The performance of the cavity BPM electronics was determined by the converter module. The module consists of a limiter, a variable attenuator, a LNA, a 3dB attenuator and a mixer. In order to check the performance in detail, signal loss (and gain) at each part was carefully measured. It was found that all parts worked as expected. The signal loss from the input to the LNA was measured to be 1.4 dB and the insertion loss of the LNA was 0.4 dB. The overall gain of the module was 18.2 dB.