonly used

can result in high exposure levelsC. Microwaves often travel long distances by

ionospheric reflectionD. 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. Use a calibrated antenna analyzerB. Use a hand calculator plus Smith-chart

equations to calculate the fieldsC. Walk around under the antennas with a neon-

lamp probe to find the strongest fieldsD. Use a computer-based antenna modeling

program to calculate field strength at accessible locations

E0A08 What does SAR measure?

A. Synthetic Aperture Ratio of the human body

B. Signal Amplification RatingC. The rate at which RF energy is absorbed

by the bodyD. 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. Make sure signals from your station are less than the controlled MPE limits

B. Make sure signals from your station are less than the uncontrolled MPE limits

C. Nothing; you need only evaluate exposure levels on your own property

D. Advise your neighbors of the results of your tests

E0A06 Why are there separate electric (E) and magnetic (H) field MPE limits?

A. The body reacts to electromagnetic radiation from both the E and H fields

B. Ground reflections and scattering make the field impedance vary with location

C. E field and H field radiation intensity peaks can occur at different locations

D. 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. 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 loopD. It should be one or more wavelengths long

E9H09 What is a receiving loop antenna?

A. A large circularly-polarized antennaB. A small coil of wire tightly wound around a

toroidal ferrite coreC. One or more turns of wire wound in the

shape of a large open coilD. 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. By reducing the permeability of the loop shieldB. By increasing the number of wire turns in the

loop and reducing the area of the loop structure

C. By reducing either the number of wire turns in the loop or the area of the loop structure

D. 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. The broad-side responses of the cardioid pattern can be aimed at the desired station

B. The response characteristics of the cardioid pattern can assist in determining the direction of the desired station

C. The extra side lobes in the cardioid pattern can pinpoint the direction of the desired station

D. 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. It automatically cancels ignition noise pickup 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 patternB. It is non-rotatableC. It receives equally well in all directionsD. It is practical for use only on VHF

bands

E9H07 Why is an RF attenuator desirable in a receiver used for direction finding?

A. It narrows the bandwidth of the received signal

B. It eliminates the effects of isotropic radiationC. It reduces loss of received signals caused by

antenna pattern nullsD. It prevents receiver overload from extremely

strong signals

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

E9H06 What is the triangulation method of direction finding?

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

B. A fixed receiving station plots three headings from the signal source on a map

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

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

Amateur Extra Licensing Class Lake Area Radio Klub Spring 2012 Feedlines & Safety.

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Transcript of Amateur Extra Licensing Class Lake Area Radio Klub Spring 2012 Feedlines & Safety.