The flashcards below were created by user
on FreezingBlue Flashcards.
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
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. Reduced safe operating voltage limits
B. Reduced losses per unit of length
C. Higher velocity factor
D. All of these choices are correct
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
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
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
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
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
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
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
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
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
What do the arcs on a Smith chart represent?
C. Points with constant resistance
D. Points with constant reactance
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
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
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
If the boom of a Yagi antenna is lengthened and the elements are properly retuned, what usually occurs?
A. The gain increases
B. The SWR decreases
C. The front-to-back ratio increases
D. The gain bandwidth decreases rapidly
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
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
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
What does the abbreviation NEC stand for when applied to antenna modeling programs?
A. Next Element Comparison
B. Numerical Electromagnetics Code
C. National Electrical Code
D. Numeric Electrical Computation
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
What type of propagation is probably occurring if an HF beam antenna must be pointed in a direction 180 degrees away from a station to receive the strongest signals?
Which amateur bands typically support long-path propagation?
A. 160 to 40 meters
B. 30 to 10 meters
C. 160 to 10 meters
D. 6 meters to 2 meters
Which of the following amateur bands most frequently provides long-path propagation?
A. 80 meters
B. 20 meters
C. 10 meters
D. 6 meters
Which of the following could account for hearing an echo on the received signal of a distant station?
A. High D layer absorption
B. Meteor scatter
C. Transmit frequency is higher than the MUF
D. Receipt of a signal by more than one path
What type of HF propagation is probably occurring if radio signals travel along the terminator between daylight and darkness?
At what time of day is gray-line propagation most likely to occur?
A. At sunrise and sunset
B. When the Sun is directly above the location of the transmitting station
C. When the Sun is directly overhead at the middle of the communications path between the two stations
D. When the Sun is directly above the location of the receiving station
What is the cause of gray-line propagation?
A. At midday, the Sun being directly overhead superheats the ionosphere causing increased refraction of radio waves
B. At twilight, D-layer absorption drops while E-layer and F-layer propagation remain strong
C. In darkness, solar absorption drops greatly while atmospheric ionization remains steady
D. At mid afternoon, the Sun heats the ionosphere decreasing radio wave refraction and the MUF
Which of the following describes gray-line propagation?
A. Backscatter contacts on the 10 meter band
B. Over the horizon propagation on the 6 and 2 meter bands
C. Long distance communications at twilight on frequencies less than 15 MHz
D. Tropospheric propagation on the 2 meter and 70 centimeter bands
Which of the following describes selective fading?
A. Variability of signal strength with beam heading
B. Partial cancellation of some frequencies within the received pass band
C. Sideband inversion within the ionosphere
D. Degradation of signal strength due to backscatter
What is the name of the high-angle wave in HF propagation that travels for some distance within the F2 region?
A. Oblique-angle ray
B. Pedersen ray
C. Ordinary ray
D. Heaviside ray
How does the maximum distance of ground-wave propagation change when the signal frequency is increased?
A. It stays the same
B. It increases
C. It decreases
D. It peaks at roughly 14 MHz
What type of polarization is best for ground-wave propagation?
What is the approximate maximum separation measured along the surface of the Earth between two stations communicating by Moon bounce?
A. 500 miles, if the Moon is at perigee
B. 2000 miles, if the Moon is at apogee
C. 5000 miles, if the Moon is at perigee
D. 12,000 miles, as long as both can “see” the Moon
What characterizes libration fading of an Earth-Moon-Earth signal?
A. A slow change in the pitch of the CW signal
B. A fluttery irregular fading
C. A gradual loss of signal as the Sun rises
D. The returning echo is several Hertz lower in frequency than the transmitted signal
When scheduling EME contacts, which of these conditions will generally result in the least pathloss?
A. When the Moon is at perigee
B. When the Moon is full
C. When the Moon is at apogee
D. When the MUF is above 30 MHz
What type of receiving system is desirable for EME communications?
A. Equipment with very wide bandwidth
B. Equipment with very low dynamic range
C. Equipment with very low gain
D. Equipment with very low noise figures
Which of the following describes a method of establishing EME contacts?
A. Time synchronous transmissions with each station alternating
B. Storing and forwarding digital messages
C. Judging optimum transmission times by monitoring beacons from the Moon
D. High speed CW identification to avoid fading
What frequency range would you normally tune to find EME signals in the 2 meter band?
A. 144.000 - 144.001 MHz
B. 144.000 - 144.100 MHz
C. 144.100 - 144.300 MHz
D. 145.000 - 145.100 MHz
What frequency range would you normally tune to find EME signals in the 70 cm band?
A. 430.000 - 430.150 MHz
B. 430.100 - 431.100 MHz
C. 431.100 - 431.200 MHz
D. 432.000 - 432.100 MHz
When a meteor strikes the Earth’s atmosphere, a cylindrical region of free electrons is formed at what layer of the ionosphere?
