Deep Dive: G9D02
The correct answer is D: Very high. The feed point impedance of an end-fed half-wave antenna is very high. End-fed half-waves have high impedance at the end (thousands of ohms) because current is minimum and voltage is maximum at the ends. For amateur radio operators, this requires impedance matching. Understanding this helps when using end-fed antennas.
Why Other Answers Are Wrong
Option A (Very low): Incorrect. End-fed half-wave doesn't have very low impedance - it has very high impedance because current is minimum at the ends. Very low is wrong. Option B (Approximately 50 ohms): Incorrect. End-fed half-wave doesn't have 50 ohms - it has very high impedance (thousands of ohms). 50 ohms is for center-fed dipoles. Option C (Approximately 300 ohms): Incorrect. End-fed half-wave doesn't have 300 ohms - it has very high impedance (thousands of ohms). 300 ohms is too low.
Exam Tip
End-fed half-wave impedance = very high. Think 'E'nd-'F'ed = 'E'nd has 'F'ull voltage = 'V'ery 'H'igh impedance. End-fed half-waves have high impedance because current is minimum and voltage is maximum at ends. Not very low, not 50Ω, not 300Ω - just very high.
Memory Aid
End-fed half-wave impedance = very high. Think 'E'nd-'F'ed = 'V'ery 'H'igh impedance. End-fed half-waves have high impedance because current is minimum and voltage is maximum at ends. Requires impedance matching.
Real-World Example
An end-fed half-wave antenna: The feed point is at the end where current is minimum and voltage is maximum. This creates very high impedance (typically 2000-5000 ohms). An impedance matching network (tuner or transformer) is required to match this high impedance to the transmitter. This is why end-fed antennas need matching networks.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G9D
Reference: 2023-2027 Question Pool · G9 - Antennas and Feed Lines
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G9D topic.