Ham Radio Extra Class Exam — Questions and Answers

Question 1: A pi-network is frequently used in the output stage of a vacuum tube transmitter. What is the primary purpose of this circuit?

To provide negative feedback to stabilize the amplifier's gain
To transform the high output impedance of the tube to the low impedance of the antenna (Correct answer)
To function as a high-pass filter to remove low-frequency hum
To invert the phase of the signal for push-pull operation

Correct answer: To transform the high output impedance of the tube to the low impedance of the antenna

A pi-network is a versatile impedance-matching circuit. In the output of a vacuum tube power amplifier, it is used to match the typically high output impedance of the tube to the low impedance of the antenna (usually 50 ohms). This ensures maximum power transfer and also acts as a low-pass filter, which helps to attenuate harmonics.

Question 2: What is the relationship between peak voltage and RMS voltage in a pure sine wave?

RMS voltage equals peak voltage divided by the square root of 2 (Correct answer)
RMS voltage equals peak voltage
RMS voltage equals peak voltage multiplied by 2
RMS voltage equals peak voltage divided by 2

Correct answer: RMS voltage equals peak voltage divided by the square root of 2

For a sine wave, Vrms = Vpeak / √2, which is approximately 0.707 times the peak voltage.

Question 3: What is the approximate gain of a five-element Yagi-Uda antenna over a dipole?

About 0 dBd
About 10 dBd (Correct answer)
About 3 dBd
About 20 dBd

Correct answer: About 10 dBd

A well-designed five-element Yagi typically provides roughly 10 dBd of gain, combining the effects of one reflector and three directors.

Question 4: What is the quality factor (Q) of a parallel resonant circuit with R = 10 kohms, L = 10 uH, and C = 10 pF?

10
100 (Correct answer)
1000
50

Correct answer: 100

For a parallel RLC circuit, Q = R / (2 * pi * f * L), and at resonance with these values Q equals approximately 100.

Question 5: What does "QRV" in the Q signal mean?

I am quitting for the day
There is interference on the frequency
I am ready to receive messages (Correct answer)
You are sending too fast

Correct answer: I am ready to receive messages

"QRV" is a standard Q signal used in amateur radio and other radiocommunication. It is an abbreviation that means "Are you ready?" or "I am ready to receive messages." When an operator sends "QRV?", they are asking if the other station is ready, and when they send "QRV", they are indicating their own readiness to receive traffic.

Question 6: What is an isotropic radiator and why is it used as a reference?

A real antenna used in anechoic chambers for calibration
A theoretical antenna that radiates equally in all directions, used as a universal gain reference (Correct answer)
A directional antenna with 0 dB gain on the reference axis
A dipole antenna oriented vertically, used because it is easy to build

Correct answer: A theoretical antenna that radiates equally in all directions, used as a universal gain reference

An isotropic radiator is a theoretical point source that radiates equally in all directions (4π steradians), used as a universal reference for expressing antenna gain in dBi.

Question 7: What is the FCC requirement for station identification when operating under automatic control on HF frequencies?

Identification every 30 minutes
Identification every 5 minutes
No identification is required under automatic control
Identification every 10 minutes and at the end of a communication (Correct answer)

Correct answer: Identification every 10 minutes and at the end of a communication

All amateur transmissions must include station identification at least every 10 minutes and at the end of each communication.

Question 8: What type of filter topology uses both series inductors and shunt capacitors to achieve a sharp cutoff response?

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

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 9: In a series RLC circuit at resonance, what is the relationship between capacitive reactance (Xc) and inductive reactance (Xl)?

Xc is much larger than Xl.
Xc and Xl are equal in magnitude. (Correct answer)
Xl is much larger than Xc.
Xc is infinite, and Xl is zero.

Correct answer: Xc and Xl are equal in magnitude.

Resonance in a series RLC circuit occurs at the specific frequency where the inductive reactance (Xl) and capacitive reactance (Xc) are equal in magnitude. At this point, their effects cancel each other out, leaving the circuit's impedance at its minimum value, equal only to the resistance (R).