A. The E layer
B. The F1 layer
C. The F2 layer
D. The D layer
Which of the following frequency ranges is well suited for meteor-scatter communications?
A. 1.8 - 1.9 MHz
B. 10 - 14 MHz
C. 28 - 148 MHz
D. 220 - 450 MHz
Which of the following is a good technique for making meteor-scatter contacts?
A. 15 second timed transmission sequences with stations alternating based on location
B. Use of high speed CW or digital modes
C. Short transmission with rapidly repeated call signs and signal reports
D. All of these choices are correct
What is transequatorial propagation?
A. Propagation between two mid-latitude points at approximately the same distance north and south of the magnetic equator
B. Propagation between any two points located on the magnetic equator
C. Propagation between two continents by way of ducts along the magnetic equator
D. Propagation between two stations at the same latitude
What is the approximate maximum range for signals using transequatorial propagation?
A. 1000 miles
B. 2500 miles
C. 5000 miles
D. 7500 miles
What is the best time of day for transequatorial propagation?
C. Afternoon or early evening
D. Late at night
Which of the following effects does Aurora activity have on radio communications?
A. SSB signals are raspy
B. Signals propagating through the Aurora are fluttery
C. CW signals appear to be modulated by white noise
D. All of these choices are correct
What is the cause of Aurora activity?
A. The interaction between the solar wind and the Van Allen belt
B. A low sunspot level combined with tropospheric ducting
C. The interaction of charged particles from the Sun with the Earth’s magnetic field and theionosphere
D. Meteor showers concentrated in the northern latitudes
Where in the ionosphere does Aurora activity occur?
A. In the F1-region
B. In the F2-region
C. In the D-region
D. In the E-region
Which emission mode is best for Aurora propagation?
By how much does the VHF/UHF radio-path horizon distance exceed the geometric horizon?
A. By approximately 15% of the distance
B. By approximately twice the distance
C. By approximately one-half the distance
D. By approximately four times the distance
Which of the following is usually responsible for causing VHF signals to propagate for hundreds of miles?
A. D-region absorption
B. Faraday rotation
C. Tropospheric ducting
D. Ground wave
From the contiguous 48 states, in which approximate direction should an antenna be pointed to take maximum advantage of aurora propagation?
Why does the radio-path horizon distance exceed the geometric horizon?
A. E-region skip
B. D-region skip
C. Downward bending due to aurora refraction
D. Downward bending due to density variations in the atmosphere
How may dangerous levels of carbon monoxide from an emergency generator be detected?
A. By the odor
B. Only with a carbon monoxide detector
C. Any ordinary smoke detector can be used
D. By the yellowish appearance of the gas
Which insulating material commonly used as a thermal conductor for some types of electronic devices is extremely toxic if broken or crushed and the particles are accidentally inhaled?
B. Zinc oxide
C. Beryllium Oxide
D. Uranium Hexaflouride
What material found in some electronic components such as high-voltage capacitors and transformers is considered toxic?
A. Polychlorinated biphenyls
D. Polymorphic silicon
What, if any, are the differences between the radiation produced by radioactive materials and the electromagnetic energy radiated by an antenna?
A. There is no significant difference between the two types of radiation
B. Only radiation produced by radioactivity can injure human beings
C. Radioactive materials emit ionizing radiation, while RF signals have less energy and can only cause heating
D. Radiation from an antenna will damage unexposed photographic film but ordinary radioactive materials do not cause this problem
When evaluating RF 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. You need only evaluate exposure levels on your own property
D. Advise your neighbors of the results of your tests
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 analyzer
B. Use a hand calculator plus Smith-chart equations to calculate the fields
C. Use an antenna modeling program to calculate field strength at accessible locations
D. All of the choices are correct
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 transmitter
B. Only commercial transmitters
C. Each transmitter that produces 5% or more of its MPE exposure limit at accessible locations
D. Each transmitter operating with a duty-cycle greater than 50%
What is one of the potential hazards of using microwaves in the amateur radio bands?
A. Microwaves are ionizing radiation
B. The high gain antennas commonly used can result in high exposure levels
C. Microwaves often travel long distances by ionospheric reflection
D. The extremely high frequency energy can damage the joints of antenna structures
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 choices are correct
What does SAR measure?
A. Synthetic Aperture Ratio of the human body
B. Signal Amplification Rating
C. The rate at which RF energy is absorbed by the body
D. The rate of RF energy reflected from stationary terrain
Which of the following injuries can result from using high-power UHF or microwave transmitters?
A. Hearing loss caused by high voltage corona discharge
B. Blood clotting from the intense magnetic field
C. Localized heating of the body from RF exposure in excess of the MPE limits
D. Ingestion of ozone gas from the cooling system