Measures the ratio of the fundamental signal power to the power of the largest signal spur at low signal level. The ratio of the fundamental sinusoidal power to the power of the next highest spurious signal. Normally the highest spurious signal is the second or third harmonic. With a signal applied to one of the channels, this is the ratio of the signal captured on the undriven channel to the signal captured on the driven channel. The graph indicates the undriven channel.
Spurious signals result any mismatch between the converters.
On the DA60 this applies for the 60 MHz mode only. The image component appears at a frequency equal to the Nyquist frequency minus the signal frequency. The amplitude plot relates the ratio of the spurious power level to the signal power level. A direct digitally synthesized signal source is used and performance is tested at 1.004 MHz, 5.04 MHz, 12.05 MHz, and 25.1 MHz. Narrow, bandpass filters are used to make these measurements to insure a clean signal source.