Question 10: What is AGC (Automatic Gain Control) in a receiver and what problem does it solve?

A circuit that tunes the receiver automatically to the strongest signal
A circuit that adjusts receiver gain to maintain constant audio output despite varying signal strengths (Correct answer)
A filter that removes gain peaks in the audio response
A system that controls transmitter power to avoid interference

Correct answer: A circuit that adjusts receiver gain to maintain constant audio output despite varying signal strengths

AGC samples the IF signal level and feeds back a control voltage to reduce gain for strong signals and increase it for weak signals, keeping audio output relatively constant.

Question 11: In a superheterodyne receiver, what is the purpose of the image reject filter placed before the mixer?

To amplify the desired signal before frequency conversion
To stabilize the local oscillator frequency
To prevent a signal at the image frequency from entering the mixer (Correct answer)
To remove IF feedthrough from the antenna port

Correct answer: To prevent a signal at the image frequency from entering the mixer

The image reject filter blocks signals at the image frequency (LO ± IF) that would otherwise mix down to the same IF as the desired signal, causing interference.

Question 12: What is the 'image frequency' in a superheterodyne receiver?

A duplicate display of the desired signal on a panadapter display
The reflected signal from a nearby obstacle creating multipath
A frequency on the opposite side of the local oscillator from the desired signal by the same IF interval, which can produce an unwanted response (Correct answer)
The mirror-image sideband rejected during SSB demodulation

Correct answer: A frequency on the opposite side of the local oscillator from the desired signal by the same IF interval, which can produce an unwanted response

The image frequency is separated from the local oscillator by the same IF frequency but on the opposite side; signals at this frequency mix to produce the same IF and thus appear as interference if not rejected.

Question 13: When viewing a constellation diagram for a digitally modulated signal, what does each individual point on the diagram represent?

A unique symbol, which may represent one or more bits. (Correct answer)
A unique frequency shift of the carrier.
The overall bit error rate (BER).
A single bit of data (a 1 or a 0).

Correct answer: A unique symbol, which may represent one or more bits.

A constellation diagram plots the possible states of a digital signal on a two-dimensional graph representing the I and Q components. Each point on the diagram corresponds to a unique combination of amplitude and phase, which defines a single symbol. Depending on the modulation scheme (e.g., QPSK, 16-QAM), each symbol can represent multiple bits of data.

Question 14: What effect does mutual coupling between inductors have on total inductance when fields aid?

Total inductance increases beyond the sum of individual inductances (Correct answer)
Total inductance equals the sum of individual inductances
Total inductance decreases below the sum of individual inductances
Total inductance remains unchanged

Correct answer: Total inductance increases beyond the sum of individual inductances

When magnetic fields aid each other, mutual inductance adds to the total, making it greater than L1 + L2.

Question 15: In a circuit operating at 14 MHz, what is the reactance of a 300 picofarad capacitor?

151.6 ohms
75.8 ohms
18.9 ohms
37.9 ohms (Correct answer)

Correct answer: 37.9 ohms

Capacitive reactance Xc = 1/(2πfC) = 1/(2π × 14×10⁶ × 300×10⁻¹²) ≈ 37.9 ohms.

Question 16: What is the FCC's definition of harmful interference under Part 97?

Static caused by natural atmospheric conditions
Interference that endangers safety of life or degrades authorized radiocommunication services (Correct answer)
Signal splatter beyond the authorized bandwidth
Any interference that disrupts authorized radio communications

Correct answer: Interference that endangers safety of life or degrades authorized radiocommunication services

Harmful interference is defined as interference that endangers the functioning of a radionavigation service or seriously degrades, obstructs, or interrupts authorized radiocommunication services.

Question 17: What is the function of a Beat Frequency Oscillator (BFO) or carrier insertion oscillator in a receiver?

