You buy a "20dBi omni" Wifi antenna, operating in the 2.4-2.5GHz band. You note that the expected range is not achieved from this 300mm long antenna. What could be wrong?
Can someone please tell me whether may approach is correct
λ(min) = 300/2500 = 0.12m = 120mm
Dipole length is therefore = 300mm/120mm = 2.5λ => 0.5λ (neglect '2' since its just a full revolution on smith chart??)
driven element have length of = 0.5λ/2 = 0.25λ
Actual gain of the antenna = 300mm/(0.25λ) = 10dB, therefore antenna in question is not 20dB and therefore thats why doesnt meet expected range. - is this the right way to calculate gain?