Inside the Metal Detector George Overton Carl Moreland is widely regarded as the definitive technical guide for understanding, designing, and building metal detection technology. Unlike typical hobbyist guides that focus on how to use a detector, this work dives deep into the engineering and physics of how these devices actually function. Amazon.com Core Technical Concepts
The book provides a thorough examination of the electronics and physics behind various detection methods: Fundamental Physics : It explains the basics of eddy currents
, which are the essential principles for detecting metallic objects underground. Detector Topologies
: Detailed coverage is provided for major categories, including: BFO (Beat Frequency Oscillator) TR (Transmitter-Receiver) VLF (Very Low Frequency)
: Focuses on ground balance and motion filtering/discrimination. Pulse Induction (PI) : Covers ground balance methods and advanced PI techniques. Modern Advancements
: Discussion of multifrequency, hybrid, and digital techniques. Practical DIY Focus
A standout feature of this work is its emphasis on hands-on application. It is particularly popular in the DIY and maker communities for including: Google Books Working Designs
: Most chapters include functional example designs with source code, CAD, and Gerber files made available through the Geotech forum
: Readers can build specific tools such as an off-resonance pinpointer, a GEB-discriminator, and microprocessor-controlled detectors. Target Response Inside the Metal Detector George Overton Carl Moreland
: It provides operational insight into how different targets behave in the field and the reasons for "complex responses" often encountered by detectorists. Amazon.com Editions and Availability
The book has evolved significantly across its editions to keep pace with technology: Inside The Metal Detector: Overton, George, Moreland, Carl
Book overview * Book overview. Inside the Metal Detector offers hard-to-find information on the technology behind metal detectors. Amazon.com Inside the Metal Detector - George Overton, Carl Moreland
In the quiet workshop of the Geotech Forums , the air was thick with the scent of solder and the hum of high-frequency oscillators. George Overton (known online as ) and Carl Moreland
, the forum's lead engineers, weren't just searching for buried treasure; they were building the maps that would let others find it.
Their goal was to pull back the curtain on a technology that had remained largely a "black box" to the public since the 1920s. They began documenting the invisible dance of induction and eddy currents, explaining how a simple coil of wire could "feel" a coin deep in the earth.
As they collaborated, they filled their project, Inside the Metal Detector, with more than just theory. They designed and shared blueprints for DIY enthusiasts to build their own gear from scratch:
The Pulse Induction (PI) Detector: A microprocessor-controlled beast that could ignore mineralized ground to find deep targets. The Verdict: The "Bible" of Metal Detector Technology
The VLF-Discriminator: A tool that could tell the difference between a rusty nail and a silver ring by analyzing phase shifts.
Coil Designs: Step-by-step guides on winding search coils to maximize sensitivity.
The "story" of their work isn't just about the electronics; it’s about a community-driven revolution. By releasing open-source code and Gerber files on Geotech, they transformed the metal detector from a mysterious factory-made gadget into a project that any "Forrest Mims" fan or aspiring engineer could build in their own garage.
Today, their work remains the "definitive" guide for those who want to see past the plastic casing and understand the heartbeat of the machines that find the world's hidden history. Inside The Metal Detector: Overton, George, Moreland, Carl
Book Review: Inside the Metal Detector by George Overton and Carl Moreland
Subtitle: The First In-Depth Explanation of How Metal Detectors Work
The Verdict: The "Bible" of Metal Detector Technology
For anyone interested in the electronics hobby, specifically the engineering behind treasure hunting, Inside the Metal Detector is widely considered the definitive text. Co-authored by George Overton (a renowned engineer and designer) and Carl Moreland (creator of the Geotech1 website), this book bridges the gap between simplistic user manuals and dense electrical engineering textbooks. The Nulling Process: The PDF instructs you to
Here is a detailed review of the work.
No article on this PDF would be complete without summarizing its most challenging chapter: The Search Coil.
Overton and Moreland dedicate 10 pages to this alone. Why? Because the electronics are useless if the coil is wrong.
The PDF includes a full winding diagram for a 10-inch concentric coil, specifying 26 AWG enameled wire and specific inductance values (e.g., TX = 300 µH, RX = 320 µH).
This is not a "how to find gold" field guide. It does not cover where to dig or the history of lost treasures.
Thousands of vintage detectors (White’s, Garrett, Fisher) from the 1980s and 1990s are still in use. When they break, modern repair shops often refuse them. The PDF gives hobbyists the circuit knowledge to replace transistors, recalibrate nulls, and revive dead machines.
The PDF begins not with a soldering iron, but with a physics lesson. Overton and Moreland explain Faraday's Law of Induction: A changing magnetic field induces a voltage in a conductor.
They illustrate how a metal detector transmits a magnetic field via a search coil (TX). When that field passes over a conductive target (a coin, ring, or relic), it induces eddy currents in the target. Those eddy currents generate a secondary magnetic field, which is received by a second coil (RX). The difference—or "imbalance"—is the signal you hear.