Ham Radio Extra Class Exam — Questions and Answers

Question 1: In a Colpitts oscillator, the feedback network consists of:

Two inductors and one capacitor forming an L-network
A crystal in series with a feedback resistor
A tapped inductor with a single capacitor
Two capacitors forming a voltage divider with an inductor (Correct answer)

Correct answer: Two capacitors forming a voltage divider with an inductor

The Colpitts oscillator uses a capacitive voltage divider (two capacitors in series) with an inductor to set frequency and provide feedback.

Question 2: What type of antenna produces a circularly polarized signal?

Helical antenna in axial mode (Correct answer)
Half-wave dipole
Yagi-Uda array
Beverage antenna

Correct answer: Helical antenna in axial mode

A helical antenna operating in axial mode produces a circularly polarized wave, useful for satellite communications.

Question 3: What is the function of a bypass capacitor placed across the emitter resistor in a common-emitter amplifier?

To stabilize the DC bias point of the transistor
To filter out power supply noise from the circuit
To prevent thermal runaway of the transistor
To increase AC voltage gain by shorting the emitter resistor at signal frequencies (Correct answer)

Correct answer: To increase AC voltage gain by shorting the emitter resistor at signal frequencies

The bypass capacitor provides a low-impedance path for AC signals around the emitter resistor, removing the negative feedback that reduces gain at signal frequencies.

Question 4: What is the maximum power output allowed for an Amateur Extra class licensee on most HF bands in the United States?

2000 watts PEP
1500 watts PEP (Correct answer)
1000 watts PEP
500 watts PEP

Correct answer: 1500 watts PEP

FCC rules allow US amateur licensees to use a maximum of 1500 watts PEP output on most HF bands.

Question 5: What type of filter topology uses both series inductors and shunt capacitors to achieve a sharp cutoff response?

A pi-network low-pass filter (Correct answer)
A single-pole Butterworth filter
A simple RC high-pass filter
A resistive T-network attenuator

Correct answer: A pi-network low-pass filter

A pi-network filter uses a capacitor-inductor-capacitor arrangement that provides steeper rolloff than simple RC filters due to multiple reactive elements.

Question 6: What does a receiver's third-order intercept point (IP3) specification describe?

The theoretical input power level at which third-order intermodulation products equal the fundamental signal amplitude (Correct answer)
The frequency offset at which spurious responses are 3 dB above the noise floor
The noise figure degradation caused by a 3 dB lossy input attenuator
The input power at which the AGC circuit reduces gain by 3 dB

Correct answer: The theoretical input power level at which third-order intermodulation products equal the fundamental signal amplitude

IP3 is a figure of merit for receiver linearity. It is the extrapolated input power where the third-order intermodulation products would theoretically reach the same level as the desired signals. A higher IP3 means the receiver handles strong nearby signals with less intermodulation distortion, which is critical in crowded band conditions.

Question 7: Under FCC Part 97, what is the maximum permitted bandwidth for a data emission on the 20-meter band?

3 kHz
500 Hz
2.8 kHz (Correct answer)
1 kHz

Correct answer: 2.8 kHz

Data emissions on frequencies below 29.7 MHz are limited to 2.8 kHz bandwidth.

Question 8: What is the function of an automatic level control (ALC) circuit in an SSB transmitter?

To automatically select the correct sideband
To compensate for antenna SWR variations
To maintain constant audio frequency response
To limit the RF output power to prevent overdrive and distortion (Correct answer)

Correct answer: To limit the RF output power to prevent overdrive and distortion

The ALC circuit senses the RF output level and reduces the drive to the final amplifier to prevent flat-topping and intermodulation distortion on peaks.

Question 9: When an antenna analyzer is being used to assess SWR, which of the following must be attached to it?

Antenna and feed line (Correct answer)
Transmitter
Receiver
All of the above

Correct answer: Antenna and feed line

An antenna analyzer is used to measure the Standing Wave Ratio (SWR) and other characteristics of an antenna system. To perform an accurate SWR assessment, the antenna analyzer must be connected directly to the antenna and its associated feed line. This allows the analyzer to send a signal down the feed line to the antenna and measure the reflected power, providing a true indication of the impedance match of the entire system.

