Deep Dive: G9A01
The correct answer is A: The distance between the centers of the conductors and the radius of the conductors. Factors that determine the characteristic impedance of a parallel conductor feed line are the distance between the centers of the conductors and the radius of the conductors. Characteristic impedance depends on geometry (spacing and conductor size), not frequency or length. For amateur radio operators, this is fundamental transmission line theory. Understanding this helps when designing feed lines.
Why Other Answers Are Wrong
Option B: Incorrect. Length doesn't determine characteristic impedance - impedance is a property of the line geometry, not length. Length affects loss, not impedance. Option C: Incorrect. Frequency doesn't determine characteristic impedance - impedance is independent of frequency (for lossless lines). Frequency affects loss, not impedance. Option D: Incorrect. Frequency and length don't determine characteristic impedance - impedance depends on geometry, not frequency or length. Both are wrong.
Exam Tip
Parallel conductor impedance = distance between centers and conductor radius. Think 'I'mpedance = 'I'nteraction between 'D'istance and 'R'adius. Characteristic impedance depends on geometry (spacing and conductor size), not frequency or length. Not length, not frequency, not frequency+length - just distance and radius.
Memory Aid
Parallel conductor impedance = distance between centers and conductor radius. Think 'I'mpedance = 'D'istance and 'R'adius. Characteristic impedance depends on geometry (spacing and conductor size), not frequency or length. Fundamental transmission line property.
Real-World Example
A parallel conductor feed line: The characteristic impedance depends on the distance between the conductor centers and the radius of the conductors. For example, wider spacing or larger conductors changes the impedance. Characteristic impedance is a property of the line geometry, not its length or the signal frequency. This is fundamental transmission line theory.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G9A
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 G9A topic.