The Constellation measurement mode (only on specific DSAM models or options) displays a constellation diagram of the demodulated digital Quadrature Amplitude Modulation (QAM) type (64 QAM or 256 QAM) signal prior to error correction. The channel of interest must be defined as either Digital or DOCSIS type, either 64 or 256 QAM, within the active channel plan. This mode also displays the channel number, channel frequency level information, Modulation Error Ratio (MER) and Bit Error Ratio (BER) Pre and Post data.

Identifying a specific constellation pattern on the grid and associating this pattern with a specific type of impairment quickly leads to troubleshooting options that minimize or eliminate the impairment.

NOTE:
A good QAM signal will show a tight grouping of dots in the center of each square on the grid.