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 'tropospheric scatter' (tropo scatter) propagation?
Answer: Scattering of VHF/UHF signals by turbulence and irregularities in the troposphere, enabling paths of 200-800+ km
Troposcatter uses the forward scatter of signals from irregularities in the troposphere to achieve beyond-line-of-sight paths at VHF/UHF, typically 200-800+ km.
What is 'sporadic-E' (Es) propagation and what frequencies does it most affect?
Answer: Unpredictable clouds of ionization in the E layer that support propagation on 6 meters, 10 meters, and even 2 meters
Sporadic-E consists of intense, localized patches of ionization at E-layer heights that can support propagation on frequencies from HF into VHF, often unexpectedly.
How does antenna take-off angle affect skip distance on HF?
Answer: Higher take-off angles produce shorter skip distances; lower angles produce longer skip distances
A high take-off angle returns a sky-wave closer to the transmitter (short skip), while a low take-off angle at the horizon returns a wave much farther away (long skip/DX).
What is 'ionospheric tilt' and how can it affect communications?
Answer: An uneven or tilted ionospheric layer that can cause signals to be reflected in unexpected directions
Ionospheric tilt, often caused by solar terminator gradients or geomagnetic activity, can deflect signals off their expected path, enabling unusual contacts or causing propagation anomalies.
What is the Lowest Usable Frequency (LUF) determined by?
Answer: The frequency below which D-layer absorption makes a path unusable despite adequate MUF
The LUF is the lowest frequency on which D-layer absorption is low enough to allow adequate signal strength over a given path — it rises during solar events.
What propagation mode allows contacts on 2-meter FM when a temperature inversion is present?
Answer: Tropospheric ducting
Temperature inversions in the lower atmosphere create a refractive duct that can guide 2-meter signals well beyond normal line-of-sight range through tropospheric ducting.
Which of the following best describes 'meteor scatter' propagation?
Answer: Brief ionized trails left by meteors entering the atmosphere used to reflect VHF signals over 800-2,000 km paths
Meteors burn up in the atmosphere leaving brief ionized trails that reflect VHF signals (typically 50-144 MHz) over paths of 800-2,000 km in short bursts.