What is the formula for converting frequency to approximate wavelength in meters?
The correct answer is D: Wavelength in meters equals 300 divided by frequency in megahertz. The formula for converting frequency to wavelength in meters is: wavelength (meters) = 300 / frequency (MHz). This formula works because the speed of light is approximately 300,000,000 meters per second, and when you divide by frequency in megahertz (millions of hertz), you get the simplified formula using 300.
This is a fundamental formula in amateur radio. For example, 146 MHz (2 meters) gives: wavelength = 300 / 146 = 2.05 meters. The formula works because: wavelength = speed of light / frequency = 300,000,000 m/s / (frequency in Hz). When frequency is in MHz, you divide by 1,000,000, which simplifies to 300 / frequency(MHz).
Exam Tip
Wavelength formula = 300 / MHz. Remember: Wavelength in meters = 300 divided by frequency in megahertz. This is one of the most important formulas to memorize.
Memory Aid
"**W**avelength = **3**00 / **M**Hz (think 'W = 3/M' = 300 divided by MHz)"
Real-World Application
You want to know the wavelength of 28.4 MHz (10 meters). Using the formula: wavelength = 300 / 28.4 = 10.56 meters. This confirms it's in the 10-meter band. For 146 MHz (2 meters): wavelength = 300 / 146 = 2.05 meters, confirming it's approximately 2 meters.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Multiplying frequency by 300 would give a very large number, not a wavelength. The relationship is division, not multiplication.
Option B: Incorrect. Dividing frequency in hertz by 300 doesn't work because the numbers are too large. You need frequency in MHz.
Option C: Incorrect. Dividing frequency in MHz by 300 gives the wrong result. You need to divide 300 by the frequency.
题目解析
The correct answer is D: Wavelength in meters equals 300 divided by frequency in megahertz. The formula for converting frequency to wavelength in meters is: wavelength (meters) = 300 / frequency (MHz). This formula works because the speed of light is approximately 300,000,000 meters per second, and when you divide by frequency in megahertz (millions of hertz), you get the simplified formula using 300. This is a fundamental formula in amateur radio. For example, 146 MHz (2 meters) gives: wavelength = 300 / 146 = 2.05 meters. The formula works because: wavelength = speed of light / frequency = 300,000,000 m/s / (frequency in Hz). When frequency is in MHz, you divide by 1,000,000, which simplifies to 300 / frequency(MHz).
考试技巧
Wavelength formula = 300 / MHz. Remember: Wavelength in meters = 300 divided by frequency in megahertz. This is one of the most important formulas to memorize.
记忆口诀
**W**avelength = **3**00 / **M**Hz (think 'W = 3/M' = 300 divided by MHz)
实际应用示例
You want to know the wavelength of 28.4 MHz (10 meters). Using the formula: wavelength = 300 / 28.4 = 10.56 meters. This confirms it's in the 10-meter band. For 146 MHz (2 meters): wavelength = 300 / 146 = 2.05 meters, confirming it's approximately 2 meters.
错误选项分析
Option A: Incorrect. Multiplying frequency by 300 would give a very large number, not a wavelength. The relationship is division, not multiplication. Option B: Incorrect. Dividing frequency in hertz by 300 doesn't work because the numbers are too large. You need frequency in MHz. Option C: Incorrect. Dividing frequency in MHz by 300 gives the wrong result. You need to divide 300 by the frequency.
知识点
Wavelength formula, Frequency conversion, Speed of light, 300 divided by MHz
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.