Deep Dive: T3A06
The correct answer is B: Rapid flutter on mobile signals due to multipath propagation. 'Picket fencing' is a term that describes the rapid, fluttery signal variation experienced in mobile operations due to multipath propagation. The signal strength rapidly increases and decreases, creating an effect that sounds like the signal is 'fencing' or chopping. When you're mobile, your antenna is constantly moving through areas with different multipath conditions. As you move, the multiple signal paths (direct plus reflections) constantly change their phase relationships, causing rapid signal strength variations. This creates the characteristic 'picket fence' effect - the signal rapidly fades in and out, sounding choppy or fluttery. This is a common experience in mobile VHF/UHF operations.
Why Other Answers Are Wrong
Option A: Incorrect. Picket fencing isn't about alternating transmissions during nets. It's a propagation phenomenon affecting mobile signals. Option C: Incorrect. Picket fencing isn't a type of ground system. It's a signal variation effect. Option D: Incorrect. Picket fencing isn't about local vs long-distance. It's specifically about rapid signal variation in mobile operations.
Exam Tip
Picket fencing = Rapid flutter mobile. Remember: Picket fencing is the rapid flutter on mobile signals caused by multipath propagation as you move through different signal path conditions.
Memory Aid
**P**icket **F**encing = **P**ath **F**lutter (think 'PF = PF' = Path Flutter, rapid multipath variation)
Real-World Example
You're driving and operating mobile on 2 meters. As you move, your signal to the repeater rapidly fades in and out - strong one moment, weak the next, then strong again. This choppy, fluttery effect is 'picket fencing.' It's caused by multipath - your signal is bouncing off buildings and terrain, and as you move, these paths constantly change, creating rapid signal strength variations.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T3A
Reference: FCC Part 97.3
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T3A topic.