Login or Register for FREE!
2024 Amateur Extra pool
65 / 602 questions need explanations
89.2% complete
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?
  • Four-tone Gaussian frequency shift keying (0% chose this)
  • Variable transmit/receive periods (0% chose this)
  • Seven different tone spacings (0% chose this)
  • All these choices are correct (0% chose this)
Register to add explanation
How does Q65 differ from JT65?
  • Keyboard-to keyboard operation is supported (0% chose this)
  • Quadrature modulation is used (0% chose this)
  • Multiple receive cycles are averaged (0% chose this)
  • All these choices are correct (0% chose this)
Register to add explanation
Which of these digital modes has the highest data throughput under clear communication conditions?
  • MFSK16 (0% chose this)
  • 170 Hz shift, 45 baud RTTY (0% chose this)
  • FT8 (0% chose this)
  • PACTOR IV (0% chose this)
Register to add explanation
What should be done to continue a long-distance contact when the MUF for that path decreases due to darkness?
  • Switch to a higher frequency HF band (0% chose this)
  • Switch to a lower frequency HF band (0% chose this)
  • Change to an antenna with a higher takeoff angle (0% chose this)
  • Change to an antenna with greater beam width (0% chose this)
Register to add explanation
What determines the speed of electromagnetic waves through a medium?
  • Resistance and reactance (0% chose this)
  • Evanescence (0% chose this)
  • Birefringence (0% chose this)
  • The index of refraction (0% chose this)
Register to add explanation
Where is transequatorial propagation (TEP) most likely to occur?
  • Between points separated by 2,000 miles to 3,000 miles over a path perpendicular to the geomagnetic equator (0% chose this)
  • Between points located 1,500 miles to 2,000 miles apart on the geomagnetic equator (0% chose this)
  • Between points located at each other’s antipode (0% chose this)
  • Through the region where the terminator crosses the geographic equator (0% chose this)
Register to add explanation
Which of the following paths is most likely to support long-distance propagation on 160 meters?
  • A path entirely in sunlight (0% chose this)
  • Paths at high latitudes (0% chose this)
  • A direct north-south path (0% chose this)
  • A path entirely in darkness (0% chose this)
Register to add explanation
At what time of day is sporadic-E propagation most likely to occur?
  • Between midnight and sunrise (0% chose this)
  • Between sunset and midnight (0% chose this)
  • Between sunset and sunrise (0% chose this)
  • Between sunrise and sunset (0% chose this)
Register to add explanation
What is the cause of short-term radio blackouts?
  • Coronal mass ejections (0% chose this)
  • Sunspots on the solar equator (0% chose this)
  • North-oriented interplanetary magnetic field (0% chose this)
  • Solar flares (0% chose this)
Register to add explanation
Which of the following signal paths is most likely to experience high levels of absorption when the A-index or K-index is elevated?
  • Transequatorial (0% chose this)
  • Through the auroral oval (0% chose this)
  • Sporadic-E (0% chose this)
  • NVIS (0% chose this)
Register to add explanation
Which of the following is the space-weather term for an extreme geomagnetic storm?
  • B9 (0% chose this)
  • X5 (0% chose this)
  • M9 (0% chose this)
  • G5 (0% chose this)
Register to add explanation
What type of data is reported by amateur radio propagation reporting networks?
  • Solar flux (0% chose this)
  • Electric field intensity (0% chose this)
  • Magnetic declination (0% chose this)
  • Digital-mode and CW signals (0% chose this)
Register to add explanation
Which of the following is used to measure SWR?
  • Directional wattmeter (0% chose this)
  • Vector network analyzer (0% chose this)
  • Antenna analyzer (0% chose this)
  • All these choices are correct (0% chose this)
Register to add explanation
Which trigger mode is most effective when using an oscilloscope to measure a linear power supply’s output ripple?
