Understanding and Building Metal Detector CIRCUITS - Opamps, Oscillators, Transmitters, Receivers ..

[jlsilicon]

I want to open this Thread up - for the discussion to understand and refine Circuits (and Parts and Tweaking) used to build Metal Detectors.

Reason being that I have been working on a few Detectors using simple circuits, such as:
* NAND and and Opamp and Transistor Oscillators, ...