This paper concerns production test of analog and RF communication devices. The use of standard digital tester channel for the acquisition of modulated analog/RF signals is investigated in order to implement low-cost functional test. The idea is to use the comparator available in a standard digital test resource to record level-crossing events on a signal coming from the device under test, and then to apply a dedicated algorithm to retrieve the signal information. The proposed method is evaluated through both simulation and hardware experiments using the popular QAM coding scheme that combines both amplitude and phase shift-keying. The approach is generic and can be applied to a broad range of modulation schemes.