Question 10: A technician is building an audio filter for a CW (Morse code) receiver to create a very narrow passband around 700 Hz. Which of the following would be the most significant advantage of using an active filter with operational amplifiers (op-amps) over a passive LC filter for this application?

Active filters do not require a power source.
Active filters can provide signal gain and are easily cascaded for higher Q. (Correct answer)
Active filters have superior performance at microwave frequencies.
Passive filters are much smaller and lighter for audio frequencies.

Correct answer: Active filters can provide signal gain and are easily cascaded for higher Q.

For audio frequency applications, active filters built with op-amps offer significant advantages. They can be designed to provide voltage gain, compensating for insertion loss or boosting the signal level. Furthermore, active filter stages can be easily cascaded (connected in series) to create very sharp, high-Q filters without the loading problems and bulky inductors associated with multi-stage passive LC filters at audio frequencies.

Question 11: What is the primary purpose of a PTT (Push-To-Talk) delay in a linear amplifier?

To reduce intermodulation distortion
To allow the amplifier tubes to reach operating temperature
To sequence keying so the transceiver is muted before high voltage is applied (Correct answer)
To prevent feedback oscillation

Correct answer: To sequence keying so the transceiver is muted before high voltage is applied

PTT delay ensures the transceiver switches to transmit before the amplifier's high voltage is applied to the output stage, preventing RF arc damage.

Question 12: Which ionospheric layer is primarily responsible for long-distance HF propagation during daylight hours?

E layer
F1 layer
F2 layer (Correct answer)
D layer

Correct answer: F2 layer

The F2 layer, highest and most stable, is the primary reflector for long-distance HF signals during the day.

Question 13: What is the purpose of an 'automatic level control' (ALC) circuit in an HF transceiver?

To automatically select the best antenna based on SWR
To keep the audio output volume constant during signal fading
To maintain a constant noise figure in the receiver's front end
To prevent the transmitter from exceeding its rated peak envelope power by reducing drive when needed (Correct answer)

Correct answer: To prevent the transmitter from exceeding its rated peak envelope power by reducing drive when needed

ALC samples the transmitter's output power and feeds a control voltage back to the driver stage to reduce gain if the PEP would otherwise exceed the set maximum, protecting finals from overdrive.

Question 14: What is the primary cause of auroral propagation on the VHF and UHF bands?

Temperature inversions in the troposphere
Solar radiation ionizing the E layer
Reflection from meteor trails
Charged particles from the sun interacting with Earth's magnetic field (Correct answer)

Correct answer: Charged particles from the sun interacting with Earth's magnetic field

Auroral propagation occurs when charged solar particles excite gases along Earth's magnetic field lines near the poles, creating ionized regions that scatter VHF and UHF signals.

Question 15: What is a 'pileup' in amateur radio DX operation?

Running high power to break through interference
Stacking multiple antennas vertically for gain
Many stations simultaneously calling a rare DX station to make contact (Correct answer)
Logging multiple QSOs in a single contest exchange

Correct answer: Many stations simultaneously calling a rare DX station to make contact

A pileup occurs when many operators simultaneously call a rare or sought-after DX station, all competing to make a contact with that station.

Question 16: What is NVIS (Near Vertical Incidence Skywave) propagation best achieved with?

A horizontal antenna mounted at a low height (0.1 to 0.2 wavelengths) (Correct answer)
A high-gain Yagi pointed at the horizon
A rhombic antenna oriented for long-path propagation
A vertical antenna with a good radial system

Correct answer: A horizontal antenna mounted at a low height (0.1 to 0.2 wavelengths)

NVIS requires high-angle radiation nearly straight up, achieved by a horizontal antenna mounted very low (0.1–0.2λ) above ground.

Question 17: What is the purpose of intermodulation distortion (IMD) testing on a transmitter?

To determine how well the transmitter suppresses unwanted mixing products in the output signal (Correct answer)
To check the accuracy of the S-meter calibration
To measure the carrier frequency accuracy
To verify the antenna SWR is within acceptable limits

Correct answer: To determine how well the transmitter suppresses unwanted mixing products in the output signal

IMD testing measures the level of unwanted spurious signals produced by nonlinear mixing within the transmitter's amplifier stages.

