In the quarter‑wavelength length formula, what unit is used for frequency?

In the quarter‑wavelength length formula, what unit is used for frequency?

• A. MHz
• B. GHz
• C. Hz
• D. kHz

Answer: (A)

Quarter-wavelength antennas rely on the wavelength, which is set by frequency. The length is λ/4, and λ = c/f, so L = c/(4f). When you use frequency in MHz and express length in meters, the common practical form becomes L ≈ 75 / f(MHz) meters. That neat constant (75) comes from c ≈ 3×10^8 m/s and the conversion between Hz and MHz, making calculations quick and intuitive for typical radio bands. Using MHz keeps the numbers small and convenient, which is why this unit is standard in the quarter-wavelength formula for practical antenna work. Using other units is perfectly valid mathematically, but it doesn’t give as handy a rule of thumb.

Quarter-wavelength antennas rely on the wavelength, which is set by frequency. The length is λ/4, and λ = c/f, so L = c/(4f). When you use frequency in MHz and express length in meters, the common practical form becomes L ≈ 75 / f(MHz) meters. That neat constant (75) comes from c ≈ 3×10^8 m/s and the conversion between Hz and MHz, making calculations quick and intuitive for typical radio bands. Using MHz keeps the numbers small and convenient, which is why this unit is standard in the quarter-wavelength formula for practical antenna work. Using other units is perfectly valid mathematically, but it doesn’t give as handy a rule of thumb.