A while ago I bought this non-contact metal detector module from an online store to see how it functions, and what I need to build it. The cheap module I received from China had no instruction manual ...

The electronic dog repellent circuit diagram below is a high output ultrasonic transmitter ... tuned RF preamplifier wired around VHF/UHF transistor 2SC2570 (C2570). Metal detector DIY metal detector ...