Amateur Extra Sample Questions

Questions from each subelement of the Amateur Extra pool. Pick an answer to see whether you're right, how everyone else did, and why.

Amateur Extra exam guide

E1 Commission rules

Who must be in physical control of the station apparatus of an amateur station aboard any vessel or craft that is documented or registered in the United States?

  1. Only a person named in an amateur station license grant
  2. Any person named in an amateur station license grant or a person holding an unrestricted Radiotelephone Operator Permit
  3. Any person holding an FCC issued amateur license or who is authorized for alien reciprocal operation
  4. Only a person with an FCC Marine Radio license grant

Answer: C, Any person holding an FCC issued amateur license or who is authorized for alien reciprocal operation. Section 97.5(a)(2) covers any vessel or craft documented or registered in the United States, within 50 km of the Earth's surface. The station apparatus must be under the physical control of a person named in an amateur station license grant, or of a person authorized for alien reciprocal operation under 97.107. The same requirement applies on land where the FCC regulates amateur radio.

What is the maximum mean power level for a spurious emission below 30 MHz with respect to the fundamental emission?

  1. - 53 dB
  2. - 73 dB
  3. - 43 dB
  4. - 63 dB

Answer: C, - 43 dB. Section 97.307(d) says that for transmitters installed after January 1, 2003, any spurious emission on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental. So 43 dB is the minimum attenuation, which makes -43 dB the highest allowed level. At 100 W, -43 dB is about 5 mW. Older transmitters follow a looser 40 dB / 50 mW limit, and VHF uses 60 dB.

Under what circumstances may a dealer sell an external RF power amplifier capable of operation below 144 MHz if it has not been granted FCC certification?

  1. It was manufactured and certificated in a country which has a reciprocal certification agreement with the FCC
  2. The amplifier is constructed or modified by an amateur radio operator for use at an amateur station
  3. The equipment dealer assembled it from a kit
  4. Gain is less than 23 dB when driven by power of 10 watts or less

Answer: B, The amplifier is constructed or modified by an amateur radio operator for use at an amateur station. Section 97.315(a) generally requires FCC certification for external RF power amplifiers made or imported for amateur use. It also bars a non-amateur from building or modifying an amplifier that works below 144 MHz without certification. Section 97.315(b)(1) waives the requirement when the amplifier is constructed or modified by an amateur radio operator for use at an amateur station.

E2 Operating procedures

What technique allows commercial analog TV receivers to be used for fast-scan TV operations on the 70-centimeter band?

  1. Transmitting on channels shared with cable TV
  2. Using converted satellite TV dishes
  3. Transmitting on the abandoned TV channel 2
  4. Using USB and demodulating the signal with a computer sound card

Answer: A, Transmitting on channels shared with cable TV. The 70 cm band (420-450 MHz) overlaps the frequencies that cable systems use for some cable TV channels. A 'cable-ready' analog TV can tune those channels, so an amateur fast-scan TV signal sent on a matching frequency can be watched on an ordinary set. ATV uses the same AM vestigial-sideband video format as analog broadcast TV, which is why it works without a special receiver.

What indicates the delay between a control operator action and the corresponding change in the transmitted signal?

  1. Anti-VOX
  2. Latency
  3. Hang time
  4. Jitter

Answer: B, Latency. Latency is the delay between when something happens at one end of a system and when it shows up at the other. In remote operation, your keystroke, PTT press or audio has to pass through computers, networks and the radio before it changes the transmitted signal. That total delay is the latency. High latency makes fast QSK CW or quick contest exchanges awkward.

How does Q65 differ from JT65?

  1. Keyboard-to keyboard operation is supported
  2. Quadrature modulation is used
  3. Multiple receive cycles are averaged
  4. All these choices are correct

Answer: C, Multiple receive cycles are averaged. Q65 is a weak-signal mode for EME, scatter and marginal paths. One of its key features is averaging: when a single receive period is too weak to decode, the software combines several cycles of the same message until it can be copied. This lets Q65 pull out signals well below what a single JT65 period could decode.

E3 Radio wave propagation

In what direction does an electromagnetic wave travel?

  1. It travels parallel to the electric and magnetic fields
  2. It travels at a right angle to the electric and magnetic fields
  3. It depends on the phase angle of the magnetic field
  4. It depends on the phase angle of the electric field

Answer: B, It travels at a right angle to the electric and magnetic fields. A radio wave is made of an electric field and a magnetic field at right angles to each other. The wave's energy moves in the direction perpendicular to both fields (the Poynting vector, E x H). The wave travels at a right angle to the electric and magnetic fields, and that holds whatever the wave's phase.

