Which agency regulates and enforces the rules for the Amateur Radio Service in the United States?
AnswerThe FCC.
The Federal Communications Commission regulates the Amateur Radio Service in the United States and enforces Part 97.
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What is the primary function of an external earth connection or ground rod at an amateur station?
AnswerLightning charge dissipation.
A grounding electrode provides a path for lightning and surge energy to reach earth as part of a properly bonded protection system.
What does a sudden ionospheric disturbance do to daytime HF propagation?
AnswerIt disrupts lower-frequency signals more than higher-frequency signals.
Solar X-rays can sharply increase D-region absorption on the sunlit side of Earth, hitting lower HF frequencies especially hard.
Which of the following is a safety hazard of a 12-volt storage battery that lacks internal protection circuitry?
AnswerShorting the terminals can cause burns, fire, or an explosion.
Low voltage does not mean low available current. A storage battery can deliver enormous current into a short circuit.
What is the major function of an antenna tuner (antenna coupler)?
AnswerIt matches the antenna system impedance to the transceiver's output impedance.
A tuner transforms impedance so the transmitter sees an acceptable load. It does not physically retune the antenna into resonance.
How does a higher sunspot number generally affect HF propagation?
AnswerIt increases the probability of good propagation at higher HF frequencies.
Greater solar activity can increase ionization that supports long-distance propagation on the higher HF bands.
Which of the following signal types has the narrowest bandwidth?
AnswerCW.
Morse-code continuous-wave signals can occupy extremely little spectrum compared with voice or image modes.
What characterizes libration fading on an EME signal?
AnswerFluttery, irregular fading.
The Moon’s apparent motion causes many reflected paths to change phase, producing rapid irregular amplitude variations.
Which of the following is part of the Basis and Purpose of the Amateur Radio Service?
AnswerAdvancing skills in the technical and communication phases of the radio art.
Amateur radio is explicitly intended to develop technical and communication skill, not simply provide another personal communications service.
What is the approximate maximum surface separation between two stations that can communicate by EME?
AnswerAbout 12,000 miles when both stations can see the Moon.
Earth-Moon-Earth communication is possible whenever both stations have the Moon above their usable horizons, allowing nearly opposite points on Earth to share a lunar path.
What is the minimum safe distance from a power line to allow when installing an antenna?
AnswerEnough so that if the antenna falls, no part of it can come within 10 feet of the power wires.
Plan for the antenna or support to fall in the worst plausible direction. Clearance must protect against accidental contact, not just normal upright spacing.
What is one way that RF energy can affect human body tissue?
AnswerIt heats body tissue.
At sufficiently high exposure levels, RF energy can be absorbed by tissue and converted to heat.
What type of electrical component stores energy in a magnetic field?
AnswerAn inductor.
Current through an inductor creates a magnetic field, and energy is stored in that field.
What is a relay?
AnswerAn electrically controlled switch.
A relay lets an electrical signal operate contacts that switch another circuit.
Which sideband is normally used for voice on 160, 75, and 40 meters?
AnswerLower sideband (LSB).
Amateur SSB convention uses LSB on the lower HF voice bands.
What analysis shows that a square wave consists of a sine wave plus odd harmonics?
AnswerFourier analysis.
Fourier analysis represents a complex periodic waveform as a sum of sinusoidal frequency components.
What is standing wave ratio (SWR)?
AnswerA measure of how well a load is matched to a transmission line.
SWR indicates the degree of impedance mismatch between the transmission line and its load.
Where should an RF power meter be installed?
AnswerIn the feed line, between the transmitter and antenna.
RF power and SWR instruments must sample the RF traveling on the transmission line, so they belong in series with the feed line.
What is an isotropic radiator?
AnswerA hypothetical lossless antenna that radiates equally in all directions and serves as a gain reference.
The isotropic radiator is an ideal reference, not a physically realizable practical antenna.
How does high SWR affect loss in a lossy transmission line?
AnswerHigh SWR increases the loss.
Reflections raise current and voltage at points along the line, so an already-lossy line dissipates more power.
Why do VHF signal strengths sometimes vary greatly when the antenna is moved only a few feet?
