Radio Wave Propagation & Modulation Flashcards
7 cards from real Ham Radio Technician Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Radio Wave Propagation & Modulation flashcards as text
What effect does a temperature inversion in the atmosphere have on VHF radio waves?
Answer: It can cause signals to travel much farther than normal
Temperature inversions can trap VHF signals near the Earth's surface, allowing them to travel far beyond the normal line-of-sight distance through ducting.
Which modulation mode is most commonly used for FM voice transmissions on VHF/UHF amateur bands?
Answer: Frequency modulation (FM)
FM is the standard mode for local VHF/UHF voice repeater operation because it provides good audio quality and rejects noise effectively.
What is the term for the lowest frequency that will be refracted back to Earth from the ionosphere at vertical incidence?
Answer: Critical frequency
The critical frequency is the highest frequency that is refracted back to Earth when a signal is transmitted straight up (vertical incidence).
Which ionospheric layer is primarily responsible for long-distance HF communication during daytime?
Answer: F2 layer
The F2 layer, found at 200–400 km altitude, is the most important layer for long-distance HF propagation because it persists day and night.
What type of propagation allows a 10-meter signal to be received across the country with very low power during high solar activity?
Answer: F2 ionospheric propagation
During periods of high solar activity, F2 layer ionization is strong enough to refract 10-meter signals back to Earth over very long distances.
What is the deviation in an FM signal?
Answer: The amount the carrier frequency shifts above and below its center frequency
Deviation is the maximum shift of the carrier frequency above and below the resting center frequency, determined by the amplitude of the modulating audio signal.
Which band is most likely to support auroral propagation?
Answer: 2 meters
Auroral propagation primarily occurs on VHF bands, especially 2 meters (144 MHz), where signals are reflected off the ionized curtain of the aurora borealis.