: Step-by-step instructions to build functional devices, such as an off-resonance pinpointer and a microprocessor-controlled PI detector. Coil Design
"Inside the Metal Detector" was first published in 2012. However, the version that has become most influential is the , released by Geotech Press in 2015 and again in 2016. This updated edition features a new cover, contains revised and corrected content based on reader feedback, and, most importantly, is the edition that has been widely shared as a PDF. The PDF's circulation has been a game-changer, democratizing access to this vital information for a global audience of electronics enthusiasts who might not have been able to afford or obtain the physical book.
Overton and Moreland cover virtually every major detection technology used today: Amazon.com BFO (Beat Frequency Oscillator):
That dynamic shifted entirely with the publication of by George Overton and Carl Moreland . Hailed as the most definitive work on hobbyist radar and induction electronics since the early 20th century, this book serves as a bridge between pure physics and practical, DIY engineering.
One oscillator uses the search coil. When metal approaches, the inductance changes, altering the frequency. The mix of the two frequencies creates an audible "beat" note that changes pitch. 🛠️ Key Technical Chapters in the Updated Editions This updated edition features a new cover, contains
While early versions of the manuscript and specific project chapters were shared on forums like Geotech , the full book is a copyrighted publication. Authorized digital versions are often available through technical book retailers or the authors' official sites.
The book systematically breaks down the three primary types of metal detection technologies, detailing the pros, cons, and electronic architecture of each. 1. Very Low Frequency (VLF) / Induction Balance
One of the highest-value aspects of the book is the inclusion of complete, tested projects:
: Extensive technical data on winding patterns, including the development of Double-D (DD) coils for improved performance in mineralized soil. Major Detection Topologies Hailed as the most definitive work on hobbyist
A digital oscilloscope is incredibly helpful when tuning the phase-demodulation circuits described by Overton and Moreland.
Explains why BFO is rarely used today outside of cheap toy detectors due to its poor sensitivity and lack of ground-rejection capabilities. 2. Induction Balance / Very Low Frequency (VLF)
| 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 |
Carl clicked 'Upload.' The progress bar crawled across the screen, and with a final ding , the blueprints for the future were gone, sent out into the digital ether for every seeker to find. who praised its accuracy and reliability.
PI systems are largely unaffected by ground mineralization, a concept the authors break down with comprehensive waveform analysis. 3. Beat Frequency Oscillator (BFO)
For decades, the metal detecting community has included an eclectic mix of hobbyists, treasure hunters, and serious engineers. Yet, for all the passion and practical knowledge available in online forums, there was a significant gap in the literature for decades — a lack of a comprehensive, technical resource that truly explains how these devices work. This is where the book , by George Overton and Carl Moreland, stepped in to fill a crucial void.
Updated sections touch on utilizing microcontrollers (like PIC or AVR chips) to handle signal processing, replacing bulky analog filtering components with software algorithms. 🏗️ DIY Projects Included
"Inside the Metal Detector" (ITMD) by George Overton and Carl Moreland, a definitive technical guide for detector electronics, has been significantly updated with a third edition released in December 2024. Expanded to over 600 pages, the new edition introduces all-new DIY projects and updated theoretical content focusing on modern digital techniques and pulse induction methods. For more details on the updated third edition, visit Amazon . Inside The Metal Detector: Overton, George, Moreland, Carl
Overton's innovative approach to metal detecting led to the development of the first-ever metal detector specifically designed for hobbyists. His design was more compact, lightweight, and user-friendly than earlier models, making it accessible to a wider audience. The Overton metal detector quickly gained popularity among enthusiasts, who praised its accuracy and reliability.