  • Single-shot (0% chose this)
  • Edge (0% chose this)
  • Level (0% chose this)
  • Line (0% chose this)
Register to add explanation
Which of the following can be measured with an antenna analyzer?
  • Velocity factor (0% chose this)
  • Cable length (0% chose this)
  • Resonant frequency of a tuned circuit (0% chose this)
  • All these choices are correct (0% chose this)
Register to add explanation
Which of the following can be measured by a two-port vector network analyzer?
  • Phase noise (0% chose this)
  • Filter frequency response (0% chose this)
  • Pulse rise time (0% chose this)
  • Forward power (0% chose this)
Register to add explanation
What is the purpose of the receiver IF Shift control?
  • To permit listening on a different frequency from the transmitting frequency (0% chose this)
  • To change frequency rapidly (0% chose this)
  • To reduce interference from stations transmitting on adjacent frequencies (0% chose this)
  • To tune in stations slightly off frequency without changing the transmit frequency (0% chose this)
Register to add explanation
Which of the following types of noise are removed by a noise blanker?
  • Broadband white noise (0% chose this)
  • Impulse noise (0% chose this)
  • Hum and buzz (0% chose this)
  • All these choices are correct (0% chose this)
Register to add explanation
How can conducted noise from an automobile battery charging system be suppressed?
  • By installing filter capacitors in series with the alternator leads (0% chose this)
  • By installing a noise suppression resistor and a blocking capacitor at the battery (0% chose this)
  • 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)
  • By installing ferrite chokes on the charging system leads (0% chose this)
Register to add explanation
What causes interference received as a series of carriers at regular intervals across a wide frequency range?
  • Switch-mode power supplies (0% chose this)
  • Radar transmitters (0% chose this)
  • Wireless security camera transmitters (0% chose this)
  • Electric fences (0% chose this)
Register to add explanation
What is the purpose of a single point ground panel?
  • Remove AC power in case of a short-circuit (0% chose this)
  • Prevent common-mode transients in multi-wire systems (0% chose this)
  • Eliminate air gaps between protected and non-protected circuits (0% chose this)
  • Ensure all lightning protectors activate at the same time (0% chose this)
Register to add explanation
What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 25 ohms, R is 100 ohms, and XL is 75 ohms?
  • 27 degrees with the voltage lagging the current (0% chose this)
  • 27 degrees with the voltage leading the current (0% chose this)
  • 63 degrees with the voltage lagging the current (0% chose this)
  • 63 degrees with the voltage leading the current (0% chose this)
Register to add explanation
What type of Y-axis scale is most often used for graphs of circuit frequency response?
  • Linear (0% chose this)
  • Scatter (0% chose this)
  • Random (0% chose this)
  • Logarithmic (0% chose this)
Register to add explanation
What is the phase relationship between current and voltage for reactive power?
  • They are out of phase (0% chose this)
  • They are in phase (0% chose this)
  • They are 90 degrees out of phase (0% chose this)
  • They are 45 degrees out of phase (0% chose this)
Register to add explanation
What combines to create the self-resonance of a component?
  • The component’s resistance and reactance (0% chose this)
  • The component’s nominal and parasitic reactance (0% chose this)
  • The component’s inductance and capacitance (0% chose this)
  • The component’s electrical length and impedance (0% chose this)
Register to add explanation
What is the primary cause of loss in film capacitors at RF?
  • Inductance (0% chose this)
  • Dielectric loss (0% chose this)
  • Self-discharge (0% chose this)
  • Skin effect (0% chose this)
Register to add explanation
What property of an LED's semiconductor material determines its forward voltage drop?
  • Intrinsic resistance (0% chose this)
  • Band gap (0% chose this)
  • Junction capacitance (0% chose this)
  • Junction depth (0% chose this)
Register to add explanation
Which of the following is a common use of a Schottky diode?
