Trying to create a circuit to allow me to adjust the frequency of AC power
I'm trying to design an EM field generator with adjustable frequency. I've got most of it figured out, but I can't seem to find anything about how to create adjustable frequency AC power. I've got two designs I'm working on, one that is DC powered and one that is AC powered, but the best I can do on either ends up with a 60Hz EM field. I'm looking for adjustable frequency, ideally from 0.1Hz to 50kHz, although I'll be pretty happy to even get any range of frequencies at all. The range from 0.1Hz to 500Hz is the most useful and interesting in particular for my purposes, but any help on figuring this out at all would be much appreciated.