In the quarter‑wavelength formula, what is the numerator constant used to calculate length in feet?

In the quarter‑wavelength formula, what is the numerator constant used to calculate length in feet?

• A. 234
• B. 468
• C. 1000
• D. 123

Answer: (A)

Quarter-wavelength length is one-fourth of the signal’s wavelength, so the physical length you need is tied to how long the wave is at that frequency. Wavelength in feet is roughly proportional to 1/frequency, and for practical quick calculations in feet with frequency in MHz, the rule of thumb is L (feet) ≈ 234 / f (MHz). The constant 234 comes from combining the speed of light and unit conversions and then using a rounded, practical factor that matches typical antenna and installation conditions. This makes 234 the standard numerator for calculating a quarter-wavelength length in feet. The other numbers don’t match the common quarter-wavelength rule: 468 would correspond to a half-wavelength length (twice as long) under the same frequency, and the remaining options aren’t standard constants used for this calculation.

Quarter-wavelength length is one-fourth of the signal’s wavelength, so the physical length you need is tied to how long the wave is at that frequency. Wavelength in feet is roughly proportional to 1/frequency, and for practical quick calculations in feet with frequency in MHz, the rule of thumb is L (feet) ≈ 234 / f (MHz). The constant 234 comes from combining the speed of light and unit conversions and then using a rounded, practical factor that matches typical antenna and installation conditions. This makes 234 the standard numerator for calculating a quarter-wavelength length in feet.

The other numbers don’t match the common quarter-wavelength rule: 468 would correspond to a half-wavelength length (twice as long) under the same frequency, and the remaining options aren’t standard constants used for this calculation.