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 is the approximate height of the F2 ionospheric layer above Earth's surface?
Answer: 200–400 km
The F2 layer exists at roughly 200–400 km altitude and is the primary layer responsible for long-distance HF sky wave propagation.
What causes 'flutter' in signals received via auroral propagation?
Answer: The rapid movement and structure of the aurora causing continuously shifting reflection points
Aurora-reflected signals exhibit a characteristic flutter or warbling sound because the aurora curtain is constantly moving and the ionized region varies rapidly.
Which type of modulation encodes information by varying the frequency of the carrier wave?
Answer: Frequency modulation (FM)
Frequency modulation (FM) varies the carrier frequency in proportion to the instantaneous amplitude of the modulating audio signal.
Why is the 10-meter band generally considered a daytime band during low solar activity?
Answer: Without adequate F2 ionization, signals are not refracted back to Earth and pass into space
During low solar activity, the F2 layer may not be ionized enough to refract 10-meter signals back to Earth, especially at night when solar ionization stops.
What is the relationship between frequency and wavelength for radio waves?
Answer: They are inversely proportional — higher frequency means shorter wavelength
Wavelength equals the speed of light divided by frequency; as frequency increases, wavelength decreases proportionally.
What does 'over-deviation' cause in an FM transmission?
Answer: Splatter into adjacent channels, causing interference to nearby frequencies
Over-deviation occurs when the FM carrier is shifted too far, causing the signal to spread into adjacent frequency channels and interfere with other users.
During a solar flare, what often happens to HF communication on the sunlit side of Earth?
Answer: HF signals are absorbed by intense D layer ionization, causing a radio blackout
Solar flares release intense X-ray radiation that dramatically increases D layer ionization, absorbing HF signals and causing sudden ionospheric disturbances (SIDs) or radio blackouts.