Measuring Phase Noise
After activating the Phase Noise measurement the tinySA asks for the frequency of the carrier used for phase noise measurement. The specified frequency is used as center for the span. Next the offset frequency for the phase noise measurement can be entered. Typical offsets are 10kHz, 100kHz or 1MHz. The span of the tinySa is set to 4 times the offset and a two markers are activated. The first marker is a tracking marker and it is automatically positioned at the carrier. The second marker is a a delta marker which is positioned in low mode at the frequency of the tracking marker plus the specified offset. In high mode the phase noise marker is positioned below the carrier to avoid the mirror of the carrier which may otherwise obscure the phase noise. The info displayed with this delta marker is in dBc/Hz to have a direct readout of the phase noise at the specified offset.
As mentioned in the limitations the Phase noise of the tinySA is not stellar. But a simple analog VCO is delivering an even worse phase noise.
First the VCO. Phase noise is given in dBc/Hz at 1MHz offset at marker 2
Second a DDS, which is better than the tinySA so this is the lower limit of what can be measured.