HAM Practice Questions 5 — Questions and Answers
Question 1: What is the effect of increasing the number of elements in a Yagi antenna while keeping the boom length constant?
- Gain increases and front-to-back ratio always improves proportionally
- Element spacing decreases, which typically reduces gain compared to an optimally spaced design (Correct answer)
- Bandwidth always increases with more elements
- Radiation resistance increases proportionally
Correct answer: Element spacing decreases, which typically reduces gain compared to an optimally spaced design
Squeezing more elements onto a fixed boom reduces inter-element spacing, which generally lowers gain and degrades pattern compared to an optimally spaced Yagi with fewer elements.
Question 2: What is a 'pi-network' tank circuit in a transmitter used for?
- To filter RF harmonics only, with no impedance transformation
- To match the amplifier's output impedance to the antenna feedline while providing harmonic suppression (Correct answer)
- To bias the output transistor into class A operation
- To stabilize the oscillator frequency against temperature drift
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 3: What is 'auroral propagation' and which amateur bands does it most affect?
- Tropospheric scattering affecting 160 and 80 meters
- VHF and UHF reflection off the ionized aurora borealis, mainly affecting 50 MHz and above (Correct answer)
- HF skywave via the E-layer enhanced by auroral activity at 10–20 MHz
- Microwave ducting along the polar front jet stream
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 4: Which parameter best describes the ratio of a power amplifier's output power to its DC input power?
- Gain
- Efficiency (Correct answer)
- Compression point
- Noise figure
Correct answer: Efficiency
Efficiency is the ratio of RF output power to DC input power, expressed as a percentage; higher efficiency means less heat dissipation for a given output power.
Question 5: What document must an amateur station have available during an FCC inspection?
- The original written license certificate only
- Station logbook showing the past 365 days of operation
- The current FCC license or a photocopy, or a displayed electronic copy (Correct answer)
- Both the license and the equipment's FCC type acceptance letters
Correct answer: The current FCC license or a photocopy, or a displayed electronic copy
FCC rules require the station license (or an electronic or photocopy) to be available at the station for inspection; original paper is not mandated.
Question 6: When computing the height of an antenna above 'effective ground' for ground-wave propagation, what soil condition produces the best results?
- Rocky, dry, mountainous terrain
- Average suburban soil
- Salt water or very moist, rich agricultural soil (Correct answer)
- Sandy desert soil
Correct answer: Salt water or very moist, rich agricultural soil
Salt water has extremely high conductivity (~4 S/m), minimizing ground-wave attenuation; rich moist soil is the next best, while rocky or sandy soils are poor conductors.
Question 7: What is the purpose of an 'automatic level control' (ALC) circuit in an HF transceiver?
- To keep the audio output volume constant during signal fading
- To prevent the transmitter from exceeding its rated peak envelope power by reducing drive when needed (Correct answer)
- To automatically select the best antenna based on SWR
- To maintain a constant noise figure in the receiver's front end
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.
HAM Practice Questions 5
What is the effect of increasing the number of elements in a Yagi antenna while keeping the boom length constant?