2024 Amateur Extra pool
52 / 602 questions need explanations
All explanations are written and maintained by ordinary users like you! Please help us finish the explanations in this pool.
Which of the following is characteristic of the FST4 mode?
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Four-tone Gaussian frequency shift keying (0% chose this)
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Variable transmit/receive periods (0% chose this)
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Seven different tone spacings (0% chose this)
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All these choices are correct (0% chose this)
How does Q65 differ from JT65?
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Keyboard-to keyboard operation is supported (0% chose this)
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Quadrature modulation is used (0% chose this)
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Multiple receive cycles are averaged (0% chose this)
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All these choices are correct (0% chose this)
Which of these digital modes has the highest data throughput under clear communication conditions?
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MFSK16 (0% chose this)
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170 Hz shift, 45 baud RTTY (0% chose this)
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FT8 (0% chose this)
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PACTOR IV (0% chose this)
What should be done to continue a long-distance contact when the MUF for that path decreases due to darkness?
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Switch to a higher frequency HF band (0% chose this)
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Switch to a lower frequency HF band (0% chose this)
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Change to an antenna with a higher takeoff angle (0% chose this)
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Change to an antenna with greater beam width (0% chose this)
Where is transequatorial propagation (TEP) most likely to occur?
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Between points separated by 2,000 miles to 3,000 miles over a path perpendicular to the geomagnetic equator (0% chose this)
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Between points located 1,500 miles to 2,000 miles apart on the geomagnetic equator (0% chose this)
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Between points located at each other’s antipode (0% chose this)
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Through the region where the terminator crosses the geographic equator (0% chose this)
Which of the following paths is most likely to support long-distance propagation on 160 meters?
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A path entirely in sunlight (0% chose this)
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Paths at high latitudes (0% chose this)
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A direct north-south path (0% chose this)
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A path entirely in darkness (0% chose this)
At what time of day is sporadic-E propagation most likely to occur?
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Between midnight and sunrise (0% chose this)
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Between sunset and midnight (0% chose this)
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Between sunset and sunrise (0% chose this)
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Between sunrise and sunset (0% chose this)
What is the cause of short-term radio blackouts?
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Coronal mass ejections (0% chose this)
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Sunspots on the solar equator (0% chose this)
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North-oriented interplanetary magnetic field (0% chose this)
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Solar flares (0% chose this)
Which of the following signal paths is most likely to experience high levels of absorption when the A-index or K-index is elevated?
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Transequatorial (0% chose this)
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Through the auroral oval (0% chose this)
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Sporadic-E (0% chose this)
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NVIS (0% chose this)
Which of the following is the space-weather term for an extreme geomagnetic storm?
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B9 (0% chose this)
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X5 (0% chose this)
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M9 (0% chose this)
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G5 (0% chose this)
What type of data is reported by amateur radio propagation reporting networks?
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Solar flux (0% chose this)
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Electric field intensity (0% chose this)
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Magnetic declination (0% chose this)
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Digital-mode and CW signals (0% chose this)
Which trigger mode is most effective when using an oscilloscope to measure a linear power supply’s output ripple?
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Single-shot (0% chose this)
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Edge (0% chose this)
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Level (0% chose this)
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Line (0% chose this)
Which of the following can be measured with an antenna analyzer?
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Velocity factor (0% chose this)
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Cable length (0% chose this)
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Resonant frequency of a tuned circuit (0% chose this)
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All these choices are correct (0% chose this)
Which of the following can be measured by a two-port vector network analyzer?
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Phase noise (0% chose this)
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Filter frequency response (0% chose this)
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Pulse rise time (0% chose this)
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Forward power (0% chose this)
What is the purpose of the receiver IF Shift control?
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To permit listening on a different frequency from the transmitting frequency (0% chose this)
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To change frequency rapidly (0% chose this)
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To reduce interference from stations transmitting on adjacent frequencies (0% chose this)
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To tune in stations slightly off frequency without changing the transmit frequency (0% chose this)
How can conducted noise from an automobile battery charging system be suppressed?
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By installing filter capacitors in series with the alternator leads (0% chose this)
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By installing a noise suppression resistor and a blocking capacitor at the battery (0% chose this)
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By installing a high-pass filter in series with the radio’s power lead and a low-pass filter in parallel with the antenna feed line (0% chose this)
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By installing ferrite chokes on the charging system leads (0% chose this)
What causes interference received as a series of carriers at regular intervals across a wide frequency range?
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Switch-mode power supplies (0% chose this)
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Radar transmitters (0% chose this)
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Wireless security camera transmitters (0% chose this)
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Electric fences (0% chose this)
What is the purpose of a single point ground panel?