AnswerMultipath propagation cancels or reinforces signals.
Reflected VHF signals can arrive by several paths. Depending on phase, those copies may reinforce one another or partially cancel.
What is the national calling frequency for FM simplex operations in the 2-meter band?
Answer146.520 MHz.
146.520 MHz is the nationally recognized 2-meter FM simplex calling frequency.
On which amateur band is phone operation prohibited?
Answer30 meters.
The 30-meter amateur allocation is limited to narrowband modes; voice operation is not permitted.
Which of the following is an appropriate power supply rating for a typical 50-watt output mobile FM transceiver?
Answer13.8 volts at 12 amperes.
A typical mobile transceiver is designed around nominal automotive-system voltage and can draw substantial current while transmitting.
Why is a 3 kHz-wide USB signal with a displayed carrier of 14.348 MHz not legal?
AnswerIts upper 1 kHz extends beyond the 20-meter band edge.
For USB, transmitted energy lies above the displayed carrier frequency, so the entire occupied bandwidth must fit below the upper band edge.
Why are short, heavy-gauge wires used for a transceiver's DC power connection?
AnswerTo minimize voltage drop when transmitting.
Transmit current can be high. Short, heavy conductors reduce resistance and keep more of the supply voltage at the radio.
What direction does an ascending amateur-satellite pass travel?
AnswerFrom south to north.
Ascending and descending describe whether the spacecraft is moving northward or southward across the equator.
What is the primary purpose of a dummy load?
AnswerTo prevent transmitting signals over the air when making tests.
A proper dummy load absorbs transmitter RF power while presenting the expected impedance, allowing testing without intentionally radiating a signal.
Which factors are used to determine RF exposure from a transmitted signal?
AnswerDuty cycle, frequency, and power density.
RF exposure evaluation depends on how much energy is present, how often it is transmitted, and the frequency involved.
Which of the following devices or circuits changes an alternating current into a varying direct current signal?
AnswerA rectifier.
A rectifier uses one-way conduction, commonly with diodes, to convert AC into a unidirectional waveform.
Which of the following increases the resonant frequency of a dipole antenna?
AnswerShortening it.
Resonant antenna length and frequency are inversely related: a shorter resonant dipole corresponds to a higher frequency.
When evaluating RF exposure at a neighbor's home, which exposure limit applies?
AnswerThe uncontrolled maximum permissible exposure (MPE) limit.
People in neighboring residences are not under the station operator’s control, so the uncontrolled/public exposure limits apply.
How does a noise blanker reduce impulse noise?
AnswerBy reducing receiver gain during a noise pulse.
A noise blanker detects short high-amplitude impulses and suppresses the receiver briefly during those events.
Under what circumstances is it safe to climb a tower without a helper or observer?
AnswerNever.
Tower work combines fall, mechanical, and electrical hazards. A qualified helper or observer is an essential part of safe work practices.
A repeater has 150 W transmitter output, 2 dB feed-line loss, 2.2 dB duplexer loss, and 7 dBd antenna gain. What is its ERP?
AnswerApproximately 286 watts ERP.
Combine gains and losses in dB: net antenna-system gain is about +2.8 dB, which raises 150 W to roughly 286 W ERP.
How is direct binary FSK generated?
AnswerBy changing an oscillator frequency directly with a digital control signal.
FSK represents data with discrete carrier frequencies; direct FSK shifts the RF oscillator itself.
Which precaution should be taken when measuring high voltages with a voltmeter?
AnswerEnsure that the voltmeter and its leads are rated for the voltages being measured.
Meters, probes, insulation, and category ratings all matter when working around hazardous voltage.
What is antenna gain?
AnswerThe increase in signal strength in a specified direction compared to a reference antenna.
Antenna gain describes directional concentration relative to a reference. It does not mean the antenna creates RF power.
What is the impedance magnitude of a series RLC circuit at resonance?
AnswerApproximately equal to the circuit resistance.
At series resonance, inductive and capacitive reactance cancel, leaving the resistive part of the impedance.
What is an electrical diagram using standard component symbols called?
AnswerA schematic.
A schematic emphasizes electrical relationships using standard symbols rather than showing the physical appearance or location of parts.
