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In the circuit model of receiving antennas, it is commonly assumed that there is no coupling between the load and the equivalent generator. Then the equivalent generator voltage is assumed to be the open-circuit voltage and the generator internal impedance is assumed to be the input impedance in the transmitting mode. In this investigation, these voltages and impedances are computed numerically for cylindrical antennas. From the numerical results, it is found that these two assumptions are not correct individually. However, it is found that the uncoupled-circuit model can yield correct results for the load current. Further, the validity of the uncoupled-circuit formula of the load current is proved by using the reciprocity theorem. Thereby, it is concluded that the uncoupled-circuit model can yield the correct result for the load current, but the open-circuit voltage and the input impedance are not at all identical to the equivalent generator voltage and the generator internal impedance, respectively.