  • In oscillator circuits as the negative resistance element (0% chose this)
  • As a variable capacitance in an automatic frequency control circuit (0% chose this)
  • In power supplies as a constant voltage reference (0% chose this)
  • As a VHF/UHF mixer or detector (0% chose this)
Register to add explanation
In Figure E6-2, which is the schematic symbol for a Schottky diode?
  • 1 (0% chose this)
  • 6 (0% chose this)
  • 2 (0% chose this)
  • 3 (0% chose this)
Register to add explanation
Which of the following digital logic families has the lowest power consumption?
  • Schottky TTL (0% chose this)
  • ECL (0% chose this)
  • NMOS (0% chose this)
  • CMOS (0% chose this)
Register to add explanation
What is piezoelectricity?
  • The ability of materials to generate electromagnetic waves of a certain frequency when voltage is applied (0% chose this)
  • 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)
  • A characteristic of materials that generate a voltage when stressed and that flex when a voltage is applied (0% chose this)
  • The ability of materials to generate voltage when an electromagnetic wave of a certain frequency is applied (0% chose this)
Register to add explanation
Why are cores of inductors and transformers sometimes constructed of thin layers?
  • To simplify assembly during manufacturing (0% chose this)
  • To reduce power loss from eddy currents in the core (0% chose this)
  • To increase the cutoff frequency by reducing capacitance (0% chose this)
  • To save cost by reducing the amount of magnetic material (0% chose this)
Register to add explanation
Which of the following materials has the highest temperature stability of its magnetic characteristics?
  • Brass (0% chose this)
  • Powdered iron (0% chose this)
  • Ferrite (0% chose this)
  • Aluminum (0% chose this)
Register to add explanation
What causes inductor saturation?
  • Operation at too high a frequency (0% chose this)
  • Selecting a core with low permeability (0% chose this)
  • Operation at excessive magnetic flux (0% chose this)
  • Selecting a core with excessive permittivity (0% chose this)
Register to add explanation
What happens to photoconductive material when light shines on it?
  • Resistance decreases (0% chose this)
  • Resistance increases (0% chose this)
  • Reflectivity increases (0% chose this)
  • Reflectivity decreases (0% chose this)
Register to add explanation
What does “positive logic” mean in reference to logic devices?
  • The logic devices have high noise immunity (0% chose this)
  • High voltage represents a 1, low voltage a 0 (0% chose this)
  • The logic circuit is in the “true” condition (0% chose this)
  • 1s and 0s are defined as different positive voltage levels (0% chose this)
Register to add explanation
What circuit is required at the output of an RF switching amplifier?
  • A filter to remove harmonic content (0% chose this)
  • A high-pass filter to compensate for low gain at low frequencies (0% chose this)
  • A matched load resistor to prevent damage by switching transients (0% chose this)
  • A temperature compensating load resistor to improve linearity (0% chose this)
Register to add explanation
What is characteristic of an emitter follower (or common collector) amplifier?
  • Low input impedance and phase inversion from input to output (0% chose this)
  • Differential inputs and single output (0% chose this)
  • Acts as an OR circuit if one input is grounded (0% chose this)
  • Input and output signals in-phase (0% chose this)
Register to add explanation
Which of the following is most frequently used as a band-pass or notch filter in VHF and UHF transceivers?
  • A Sallen-Key filter (0% chose this)
  • A helical filter (0% chose this)
  • A swinging choke filter (0% chose this)
  • A finite impulse response filter (0% chose this)
Register to add explanation
How does a switchmode voltage regulator work?
  • By alternating the output between positive and negative voltages (0% chose this)
  • By varying the duty cycle of pulses input to a filter (0% chose this)
  • By varying the conductivity of a pass element (0% chose this)
  • By switching between two Zener diode reference voltages (0% chose this)
Register to add explanation
What is the purpose of an inverter connected to a solar panel output?
