Efficiency transition point for inductively loaded monopole

Whip or monopole antennas less than a quarter wavelength long can be significantly improved through series inductive loading in the antenna wire, provided that the coil losses are less than the improved radiation resistance. However, if the antenna is too short or the coil too lossy, the performance may degrade instead of improve. The combination of antenna length, radius, and coil Q factor for which the efficiency is 50% is an important design guide. This transition point varies with Q1/3 and even more slowly with length/radius ratio. For Q = 300, the transition point occurs for monopole lengths between 0.05 and 0.07 wavelengths.