Active loop-dipole aerials

A theoretical study of the input impedance of active loop-dipole aerials which possess height-reduction properties at resonance is made. This is compared with measurements on an aerial containing a BFY 90 transistor at 200 MHz for which the transistor parameters are available. Reasonable agreement is obtained. The existence of separate power gains and radiation patterns for transmitting and receiving is also established, and a comparison of the theoretical and experimental radiation patterns in the two cases is made. Numerical values of radiation resistance for these aerials are also calculated.