| Problem | Likely cause (per Overton & Moreland) | Fix | |---------|----------------------------------------|-----| | Constant beep/no null | Coil misalignment | Adjust RX position / add trim cap | | Weak depth | Low TX amplitude | Increase TX voltage or coil turns | | False signals on wet ground | No ground balance | Add ground balance pot or auto circuit | | Poor discrimination | Phase reference drift | Use crystal oscillator; stabilize supply |