Question 18: What is the 'gray line' in HF propagation?

The twilight zone between daylight and darkness on the Earth's surface that can enhance HF propagation along its path (Correct answer)
The boundary between the E and F ionospheric layers
A term for the noise floor on a specific HF band
A line on a map showing the maximum skip distance

Correct answer: The twilight zone between daylight and darkness on the Earth's surface that can enhance HF propagation along its path

The gray line is the terminator between day and night on Earth where ionospheric conditions can create an enhanced propagation path along the twilight boundary.

Question 19: Why is a Zener diode sometimes placed across the gate of a MOSFET in an RF power amplifier?

To set the operating bias point precisely
To protect the gate oxide from excessive voltage spikes (Correct answer)
To linearize the amplifier transfer characteristic
To reduce thermal runaway at high power levels

Correct answer: To protect the gate oxide from excessive voltage spikes

MOSFET gate oxide is extremely thin and can be destroyed by voltage spikes; a Zener diode clamps the gate voltage to a safe level.

Question 20: What does the slew rate of an operational amplifier specify?

The maximum DC gain before saturation
The input offset voltage drift with temperature
The common-mode rejection ratio at high frequencies
The maximum rate of change of the output voltage in V/µs (Correct answer)

Correct answer: The maximum rate of change of the output voltage in V/µs

Slew rate is the maximum speed at which an op-amp's output voltage can change, expressed in volts per microsecond.

Question 21: What is the Amateur Radio Emergency Service (ARES)?

A federal mandate requiring all hams to serve in emergencies
An FCC enforcement unit for emergency band monitoring
A FEMA program using ham radio for disaster relief
An ARRL-organized group of licensed amateurs registered for emergency communications (Correct answer)

Correct answer: An ARRL-organized group of licensed amateurs registered for emergency communications

ARES is an ARRL program where licensed amateur operators register to provide emergency communications support during disasters.

Question 22: Which of the following describes the function of a circulatory in a repeater system?

It isolates the transmitter and receiver when sharing a single antenna (Correct answer)
It provides DC power distribution to all repeater components
It rotates the polarization of the transmitted signal
It switches between multiple antennas automatically

Correct answer: It isolates the transmitter and receiver when sharing a single antenna

A circulator allows the transmitter and receiver to share one antenna by directing RF energy in only one direction, providing isolation between them.

Question 23: Which of the following best describes impedance in an AC circuit?

The total opposition to current flow, including both resistance and reactance. (Correct answer)
The opposition to current flow from capacitors only.
The opposition to current flow from inductors only.
The in-phase component of opposition to AC current.

Correct answer: The total opposition to current flow, including both resistance and reactance.

Impedance (Z) is the comprehensive measure of opposition to current in an AC circuit. It includes both resistance (R), which dissipates energy, and reactance (X), which stores and releases energy in electric or magnetic fields. Impedance is a complex quantity combining these two effects.

Question 24: Which antenna type uses a driven element, a reflector, and one or more directors?

Yagi-Uda antenna (Correct answer)
Log-periodic dipole array
Quad loop antenna
Collinear array

Correct answer: Yagi-Uda antenna

The Yagi-Uda antenna uses a driven element, a slightly longer reflector behind it, and one or more shorter directors in front.

Question 25: Under what specific condition is an amateur station authorized to transmit messages encoded to obscure their meaning?

During a declared national emergency.
When transmitting control commands to a space station. (Correct answer)
When using digital modes on frequencies above 450 MHz.
For communications supporting public safety officials.

Correct answer: When transmitting control commands to a space station.

FCC Part 97.113(a)(4) generally prohibits amateur stations from transmitting messages encoded to obscure their meaning. However, a specific exception is made for telecommand of a space station, allowing for the protection of the satellite's control systems.

Question 26: In a Class AB amplifier, what advantage does it offer over a Class B amplifier?

Lower component count
Reduced crossover distortion (Correct answer)
Higher power efficiency
Greater voltage gain

Correct answer: Reduced crossover distortion

Class AB biases both transistors slightly into conduction, eliminating the dead zone at the crossover point that causes distortion in Class B designs.

