We can see a level fluctuation of output signal after changing ATT on HMC424ALP3E.Could you please look at following pictures. They are in case of ATT 0dB to 16dB and 16dB to 0dB. Almost same situation as for other ATTs.
Does HMC424ALP3E has like this fluctuation of signal level? Or is it external problem of HMC424ALP3E?