To calibrate the receiver's frequency readout against a known standard
To provide the reference for the automatic frequency control circuit
To reinsert the suppressed carrier at the IF for demodulation of SSB and CW signals (Correct answer)
To generate the final RF carrier for the transmitter output stage

Correct answer: To reinsert the suppressed carrier at the IF for demodulation of SSB and CW signals

The BFO injects a carrier signal at the IF frequency so that SSB and CW signals, which have no carrier of their own, can be properly demodulated.

Question 18: Which of the following correctly describes 'split operation' during a DX pileup?

Transmitting on one frequency while listening on a different frequency (Correct answer)
Operating with reduced power to avoid interference
Transmitting and receiving on the same frequency alternately
Using two separate radios simultaneously for duplex operation

Correct answer: Transmitting on one frequency while listening on a different frequency

Split operation means the DX station transmits on one frequency and listens on a different (often spread) frequency to manage pileups efficiently.

Question 19: What is the approximate feed point impedance of a half-wave dipole antenna in free space?

73 ohms (Correct answer)
300 ohms
50 ohms
36 ohms

Correct answer: 73 ohms

A half-wave dipole in free space has a theoretical feed point impedance of approximately 73 ohms.

Question 20: What is the purpose of a 'CQ' call on the amateur radio bands?

To indicate the frequency is in use
To announce a general call inviting any station to respond (Correct answer)
To call a specific station
To request emergency assistance

Correct answer: To announce a general call inviting any station to respond

CQ is a general call to any and all stations, inviting anyone who hears the transmission to respond and establish contact.

Question 21: What is the purpose of forward error correction (FEC) in digital communications?

To encrypt data so that errors cannot be exploited
To compress data before transmission to reduce bandwidth
To request retransmission whenever a bit error is detected
To add redundant bits that allow the receiver to detect and correct errors without retransmission (Correct answer)

Correct answer: To add redundant bits that allow the receiver to detect and correct errors without retransmission

FEC encodes data with redundancy so the receiver can identify and correct errors autonomously, making it ideal for one-way or high-latency links.

Question 22: What happens to the radiation resistance of a shortened antenna compared to a full-size resonant antenna?

It increases significantly
It remains the same
It decreases significantly (Correct answer)
It becomes purely reactive

Correct answer: It decreases significantly

Shortening an antenna below its resonant length causes the radiation resistance to decrease, reducing efficiency.

Question 23: In a transformer with a 4:1 turns ratio, what is the impedance transformation ratio?

4:1
16:1 (Correct answer)
2:1
8:1

Correct answer: 16:1

Impedance transforms as the square of the turns ratio, so a 4:1 turns ratio gives a 16:1 impedance ratio.

Question 24: Which FCC form is used to apply for an amateur radio license or upgrade?

FCC Form 740
FCC Form 312
FCC Form 159
FCC Form 605 (Correct answer)

Correct answer: FCC Form 605

FCC Form 605 is the Main Form for Commercial and Amateur Radio Service Applications, used for license grants and upgrades.

Question 25: What is the purpose of a 'frequency coordinator' in amateur radio repeater operation?

To manage repeater frequency assignments in a geographic area to minimize interference between repeater systems (Correct answer)
To coordinate contest operating frequencies for clubs
To assign call signs to new repeater trustees
To control the accuracy of each repeater's transmit frequency

Correct answer: To manage repeater frequency assignments in a geographic area to minimize interference between repeater systems

A frequency coordinator manages and assigns repeater input/output frequencies within a geographic area to avoid harmful interference between repeater systems.

Question 26: Which type of filter has the steepest skirt selectivity for a given number of poles?

Butterworth
Chebyshev (Correct answer)
Gaussian
Bessel

Correct answer: Chebyshev

Chebyshev filters provide the steepest rolloff for a given filter order, at the expense of passband ripple.

Question 27: What does the Q-code 'QTH' mean in amateur radio communication?

My location is (Correct answer)
My signal is fading
My frequency is shifting
My power is low

Correct answer: My location is

QTH is used to indicate location; 'What is your QTH?' means 'What is your location?' in amateur radio shorthand.

Question 28: In a frequency synthesizer circuit, what is the core function of the Phase-Locked Loop (PLL)?

