tinySA | Main / MODULATION

Modulation Menu

When no span for sweeping is selected the output can be modulated according to a limited set of formats.

NONE sets no modulation
AM sets an AM modulation. Depth is about 50%.
Narrow FM sets narrow FM modulation. Width is about 3kHz.
Wide FM sets wide FM modulation.
EXTERNAL disables the internal LO driving the mixer and enables the high input as mixer LO input. Minimum external LO input frequency is 5MHz.
FREQ activates a keypad to set the modulation frequency between 100Hz and 6kHz.
BACK will move back to the previous menu

The AM and FM modulation is done using a 8 point approximation of a sine wave. This limited approximation does contain harmonics and has some steep level steps as can be seen in this measurement of the AM modulation

In the EXTERNAL modulation mode a second tinySA working as a spectrum analyzer in low input mode and outputting its LO from its high connector enabled by setting the LO OUTPUT can drive the mixer of the tinySA in low output mode. By setting the frequency to zero Hz the output will follow the sprectrum analyzer with zero Hz offset and can be used a tracking generator.

Make sure you enable the LO output in CONFIG/EXPERT CONFIG

The settings for the tracking generator tinySA

First normalize the tinySA so you have a clean 0dB level

And then you can connect a filter and do a wide scan

Or do a narrow scan

The dynamic range in this setup is limited due to the reverse leakage thru the mixers. Best would be to add an attenuator and amplifier between the LO output and the tracking generator input to stop the leakage. If you use a external mixer you can set the TG to an offset allowing measurement of the conversion loss of a mixer