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TESTING THE MINELAB

Minelab Electronics SD-2100 Metal Detector

Reprinted with permission from Lost Treasure Field Test By Andy Sabisch From page 43 of the January 1998 issue of Lost Treasure magazine.

Minelab Electronics has been building metal detectors designed for electronic prospecting for more than a decade and during that time, they have acquired the reputation of a company that produces a high-quality product that gets consistent results where it counts -- in the field! Beginning with the GS 15000, Minelab detectors have been responsible for the recovery of literally thousands of ounces of gold in Australia, the United States, South Africa and South America. Despite the success experienced by Minelab customers over the years, the engineering staff has continued to solicit feedback from users in an effort to "build a better mousetrap." The new SD-2100 is the latest metal detector developed by Minelab for the electronic prospecting market.

FEATURES
The SD-2000, which was released in 1995, earned the reputation of a metal detector that was completely unaffected by even the most severe ground mineralization. It was the first detector to use the patented Minelab circuit called Multi Period Sensing or MPS for short. This circuit was designed to allow targets, both large and small, to be detected at maximum depths even in areas of extreme mineralization. Feedback from users as well as additional testing by the Minelab staff, identified several enhancements that could be made to the SD-2000's design, and after two years in development, an entirely new model called SD-2100 was released. The first thing that stands out when you unpack the SD-2100 is it's unique configuration. Due to the SD's inherent sensitivity, the shaft is considerably longer than that of a conventional metal detector in order to keep any metal away from the coil itself. In addition, the detector uses a rechargeable 6 Volt gel-cell battery which is about the size of a motorcycle battery. To keep the weight of the actual detector assembly at a minimum for operator comfort and keep it away from the coil, the battery is held in a small nylon backpack. To put the SD-2100's sensitivity in perspective, the manual states that "if the battery pack is worn on your side, the 18-inch coil will detect it resulting in false signals." The SD-2100 has two toggle switches, three knobs and two internal potentiometers that control it's operation. The ON/OFF switch is located in the center of the rear panel. Beneath the toggle switch is an LED indicator which warns the operator when the battery voltage becomes low and should require recharging. The gel cell should provide approximately 20 hours of use between charges. The Threshold knob below the LED allows one to set the background audio signal to a level at which faint signals are easily discerned. Beneath the Threshold knob are two plastic caps. Removing the caps will reveal small potentiometers which can be adjusted using the special screwdriver that comes with the SD-2100. The control on the right is labeled Tone and allows you to vary the pitch of the signal produced by a target. The other control labeled Tune is designed to allow the operator to reduce or completely eliminate the effect of external electrical interference such as that caused by power lines, transformers or even radio signals. This feature greatly enhances the actual in-field performance of the SD-2100 as compared to other detectors which must typically be run at lower sensitivity settings when used near any source of electrical interference.

The control panel.

The control panel.
On the front panel, there are two knobs labeled Balance 1 and Balance 2 along with a three-position toggle switch. This panel really holds the secret of the SD-2100's overall success in the field. Each balance control is used to compensate for the mineralization present in the ground independently of the other. Minelab describes the SD-2100 as "essentially two detectors in one where each half must be ground balanced separately." Ground balancing, while being manual in nature, is simple and straightforward. Once the detector has been ground balanced in both the Balance 1 and Balance 2 setting, the toggle switch is placed in the center Search position to begin hunting. The location of the three-position toggle switch makes it quite easy to periodically check the ground balance settings as you move from one area to another to ensure the SD-2100 is always operating at it's optimum setting. The SD-2100 comes with two search coils -- an 8-inch Mono Loop (similar to a standard concentric design) and an 11-inch Double-D. The 8-inch coil is designed to provide maximum sensitivity to smaller targets. The 11-inch coil provides maximum coverage with each sweep due to the Double-D design and will detect medium to large sized targets some 25 to 40 percent deeper than the 8-inch coil. An optional 18-inch Mono Loop coil is available for maximum detection depth in areas where targets may be buried at extreme depths. The SD-2100 does not have an internal speaker so a set of comfortable, durable stereo headphones come with the detector. Other accessories provided at no charge include both a 110-volt and 12-volt cigarette lighter battery recharger (so you can charge the battery in your vehicle), coil covers for both coils, trash pouch and audio and video instructional tapes that cover all aspects of the detectors operation.

FIELD TEST
I'm fortunate to live in the area I do since it offers me a wide range of choices when it comes to treasure hunting. From Civil War campsites and popular swimming beaches to old parks and the Georgia gold fields, it affords me the ability to test virtually all metal detectors under the conditions they were designed for. As a matter of fact, my home is situated in a section of the north-Georgia gold belt that was one of the most productive of the 1800s -- with several profitable gold mines operating nearby from the 1820s up until the 1930s.