  • Reduce AC ripple on the output (0% chose this)
  • Maintain voltage with varying illumination levels (0% chose this)
  • Prevent discharge when panel is not illuminated (0% chose this)
  • Convert the panel’s output from DC to AC (0% chose this)
Register to add explanation
What is the frequency response of the circuit in E7-3 if a capacitor is added across the feedback resistor?
  • High-pass filter (0% chose this)
  • Low-pass filter (0% chose this)
  • Band-pass filter (0% chose this)
  • Notch filter (0% chose this)
Register to add explanation
Which of the following describes a signal in the time domain?
  • Power at intervals of phase (0% chose this)
  • Amplitude at different times (0% chose this)
  • Frequency at different times (0% chose this)
  • Discrete impulses in time order (0% chose this)
Register to add explanation
What is the benefit of making voltage measurements with a true-RMS calculating meter?
  • An inverse Fourier transform can be used (0% chose this)
  • The signal’s RMS noise factor is also calculated (0% chose this)
  • The calculated RMS value can be converted directly into phasor form (0% chose this)
  • RMS is measured for both sinusoidal and non-sinusoidal signals (0% chose this)
Register to add explanation
What is frequency division multiplexing (FDM)?
  • The transmitted signal jumps from band to band at a predetermined rate (0% chose this)
  • Dividing the transmitted signal into separate frequency bands that each carry a different data stream (0% chose this)
  • The transmitted signal is divided into packets of information (0% chose this)
  • Two or more information streams are merged into a digital combiner, which then pulse position modulates the transmitter (0% chose this)
Register to add explanation
What is Quadrature Amplitude Modulation or QAM?
  • A technique for digital data compression used in digital television which removes redundancy in the data by comparing bit amplitudes (0% chose this)
  • Transmission of data by modulating the amplitude of two carriers of the same frequency but 90 degrees out of phase (0% chose this)
  • A method of performing single sideband modulation by shifting the phase of the carrier and modulation components of the signal (0% chose this)
  • A technique for analog modulation of television video signals using phase modulation and compression (0% chose this)
Register to add explanation
What is the bandwidth of an FT8 signal?
  • 10 Hz (0% chose this)
  • 50 Hz (0% chose this)
  • 600 Hz (0% chose this)
  • 2.4 kHz (0% chose this)
Register to add explanation
What is described by the constellation diagram of a QAM or QPSK signal?
  • How many carriers may be present at the same time (0% chose this)
  • The possible phase and amplitude states for each symbol (0% chose this)
  • Frequency response of the signal stream (0% chose this)
  • The number of bits used for error correction in the protocol (0% chose this)
Register to add explanation
What does the term “ground gain” mean?
  • The change in signal strength caused by grounding the antenna (0% chose this)
  • The gain of the antenna with respect to a dipole at ground level (0% chose this)
  • To force net gain to 0 dB by grounding part of the antenna (0% chose this)
  • An increase in signal strength from ground reflections in the environment of the antenna (0% chose this)
Register to add explanation
Which frequency band has the smallest first Fresnel zone?
  • 5.8 GHz (0% chose this)
  • 3.4 GHz (0% chose this)
  • 2.4 GHz (0% chose this)
  • 900 MHz (0% chose this)
Register to add explanation
What is the purpose of feeding an off-center-fed dipole (OCFD) between the center and one end instead of at the midpoint?
  • To create a similar feed point impedance on multiple bands (0% chose this)
  • To suppress off-center lobes at higher frequencies (0% chose this)
  • To resonate the antenna across a wider range of frequencies (0% chose this)
  • To reduce common-mode current coupling on the feed line shield (0% chose this)
Register to add explanation
Approximately how long is a Yagi’s driven element?
  • 234 divided by frequency in MHz (0% chose this)
  • 1005 divided by frequency in MHz (0% chose this)
  • 1/4 wavelength (0% chose this)
  • 1/2 wavelength (0% chose this)
Register to add explanation
Why do most two-element Yagis with normal spacing have a reflector instead of a director?