Question 27: What is the primary function of a low-noise amplifier (LNA) placed at the front end of a receiver?

To convert the RF signal to a lower intermediate frequency
To establish the noise figure of the entire receive chain (Correct answer)
To provide automatic gain control for strong signals
To filter out-of-band interference before the antenna

Correct answer: To establish the noise figure of the entire receive chain

The first amplifier in a cascade dominates overall noise figure per Friis's formula, so an LNA with low noise figure minimizes the receiver's noise floor.

Question 28: What is a 'DXpedition' in amateur radio?

A software tool for logging DX contacts
A portable antenna system designed for travel
An organized trip to a rare or unactivated location to operate amateur radio for contacts worldwide (Correct answer)
A special contest event for DX stations only

Correct answer: An organized trip to a rare or unactivated location to operate amateur radio for contacts worldwide

A DXpedition is when amateur operators travel to a rare geographic entity or location specifically to activate it and provide contacts to other amateurs around the world.

Question 29: What type of amateur license examination is administered by a Volunteer Examiner Coordinator (VEC)?

Only Technician class exams
Only upgrade exams from General to Extra
Technician, General, and Amateur Extra class exams (Correct answer)
Only Extra class exams

Correct answer: Technician, General, and Amateur Extra class exams

VECs coordinate the administration of all three classes of amateur radio exams: Technician, General, and Amateur Extra.

Question 30: What is the self-resonant frequency of an antenna primarily determined by?

The physical length of the antenna relative to the wavelength (Correct answer)
The type of coaxial cable used
The antenna's radiation resistance
The feedpoint impedance

Correct answer: The physical length of the antenna relative to the wavelength

An antenna's self-resonant frequency is primarily determined by its physical length, which must be an electrical multiple of the operating wavelength.

Question 31: What does the term 'third-order intercept point' (IP3) indicate about an amplifier?

The power level at which the transistor saturates
The frequency where gain drops 3 dB
The minimum detectable signal level
A measure of the amplifier's linearity and susceptibility to intermodulation distortion (Correct answer)

Correct answer: A measure of the amplifier's linearity and susceptibility to intermodulation distortion

IP3 is a theoretical point extrapolated from gain curves that indicates how well an amplifier handles strong signals without generating intermodulation products.

Question 32: What is the phase angle between voltage and current in a purely inductive circuit?

Voltage and current are in phase
Current leads voltage by 90 degrees
Voltage leads current by 90 degrees (Correct answer)
Voltage leads current by 45 degrees

Correct answer: Voltage leads current by 90 degrees

In a purely inductive circuit, voltage leads current by exactly 90 degrees due to the inductor opposing changes in current.

Question 33: What is the effect of over-deviation in an FM transmitter?

Lower transmitter power output
Reduced audio quality only
Excessive bandwidth and potential interference to adjacent channels (Correct answer)
Increased signal-to-noise ratio

Correct answer: Excessive bandwidth and potential interference to adjacent channels

Over-deviation causes the FM signal to occupy more bandwidth than necessary, which can cause splatter and interference on adjacent frequencies.

Question 34: Which of the following best describes the radiation pattern of a two-element Yagi antenna?

A cardioid pattern with maximum radiation toward the director (Correct answer)
A figure-eight pattern broadside to the elements
Equal radiation in all directions including vertical
An omnidirectional pattern in the horizontal plane

Correct answer: A cardioid pattern with maximum radiation toward the director

A two-element Yagi produces a cardioid-shaped pattern with the main lobe directed from the reflector toward the director.

Question 35: A voltage doubler rectifier circuit produces approximately what output DC voltage compared to the AC input RMS voltage?

Equal to the RMS voltage
Equal to the peak voltage (1.414 × RMS)
Equal to the average value (0.637 × peak)
Approximately twice the peak voltage (2.828 × RMS) (Correct answer)

Correct answer: Approximately twice the peak voltage (2.828 × RMS)

A voltage doubler charges two capacitors in series, each to the peak voltage, yielding approximately twice the peak (or about 2.83× RMS) at no load.

