FIELD TEST

Minelab's American Goldstriker
By Reg Sniff
From Page 24
November, 1994 issue of Lost Treasure

Several years ago, I read that finding a quarter ounce nugget is as rare as finding a 5-carat diamond. Obviously, looking for diamonds with a metal detector is impractical, but looking for gold nuggets is not. In fact, I would venture to guess that nugget hunting is rapidly becoming one of the most popular forms of metal detecting.

A person can hunt for nuggets with almost any good metal detector, but a serious hunter will opt for a detector especially designed for such a task. One of the newest nugget hunting detectors destined to be one of the most popular because of its ability is the American Goldstriker from Minelab.

The reason the American Gold-striker will be successful is twofold: 1) Ease of use and 2) the detectors great sensitivity. Similar in many ways to Minelabs very popular XT 17000, the Goldstriker only operates at 32 kHz and lacks the ferrous discrimination feature found on the XT 17000. Present on this new detector is Minelabs excellent automatic ground balance feature. Also present on the American Goldstriker, not found on the XT 17000 is a couple of audio improvement features which enhance the signals from targets.

Layout of the controls on the American Goldstriker is very similar to layout of the XT 17000. At the top are two toggle switches. The first, labeled the Gold Switch, is a 3-position toggle switch marked Boost! Coarse/Fine. In the Boost mode, signal amplification is increased over other switch settings. This setting gives the greatest overall signal response and works best in low mineralized ground.

In the Coarse setting, a target causes both an increase in volume and a small change in tone or pitch. The Coarse setting is recommended when searching for large deep nuggets. The Fine setting is recommended when searching for very small nuggets near the surface. In this setting, a target causes the audio to change distinctly in both volume and frequency. This technique makes the detection of very small targets more noticeable.

The second toggle switch marked Difficult/Normal is a soil or ground adjust switch. The normal setting provides the greatest sensitivity and is generally used in less mineralized ground. The Difficult setting reduces the sensitivity somewhat which also reduces the audio variations caused by wide changes in ground conditions or hotrocks.

The middle row has two controls, one a tone adjust, which sets the initial tone of the threshold signal. With this control, an operator can adjust the tone or frequency that best suits their ear. The second control is a two-position ground tracking selector switch. Normal setting of this control is the lower position marked Track. In the track mode, ground balance is automatic. To ground balance the instrument, the operator only has to raise and lower the search coil near the ground a couple of times. The other setting of the ground-tracking switch is the Fix mode. In this mode, the automatic ground tracking is locked at the last adjustment. This mode is usually used to check for suspected deep targets where the track mode might alter the signal.

The third horizontal row of controls consists of a Threshold, Sensitivity and Volume/On/Off control. Also, located on this layer is the earphone jack. The three controls are similar in their adjustments to those found on other detectors with the exception of the Volume control. This control turns the instrument on and off but limits the maximum volume rather than adjusts the volume of all signals. This may sound confusing so I will try to explain it.

Instead of adjusting the volume of all signals from the weakest to the strongest, the Volume limiting feature allows weak signals to be amplified the same regardless of the volume setting. What is limited is the maximum audio level. Where this feature is extremely useful is in using earphones having different sensitivities. As many people know, extremely sensitive earphones can produce extremely loud ear splitting signals from large targets located near the surface. The Volume limiting control simply limits the maximum signal level making the use of extremely sensitive earphones both comfortable and advantageous. The headphone socket allows the use of almost any stereo earphones with an impedance of 8 ohms, or more.

Other features of the American Goldstriker include the 10-inch elliptical widescan coil especially designed to be used on this 32 kHz detector and the quick release shaft mounting arrangement. The control unit simply slides on the shaft-mounting bracket for normal operations or the control unit can be slid into the included protective pouch used for body mounting the instrument. The unit is powered by a ni-cad battery pack. Battery pack and charger are included.

INITIAL TESTING:

Assembly of the Minelab American Goldstriker was a breeze, but initial usage was delayed because of the requirement of charging the standard ni-cad batteries for about 12 hours. A strong recommendation I have is the purchase of the optional alkaline adaptor kit which allows the use of 8 AA alkaline batteries.

Once the batteries were charged, I began to put the American Gold-striker through the paces carefully checking this detectors ability to rapidly automatic ground balance over any adverse condition I could create. To test thoroughly, I elected to use small pieces of gold as targets and simulating the difficult conditions that occur in the field.

There are areas where gold is found where ground conditions dont change much, but in most cases, where gold is present, the ground can change quickly and do so dramatically. Also, there is the ever-present problem of hotrocks (rocks containing magnetite) that respond with strong negative reactions. The response from these rocks can easily hide reasonably large nuggets. Past experience has taught me that the ability of a detector to adjust automatically to these conditions is a vital asset.

