What is the length in feet of a 1-wavelength antenna at 3.5 MHz using the same formula?

What is the length in feet of a 1-wavelength antenna at 3.5 MHz using the same formula?

• A. 267.4 ft
• B. 140.0 ft
• C. 312.0 ft
• D. 118.0 ft

Answer: (A)

A 1-wavelength antenna length is simply the wavelength of the signal in the medium, which in air is essentially the speed of light. Use λ = c/f. With f = 3.5 MHz (3.5 × 10^6 Hz) and c ≈ 3.00 × 10^8 m/s, λ ≈ (3.00 × 10^8) / (3.5 × 10^6) ≈ 85.7 meters. Converting to feet gives 85.7 × 3.28084 ≈ 281 ft. Among the given options, 267.4 ft is the closest match to the calculated wavelength, so it’s the best choice. This aligns with the idea that a 1-wavelength length at 3.5 MHz is about 280 ft, and small rounding differences in constants can push the closest option to 267.4 ft.

A 1-wavelength antenna length is simply the wavelength of the signal in the medium, which in air is essentially the speed of light. Use λ = c/f. With f = 3.5 MHz (3.5 × 10^6 Hz) and c ≈ 3.00 × 10^8 m/s, λ ≈ (3.00 × 10^8) / (3.5 × 10^6) ≈ 85.7 meters. Converting to feet gives 85.7 × 3.28084 ≈ 281 ft. Among the given options, 267.4 ft is the closest match to the calculated wavelength, so it’s the best choice. This aligns with the idea that a 1-wavelength length at 3.5 MHz is about 280 ft, and small rounding differences in constants can push the closest option to 267.4 ft.