A true Wobbulator is a quite expensive instrument to measure a characteristic curve of a circuit. However there are neat modules like the AD9850 DDS from eBay which also do the job. They work fully digitally and they called DDS
The circuit to alanlyse is an simple choke. The image on the right hand side shows the characteristic of the choke as an oscillogram. The X-axis needs to be logarithmic in order to get a realistic plot.