Updated: Dec 9, 2025 | Source: 2024-2028 Question Pool | Topic: E4E
E4E11E4E

What could be the cause of local AM broadcast band signals combining to generate spurious signals on the MF or HF bands?

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Deep Dive: E4E11

The correct answer is B: Nearby corroded metal connections are mixing and reradiating the broadcast signals. What could be the cause of local AM broadcast band signals combining to generate spurious signals on the MF or HF bands is that nearby corroded metal connections are mixing and reradiating the broadcast signals. Corroded connections can act as nonlinear mixers. For amateur radio operators, this is important for troubleshooting interference. Understanding this helps when identifying interference sources.

Why Other Answers Are Wrong

Option A: Incorrect. Broadcast stations transmitting over-modulated signal isn't the cause - corroded connections mixing signals is the cause. Over-modulation isn't the cause. Option C: Incorrect. Receiving skywave signals from distant station isn't the cause - corroded connections mixing signals is the cause. Skywave isn't the cause. Option D: Incorrect. Receiver IF amplifier overload isn't the cause - corroded connections mixing signals is the cause. IF overload isn't the cause.

Exam Tip

AM broadcast signals generating spurious on MF/HF = nearby corroded metal connections mixing and reradiating. Think 'A'M 'B'roadcast 'S'purious = 'C'oroded 'C'onnections 'M'ixing. Corroded connections can act as nonlinear mixers. Not over-modulation, not skywave, not IF overload - just corroded connections mixing.

Memory Aid

AM broadcast signals generating spurious on MF/HF = nearby corroded metal connections mixing and reradiating. Think 'A'M 'B'roadcast = 'C'oroded 'M'ixing. Corroded connections can act as nonlinear mixers. Important for troubleshooting interference.

Real-World Example

Local AM broadcast band signals combining to generate spurious signals on MF or HF bands: The cause could be nearby corroded metal connections (like rusty pipes, fences, or gutters) that are mixing and reradiating the broadcast signals. The corrosion creates nonlinear junctions that mix frequencies. This is the cause - corroded connections mixing signals.

Source & Coverage

Question Pool: 2024-2028 Question Pool

Subelement: E4E

Reference: 2024-2028 Question Pool · E4 - Amateur Practices

Key Concepts

Local AM broadcast band signals Combining to generate spurious signals MF or HF bands Nearby corroded metal connections Mixing and reradiating

Verified Content

Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E4E topic.