Understanding Metal Detector Frequencies
Operating frequency is one of the fundamental specifications of a metal detector and affects what targets it finds best. Understanding frequency helps you choose the right detector for your goals and explains why some machines perform differently than others on the same targets.
The Basics
Metal detectors transmit an electromagnetic field at a specific frequency (measured in kHz). When this field encounters a metallic object, it induces a current in that object, which creates its own field that the detector receives and interprets. Different frequencies interact differently with different metals and target sizes.
Low Frequency (3-7 kHz)
Lower frequencies penetrate deeper into the ground and respond well to larger, higher-conductivity targets like silver coins, copper, and larger brass items. They're less sensitive to small, low-conductivity targets like thin gold jewelry and tiny lead pieces.
Mid Frequency (7-15 kHz)
The general-purpose range. Good all-around performance on coins and relics of various sizes. Most popular beginner detectors operate in this range because it handles the widest variety of targets reasonably well.
High Frequency (15-40+ kHz)
Higher frequencies are more sensitive to small, low-conductivity targets — tiny gold nuggets, gold jewelry, and small lead objects. They sacrifice some depth on large, high-conductivity targets. Specialized gold prospecting machines operate at very high frequencies.
Multi-Frequency
Some detectors transmit multiple frequencies simultaneously (simultaneous multi-frequency or SMF) to get the benefits of both low and high frequencies. This technology, available from several manufacturers, handles a wider range of target types and soil conditions than any single frequency. It's increasingly common in mid-range and higher-end machines.