Difficulty: Easy
Correct Answer: Atmospheric noise (static from lightning and storms)
Explanation:
Introduction / Context:
Understanding noise sources helps engineers design front ends and set expectations for minimum discernible signal. Not all noise originates in the receiver; significant components arrive from the environment.
Given Data / Assumptions:
Concept / Approach:
Solar, cosmic, and galactic noises are extraterrestrial. Atmospheric noise, also called static, is produced by lightning discharges and other meteorological electrical activity in Earth’s atmosphere. Its intensity varies with time of day, season, and storm activity, and it is more severe at lower frequencies (e.g., HF).
Step-by-Step Solution:
Identify source domains: extraterrestrial vs terrestrial.Classify: solar (Sun), cosmic (outside the galaxy), galactic (within Milky Way), atmospheric (Earth’s atmosphere).Conclude: atmospheric noise is the one with terrestrial origin.
Verification / Alternative check:
Radio propagation texts show atmospheric noise curves dominating the external noise temperature at HF and reducing at VHF/UHF as sky noise becomes more relevant.
Why Other Options Are Wrong:
Common Pitfalls:
Final Answer:
Atmospheric noise (static from lightning and storms)
Discussion & Comments