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Remove AC power in case of a short-circuit (0% chose this)
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Prevent common-mode transients in multi-wire systems (0% chose this)
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Eliminate air gaps between protected and non-protected circuits (0% chose this)
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Ensure all lightning protectors activate at the same time (0% chose this)
What is the phase relationship between current and voltage for reactive power?
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They are out of phase (0% chose this)
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They are in phase (0% chose this)
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They are 90 degrees out of phase (0% chose this)
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They are 45 degrees out of phase (0% chose this)
What combines to create the self-resonance of a component?
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The component’s resistance and reactance (0% chose this)
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The component’s nominal and parasitic reactance (0% chose this)
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The component’s inductance and capacitance (0% chose this)
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The component’s electrical length and impedance (0% chose this)
What is the primary cause of loss in film capacitors at RF?
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Inductance (0% chose this)
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Dielectric loss (0% chose this)
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Self-discharge (0% chose this)
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Skin effect (0% chose this)
What property of an LED's semiconductor material determines its forward voltage drop?
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Intrinsic resistance (0% chose this)
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Band gap (0% chose this)
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Junction capacitance (0% chose this)
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Junction depth (0% chose this)
Which of the following is a common use of a Schottky diode?
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In oscillator circuits as the negative resistance element (0% chose this)
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As a variable capacitance in an automatic frequency control circuit (0% chose this)
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In power supplies as a constant voltage reference (0% chose this)
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As a VHF/UHF mixer or detector (0% chose this)
In Figure E6-2, which is the schematic symbol for a Schottky diode?
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1 (0% chose this)
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6 (0% chose this)
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2 (0% chose this)
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3 (0% chose this)
Which of the following digital logic families has the lowest power consumption?
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Schottky TTL (0% chose this)
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ECL (0% chose this)
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NMOS (0% chose this)
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CMOS (0% chose this)
What is piezoelectricity?
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The ability of materials to generate electromagnetic waves of a certain frequency when voltage is applied (0% chose this)
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A characteristic of materials that have an index of refraction which depends on the polarization of the electromagnetic wave passing through it (0% chose this)
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A characteristic of materials that generate a voltage when stressed and that flex when a voltage is applied (0% chose this)
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The ability of materials to generate voltage when an electromagnetic wave of a certain frequency is applied (0% chose this)
Why are cores of inductors and transformers sometimes constructed of thin layers?
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To simplify assembly during manufacturing (0% chose this)
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To reduce power loss from eddy currents in the core (0% chose this)
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To increase the cutoff frequency by reducing capacitance (0% chose this)
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To save cost by reducing the amount of magnetic material (0% chose this)
Which of the following materials has the highest temperature stability of its magnetic characteristics?
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Brass (0% chose this)
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Powdered iron (0% chose this)
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Ferrite (0% chose this)
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Aluminum (0% chose this)
What causes inductor saturation?
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Operation at too high a frequency (0% chose this)
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Selecting a core with low permeability (0% chose this)
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Operation at excessive magnetic flux (0% chose this)
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Selecting a core with excessive permittivity (0% chose this)
What does “positive logic” mean in reference to logic devices?
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The logic devices have high noise immunity (0% chose this)
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High voltage represents a 1, low voltage a 0 (0% chose this)
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The logic circuit is in the “true” condition (0% chose this)
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1s and 0s are defined as different positive voltage levels (0% chose this)
What circuit is required at the output of an RF switching amplifier?
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A filter to remove harmonic content (0% chose this)
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A high-pass filter to compensate for low gain at low frequencies (0% chose this)
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A matched load resistor to prevent damage by switching transients (0% chose this)
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A temperature compensating load resistor to improve linearity (0% chose this)
What is characteristic of an emitter follower (or common collector) amplifier?
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Low input impedance and phase inversion from input to output (0% chose this)
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Differential inputs and single output (0% chose this)
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Acts as an OR circuit if one input is grounded (0% chose this)
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Input and output signals in-phase (0% chose this)
Which of the following is most frequently used as a band-pass or notch filter in VHF and UHF transceivers?
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A Sallen-Key filter (0% chose this)
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A helical filter (0% chose this)
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A swinging choke filter (0% chose this)
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A finite impulse response filter (0% chose this)
What is the frequency response of the circuit in E7-3 if a capacitor is added across the feedback resistor?
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High-pass filter (0% chose this)
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Low-pass filter (0% chose this)
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Band-pass filter (0% chose this)
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Notch filter (0% chose this)
What is Quadrature Amplitude Modulation or QAM?
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A technique for digital data compression used in digital television which removes redundancy in the data by comparing bit amplitudes (0% chose this)
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Transmission of data by modulating the amplitude of two carriers of the same frequency but 90 degrees out of phase (0% chose this)
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A method of performing single sideband modulation by shifting the phase of the carrier and modulation components of the signal (0% chose this)
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A technique for analog modulation of television video signals using phase modulation and compression (0% chose this)
What is the bandwidth of an FT8 signal?
