Deep Dive: G9A03
The correct answer is D: 450 ohms. The nominal characteristic impedance of 'window line' transmission line is 450 ohms. Window line (ladder line) is a type of parallel conductor feed line with 450-ohm characteristic impedance. For amateur radio operators, this is important when selecting feed lines. Understanding this helps when designing antenna systems.
Why Other Answers Are Wrong
Option A (50 ohms): Incorrect. 50 ohms is for coaxial cable, not window line - window line is 450 ohms. 50 ohms is wrong. Option B (75 ohms): Incorrect. 75 ohms is for TV coax, not window line - window line is 450 ohms. 75 ohms is wrong. Option C (100 ohms): Incorrect. 100 ohms isn't a standard window line impedance - window line is 450 ohms. 100 ohms is wrong.
Exam Tip
Window line impedance = 450 ohms. Think 'W'indow 'L'ine = 'W'ide spacing = '4'50 ohms. Window line (ladder line) has 450-ohm characteristic impedance. Not 50 ohms (coax), not 75 ohms (TV coax), not 100 ohms - just 450 ohms.
Memory Aid
Window line impedance = 450 ohms. Think 'W'indow 'L'ine = '4'50 ohms. Window line (ladder line) has 450-ohm characteristic impedance. Standard window line impedance.
Real-World Example
Window line (ladder line): This parallel conductor feed line has a nominal characteristic impedance of 450 ohms. It's called 'window line' because of the window-like openings in the insulation. Window line is commonly used for multiband antennas because of its low loss and 450-ohm impedance.
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.