Deep Dive: T7C03
The correct answer is B: A non-inductive resistor mounted on a heat sink. A dummy load consists of a non-inductive resistor mounted on a heat sink. The resistor (typically 50 ohms) absorbs the RF power and converts it to heat, which the heat sink dissipates. The resistor must be non-inductive (wire-wound resistors have inductance that affects RF performance) and must be able to handle the power without burning up. For amateur radio operators, understanding dummy load construction helps when building or selecting dummy loads. The heat sink is essential because the resistor generates significant heat when absorbing transmitter power.
Why Other Answers Are Wrong
Option A: Incorrect. A dummy load doesn't contain an amplifier or TR switch - it's just a resistive load. Amplifiers and switches are active components, not part of a dummy load. Option C: Incorrect. A dummy load doesn't contain a power supply or relay - it's a passive device. Power supplies and relays are active components. Option D: Incorrect. A dummy load is a resistive load, not a reactive load. Reactance (inductance or capacitance) would affect the impedance at different frequencies, which is undesirable.
Exam Tip
Dummy load = non-inductive resistor + heat sink. Think 'D'ummy load = 'D'issipates power as heat. Non-inductive resistor (50 ohms) on a heat sink. It's a passive resistive load, not an active circuit.
Memory Aid
Dummy load = non-inductive resistor + heat sink. Think 'D'ummy load = 'D'issipates power. Non-inductive 50-ohm resistor on heat sink. Passive resistive load.
Real-World Example
A 100-watt dummy load contains a 50-ohm non-inductive resistor (often carbon composition or metal film) mounted on an aluminum heat sink with fins. When you connect your transmitter, the resistor absorbs the RF power and converts it to heat. The heat sink dissipates this heat, preventing the resistor from overheating. The non-inductive design ensures the impedance stays 50 ohms across the frequency range.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T7C
Reference: 2022-2026 Question Pool · T7 - Practical circuits
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T7C topic.