Metal Detectors
Metal detectors find all sorts of metal, from gold through to coins and jewelry, by using an electromagnetic field which penetrates the ground and "detects" gold by sensing changes in the electromagnetic field in the ground.
Until recent technology stepped in, the naturally occurring salts and minerals in the ground used to interfere with the signals and make it hard to detect any gold. Enter the recently developed Minelab GPX-4000 detector, that can handle these conditions exceptionally well.
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Automatic Ground Tracking (AGT) is when the detector adjusts itself to track over ground that has changes in its mineralisation. You need a machine like this, else you will be stopping to adjust settings manually.
Frequencies are measured in kilohertz (kHz) and are the number of times the signal is transmitted into the ground and received back, per second. The lower the frequency, the deeper it can normally transmit, but usually lower frequencies means that sensitivity is reduced. So generally, use higher frequencies to find coins and treasure, and lower frequencies to find small gold nuggets.
The exception is the MPS type of detector that are both sensitive and deep-seeking at the same time.
Coils are the round things on the end of your metal detector, about the size of dinner plates. The size of the coil effects the depth and sensitivity by which gold is detected. Different coils have different search patterns. Minelab coils use two coil types; a Double-D and a Monoloop. By changing the size or design, detectors can become more versatile in changing conditions.
Broad Band Spectrum (BBS) in a Minelab detector means it transmits 17 separate frequencies over a range from 1.5kHz to 25.5kHz, giving you more depth, accuracy and greater sensitivity. Most other detectors only operates on one or two frequencies.
Difficult Soil and Quiet Ground are opposites, where the former contains minerals and the latter does not, making ground balancing easier for the machine / coil.
Choosing A Detector should be based on the type of detecting you want to do, remembering that trying to do both things with any one detector is a trade-off on abilities. You are much better off choosing one type because machines that are great at finding coins are not as good at detecting nuggets, and vica versa.
Minelab's MPS (multi period sensing) and the SmartFind (Explorer) series of detectors have opened up a new way of prospecting for gold and treasure. These technologies have a hugely improved method of detecting with Depth, Sensitivity, Discrimination and Ground Balance.
