Deep Dive: G8B13
The correct answer is C: 2F1-F2. Which of the following is an odd-order intermodulation product of frequencies F1 and F2 is 2F1-F2. Odd-order products have odd coefficients (1, 3, 5, etc.) in the formula. 2F1-F2 has coefficients 2 and 1, but the order is determined by the sum: 2+1=3 (odd). For amateur radio operators, this is important for IMD analysis. Understanding this helps when analyzing interference.
Why Other Answers Are Wrong
Option A (5F1-3F2): Incorrect. 5F1-3F2 has coefficients 5 and 3, sum = 8 (even order), not odd. Even-order product. Option B (3F1-F2): Incorrect. 3F1-F2 has coefficients 3 and 1, but this might be considered, though 2F1-F2 is the standard odd-order example. 3F1-F2 is also odd-order, but 2F1-F2 is the answer. Option D: Incorrect. Since A is even-order and only C is clearly odd-order, 'all of the above' cannot be correct. Only 2F1-F2 is the standard odd-order product.
Exam Tip
Odd-order IMD product = 2F1-F2. Think 'O'dd-order = 'O'ne 'D'ifference term with 'D'ifferent coefficients. 2F1-F2 has sum of coefficients = 2+1 = 3 (odd order). Not 5F1-3F2 (even), not all - just 2F1-F2.
Memory Aid
Odd-order IMD product = 2F1-F2. Think 'O'dd-order = '2'F1-'F'2. 2F1-F2 has sum of coefficients = 3 (odd order). Standard odd-order IMD product that's close to original frequencies.
Real-World Example
Two frequencies F1 and F2: Odd-order intermodulation product 2F1-F2. For F1=14.2 MHz, F2=14.3 MHz: 2F1-F2 = 28.4 - 14.3 = 14.1 MHz (close to original frequencies). 2F1-F2 is a standard odd-order IMD product - it's close to the original frequencies and is problematic. This is why odd-order products are most concerning.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G8B
Reference: 2023-2027 Question Pool · G8 - Signals and Emissions
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G8B topic.