The gain of the helical antenna strongly depends on the reflector. The above classical formulas assume that the reflector has the form of a circular resonator (a circular plate with a rim) and the pitch angle is optimal for this type of reflector. Nevertheless, these formulas overestimate the gain for several dB. The optimal pitch that maximizes the gain for a flat ground plane is in the range from 3° to 10° and it depends on the wire radius and antenna length.