What is the minimum discharge voltage commonly used for maximum life of a standard 12-volt lead-acid battery?
AnswerAbout 10.5 volts.
Deeply discharging a lead-acid battery below its normal endpoint shortens its useful life.
What is a beam antenna?
AnswerAn antenna that concentrates signals in one direction.
A directional or beam antenna redistributes RF energy so that more signal is transmitted and received in selected directions.
What is one common analog-to-digital conversion method?
AnswerSuccessive approximation.
A successive-approximation ADC tests candidate bit values step by step until it converges on a digital representation of the input voltage.
What electrical component stores energy in an electric field?
AnswerA capacitor.
A capacitor stores separated electric charge and therefore energy in an electric field between conductive surfaces.
Which sideband is normally used for voice at 14 MHz and above?
AnswerUpper sideband (USB).
The usual amateur convention is USB on 20 meters and higher-frequency HF bands.
In which type of circuit is the current always the same through all components?
AnswerSeries.
A series circuit provides only one path for current, so the same current passes through each component.
What antenna polarization is normally used for long-distance CW and SSB contacts on the VHF and UHF bands?
AnswerHorizontal.
Weak-signal VHF/UHF CW and SSB activity normally uses horizontal polarization, unlike most local FM mobile and repeater work.
On which HF/MF bands are there portions where General class licensees cannot transmit?
Answer80, 40, 20, and 15 meters.
Those bands contain segments reserved for Amateur Extra privileges, so a General license does not open the entire band.
What does a spectrum analyzer plot on its axes?
AnswerSignal amplitude versus frequency.
A spectrum analyzer shows how signal energy is distributed across frequency, unlike an oscilloscope, which normally shows amplitude versus time.
What is the electrical term for the force that causes electron flow?
AnswerVoltage.
Voltage is electrical potential difference. That difference provides the push that can drive current through a circuit.
Which of the following is used to convert a signal from one frequency to another?
AnswerA mixer.
A mixer combines signals so that sum and difference frequencies are produced, allowing frequency conversion in receivers and transmitters.
What limits the highest-frequency signal that a digital oscilloscope can accurately display?
AnswerThe analog-to-digital converter sampling rate.
A digital scope must sample fast enough to represent the waveform; insufficient sample rate loses waveform detail and can create aliases.
What is the purpose of a notch filter in an HF receiver?
AnswerTo reduce interference from carriers in the receiver passband.
A notch filter removes a narrow slice of audio or IF spectrum, making a steady interfering carrier much less objectionable.
Which of the following is used to determine if an antenna is resonant at the desired operating frequency?
AnswerAn antenna analyzer.
An antenna analyzer measures impedance-related behavior across frequency and is especially useful for finding resonance and evaluating an antenna system.
What is a common repeater frequency offset in the 2-meter band?
AnswerPlus or minus 600 kHz.
Two-meter FM repeaters commonly separate receive and transmit frequencies by 600 kHz.
Which components are commonly used in a power-supply filter network?
AnswerCapacitors and inductors.
Capacitors shunt ripple while inductors oppose changing current, so the combination can smooth rectified DC.
Which of the following is a form of amplitude modulation?
AnswerSingle sideband (SSB).
SSB is derived from amplitude modulation by suppressing the carrier and one sideband, making it more bandwidth- and power-efficient for voice communication.
What is characteristic of an inverting linear satellite transponder?
AnswerSignal position and sideband sense are inverted between uplink and downlink.
An inverting transponder reverses the spectral relationship: a signal near one end of the uplink passband appears near the opposite end of the downlink, and USB/LSB sense swaps.
Electrical power is measured in which of the following units?
AnswerWatts.
Electrical power describes the rate at which electrical energy is transferred or used.
What happens when inductive and capacitive reactance are equal in a series LC circuit?
AnswerThe circuit is resonant and its impedance becomes very low.
At series resonance, equal and opposite reactances cancel, leaving mainly the circuit resistance.
Electrical current is measured in which of the following units?
AnswerAmperes.
Current is the rate of electric charge flow and is measured in amperes, usually shortened to amps.
What does a decade counter do?
AnswerIt produces one output pulse for every 10 input pulses.
