Deep Dive: E4B06
The correct answer is D: 75 watts. How much power is being absorbed by the load when a directional power meter connected between a transmitter and a terminating load reads 100 watts forward power and 25 watts reflected power is 75 watts. Absorbed power = forward - reflected = 100 - 25 = 75 watts. For amateur radio operators, this is important for power measurements. Understanding this helps when measuring power.
Why Other Answers Are Wrong
Option A (100 watts): Incorrect. 100 watts is forward power, not absorbed - absorbed = forward - reflected = 75 watts. 100 watts is forward. Option B (125 watts): Incorrect. 125 watts is forward + reflected, not absorbed - absorbed = forward - reflected = 75 watts. 125 watts is wrong. Option C (112.5 watts): Incorrect. 112.5 watts isn't the calculation - absorbed = forward - reflected = 100 - 25 = 75 watts. 112.5 watts is wrong.
Exam Tip
Absorbed power = forward power - reflected power. Think 'A'bsorbed = 'F'orward - 'R'eflected. Absorbed power = 100 - 25 = 75 watts. Not 100W (forward), not 125W (sum), not 112.5W - just 75 watts (difference).
Memory Aid
Absorbed power = forward power - reflected power. Think 'A'bsorbed = 'F'orward - 'R'eflected. Absorbed power = 100 - 25 = 75 watts. Important for power measurements.
Real-World Example
A directional power meter reads 100 watts forward and 25 watts reflected: The power absorbed by the load is forward power minus reflected power = 100 - 25 = 75 watts. The reflected power is lost, so only the difference is absorbed. This is the calculation - 75 watts absorbed.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E4B
Reference: 2024-2028 Question Pool · E4 - Amateur Practices
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E4B topic.