Question 36: What advantage does a log-periodic amplifier offer compared to a single-tuned amplifier in a wideband receiver?

Lower noise figure at VHF frequencies
Higher gain at a single specific frequency
Relatively constant gain over a wide frequency range (Correct answer)
Better image rejection without a preselector

Correct answer: Relatively constant gain over a wide frequency range

Log-periodic amplifier designs provide approximately uniform gain across a wide bandwidth, making them suitable for broadband receiver front ends.

Question 37: What is the role of a varactor diode in a voltage-controlled oscillator (VCO)?

To vary the tank circuit capacitance with applied voltage, tuning the frequency (Correct answer)
To multiply the oscillator output frequency by an integer
To provide temperature-compensated bias to the active device
To stabilize the oscillator amplitude via automatic gain control

Correct answer: To vary the tank circuit capacitance with applied voltage, tuning the frequency

A varactor's junction capacitance changes with reverse bias voltage, allowing electronic tuning of the LC tank circuit resonant frequency.

Question 38: What does the term 'pileup' describe in amateur radio DXing?

A digital mode that stacks multiple signals in one passband
A malfunction where multiple signals overlay a single frequency
Many stations calling simultaneously to work a rare DX station (Correct answer)
A repeater that queues transmissions for orderly relay

Correct answer: Many stations calling simultaneously to work a rare DX station

A pileup occurs when a rare or sought-after DX station attracts many callers simultaneously, all competing to make contact.

Question 39: What is a 'net' in amateur radio operations?

An internet linking system connecting repeaters worldwide
A network-connected SDR operating on a remote server
A method of measuring antenna efficiency
An organized group of stations meeting on a specific frequency at a scheduled time for a common purpose (Correct answer)

Correct answer: An organized group of stations meeting on a specific frequency at a scheduled time for a common purpose

A net is an organized gathering of amateur stations on a specific frequency at a scheduled time, often for emergency communications, traffic handling, or social purposes.

Question 40: What must an amateur station operator do before operating at power levels that could exceed FCC MPE limits, if the station is not categorically excluded?

Obtain a special variance permit from the FCC
Install an RF power limiter on the transmitter output
Notify all neighbors within 500 feet of the antenna
Perform a routine RF exposure evaluation (Correct answer)

Correct answer: Perform a routine RF exposure evaluation

FCC rules (Part 97.13) require amateur stations not categorically excluded to perform a routine RF exposure evaluation to ensure compliance with MPE limits.

Question 41: What is the advantage of a superheterodyne receiver design compared to a direct conversion receiver?

Fixed-frequency IF stages allow superior selectivity and sensitivity through optimized filters and amplifiers (Correct answer)
Superheterodyne receivers are immune to image frequency responses
The superheterodyne requires fewer components and is simpler to build
Direct conversion receivers require more complex local oscillator designs

Correct answer: Fixed-frequency IF stages allow superior selectivity and sensitivity through optimized filters and amplifiers

Because the superheterodyne converts all signals to a fixed IF, highly optimized narrow-band filters and high-gain amplifiers can be designed for that single frequency, yielding excellent selectivity and sensitivity.

Question 42: What is the critical frequency of an ionospheric layer?

The lowest frequency that will pass through the layer
The highest frequency that will be reflected back when transmitted vertically (Correct answer)
The frequency at which maximum absorption occurs
The frequency used to measure solar flux index

Correct answer: The highest frequency that will be reflected back when transmitted vertically

The critical frequency is the highest frequency that will be reflected straight back down when a signal is transmitted vertically into an ionospheric layer.

Question 43: What is a 'pi-network' tank circuit in a transmitter used for?

To filter RF harmonics only, with no impedance transformation
To stabilize the oscillator frequency against temperature drift
To bias the output transistor into class A operation
To match the amplifier's output impedance to the antenna feedline while providing harmonic suppression (Correct answer)

Correct answer: To match the amplifier's output impedance to the antenna feedline while providing harmonic suppression

A pi-network acts as both a low-pass filter to suppress harmonics and an impedance-matching network between the amplifier output and the transmission line.

