T9B08: A source of loss in coaxial feed line

Q: Which of the following is a source of loss in coaxial feed line?

The correct answer is D: All these choices are correct. The correct answer is D: All these choices are correct. Sources of loss in coaxial feed line include water intrusion into connectors, high SWR, and multiple connectors in the line. Water in connectors increases losses and can cause corrosion. High SWR causes reflected power, which increases losses. Each connector adds some loss, and multiple connectors compound this. For amateur radio operators, understanding these loss sources helps maintain feed line performance. Keeping connectors sealed, maintaining low SWR, and minimizing the number of connectors all help reduce losses.

Updated: Dec 9, 2025 | Source: 2022-2026 Question Pool | Topic: T9B

T9B08T9B

Which of the following is a source of loss in coaxial feed line?

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Deep Dive: T9B08

The correct answer is D: All these choices are correct. Sources of loss in coaxial feed line include water intrusion into connectors, high SWR, and multiple connectors in the line. Water in connectors increases losses and can cause corrosion. High SWR causes reflected power, which increases losses. Each connector adds some loss, and multiple connectors compound this. For amateur radio operators, understanding these loss sources helps maintain feed line performance. Keeping connectors sealed, maintaining low SWR, and minimizing the number of connectors all help reduce losses.

Why Other Answers Are Wrong

Option A: While correct, this is incomplete. High SWR and multiple connectors also cause losses. Option B: While correct, this is incomplete. Water intrusion and multiple connectors also cause losses. Option C: While correct, this is incomplete. Water intrusion and high SWR also cause losses.

Exam Tip

All three cause feed line loss: water intrusion, high SWR, multiple connectors. When all listed sources are valid causes of loss, 'all of the above' is usually the answer. All contribute to reduced feed line efficiency.

Memory Aid

All three cause feed line loss: Water intrusion, High SWR, Multiple connectors. Think 'A'll 'L'oss 'S'ources. Keep connectors sealed, maintain low SWR, minimize connectors to reduce losses.

Real-World Example

Your feed line has high losses. Investigation reveals: (1) Water entered through a loose connector, increasing losses and causing corrosion, (2) Your antenna has 3:1 SWR, causing significant reflected power and losses, (3) You have 4 connectors in the line (transceiver, tuner, switch, antenna), each adding loss. All three factors contribute to your feed line losses.

Source & Coverage

Question Pool: 2022-2026 Question Pool

Subelement: T9B

Reference: 2022-2026 Question Pool · T9 - Antennas and feed lines

Key Concepts

Feed line losses Water intrusion High SWR Connector losses

Verified Content

Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T9B topic.