Where is transequatorial propagation (TEP) most likely to occur?

  1. Between points located 1,500 miles to 2,000 miles apart on the geomagnetic equator
  2. Through the region where the terminator crosses the geographic equator
  3. Between points located at each other’s antipode
  4. Between points separated by 2,000 miles to 3,000 miles over a path perpendicular to the geomagnetic equator

Answer: D, Between points separated by 2,000 miles to 3,000 miles over a path perpendicular to the geomagnetic equator. Transequatorial propagation uses dense ionization on both sides of the geomagnetic equator. That makes it work between stations about 2,000 to 3,000 miles apart on a roughly north-south path crossing the equator at a right angle. It peaks in the afternoon and evening near the equinoxes and can carry signals up into the VHF range.

Which of the following is the space-weather term for an extreme geomagnetic storm?

  1. X5
  2. B9
  3. M9
  4. G5

Answer: D, G5. NOAA's space-weather scales use three letters. G stands for geomagnetic storms, S for solar radiation storms and R for radio blackouts. Each is rated from 1 (minor) to 5 (extreme). A G5 storm is the most severe geomagnetic disturbance. It brings widespread HF blackouts, strong auroras far from the poles, and possible damage to power grids.

E4 Amateur practices

Which of the following factors most affects the accuracy of a frequency counter?

  1. Time base accuracy
  2. Input attenuator accuracy
  3. Temperature coefficient of the logic
  4. Decade divider accuracy

Answer: A, Time base accuracy. A frequency counter counts input cycles during a gate interval set by its internal time base, usually a crystal oscillator. Any fractional time base error shows up as the same fractional error in every reading: 10 ppm at 146 MHz is 146,000,000 Hz x 0.00001 = 1,460 Hz. That's why precision counters use temperature-compensated, oven-controlled or GPS-disciplined references.

What does a receiver noise floor of -174 dBm represent?

  1. The theoretical noise in a 1 Hz bandwidth at the input of a perfect receiver at room temperature
  2. The noise figure of a 1 Hz bandwidth receiver
  3. The receiver noise is 6 dB above the theoretical minimum
  4. The receiver noise is 3 dB above theoretical minimum

Answer: A, The theoretical noise in a 1 Hz bandwidth at the input of a perfect receiver at room temperature. Thermal noise power is P = kTB. At room temperature (about 290 K) in a 1 Hz bandwidth, P = 1.38 x 10^-23 J/K x 290 K x 1 Hz = 4 x 10^-21 W, which is -174 dBm. That is the noise a perfect, noiseless receiver would see. A real receiver's noise floor is higher by its noise figure plus 10 log of its bandwidth in hertz.

Which of the following types of noise can often be reduced by a digital noise reduction?

  1. Broadband white noise
  2. Ignition noise
  3. Power line noise
  4. All these choices are correct

Answer: D, All these choices are correct. DSP noise reduction separates signal from noise statistically. It keeps components that are correlated or predictable, such as speech or CW tones, and suppresses random ones. Broadband white (hiss) noise is reduced this way. Ignition noise and power line noise are random or rough enough that the same algorithms often reduce them too. So all three types can often be improved, though how much varies with the receiver and the noise.

E5 Electrical principles

What is the result of increasing the Q of an impedance-matching circuit?

  1. Harmonics increase
  2. Losses increase
  3. Matching bandwidth is decreased
  4. Matching bandwidth is increased

Answer: C, Matching bandwidth is decreased. Bandwidth and Q are inversely related: BW = f0 / Q. A higher-Q matching network has a sharper response, so it holds a good match over a narrower range of frequencies. You must retune it more often as you move across a band.

How is impedance in polar form converted to an equivalent admittance?

  1. Take the reciprocal of the magnitude and change the sign of the angle
  2. Square the magnitude and subtract 90 degrees from the angle
  3. Take the square root of the magnitude and add 180 degrees to the angle
  4. Take the reciprocal of the angle and change the sign of the magnitude

Answer: A, Take the reciprocal of the magnitude and change the sign of the angle. Admittance is the reciprocal of impedance, Y = 1/Z. Dividing 1 by a polar quantity takes the reciprocal of the magnitude and subtracts the angle, so a Z of magnitude |Z| at angle θ becomes a Y of magnitude 1/|Z| at angle -θ. For example, Z = 50 Ω at 30° gives Y = 1/50 = 0.02 S at -30°. An inductive impedance with a positive angle therefore becomes an admittance with a negative angle.

What is the primary cause of loss in film capacitors at RF?

