Deep Dive: G4E06
The correct answer is C: Operating bandwidth may be very limited. A disadvantage of using a shortened mobile antenna as opposed to a full-size antenna is that operating bandwidth may be very limited. Shortened antennas with loading have high Q (narrow bandwidth), making them sensitive to frequency changes. For amateur radio operators, this requires frequent retuning. Understanding this helps explain shortened antenna limitations.
Why Other Answers Are Wrong
Option A: Incorrect. Short antennas don't cause signal distortion - distortion comes from other sources. Signal distortion isn't a shortened antenna disadvantage. Option B: Incorrect. Short antennas don't have very low Q - they have high Q (narrow bandwidth). Low Q would mean wide bandwidth, which isn't the case. Option D: Incorrect. Short antennas don't increase harmonic radiation - harmonics come from non-linear operation, not antenna length. Harmonic radiation isn't a shortened antenna issue.
Exam Tip
Shortened antenna disadvantage = operating bandwidth may be very limited. Think 'S'hortened 'A'ntenna = 'S'lim 'A'perture (narrow bandwidth). Shortened antennas with loading have high Q (narrow bandwidth). Not distortion, not low Q, not harmonics - just limited bandwidth.
Memory Aid
Shortened antenna disadvantage = operating bandwidth may be very limited. Think 'S'hortened 'A'ntenna = 'S'lim 'A'perture. Shortened antennas with loading have high Q (narrow bandwidth). Requires frequent retuning.
Real-World Example
You use a shortened mobile antenna for 40 meters. The antenna has a narrow bandwidth (e.g., 50 kHz) compared to a full-size antenna (e.g., 200 kHz). As you change frequency, you must retune the antenna. The limited bandwidth is a significant disadvantage of shortened antennas.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G4E
Reference: 2023-2027 Question Pool · G4 - Amateur Radio Practices
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G4E topic.