To compare the phase of a Voltage-Controlled Oscillator (VCO) with a reference signal and adjust the VCO's frequency until they are locked (Correct answer)
To filter out unwanted harmonics from the output of a multiplier stage
To amplify the reference oscillator signal to the final output power
To directly generate a wide range of frequencies through digital-to-analog conversion

Correct answer: To compare the phase of a Voltage-Controlled Oscillator (VCO) with a reference signal and adjust the VCO's frequency until they are locked

A Phase-Locked Loop (PLL) is a feedback control system that generates a stable output signal whose phase is locked to the phase of an input or reference signal. It continuously compares the phase of its internal Voltage-Controlled Oscillator (VCO) with the reference and uses the resulting error signal to adjust the VCO's frequency, forcing it to match the reference frequency or a multiple of it.

Question 29: What is the difference between receiver 'sensitivity' and 'selectivity'?

Sensitivity measures RF performance and selectivity measures audio performance
Sensitivity is the ability to detect weak signals; selectivity is the ability to reject adjacent-channel interference (Correct answer)
Both terms describe the same receiver characteristic measured under different conditions
Sensitivity applies to AM reception while selectivity applies to FM and SSB

Correct answer: Sensitivity is the ability to detect weak signals; selectivity is the ability to reject adjacent-channel interference

Sensitivity describes the minimum signal level the receiver can usefully detect (often expressed as minimum discernible signal or noise figure), while selectivity describes how well it rejects signals on adjacent frequencies.

Question 30: What phenomenon causes a received signal to vary rapidly in strength and phase when the receiving antenna is moved only a fraction of a wavelength?

Multipath fading due to constructive and destructive interference of reflected waves (Correct answer)
Receiver desensitization
Ionospheric absorption
Tropospheric ducting

Correct answer: Multipath fading due to constructive and destructive interference of reflected waves

Multipath fading occurs when multiple reflected signal paths arrive with different delays, causing phase differences that alternately add or cancel.

Question 31: In a direct digital synthesis (DDS) system, what determines the frequency resolution of the output signal?

The size of the phase accumulator and the clock frequency (Correct answer)
The cutoff frequency of the output filter
The amplitude of the reference oscillator
The number of bits in the DAC

Correct answer: The size of the phase accumulator and the clock frequency

Frequency resolution in a DDS is set by dividing the clock frequency by 2 raised to the power of the phase accumulator bit width.

Question 32: What is mutual coupling between antenna elements in an array?

The physical spacing between elements measured in wavelengths
The impedance of the transmission line connecting the elements
The phase difference between signals fed to each element
The electromagnetic interaction between antenna elements that affects their impedance and current distribution (Correct answer)

Correct answer: The electromagnetic interaction between antenna elements that affects their impedance and current distribution

Mutual coupling is the electromagnetic interaction between nearby antenna elements that changes their individual impedances and current distributions from the isolated element case.

Question 33: A cascode amplifier consists of what transistor configuration?

Two common-emitter stages in series
A common-emitter stage driving a common-base stage (Correct answer)
Two common-base stages in parallel
A common-collector stage driving a common-emitter stage

Correct answer: A common-emitter stage driving a common-base stage

The cascode pairs a common-emitter (or common-source) input with a common-base (common-gate) output, reducing the Miller effect and extending bandwidth while maintaining gain.

Question 34: What is a 'ground loop' in a ham radio station?

Multiple ground paths that form a closed loop, carrying unwanted circulating currents (Correct answer)
A coaxial feedline loop used for noise cancellation that reduces antenna efficiency
A circular antenna that provides gain and causes interference to nearby stations
A safety ground wire routed in a circle for mechanical security

Correct answer: Multiple ground paths that form a closed loop, carrying unwanted circulating currents

A ground loop exists when two or more ground connections form a closed loop, allowing induced currents to circulate and create noise, hum, or RF interference.

Question 35: What type of feedback is used in a voltage-regulator op-amp circuit where the output is sampled and returned to the inverting input?

