The shape of the i = 2 minimum of the ac longitudinal resistance R-x of a q
uantum Hall device has been obtained at different frequencies from 160 Hz t
o 16 kHz, The frequency dependence of the resistance and the virtual reacta
nce! measured at the i = 2 and i = 4 plateau centers with different circuit
conditions, have been analyzed, The measurements have been performed with
a ner system, which includes dedicated electronic units to maintain close t
o zero the voltage at the current measurement terminal of the del-ice and t
he current at the voltage terminals, Within the validity of the equivalent
circuit adopted to represent the quantum Hall device and the measuring syst
em, R-x was found to follow an increasing function of frequency, in agreeme
nt with previous investigations.