AUTHOR FIELD TESTING MINELABS'S SD-2100 METAL DETECTOR
While this area has produced a large quantity of gold over the years, the highly mineralized red clay and hot rocks have limited the ability of metal detectors to be used with any degree of success. I was hoping that the SD-2100's new MPS technology would enable me to work some of the old mine sites without the adverse affect the ground mineralization typically produces. The first site I took the SD-2100 to was a wooded area with a small creek running through it. The creek had been heavily mined several times over the last 150 plus years and much of the gold recovered had been in the form of coarse nuggets. Installing the 8-inch coil, ground balancing the detector and adjusting the audio threshold to a faint hum, I began searching the gravel bar on the inside bend of the creek. After a short period of time, I was able to distinguish the difference between the repeatable sound produced when the coil passed over a target and the random signal caused by changing ground conditions. I had moved only a short distance when a smooth, repeatable signal came through the headphones. Using a trick I picked up from some seasoned prospectors in Alaska, I put a shovel-full of gravel into a large plastic gold pan and then passed the coil over it to see if the target had been recovered. I repeated this process several times until I had the target in the pan and there was no longer any signal in the hole. Typically I would have dumped the contents into a 5-gallon plastic bucket and continued hunting -- waiting until the bucket was full before panning the contents down and recovering the targets. Curious to see what I had found, I walked over to a pool and panned out the sand and gravel. Unfortunately, I hadn't found a nugget but rather a lead fragment from a modern bullet. This had been nearly 10-inches deep so I was still hopeful that the SD-2100 would prove productive at the site. As I walked along the creek bank, I found that a minor adjustment of the two balance controls was needed on occasion to accurately compensate for changes in the mineralization. This was easily done by simply tipping the control housing to one side and "tweaking" the two ground balance knobs and returning the 3-position toggle to the Search mode. Near an outcropping of bedrock the SD-2100 produced a sharp signal. Clearing away all of the surrounding gravel, I found that the signal was coming from a narrow crack in the rock. Laying the detector on the ground, I used a hammer and pry bar to break off a portion of the rock. Brushing out the debris, I saw a beautiful coarse gold nugget wedged in the bottom of the crevice. While weighing just under a pennyweight, it was probably the nicest specimen of Georgia gold that I've recovered in the last few years. And considering it had been buried under nearly 6 inches of coarse gravel and then encased in 3-4 inches of mineralized bedrock, the SD-2100 had done an excellent job in detecting a nugget in an heavily-hunted area. I continued searching a short section of the creek and over the next few hours recovered three more nuggets, along with an assortment of other metallic objects including bullets, shell casings, several square nails and even a deeply buried screw cap. Many of the targets had come from depths exceeding 12-inches which was indicative of the unit's strong in-field performance. I tried the SD-2100 at several other sites throughout north Georgia and in each case I found that the high mineralization and hot rocks which had plagued me and others in the past were not even noticeable. Once the ground balance controls had been adjusted, the response of a target was clearly distinguishable from the slight variations caused by changes in ground mineralization. I'd like to say that I found enough gold to retire on, but such was not the case. I did find a number of deeply-buried targets at depths far greater than I had recovered similar targets with other detectors so I know that had I gone over that 100 plus ounce nugget I would have found it.

SUMMARY
The SD-2100 was developed by Minelab in response to feedback from prospectors world-wide who found that most of the productive gold fields contained highly mineralized ground that adversely affected virtually every other detector on the market. While these detectors were able to locate small pieces of gold at limited depths, seasoned prospectors wanted a detector that would be able to find the larger, and more valuable, specimens at the maximum depth possible. Based on the results of my field tests as well as feedback received from prospectors in the United States, Australia and South Africa, Minelab's engineering staff obviously did their homework. The SD-2100 does what it was designed to -- detect gold nuggets at previously unreachable depths with a only a limited amount of adjustment required on the part of the operator. At $2,995 the SD-2100 is admittedly one of the most expensive detectors on the market; however, when you look at the performance it provides in the field, it would be easy to recoup your investment in a short period of time hunting areas that others have had trouble searching due to adverse ground conditions or where targets are buried beyond the range of conventional detectors.

Copyright 1999 Lost Treasure, Inc.

For additional information on Minelab metal detectors contact:

Minelab Electronics
PO Box 537
Torrensville Plaza
South Australia
Australia 5031

Phone: 61 8 8238 0888
Fax: 61 8 8238 0890

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