  1. Self-discharge
  2. Inductance
  3. Skin effect
  4. Dielectric loss

Answer: C, Skin effect. Film capacitors use low-loss plastic dielectrics such as polypropylene, so the dielectric itself wastes little energy. At RF, current crowds onto the surfaces of the very thin metal films and leads. That skin effect raises their resistance. This resistance becomes the main source of loss, appearing as equivalent series resistance (ESR).

E6 Circuit components

In what application is gallium arsenide used as a semiconductor material?

  1. In microwave circuits
  2. In high-current rectifier circuits
  3. In high-power audio circuits
  4. In very low-frequency RF circuits

Answer: A, In microwave circuits. Electrons move much faster in gallium arsenide (GaAs) than in silicon. This high electron mobility lets GaAs transistors switch and amplify at very high frequencies with low noise. That is why GaAs FETs and MMICs are common in microwave preamplifiers and amplifiers.

Which of the following is a Schottky barrier diode?

  1. PIN junction
  2. Electrolytic rectifier
  3. Metal-semiconductor junction
  4. Thermionic emission diode

Answer: C, Metal-semiconductor junction. A Schottky barrier diode is made by bonding a metal directly to a lightly doped semiconductor, usually N-type silicon, rather than joining P and N material. This metal-semiconductor barrier rectifies with a low forward drop. It also stores almost no minority-carrier charge, which gives it the fast switching used in RF detectors, mixers and switching power supplies.

Why do CMOS digital integrated circuits have high immunity to noise on the input signal or power supply?

  1. The input switching threshold is about half the power supply voltage
  2. Bandwidth is very limited
  3. Large bypass capacitance is inherent
  4. The input switching threshold is about twice the power supply voltage

Answer: A, The input switching threshold is about half the power supply voltage. A CMOS input switches at about half the supply voltage, so noise must move an input nearly halfway across the supply range to cause a false transition. For example, with a 5 V supply the threshold is near 2.5 V, which leaves large noise margins for both the high and low states. TTL is more vulnerable, because its threshold sits near 1.4 V, close to the low logic level.

E7 Practical circuits

How frequently must an analog signal be sampled to be accurately reproduced?

  1. At least twice the rate of the highest frequency component of the signal
  2. At the same rate as the highest frequency component of the signal
  3. At four times the rate of the highest frequency component of the signal
  4. At least half the rate of the highest frequency component of the signal

Answer: A, At least twice the rate of the highest frequency component of the signal. The Nyquist criterion says the sample rate must be at least twice the highest frequency component: fs ≥ 2 x fmax. For example, audio extending to 3 kHz needs at least 6 kHz sampling. Below this rate, high frequencies fold back as false lower-frequency aliases that cannot be removed afterward. This is why an anti-aliasing low-pass filter is placed ahead of the ADC.

What is the typical output impedance of an op-amp?

  1. Very low
  2. Very high
  3. 10,000 ohms
  4. 100 ohms

Answer: A, Very low. An ideal op-amp has zero output impedance, so it can drive a load without its output voltage sagging. Real op-amps come close, especially with negative feedback, which lowers the effective output impedance far below the open-loop value. This is why an op-amp makes a good buffer between a high-impedance source and a lower-impedance load.

How is positive feedback supplied in a Colpitts oscillator?

  1. Through a neutralizing capacitor
  2. Through link coupling
  3. Through a capacitive divider
  4. Through a tapped coil

Answer: C, Through a capacitive divider. In a Colpitts oscillator, two capacitors in series across the tank circuit form a capacitive divider. The tap between them returns part of the output signal, in phase, to the active device's input to sustain oscillation. Compare the Hartley, which takes its feedback from a tapped coil. A handy memory aid: Colpitts uses Capacitors.

E8 Signals and emissions

What determines the PEP-to-average power ratio of an unprocessed single-sideband phone signal?

  1. The frequency of the modulating signal
  2. The degree of carrier suppression
  3. Amplifier gain
  4. Speech characteristics

Answer: D, Speech characteristics. An SSB transmitter's RF envelope follows the audio, so the PEP-to-average ratio depends on the voice itself: how often the talker pauses, how strong the peaks are compared with ordinary syllables, accent, pitch and talking rhythm. Different voices produce different ratios. Processing or compression changes the ratio by reshaping those speech characteristics.

What is the bandwidth of an FT8 signal?

  1. 50 Hz
  2. 10 Hz
  3. 2.4 kHz
  4. 600 Hz

Answer: A, 50 Hz. FT8 uses 8-tone frequency shift keying (8-FSK) with tones spaced 6.25 Hz apart. The signal occupies 8 x 6.25 Hz = 50 Hz. That narrow footprint lets dozens of FT8 signals fit side by side in one 3 kHz SSB passband.