  • Lower SWR (0% chose this)
  • Higher receiving directivity factor (0% chose this)
  • Greater front-to-side (0% chose this)
  • Higher gain (0% chose this)
Register to add explanation
What is the purpose of making a Yagi’s parasitic elements either longer or shorter than resonance?
  • Wind torque cancellation (0% chose this)
  • Mechanical balance (0% chose this)
  • Control of phase shift (0% chose this)
  • Minimize losses (0% chose this)
Register to add explanation
Which matching system for Yagi antennas requires the driven element to be insulated from the boom?
  • Gamma (0% chose this)
  • Beta or hairpin (0% chose this)
  • Shunt-fed (0% chose this)
  • T-match (0% chose this)
Register to add explanation
What Yagi driven element feed point impedance is required to use a beta or hairpin matching system?
  • Capacitive (driven element electrically shorter than 1/2 wavelength) (0% chose this)
  • Inductive (driven element electrically longer than 1/2 wavelength) (0% chose this)
  • Purely resistive (0% chose this)
  • Purely reactive (0% chose this)
Register to add explanation
What is the purpose of using multiple driven elements connected through phasing lines?
  • To control the antenna’s radiation pattern (0% chose this)
  • To prevent harmonic radiation from the transmitter (0% chose this)
  • To allow single-band antennas to operate on other bands (0% chose this)
  • To create a low-angle radiation pattern (0% chose this)
Register to add explanation
What indicates the correct value of terminating resistance for a Beverage antenna?
  • Maximum feed point DC resistance at the center of the desired frequency range (0% chose this)
  • Minimum low-angle front-to-back ratio at the design frequency (0% chose this)
  • Maximum DC current in the terminating resistor (0% chose this)
  • Minimum variation in SWR over the desired frequency range (0% chose this)
Register to add explanation
What is the function of a Beverage antenna’s termination resistor?
  • Increase the front-to-side ratio (0% chose this)
  • Absorb signals from the reverse direction (0% chose this)
  • Decrease SWR bandwidth (0% chose this)
  • Eliminate harmonic reception (0% chose this)
Register to add explanation
What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna?
  • Cardioid (0% chose this)
  • Bidirectional (0% chose this)
  • Omnidirectional (0% chose this)
  • Hyperbolic (0% chose this)
Register to add explanation
What is meant by “100% tie-off” regarding tower safety?
  • All loose ropes and guys secured to a fixed structure (0% chose this)
  • At least one lanyard attached to the tower at all times (0% chose this)
  • All tools secured to the climber’s harness (0% chose this)
  • All circuit breakers feeding power to the tower must be tied closed with tape, cable, or ties (0% chose this)
Register to add explanation
Which of the following types of equipment are exempt from RF exposure evaluations?
  • Transceivers with less than 7 watts of RF output (0% chose this)
  • Antennas that radiate only in the near field (0% chose this)
  • Hand-held transceivers sold before May 3, 2021 (0% chose this)
  • Dish antennas less than one meter in diameter (0% chose this)
Register to add explanation
When must an RF exposure evaluation be performed on an amateur station operating on 80 meters?
  • An evaluation must always be performed (0% chose this)
  • When the ERP of the station is less than 10 watts (0% chose this)
  • When the station’s operating mode is CW (0% chose this)
  • When the output power from the transmitter is less than 100 watts (0% chose this)
Register to add explanation
To what should lanyards be attached while climbing?
  • Antenna mast (0% chose this)
  • Guy brackets (0% chose this)
  • Tower rungs (0% chose this)
  • Tower legs (0% chose this)
Register to add explanation
Where should a shock-absorbing lanyard be attached to a tower when working above ground?
  • Above the climber’s head level (0% chose this)
  • To the belt of the fall-arrest harness (0% chose this)
  • Even with the climber's waist (0% chose this)
  • To the next lowest set of guys (0% chose this)
Register to add explanation