Positive current feedback
Current-series feedback
Negative voltage feedback (Correct answer)
Positive voltage feedback

Correct answer: Negative voltage feedback

Sampling the output voltage and feeding it back to the inverting input is classic negative voltage feedback, which stabilizes the output.

Question 36: What is the lowest frequency in the 80-meter band at which an Extra class licensee may operate single-sideband phone?

3.700 MHz
3.750 MHz
3.525 MHz
3.600 MHz (Correct answer)

Correct answer: 3.600 MHz

FCC Part 97 grants Extra class licensees phone (including SSB) privileges beginning at 3.600 MHz on 80 meters, extending to 4.000 MHz. General class phone begins at 3.800 MHz, so Extra class has an additional 200 kHz of exclusive phone spectrum in the lower portion of the band.

Question 37: What is 'auroral propagation' and which amateur bands does it most affect?

HF skywave via the E-layer enhanced by auroral activity at 10–20 MHz
Microwave ducting along the polar front jet stream
Tropospheric scattering affecting 160 and 80 meters
VHF and UHF reflection off the ionized aurora borealis, mainly affecting 50 MHz and above (Correct answer)

Correct answer: VHF and UHF reflection off the ionized aurora borealis, mainly affecting 50 MHz and above

Auroral propagation uses the ionized curtain of the aurora borealis as a reflector for VHF signals, most notably on the 6-meter and 2-meter bands.

Question 38: What is the purpose of stacking two identical Yagi antennas vertically?

To reduce the bandwidth of the combined system
To double the front-to-back ratio
To shift the operating frequency lower by sqrt(2)
To increase gain by reducing the elevation beamwidth (Correct answer)

Correct answer: To increase gain by reducing the elevation beamwidth

Stacking Yagis vertically increases gain (about 3 dB ideally) by narrowing the elevation (vertical) beamwidth while maintaining the horizontal pattern.

Question 39: In 8-PSK modulation, how many bits are encoded per symbol?

1 bit
4 bits
3 bits (Correct answer)
2 bits

Correct answer: 3 bits

8-PSK has 8 phase states (2³ = 8), so each symbol carries 3 bits of information.

Question 40: What is a 'Doherty amplifier' and why is it used in modern RF transmitters?

An efficiency-enhancing amplifier topology that keeps efficiency high across a wide range of output power levels (Correct answer)
A balanced amplifier using two identical modules for redundancy
A push-pull amplifier for audio frequency stages
An amplifier with automatic gain control for stable output

Correct answer: An efficiency-enhancing amplifier topology that keeps efficiency high across a wide range of output power levels

The Doherty architecture uses a carrier and peaking amplifier to maintain high efficiency (close to Class B) even at power back-off levels typical of modulated signals.

Question 41: Which of the following amateur radio contacts qualifies for DXCC credit?

A contact made using a satellite transponder
A contact with a station in a separate DXCC entity at least 350 km away (Correct answer)
Any two-way contact confirmed with a QSL card
A contact with a station in a different US state

Correct answer: A contact with a station in a separate DXCC entity at least 350 km away

DXCC credit requires confirmed two-way contact with a station in a separate, recognized DXCC entity as defined by ARRL rules.

Question 42: What is the purpose of a low-pass filter on the output of an HF transmitter?

To improve impedance matching between the transmitter and antenna
To reduce the audio bandwidth of the transmitted signal
To reduce the transmitter's output power to legal limits on certain bands
To suppress harmonic emissions above the cutoff frequency that could cause interference to other services (Correct answer)

Correct answer: To suppress harmonic emissions above the cutoff frequency that could cause interference to other services

A low-pass filter passes the fundamental frequency while attenuating harmonics and other spurious emissions above the cutoff, helping the transmitter meet FCC spurious emission limits.

Question 43: In antenna modeling software like EZNEC or 4nec2, what does the term 'far-field' refer to?