Question 44: When using a field-effect transistor (FET) as an RF amplifier, what is the advantage of its high input impedance?

It increases the amplifier's output power
It allows the circuit to operate at lower supply voltages
It reduces thermal noise in the drain circuit
It minimizes loading of the signal source or preceding stage (Correct answer)

Correct answer: It minimizes loading of the signal source or preceding stage

A high input impedance prevents the FET gate from loading down the signal source, preserving signal amplitude and avoiding bandwidth degradation.

Question 45: Which of the following digital modes uses a combination of frequency shift and multiple tones to achieve a low-baud-rate, high-sensitivity signal suited for weak-signal HF work?

Packet AX.25
RTTY
JT65 (Correct answer)
SSTV

Correct answer: JT65

JT65 uses 65 orthogonal tones with very low symbol rate and strong FEC, enabling contacts at signal levels well below what SSB voice can achieve.

Question 46: What is the maximum RF power density allowed in an occupational (controlled) environment at frequencies between 30 and 300 MHz?

0.5 mW/cm²
0.2 mW/cm²
5.0 mW/cm²
1.0 mW/cm² (Correct answer)

Correct answer: 1.0 mW/cm²

The FCC allows 1.0 mW/cm² in controlled (occupational) environments at 30–300 MHz, which is five times the 0.2 mW/cm² limit for uncontrolled (general public) environments.

Question 47: Which component characteristic is most important when selecting a capacitor for use in a high-Q resonant circuit?

High ESR (equivalent series resistance)
High temperature coefficient
Large physical size
Low ESR and low dielectric loss (high Q) (Correct answer)

Correct answer: Low ESR and low dielectric loss (high Q)

Low ESR and low dielectric loss ensure minimal energy dissipation, maintaining the high Q of the resonant circuit.

Question 48: What happens to the noise figure of a receiver when a lossy component is placed before the first amplifier stage?

The noise figure is cut in half
The noise figure remains unchanged
The noise figure improves proportionally
The noise figure degrades by approximately the loss of the component (Correct answer)

Correct answer: The noise figure degrades by approximately the loss of the component

Any loss before the first amplifier stage directly adds to the receiver's noise figure by approximately the same amount in dB.

Question 49: What is the input impedance of a quarter-wavelength transmission line section terminated with a short circuit?

0 ohms (short circuit)
Purely resistive and equal to the line's characteristic impedance Z0
Infinite impedance (open circuit) (Correct answer)
Z0 squared divided by the terminating impedance

Correct answer: Infinite impedance (open circuit)

A quarter-wave transmission line acts as an impedance inverter. A short circuit (0 Ω) at the far end appears as an open circuit (infinite impedance) at the input, and vice versa. This property is widely used in antenna matching networks and stub filters.

Question 50: What is the relationship between skin depth and frequency in a conductor?

Skin depth increases as frequency increases
Skin depth is independent of frequency
Skin depth decreases as frequency increases (Correct answer)
Skin depth increases only above 30 MHz

Correct answer: Skin depth decreases as frequency increases

Skin depth decreases as frequency increases because the skin effect forces current to flow closer to the conductor's surface at higher frequencies.

Question 51: What is the approximate gain of a typical 5-element Yagi antenna over a dipole?

18 to 22 dBd
6 to 9 dBd (Correct answer)
2 to 3 dBd
12 to 15 dBd

Correct answer: 6 to 9 dBd

A 5-element Yagi typically provides 6 to 9 dBd gain over a reference dipole, depending on element spacing and design.

Question 52: What is the purpose of a 'loading coil' placed at the base of a short vertical antenna?

To increase the antenna's radiation resistance
To match the antenna impedance to exactly 50 ohms
To provide a DC ground path for lightning protection
To resonate the electrically short antenna at the operating frequency by adding inductive reactance (Correct answer)

Correct answer: To resonate the electrically short antenna at the operating frequency by adding inductive reactance

A loading coil adds inductive reactance to cancel the capacitive reactance of an electrically short antenna, bringing it into resonance at the desired frequency.

Ham Radio Extra Class Exam

The FCC Extra Class exam is the highest amateur radio license, covering all amateur bands.

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