Become the proud owner of a low-cost, wrist-band metal detector... plus a useful companion to your main "search tool."

Beat frequency operation (BFO) metal detectors were very popular in the 60s and 70s, soon after the advent of the first commercial transistors. Some models sold thousands of times over. But these quickly went out of fashion as superior induction balance (IB) and pulse induction (PI) designs appeared on the market.

However, BFO metal detectors still have significant advantages in the areas of cost and ease of construction, and may be better suited to certain applications, such as pipe-finding or probing. Also, they are particularly well suited to miniaturization. It is this last feature, especially, which is exploited in this present article, which describes how to build a truly miniature BFO metal detector which may be worn on the wrist. For good measure, and just a few additional items, a Pinpointer, which is used to pinpoint items found with a larger detector, is also described.

While the performance of this EPE Mini Metal Detector is nothing to write home about, it is sufficiently sensitive to be of genuine use. It will clearly detect an old Victorian penny at a depth of 55mm, and a tiny 15mm diameter coin at 35mm. It will vaguely detect these at 70mm and 45mm respectively. When properly tuned, it will pick up a pin. It will also discriminate between ferrous and non-ferrous metals (e.g. iron and copper), thus giving a good indication as to whether a “noble” metal has been found, or just a rusty piece of iron.