What parameter evaluates distortion of an AFSK signal caused by excessive input audio levels?

  1. Intermodulation Distortion (IMD)
  2. Signal-to-noise ratio
  3. Baud error rate
  4. Repeat Request Rate (RRR)

Answer: A, Intermodulation Distortion (IMD). Too much audio drive makes the transmitter nonlinear, so the tones mix and create intermodulation products next to the wanted signal. IMD expresses how strong those products are relative to the desired signal, in dB. Software for modes like PSK31 often displays an IMD reading. A more negative IMD figure means a cleaner, properly driven signal.

E9 Antennas and transmission lines

What type of radiation pattern is created by two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase?

  1. A figure-eight broadside to the axis of the array
  2. Cardioid
  3. Omni-directional
  4. A figure-eight end-fire along the axis of the array

Answer: B, Cardioid. With 1/4-wavelength (90°) spacing and a 90° feed difference, the delays cancel in one direction along the axis: 90° − 90° = 0°, so the signals add fully. In the opposite direction they combine: 90° + 90° = 180°, so the signals cancel to a null. Strong radiation one way and a deep null the other gives a heart-shaped cardioid pattern.

How is a Smith chart normalized?

  1. Reassign the prime center to the reactance axis
  2. Reassign the prime center’s impedance value
  3. Reassign the reactance axis with resistance values
  4. Reassign the resistance axis with reactance values

Answer: B, Reassign the prime center’s impedance value. To normalize, divide every impedance by a reference, usually the line's characteristic impedance Z0. The prime center then stands for that reference value, read as 1 + j0. For example, with 50-ohm coax, 100 + j50 ohms plots as 2 + j1. This lets one chart serve a line of any impedance.

Which is generally true for 160- and 80-meter receiving antennas?

  1. Atmospheric noise is so high that directivity is much more important than losses
  2. They must be erected at least 1/2 wavelength above the ground to attain good directivity
  3. Low loss coax transmission line is essential for good performance
  4. All these choices are correct

Answer: A, Atmospheric noise is so high that directivity is much more important than losses. On 160 m and 80 m, atmospheric noise is far stronger than receiver noise. An inefficient antenna lowers signal and noise together, so the signal-to-noise ratio barely changes. What improves reception is rejecting noise and interference from other directions. That is why lossy but directive antennas, such as Beverages and small loops, work so well on these bands.

E0 Safety

What is the primary function of an external earth connection or ground rod?

  1. Prevent static build up on power lines
  2. Protect breaker panel from power surges
  3. Lightning charge dissipation
  4. Reduce RF current flow between pieces of equipment

Answer: C, Lightning charge dissipation. A ground rod driven into the earth gives lightning energy a short, low-impedance path into the soil. The charge then dissipates outside the house instead of through your equipment. The rod is part of a lightning protection system bonded to the electrical service ground. It is not an RF ground: the long lead to the rod has high impedance at radio frequencies.

When evaluating RF exposure levels from your station at a neighbor’s home, what must you do?

  1. Ensure signals from your station are less than the uncontrolled maximum permissible exposure (MPE) limits
  2. Ensure signals from your station are less than the controlled maximum permissible exposure (MPE) limits
  3. Ensure signals from your station are less than the controlled maximum permissible emission (MPE) limits
  4. Ensure signals from your station are less than the uncontrolled maximum permissible emission (MPE) limits

Answer: A, Ensure signals from your station are less than the uncontrolled maximum permissible exposure (MPE) limits. A neighbor's home is a general-population area: the people there don't know about your signals and can't control their exposure. Under Section 97.13(c) and 47 CFR 1.1310, such areas fall under the uncontrolled-environment limits. Those limits are stricter than the controlled limits, generally five times lower in power density. MPE stands for maximum permissible exposure.

What hazard is created by operating at microwave frequencies?

  1. The extremely high frequency energy can damage the joints of antenna structures
  2. Microwaves are ionizing radiation
  3. Microwaves are in the frequency range where wave velocity is higher
  4. The high gain antennas commonly used can result in high exposure levels

Answer: D, The high gain antennas commonly used can result in high exposure levels. Microwave stations often use dishes and other high-gain antennas that concentrate power into a narrow beam. Even modest transmitter power can then produce high power density in the main lobe. Standing in front of a dish, or looking into a waveguide or feed horn while transmitting, can cause excessive exposure. The eyes are especially vulnerable to heating.