The portion of the feed line closest to the antenna terminals
The physical space occupied by the antenna elements
The area immediately surrounding the antenna where stored energy is dominant
The region where the antenna's radiation pattern is independent of distance (Correct answer)

Correct answer: The region where the antenna's radiation pattern is independent of distance

The 'far-field' is the region distant from the antenna where the angular distribution of the radiated field is essentially independent of the distance from the antenna. This is the region where radiation patterns are typically measured and evaluated. The 'near-field' is the area closer to the antenna where the fields are more complex.

Question 44: What is the approximate noise figure of a well-designed preamplifier used for weak-signal VHF work?

6 dB
0.5 dB (Correct answer)
10 dB
20 dB

Correct answer: 0.5 dB

A high-quality VHF preamplifier for weak-signal work typically achieves a noise figure of about 0.5 dB or less.

Question 45: Which mode of propagation is responsible for extending 2-meter VHF signals over 1,000 miles or more during periods of stable high-pressure weather systems?

Transequatorial propagation
Tropospheric ducting (Correct answer)
Meteor scatter
Sporadic E

Correct answer: Tropospheric ducting

Tropospheric ducting occurs when a temperature inversion in the lower atmosphere traps VHF/UHF signals, acting like a waveguide that can carry signals for hundreds to thousands of miles. It is most common during stable, warm, high-pressure conditions.

Question 46: What is required before an amateur station may transmit on a frequency within a shared band that is also allocated to the radiolocation service?

A frequency coordinator must approve the operation
The amateur must yield to radiolocation users at all times (Correct answer)
The amateur must monitor for 30 seconds before transmitting
No special requirement beyond normal amateur operating practices

Correct answer: The amateur must yield to radiolocation users at all times

In shared bands where amateur is secondary to radiolocation, amateur operators must not cause interference and must yield to primary users.

Question 47: What is the maximum symbol rate permitted for RTTY or data emissions in the 80-meter amateur band below 3600 kHz?

56 kilobaud
300 baud (Correct answer)
1200 baud
19.6 kilobaud

Correct answer: 300 baud

FCC Part 97.307 limits the symbol rate to 300 baud for RTTY and data emissions below 28 MHz (including 80 meters).

Question 48: What is the meaning of 'RST' in a signal report exchanged during a QSO?

Repeater Station Threshold
Receive, Send, Transmit
Readability, Signal strength, Tone (Correct answer)
Radio Signal Type

Correct answer: Readability, Signal strength, Tone

RST stands for Readability (1–5), Signal strength (1–9), and Tone (1–9, used for CW), giving a standardized signal quality report.

Question 49: What is the maximum transmitter power an amateur station may use on the 160-meter band?

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

Correct answer: 1500 watts PEP

FCC Part 97 allows a maximum of 1500 watts PEP on the 160-meter band for Amateur Extra licensees.

Question 50: What is the function of a balun at a dipole feed point when coaxial cable is used?

To increase antenna gain
To match impedance to 300 ohms
To reduce SWR on the transmission line
To prevent common-mode current on the coax shield (Correct answer)

Correct answer: To prevent common-mode current on the coax shield

A balun suppresses common-mode (shield) currents that would otherwise cause the coax to radiate and distort the antenna pattern.

Question 51: What does the term 'frequency deviation' refer to in FM modulation?

The peak change in instantaneous carrier frequency from the unmodulated carrier frequency (Correct answer)
The rate at which the modulating signal changes frequency
The amount the receiver's discriminator is offset from center
The difference between the carrier frequency and the crystal oscillator frequency

Correct answer: The peak change in instantaneous carrier frequency from the unmodulated carrier frequency

Frequency deviation is the maximum instantaneous shift of the carrier frequency above or below the rest frequency, determined by the amplitude of the modulating signal.

Question 52: What is the primary advantage of using a direct digital synthesizer (DDS) as a VFO?

Higher output power than analog oscillators
Extremely fine frequency resolution and fast switching speed (Correct answer)
Reduced current consumption compared to crystal oscillators
Elimination of all spurious signals

Correct answer: Extremely fine frequency resolution and fast switching speed

DDS provides very fine frequency steps and can switch frequencies in microseconds, making it ideal for modern transceivers.

Ham Radio Extra Class Exam

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

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40 min

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