Radio Wave Propagation Flashcards
7 cards from real Ham Radio General Class 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 flashcards as text
What is the primary cause of sky-wave propagation on HF bands?
Answer: Refraction by the ionosphere
Sky-wave propagation occurs when HF signals are refracted (bent) back to Earth by the ionized layers of the ionosphere.
Which ionospheric layer is primarily responsible for long-distance HF propagation during daylight hours?
Answer: F2 layer
The F2 layer, located at roughly 200-400 km altitude, provides the longest skip distances and is the primary layer for HF DX propagation.
What is 'gray line' propagation?
Answer: Enhanced propagation along the terminator between daylight and darkness
The gray line (terminator) is the boundary between day and night where the D layer is absent but F layer ionization remains, enabling enhanced propagation.
What effect does a sudden ionospheric disturbance (SID) have on HF communications?
Answer: It absorbs HF signals on the sunlit side of Earth, causing a radio blackout
A SID is caused by a solar X-ray flare that dramatically increases D-layer ionization, absorbing HF signals on the Earth's sunlit side.
What is 'transequatorial propagation' (TEP)?
Answer: Propagation via F layer ionization across the magnetic equator, often reaching 50 MHz or above
TEP is a mode where signals propagate via enhanced F layer ionization on both sides of the magnetic equator and can extend into VHF frequencies.
How does increasing solar flux affect the Maximum Usable Frequency (MUF)?
Answer: Higher solar flux raises the MUF by increasing ionospheric ionization
Greater solar flux produces more ionization in the F layer, which raises the critical frequency and therefore increases the MUF for a given path.
What is 'auroral propagation' and on which bands is it most common?
Answer: Distorted, flutter-type signals scattered by the aurora on VHF bands like 6 meters and 2 meters
Auroral propagation occurs when VHF signals scatter off the ionized curtain of the aurora borealis, producing characteristic fluttery, distorted audio.