Deep Dive: E2E09
The correct answer is D: PSK31. Which of the following HF digital modes uses variable-length character coding is PSK31. PSK31 uses Varicode, which is a variable-length code. For amateur radio operators, this is important for understanding PSK31. Understanding this helps when operating PSK31.
Why Other Answers Are Wrong
Option A (RTTY): Incorrect. RTTY uses fixed-length character coding (5 bits per character), not variable-length - PSK31 uses variable-length. RTTY isn't variable-length. Option B (PACTOR): Incorrect. PACTOR doesn't use variable-length character coding - PSK31 uses variable-length. PACTOR isn't variable-length. Option C (MT63): Incorrect. MT63 doesn't use variable-length character coding - PSK31 uses variable-length. MT63 isn't variable-length.
Exam Tip
HF digital mode with variable-length coding = PSK31. Think 'P'SK31 = 'V'aricode (variable-length). PSK31 uses Varicode, which is a variable-length character code. Not RTTY, not PACTOR, not MT63 - just PSK31.
Memory Aid
HF digital mode with variable-length coding = PSK31. Think 'P'SK31 = 'V'aricode. PSK31 uses Varicode, which is a variable-length character code. Important for understanding PSK31.
Real-World Example
PSK31 mode: It uses variable-length character coding (Varicode). Common characters like 'e' and space get short codes, less common characters get longer codes. This makes PSK31 efficient. RTTY, PACTOR, and MT63 use fixed-length coding. This is the mode - PSK31 uses variable-length character coding.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E2E
Reference: 2024-2028 Question Pool · E2 - Operating Procedures
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E2E topic.