Re: Square wave generator - low cost

This is a good unit. The problem is, depending on the specific components used, it can produce a frequency that is between 3.0 Hz and 5.0 Hz and you do not know the exact frequency at any time unless you are hooked to a frequency meter that provides a period output with at least a 10 second timebase.

If you want true 1/2 earth resonance, then you need to produce 3.915 Hz and this is hard to produce without a crystal timebase.