A decade counter cycles through ten states, so an appropriate output provides divide-by-ten behavior.
What electrical component opposes the flow of current in a DC circuit?
AnswerA resistor.
A resistor provides resistance, limiting current and producing a voltage drop according to Ohm's Law.
What is the term for the flow of electrons in an electric circuit?
AnswerCurrent.
Electrical current describes the movement of electric charge through a circuit.
Where is gallium arsenide commonly used as a semiconductor material?
AnswerMicrowave circuits.
GaAs supports high-frequency operation because of favorable carrier mobility and device characteristics.
What determines the characteristic impedance of a parallel-conductor feed line?
AnswerThe spacing between conductor centers and the conductor radius.
Transmission-line impedance is set by conductor geometry and dielectric properties rather than by line length.
What type of amateur station simultaneously retransmits the signal of another amateur station on a different channel or channels?
AnswerA repeater station.
A repeater receives a signal and simultaneously retransmits it on another channel, extending practical coverage.
What is a characteristic of single sideband (SSB) compared with FM?
AnswerSSB signals have narrower bandwidth.
Typical SSB voice occupies only a few kilohertz, substantially less spectrum than ordinary amateur FM voice.
What is the function of a power-supply bleeder resistor?
AnswerIt discharges filter capacitors after power is removed.
Large filter capacitors can retain dangerous voltage. A bleeder provides a controlled discharge path after shutdown.
What can make the voltage across a reactance in a series RLC circuit exceed the applied voltage?
AnswerResonance.
At resonance, circulating current can be large and the individual voltages across L and C can greatly exceed the source voltage while canceling each other in the series sum.
What hazard exists in a power supply immediately after turning it off?
AnswerCharge stored in filter capacitors.
Large capacitors can retain dangerous voltage after AC power is removed, so “off” does not necessarily mean electrically safe.
What hazard occurs when rapidly charging or discharging an unprotected battery?
AnswerOverheating or out-gassing.
High charge or discharge rates can create damaging heat and may cause gases to be released, depending on battery chemistry and condition.
Which semiconductor material contains excess free electrons?
AnswerN-type material.
Doping creates majority carriers: electrons in N-type material and holes in P-type material.
What do the FCC rules state regarding the use of a phonetic alphabet for station identification in the Amateur Radio Service?
AnswerIt is encouraged when using phone emissions.
Phonetics improve intelligibility when voice conditions are difficult, but the rules do not make a particular phonetic alphabet mandatory for ordinary identification.
What is an advantage of a battery with low internal resistance?
AnswerIt can deliver high discharge current.
Low internal resistance produces less internal voltage drop and heating when a large current is drawn.
Which term describes the ability of a receiver to detect the presence of a signal?
AnswerSensitivity.
Receiver sensitivity describes how weak a signal can be and still be detected or used.
What modulation changes the phase angle of an RF signal to convey information?
AnswerPhase modulation (PM).
In PM, information is represented by controlled changes in carrier phase.
What electronic component allows current to flow in only one direction?
AnswerA diode.
A diode is designed to conduct readily in the forward direction while strongly restricting current in the reverse direction.
For a properly adjusted 3 kHz LSB signal, how far above a lower band edge must the displayed carrier be?
Answer3 kHz above the lower band edge.
LSB energy extends below the displayed carrier, so enough clearance is required to keep the whole emission inside the band.
In which type of circuit is the voltage always the same across all components?
AnswerParallel.
Parallel branches connect across the same two electrical nodes, so each branch sees the same voltage.
What is a transceiver?
AnswerA device that combines a receiver and transmitter.
Most modern amateur radios combine both functions in one unit, hence transmitter + receiver = transceiver.
Which common digital circuit is bistable?
AnswerA flip-flop.
A flip-flop has two stable states and can store one bit of information.
What is reactance?
AnswerOpposition to alternating current caused by capacitance or inductance.
Unlike resistance, reactance depends on frequency and arises from energy storage in electric or magnetic fields.
What type of circuit controls the amount of voltage from a power supply?
AnswerA regulator.
A voltage regulator maintains or controls supply voltage despite changes in input or load within its operating limits.