Originally Posted by Ted Ewert

However, it’s a whole different machine once it falls into resonance. The output becomes strong and regular, the pendulum takes very little energy to keep it swinging and you can see immediately what Milkovic is talking about.
You really need to build one and test it to get a better understanding of the principal involved. Then you can try and get it into resonance, which will teach you in no uncertain way the difference between a resonant and a non-resonant device.

Ted