What is the length in feet of a 1-wavelength antenna at 1.5 MHz?

What is the length in feet of a 1-wavelength antenna at 1.5 MHz?

• A. 624 ft
• B. 312 ft
• C. 156 ft
• D. 208 ft

Answer: (A)

A full wavelength length is found from λ = c / f, using the speed of light and the frequency. With f = 1.5 MHz (1.5 x 10^6 Hz) and c ≈ 3.0 x 10^8 m/s, the wavelength is 3.0 x 10^8 / 1.5 x 10^6 = 200 meters. Converting to feet (1 meter ≈ 3.28084 ft) gives 200 x 3.28084 ≈ 656 feet. So a 1-wavelength antenna at 1.5 MHz is about 656 feet long. Among the supplied choices, 624 feet is the closest approximation, which is why it’s the best pick. The other options correspond to fractions of a wavelength (half, quarter, etc.) and thus do not represent a full wavelength at this frequency.

A full wavelength length is found from λ = c / f, using the speed of light and the frequency. With f = 1.5 MHz (1.5 x 10^6 Hz) and c ≈ 3.0 x 10^8 m/s, the wavelength is 3.0 x 10^8 / 1.5 x 10^6 = 200 meters. Converting to feet (1 meter ≈ 3.28084 ft) gives 200 x 3.28084 ≈ 656 feet. So a 1-wavelength antenna at 1.5 MHz is about 656 feet long. Among the supplied choices, 624 feet is the closest approximation, which is why it’s the best pick. The other options correspond to fractions of a wavelength (half, quarter, etc.) and thus do not represent a full wavelength at this frequency.