Though largely obsolete in commercial machines due to poor sensitivity, BFO is the simplest technology to understand and build. The book uses BFO circuits as an educational stepping stone, teaching readers how two mixing frequencies create an audible "beat" note that changes pitch in the presence of metal. Share public link
Uses physically separated transmit and receive coils to spot imbalances. Classic vintage discrimination designs.
The authors position their work as a vital update to the field, noting it as the first in-depth exploration of the technology since 1927. A core theme of the book is the transition from simple analog systems to complex digital and hybrid methods. They trace these developments through various topologies, illustrating how each innovation addressed limitations in depth, discrimination, and soil interference. Core Technical Principles Though largely obsolete in commercial machines due to
The text thoroughly breaks down the three dominant architectures used in modern metal detection. 1. Very Low Frequency (VLF) / Induction Balance
What sets Inside the Metal Detector apart from generic text books is its inclusion of and complete project builds. Some of the most sought-after projects discussed in the editions include: Classic vintage discrimination designs
Measures phase-shift continuously using continuous-wave induction. Standard coin, jewelry, and relic hunting.
: Uses two oscillators—one stable internal reference oscillator and one search-loop oscillator. and relic hunting.
: Information on coil types, construction techniques, and performance comparisons—often a "black art" in the industry.