On the Goldstriker, the automatic ground balance adjusted without a flaw in all modes and all conditions I could throw at it. Instead of my constantly readjusting a multi-turn control as is the case on sensitive gold machines equipped with manual controls, the auto ground balancing of the American Goldstriker was as simple as raising and lowering the coil close to the ground a couple of times, or, in the case of encountering negative hotrocks, passing over them a couple of times.

On a manual ground balance machine, when the detector is properly ground balanced to the normal terrain, the magnetite hotrocks will give a strong negative response which can easily mask any small nugget nearby. In fact as mentioned before, fair sized nuggets (up to a 1/ 4 ounce) can be easily hidden by the response from the rock. To eliminate this possibility, the ground balance should be readjusted to minimize a rocks response each and every time one is encountered.

With the American Goldstriker, nulling out or at least minimizing the audio responses from the most difficult hotrock was as simple as making a couple of passes over the rock with the detector in auto track. To see how effective the ground track was, I initially adjusted the Goldstriker over mineralized ground, set the ground tracking to Fix (which locks the ground adjust to the last adjustment). Next, I passed over a typical hotrock with a nice small nugget (about 1/8 ounce) next to the rock. The rock responded with a strong negative response, and the nugget was ignored.

Next, I reset the ground track to Track and repeated the test. After a couple of passes over the rock, the response from rock was minimized as well as could be done on a detector with a manually ground balance and the nugget detected with a solid positive response. The big difference was, instead of having to fiddle with the ground balance control to get the best response, the detector did it all.

Testing over other gold targets began by using a 1 grain nugget as a test target. Settings of the different controls varied for different stages of the testing. For example, I initially set the gold switch to Boost, soil switch to Normal, sensitivity to maximum and ground tracking switch to Track. With this setting the American gold striker could easily pick up the small nugget lying on top of mineralized soil.

Switching the gold switch from Boost to Coarse resulted in a slight reduction of sensitivity and again changing to Fine setting, the response of the 1 grain nugget was reduced further but the signal was distinct because there was both atone change and an audio increase.

The next test repeated the hidden nugget test only using a couple of very small nuggets having a total weight of about 4 or 5 grains (about 1/100 of an ounce) near a magnetite hotrock. The reason for this test was, it is a realistic condition gold country. What I found was surprising. In both the Boost and the Coarse modes sensing the gold was difficult because of the slight response from the large rock. The gold could be heard but, in my opinion would only be noticeable to the experienced ear. However, in the Fine mode the auto ground tracking would adjust for the rock and the nuggets could easily be heard.

The big question is, how does this compare to a manual ground balanced instrument? Simply stated, it would take a very experienced person to match the ground adjust capabilities of the American Goldstriker.

Various tests were then done over my standard buried targets, included several pieces of lead buried at various depths. The reason for using lead is this metal responds similar to gold and is easy to come by. More importantly, if lost, doesnt cause the concern that the loss of gold might.

Checking different sizes of lead targets buried at various depths left me impressed. In fact, the American Goldstriker matched or exceeded the most sensitive of detectors I have tested in all respects. Tests included targets buried to depths exceeding 1 foot. One other test was the detection of a test target (a nickel buried to a depth of 9 inches). The American detected the nickel reliably.

IN THE FIELD:

Because the Goldstriker arrived in the summer, I elected not to attempt a trip to my favorite gold hunting spots in Arizona, instead I picked a couple of spots in Colorado.

I didnt have any success in finding gold, but I did detect more than my share of small pieces of iron and lead. Several targets did cause heartthrobs but turned out to be pieces ofjunk. As any serious nugget hunter can tell you, pieces of junk, including boot tacks and pieces of lead can wedge themselves into the most illogical places.

During the field testing, the auto ground tracking worked flawlessly, quickly reacting to the worst of ground conditions. The only oddball signals were from some positive responding rocks, a common problem with all detectors.

CONCLUSION:

 As stated earlier, the American Goldstriker is destined to be one of the most popular gold machines simply because of its sensitivity and ease of use. The most inexperienced user can, in a few days, be as proficient with the Goldstriker as a serious nugget hunter who has been using a manually ground balance detector for years.

The Goldstriker has all the features of the more expensive Minelab XT 17000 except the iron discrimination and 6.4 kHz features. The Goldstriker has one feature the XT 17000 doesnt, a VCO feature (frequency changes) in the Fine mode.

The auto ground track system found on the Goldstriker is the best! have used. The ground balancing system is smooth, consistent, and has little or no noticeable overshoot even under the worst of conditions. Furthermore, making a couple passes over the most severe negative responding rocks all but eliminates the problems caused by them.

I dont recommend the Goldstriker for coinhunting, but I hardily recommend the Goldstriker to anyone serious about finding gold nuggets. The detector is extremely versatile, sensitive, and easy to use.

For more information about the American Goldstriker or any other Minelab instrument, please contact; Down Under Treasures, P. 0. Box 92080, Henderson, NV 89009. Phone: (702) 565-1353.

 



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