Radio Wave Propagation Flashcards
7 cards from real GROL 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 flashcards as text
What is the Maximum Usable Frequency (MUF) in HF propagation?
Answer: The highest frequency that will be refracted back to Earth by the ionosphere at a given angle
The MUF is the highest frequency that will be refracted back to Earth by the ionosphere for a given path and angle of radiation.
Which ionospheric layer is primarily responsible for long-distance HF communication during daylight hours?
Answer: F2 layer
The F2 layer, located at approximately 200–400 km altitude, is the primary layer for long-distance HF sky-wave propagation, persisting day and night.
What is 'skip distance' in HF radio propagation?
Answer: The minimum distance from the transmitter at which a sky-wave signal can be received
Skip distance is the minimum distance from a transmitter at which a sky-wave signal returns to Earth, leaving a 'skip zone' where the signal cannot be received.
What effect does increasing frequency have on ionospheric refraction?
Answer: Higher frequencies require a denser ionosphere to be refracted back to Earth
Higher frequencies penetrate deeper into the ionosphere and require a denser plasma to bend them back to Earth, making refraction increasingly difficult at higher frequencies.
What is the D layer's primary effect on HF radio signals?
Answer: It absorbs lower HF frequencies, especially during daylight
The D layer, present only during daylight, absorbs lower HF frequencies (below about 10 MHz) rather than refracting them, limiting daytime low-band HF propagation.
What is the Frequency of Optimum Traffic (FOT) relative to the MUF?
Answer: Approximately 85% of the MUF
The FOT (also called Optimum Working Frequency) is typically about 85% of the MUF, providing a practical operating margin below the MUF to account for ionospheric variability.
During which part of the solar cycle is HF long-distance propagation generally best?
Answer: Solar maximum, because the ionosphere is more densely ionized
Near solar maximum, increased solar radiation produces a more densely ionized F2 layer, raising the MUF and enabling more reliable long-distance HF propagation.