Testing The
Minelab SD-2200D Metal Detector
Reprinted with permission from W&E Treasures: V34 June 2000
By Jim Straight

Introduction
This field test is not a rehash of the Minelab SD-2200D oper­ating manual or even an impres­sive list of great finds that were made with the detector. I’m not a Minelab dealer, or in any way connected with the company. I bought the detector used in this field test from a nearby dealer, even paying California state tax on it. For those of you who are not familiar with Minelab, they are a relatively new kid on the block. Since 1985, this Australian com­pany has developed metal detec­tors capableof nugget shooting the mineralized Australian soils, and been a pioneer in the devel­opment of both Automatic Ground Tracking (AGT) and Multi-Period Sensing (M-PS) technologies.
Minelab SD-2200D
“SD” stands for Super Detector. For those of you who are familiar with earlier SD mod­els— the 2000, 2100, and 2200— the SD-2200D has additional features such as automatic ground balancing, a boost amplifier, a tuning control, and a limited, fer­rous-iron discrimination function not found in earlier SD machines. The SD-2200D uses M-PS technology, which I understand is some variation of Pulse Induction (P1). It is not a complicated machine to learn to use. The operating man­ual is well written, and the machine comes with a video­tape featuring Doug Stone, a well-known Aus­tralian gold prospector. Currently, the SD-2200D is available from Minelab only as a shaftmount. It does not have an internal speaker, and the operator must use headphones. The con­trols consist of a Power Off/On switch, a single-turn Threshold control, a three-position (shallow, normal, deep) Audio control, a Tone control, a Channel 1 & 2 control, a Fixed or Tracking Ground Balance control, an Iron Discrimination control, and a Level Adjust to control the amount of iron discrimination or ground tracking. The unit comes equipped with two 11” circular search-coils— one a DD, and the other a Monoloop. The Disc + ID mode functions while using either coil; however, the Disc mode doesn’t function while using the Monoloop coil.
Field Test
Bench Testing. I have learned that with any new detector, after carefully reading the operating manual, it’s important to become familiar with it by bench or air-testing it. However, due to electrical interference, I found that the SD-2200 is not a machine you can bench test with­in a house or yard. Therefore, accompanied by Jack Leuf, I went to a nearby park to bench test it. Because we both wanted to listen to the sounds, and as the machine doesn’t have an inter­nal speaker, we plugged in an external amplified speaker sys­tem as used with computers. Then, to become familiar with the machine’s modes, features, and searchcoils, we air tested it using a variety of targets and control settings.
Coin Hunting
Since the detector doesn’t have a full-range coin discrimination circuitry, and exact pinpointing is a little tricky (even in all-metal mode) with either of the 11” coils, I definitely don’t recommend digging down a foot or so in a well-manicured lawn only to recover a rusted bolt as a way to keep any groundskeepers happy! Howev­er, due to its sensitivity and depth, the SD-2200D could be a choice for a dedicated “deep target” hunter willing to dig trash while hoping to find old coins and jewelry worthy of a Find-Of-The-Month (or year) award. The challenge is in skillfully re-filling the deep recovery holes. Therefore, with this in mind, we stayed away from parks and schools. Instead, accompanied by Hye McCall, we searched along c.1900 flagstone curbs in the rural areas of Redlands, California. And yes, I carefully filled after every dig, compacting the loose soil with my foot. While I didn’t find any old coins, I locat­ed small brass screws and bits and pieces of an old pocket watch, all 12” or more in depth.
Cache Relic Hunting.
The SD-2200D certainly finds deep targets and could be the machine of choice over a two-box detector in some “buried trea­sure” searches. In the past I have found it pro­ductive to search old desert sites having visible rusty cans, especially cans with soldered seams &/or shards of purple glass glittering in the sunlight. While using the SD-2200D with the 11” DD searchcoil, I hunted an old dump area along the south side of State Highway 6 on the outskirts of Tonopah, Nevada. Here, years ago and over a long period of time, old car bodies, household junk, and just about everything else was discarded over a large area. On this trip I recovered an old brass cartridge case stamped W.R.A. Co. 40-60 W.C.F., and also a deeply buried, nickel-sized brass token with the initials E and H on either side. I also recovered an interesting pouch full of trash: a stove pipe damper, a badly rusted old Ford Script sparkplug, and even a brass winged radiator cap once used on a Model T Ford. Incidentally, the cartridge case was manufactured by the Winchester Repeating Arms Co. and it was of .40 caliber and used 60 grains of powder. The W.C.F. stood for Winchester Center Fire. As for the token, research revealed that it was likely from the old Esmeralda Hotel in near­by Goldfield.
Beach Hunting
Minelab gives fair warning that the search-coils for the SD-2200D are not waterproof. However, as anyone who hunts ocean beaches knows, during low tide a lot of dry beach can be hunted. Since the control box represents a lot of money, I took care to use the detector only in dry areas, and never set the control box down onto the sand. Accompanied by our wives, Hye McCall and I took the SD­2200D to Seal Beach for a few hours of hunting. The weather was miserable, and we had the beach to ourselves. While I did the detecting, Hye did the digging, and we worked the dry and wet slope down to the water’s edge. One thing I can say is that the SD-2200D surely goes deep, and it kept Hye busy scooping out and filling holes. I told Hye that he could keep any of the finds for his efforts. However, other than pieces of aluminum (mostly can bottoms), wire, and bottle caps, the only “treasure” we found was a deeply buried, corroded copper penny in sad shape and a large man’s ring. If the ring had been solid gold, and the stone a real diamond instead of a fake, Hye would be rich!
