ResearchAn Introduction to Treasure Hunting with Metal Detectors
Treasure hunting is pursued as a popular hobby in many parts of the world. The motivations range from chasing that potential undiscovered fortune to the intrigue of discovering new pieces of history. The hobbyist activities involving metal detectors can be broken down into four categories: Prospecting is searching for natural deposits of precious metal ore. Coin shooting is searching for lost coins and jewelry. Relic hunting is the continuing search for historic artifacts. And treasure hunting proper is the search for intentionally buried hordes of treasure.
Hobbyist treasure hunters sometimes contribute to historical discoveries and solve mysteries that have evaded answers for centuries. But even if you don't make a big find that lands you on the front page headlines, you can still turn a decent profit cashing in your finds, and there's much to be said for the fascinating process of finding some obscure item of history, then researching and learning about it, even if it isn't particularly valuable.
Metal detectors can use three kinds of technology. Beat frequency oscillators (BFO) use two wire coils, one located in the search probe and the other in a control pack. BFOs generate radio waves which are affected by the presence of a metal object which causes interference that can be picked up by the unit. These are the cheapest kinds of units, but their accuracy and depth is very poor and they don't distinguish well between different types of metal.
Very low frequency (VLF) technology uses one coil in the probe to transmit electric pulses many times per second, and a second receiver coil that catches signals bounced back from whatever the probe is pointed at. This type is best for differentiating between different kinds of metal.
Pulse induction (PI) use many coils together to generate a strong magnetic field. The PI unit reverses the direction of this field many times per second, producing the equivalent of a sonar echo but in the magnetic spectrum. This variety is also poor at distinguishing different kinds of metal, but has the greatest depth of the three technologies and can work in environments such as salt water where other technology fails.
Technique is important. We've all seen treasure hunters at the beach scouting the sand, but one can't simply start waving it around and hope to find something. First you must tune the unit to the ground so it recognizes the terrain as the medium - that, or get a self-tuning unit. Then, setting a brisk pace, you hover the detector's probing end just skimming the ground surface, sweeping the unit back and forth in tight, overlapping arcs.
This technique is necessary because metal detectors have to be in motion in order to work - like sound frequencies, the signal needs some variation over time to give any useful input.
Always remember to check first to make sure that you can legally search the area and that you can keep whatever you find. Some countries regulate where you can and can't use a metal detector, and many historic areas and national parks restrict treasure hunters - the purpose is to not disturb historic sites of scholarly interest.