There’s no gold left in those old nugget patches! The surface gold was cleaned out long ago by VLFs in the 1980s, and the deeper ones were plucked out by the SDs in the mid ‘90s. Say that to the new owners of a GP extreme and they’ll just rattle their pokes at you and smile – or perhaps the smarter ones won’t.

Minelab’s newest addition, the GP extreme, comes in its own heavy-duty, plastic carrying case that has an inner skin molded to the shape of the detector’s components. It is supplied with both 11” and 18” extreme coils, metallic blue control box, armrest, shafts, handle assembly, 6 volt/10 AH battery, curly power cable, 110 volt charger, 12 volt vehicle charger, 600 ohm Telex headphones, battery pack and instruction manual. While its overall appearance is ergonomically similar to the SDs, you can rest assured that this is not merely a 2200d wrapped up in a fancy new package.

In fact, it is the first gold detector to utilize Dual Voltage Technology (DVT). This new technology was developed based on the existing Bi-Polar technology used in their military mine detectors. DVT, refers to changes in voltage used to create the electro-magnetic field, transmitted by the coil into the ground. It has nothing to do with the power supply. The magnetic fields, which are transmitted by a metal detector, can ‘magnetically-saturate’ the ground, especially if the coil is held close to the surface. Minelab discovered that by applying two different voltages to the transmit coil they were able to cancel out many of the signals caused by this magnetic saturation. Thereby improving the detector’s sensitivity, depth and its ability to balance out mineralization.

Listed below is a very brief description of some of the more important features found on the new GP extreme. The Rx setting changes the characteristics of the new ‘extreme’ coils by altering their transmit and receive fields, giving them the ability to change their configuration pattern with the simple flip of a switch. When the Rx switch is set in the Normal position the coil will function as a conventional Double D. If the Rx switch is set in the E (Enhance) position the coil will essentially function as a ‘pseudo’ monoloop. By this I mean, it will exhibit some of the characteristics of a traditional monoloop coil. When operated in this mode the GP’s detection depth is still good, but sensitivity on the right hand side of the coil is virtually non-existent. The Cancel feature changes the electro-magnetic field of the coil so that it is relatively stable in areas of electrical interference. This feature is especially useful when hunting near power lines, electrical fences or under poor atmospheric conditions.

The Boost feature allows the operator to select the type of processing and filtering used while hunting, thereby enhancing the signals produced by different types of targets. Shallow amplifies signals from small, faint targets near the surface. N (Normal) can be used in most any soil conditions. This setting does not boost any signals, regardless of size or depth. Deep may be used when searching for large nuggets in highly mineralized ground at depth.

The Soil feature optimizes the detector for different soil conditions and targets by changing the signal processing. This switch offers three different settings: Normal, Sensitive and Salt. The Normal (N) setting may be used in all types of ground, ranging from lightly to highly mineralized soils. This is my preferred setting for the Soil switch. The Sensitive setting is useful when searching for tiny, shallow gold nuggets. The Salt setting enables the GP to search in areas containing large amounts of conductive salts. Although I have not had an opportunity to test the GP on the salt, I have talked with several professional Australian hunters who are impressed with its capabilities. My advice is this; unless you are hunting the dry salt lakes of the outback avoid using this setting, as it reduces sensitivity towards small nuggets. You will find that the American goldfields are much less mineralized and using this setting is largely unnecessary.

Like its predecessor, the SD 2200d, the GP extreme is also equipped with automatic ground balancing (AGB). The Balance switch, which controls the ground balance function, is located on the front panel. Unlike manual ground balancing detectors, the GP, when placed in the Tracking mode will continually adjust to minimize the effects of ground mineralization. It also has the ability to be dialed or ‘tuned’ in for a particular piece of ground when placed in the Fixed position. Strangely enough, it has come to my attention that the AGB feature often works too well. Tiny or deeply buried gold nuggets are often difficult to hear because of the feeble signal they emit. Usually these signals are in the form of a small dip or rise in the threshold level, and are often so weak they’re nearly impossible to distinguish from the background noise.

Unfortunately the GP, because of its improved canceling ability, may interpret these subtle responses as being nothing more than ground noise and attempt to balance them out. This problem can be remedied by leaving the machine in the Fixed position after it has been properly balanced. Based on my own findings and the comments of others, the general consensus towards the Balance feature is the following. If the ground is quiet to medium mineralized there is a sensitivity advantage if the Fixed position is used for searching. Not to mention, the machine will not accidentally balance out those faint murmurs. If the ground is variably mineralized and noisy, then Tracking is the preferred position.

The GP is outfitted with an Iron Discriminate feature, which allows the user to select between a Disc or an All Metal mode. In the All Metal mode, the detector will respond to all types of metallic targets, including ferrous (iron) items. In the Disc mode, the detector will cause the threshold to be ‘blanked’ or silenced when the coil is passed over a fairly large ferrous target.