Nugget shooting
I had a lot of fun while testing the machine in the broad Mojave Desert area near Randsburg, California. I hunted with George Elwood, a full-timer, and also with Roger Schorg both successful hunters with SD-2200D’s of their own. Also, Hye McCall, Jack Leuf, Rick DiBacco, and Lee Pennington took turns using mine. After working with it, using various settings and both the 11” DD and Monoloop searchcoils, we all agreed: “It goes deeper!” There was also a consensus that it could be used to advantage in areas known to have shallow gravel overburden. Out of all of this testing, a strategy was developed. For the field test I used the headphones that came with the machine. Since I have a hearing loss, I found the audio Tone control very helpful in selecting the right sound pitch. Although, as mentioned, the machine came with two circular 11,’ coils, a Monoloop and a DD, I have used DD coils for years and understand their advantages; so, the DD was my choice with the SD-2200D, too. While the DD may not be as sensitive as the Monoloop coil to small targets, DD’ s are very stable in mineral­ized areas. Due to a cone-shaped detection pattern, the Monoloop coils require much more overlap than the DD’s, which have a longer heel-to-toe, but narrower paintbrush-like window of target acceptance. This requires a lot less searchcoil overlap, a decided advantage when you are on the edge of a known dry placer, looking for a continuance of the pay streak. Since I wear boots I used two bungee cords to counterbalance the coil weight. I hooked one bungee to each side of the battery harness shoulder “D” rings and pushed the shaft out against them, thereby keeping the DD coil far enough forward so as not to detect the metal eyelet in my boots. This worked great, as it not only gave me a good coil swing, but kept the weight off my arms. Also, I was able to keep the coil height just above the ground contour. Through experimentation, I found that by setting the Level Adjust control nearly fully clock­wise and operating in Disc mode, most ferrous wire with the exception of a small, thin piece of spring steel and other ferrous junk, such as the rusted end of an old 12 gauge shotgun shell could be canceled out. In trashy areas, I moved the coil fairly slowly. I hunted in Disc and Tracking; but as soon as I got a target, I went to Fix. Then I scraped off the top dirt with my boot and pinpointed in All Metal. Then I flipped back to Disc and used both hands to con­trol a fast, short, back-and-fo rth coil swing. I actually whipped the coil with short strokes above the target. If the signal came in clear and persistent, I dug it, and in all cases it was a nonferrous target such as a brass .22 caliber shell casing or a larger, such as a .38 caliber lead bullet. The real point, of course, is that it could have been a gold nugget. If the signal was “iffy,” I still dug it anyway, as I didn’t want to miss a small nugget. I would like to say that I found a handful of nuggets, but must limit my bragging to a couple. The first was small and chunky, and weighed about a half -pennyweight. It was found in the Summit Range, within the side-berm along the outer edge of a graded gravel road, and was only about an inch deep. The other, a splintery looking nugget weighing about a pennyweight, was found on the Rand Mountain slope, was down about 4” and gave a good signal. To my delight, I found it in schist bedrock away from the main dig­gings, so there could be a lot more nearby, waiting to be found on my next trip out.
Personal Impressions
 Not only is the SD-2200D an automatic ground balancing machine, but it also has a limited capability to discriminate out shallower pieces of iron junk. I have used both manual detectors (since 1979) and automatic ground balance detectors (since 1989) to find gold. Therefore, I understand, like, and can use either one. The 2200D Ground Balance mode has both a Track­ing and Fix control. I was very pleased to find that by using the Tune button, I could operate the SD-2200D reasonably near another machine, and other detectorists didn’t throw rocks at me for causing interference. The need to carry the rechargeable battery in a back­pack seemed awkward at first, but I soon got used to it. I must admit that I used the smaller accessory battery instead of the one that came in the box with the detector. However, I did use the larger one as a backup. I found that using the car charger to charge and “top off’ the battery, while driving to and from the goldfields, ensured satisfactory service. Due to my prior inexperience with the SD-2200D, and also my frequency hearing loss, I found the Disc + ID mode tricky, but I loved the Disc mode. While using the DD coil in Disc, I found that most shallower ferrous trash was blanked out, whereas deeper trash gave a good signal. Howev­er, I also discovered that upon digging and then rechecking by swinging the coil rapidly back and forth over the suspected tar­get, the trash would blank out. The toe and heel of the DD searchcoil are full of energy, which is an advantage when pushing the coil forward and backward between rocks and into brushy areas. I have used large coils and know they can become heavy over a short time. However, by using two bungee cords instead of one, the weight of the shaft mounted control box seems to counterbalance the searchcoil; and due to the alternating stretching and slackening of the two bungee's, inertia of the coil swing is damp within reasonable limits. Further, since the 2200D doesn’t pick up “hand” sounds, the usual plastic cups, mugs, or pans aren’t needed to recover small targets. Summary If detecting for a tiny and shallow bit of gold is your game, the 2200D is probably not for you. Depending upon the shape of the nugget, the 2200D can detect a nugget as small, or even smaller, as two or three grains. However, the 480 grains to the ounce, and gold hovering, as I write this, around $300/troy oz., a three-grain nugget is only worth a couple of dollars. Although so far I can only claim finding two small nuggets with my own Minelab SD­2200D, it has an established track record as a gold machine and can be used to advantage in areas where larger nuggets have been found in shallow gravel. In some desert dry placer goldfields, a false clay or caliche bedrock may be covered by only a foot of so of overburden. It is within these broad regional areas where large, multi-pound nuggets are occa­sionally found. Like a deep-coin hunter, I guess I can say I’m a “deep nugget” hunter. It is in the open areas, away from the trashy main digging's, that I patiently search— finding old bullets, cartridge cases, and an occasional old coin, but hoping to someday find a really big nugget!