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10 Hz (0% chose this)
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50 Hz (0% chose this)
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600 Hz (0% chose this)
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2.4 kHz (0% chose this)
What does the term “ground gain” mean?
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The change in signal strength caused by grounding the antenna (0% chose this)
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The gain of the antenna with respect to a dipole at ground level (0% chose this)
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To force net gain to 0 dB by grounding part of the antenna (0% chose this)
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An increase in signal strength from ground reflections in the environment of the antenna (0% chose this)
Which frequency band has the smallest first Fresnel zone?
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5.8 GHz (0% chose this)
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3.4 GHz (0% chose this)
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2.4 GHz (0% chose this)
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900 MHz (0% chose this)
What is the purpose of feeding an off-center-fed dipole (OCFD) between the center and one end instead of at the midpoint?
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To create a similar feed point impedance on multiple bands (0% chose this)
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To suppress off-center lobes at higher frequencies (0% chose this)
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To resonate the antenna across a wider range of frequencies (0% chose this)
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To reduce common-mode current coupling on the feed line shield (0% chose this)
Approximately how long is a Yagi’s driven element?
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234 divided by frequency in MHz (0% chose this)
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1005 divided by frequency in MHz (0% chose this)
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1/4 wavelength (0% chose this)
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1/2 wavelength (0% chose this)
Why do most two-element Yagis with normal spacing have a reflector instead of a director?
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Lower SWR (0% chose this)
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Higher receiving directivity factor (0% chose this)
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Greater front-to-side (0% chose this)
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Higher gain (0% chose this)
What is the purpose of making a Yagi’s parasitic elements either longer or shorter than resonance?
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Wind torque cancellation (0% chose this)
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Mechanical balance (0% chose this)
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Control of phase shift (0% chose this)
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Minimize losses (0% chose this)
Which matching system for Yagi antennas requires the driven element to be insulated from the boom?
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Gamma (0% chose this)
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Beta or hairpin (0% chose this)
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Shunt-fed (0% chose this)
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T-match (0% chose this)
What Yagi driven element feed point impedance is required to use a beta or hairpin matching system?
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Capacitive (driven element electrically shorter than 1/2 wavelength) (0% chose this)
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Inductive (driven element electrically longer than 1/2 wavelength) (0% chose this)
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Purely resistive (0% chose this)
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Purely reactive (0% chose this)
What is the purpose of using multiple driven elements connected through phasing lines?
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To control the antenna’s radiation pattern (0% chose this)
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To prevent harmonic radiation from the transmitter (0% chose this)
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To allow single-band antennas to operate on other bands (0% chose this)
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To create a low-angle radiation pattern (0% chose this)
What indicates the correct value of terminating resistance for a Beverage antenna?
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Maximum feed point DC resistance at the center of the desired frequency range (0% chose this)
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Minimum low-angle front-to-back ratio at the design frequency (0% chose this)
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Maximum DC current in the terminating resistor (0% chose this)
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Minimum variation in SWR over the desired frequency range (0% chose this)
What is the function of a Beverage antenna’s termination resistor?
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Increase the front-to-side ratio (0% chose this)
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Absorb signals from the reverse direction (0% chose this)
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Decrease SWR bandwidth (0% chose this)
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Eliminate harmonic reception (0% chose this)
What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna?
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Cardioid (0% chose this)
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Bidirectional (0% chose this)
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Omnidirectional (0% chose this)
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Hyperbolic (0% chose this)
What is meant by “100% tie-off” regarding tower safety?
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All loose ropes and guys secured to a fixed structure (0% chose this)
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At least one lanyard attached to the tower at all times (0% chose this)
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All tools secured to the climber’s harness (0% chose this)
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All circuit breakers feeding power to the tower must be tied closed with tape, cable, or ties (0% chose this)
Which of the following types of equipment are exempt from RF exposure evaluations?
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Transceivers with less than 7 watts of RF output (0% chose this)
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Antennas that radiate only in the near field (0% chose this)
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Hand-held transceivers sold before May 3, 2021 (0% chose this)
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Dish antennas less than one meter in diameter (0% chose this)
When must an RF exposure evaluation be performed on an amateur station operating on 80 meters?
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An evaluation must always be performed (0% chose this)
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When the ERP of the station is less than 10 watts (0% chose this)
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When the station’s operating mode is CW (0% chose this)
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When the output power from the transmitter is less than 100 watts (0% chose this)
Where should a shock-absorbing lanyard be attached to a tower when working above ground?
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Above the climber’s head level (0% chose this)
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To the belt of the fall-arrest harness (0% chose this)
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Even with the climber's waist (0% chose this)
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To the next lowest set of guys (0% chose this)
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