The Worlds First Programmable Detector
By Jim Martin
From Page 18
May, 1985 issue of Lost Treasure
Finding three wheat-eared pennies may not sound like an earthshaking treasure hunting accomplishment. Yet, I re-covered the trio in a heavily-hunted campground area near my home in northern California, and that defi-nitely got my attention. The discov-ery of four more wheaties the fol-lowing afternoon in the same area served to demonstrate further the Teknetics Mark 1 has a definite knack for sniffing out older, deeper coins in trash-laden grounds.
Considerable credit for these finds, plus an impressive number of other wheat-backs and several silver dimes and quarters I later recovered, can be attributed to the Mark ls ability to alert the operator to the presence of buried coins by means of a unique feature called Audio Target Identifi-cation. AT! is a fascinating bit of electronics wizardry that certainly made my field-testing endeavors with the instrument both pleasant and rewarding. Ill discuss the merits of AT! shortly, but first lets take a closer look at the Teknetics Mark 1, one of the best performing of the so-called metal detector sophisti-cates I have ever had the pleasure of evaluating.
The overall profile of the Mark 1 is almost identical to the Teknetics 9000 B, which I discussed in the May 1984 issue of this magazine. The futuristic lines of the high- impact engineering plastic body, the distinctive carrying grip, the 7/4-inch loop, the adjustable rectangular shaft and the stylish black and gray color tones clearly identify the Mark I as a member of the Teknetics fam-ily.
The top-mounted control panel with its eight single-turn knobs also has a familiar look. Neatly arranged in two rows, and so labeled are the following: Tuner, Tone, GND Sens (Ground Sensitivity), GND Balance (Ground Balance), GB Disc (Ground Balance Discriminate), TGT Set (Target Select), Power, and Volume.
Something new has been added, however. The dial of each control features a blue-colored preset area. When the individual dial pointers are positioned in the blue, the detector is ready for operation under normal search conditions. This quick-set feature will definitely be appreciated by the eager beaver beeper who is anxious to make things happen as soon as possible.
While the factory-recommended preset positions should prove ac-ceptable for a typical treasure hunt-ing adventure, one can fine-tune the controls, if necessary, to cope with out-of-the-ordinary search condi-tions. The function and adjustment procedure for each control are ex-plained in the owners instruction manual, so Ill not repeat them as a part of this report.
A noticeable change is in the de-sign of the visual meter positioned at the top of the control panel. Instead of a liquid crystal display (LCD) panel as is featured on the 9000 B, the Mark 1 has a four-band, multi-purpose meter to visually show prob-able target identities and estimate tar-get depths, as well as indicating the condition of the batteries. Conve-niently placed within easy eyeball-ing range, the meter can be seen clearly no matter which hand is hold-ing the instrument.
Significant changes internally en-able the Mark 1 to fill a previously existing gap in the Teknetics lineup of quality-built VLF-Discriminating detectors. Rather than using the type of four-filter system employed with the 9000 B (which is a fast sweep in-strument intended for use in highly mineralized areas), the Mark 1 has been designed with a two-filter sys-tem that is recommended for use in either low- or no-mineralization ar-eas such as the beaches along the Florida coastline and similar happy hunting grounds.
The Mark 1 has two search modes: GB All Metal for use when hunting relics or on other search missions where no discrimination is desired, and GB Discrimination, the prefer-red mode for coinshooting. GB Disc, which allows for both ground neutralization and selective target discrimination at the same time, is a slow-motion mode in which a slight amount of search coil movement is required in order to obtain signals.
Mode changes can be made quickly by flicking the toggle switch at the end of the carrying handle. Press the switch to the left and re-lease, and the detector is operating in the All Metals mode. To activate the GB Discriminate mode, press the switch to the right and release. Each time the toggle is pressed and re-leased,, the detector is retuned to its original threshold audio point.
When operated in the All Metal mode, the Mark 1 will sound off with an audio response whenever the transmitted signal encounters a metal object in the ground. As a bonus, the instrument features a Tone control with which, to adjust the audio fre-quency to that most comfortable to the operators ears. Move the single-turn knob completely counter-clockwise and you will hear low, al-most guttural tones. Turning it all the way to the right will produce a high-pitched signal. My ears tend to favor the tone thats produced when the in-dicator is positioned in the blue, so as far as Im concerned the Tone control is in the set and forget cate-gory. The pitch of the signal will be the same for all types of metal targets as long as the detector is being oper-ated in the GB All Metal mode. Both treasures and trash will sound alike.
Ah, but what wonderful things will happen when you press the toggle switch to the right and activate the GB Discriminate mode. So pro-grammed, the instrument will now either accept or reject designated tar-gets depending upon the position of the pointer on the GB Disc dial. The detector will also tell you whether a target is good or bad by means of the Audio Target Identification cir-cuitry. You can now actually hear whether an object is treasure or trash.
AT! played such a vital role in the success of my coinshooting efforts, Id like to discuss it in detail. For openers, lets perform a few simple air checks.
Following the recommended pre-set procedure, well set the pointer of each of the controls in the blue-colored segment of the dial. Now that the instrument has been turned on, flip the toggle switch to the left and release, thus activating the GB All Metal Mode.
Next, place the detector across the arms of a chair, on a table or some other place where the loop is ex-tended out and away from any metal object.
Pass a variety of metal objects, in-cluding both treasures and trash, in front of the search coil. Im using a penny, nickel, dime, quarter, a pull-tab, rusty nail, bottle cap and an alu-minum screw cap.
Notice that each of the objects pro-duces an audio response and that in each instance the tone of the audio signal is identical.
As Step #2, flip the toggle switch to the right in order to move into the GB Discriminate mode and repeat the air checks with the same objects. Because the preset discrimination level is between iron and foil, the rusty nail no longer produces an au-dio signal, while the other targets continue to evoke audio responses. But notice the differences in signal tones, and how the various coins pro-duce high-pitched signals. That is Audio Target Identification in action.
Lets continue the test process by repositioning the GB Disc control to the indicated setting for screw caps, and then passing the same objects across the face of the loop.
Notice how the detector still pro-vides audio signals on the penny, dime and quarter, but does not re-spond to any of the other objects, in-cluding the nickel. I'll tell you how to obtain a response from five-cent pieces (and small gold rings) later, but for the moment lets concentrate on listening to those high-pitched signals from the good targets. These are the sweet sounds you should be waiting to hear when coinshooting. You must also be observant.
Working in conjunction with the AT! circuitry to provide a means of target identification is the multi-purpose visual meter which shows indicated settings for nickels, pen-nies, dimes, quarters and half dol-lars, as well as such undesirables as iron, foil, pull-tabs and screw caps. Not only will the meter tell you the probable identification of the target, it can also reveal approximately how far from the surface of the coil the target lies.
To ascertain the depth of a target, press the toggle switch to the left and release. Now pass the coil back over the target area and watch how the needle will move to somewhere be-tween the 2- and 10-inch readings on the distance band. To hold the needle on a desired setting, keep the toggle switch depressed to the left.
These show-and-tell capabilities of the Mark 1 can certainly add to the enjoyment of a coinshooting adven-ture. True, I will attempt to recover a target any time a detector tells me that it is worth investigating. How-ever, my investigative efforts are performed with much more zeal when a meter indicates that the target is a dime or a quarter at a depth in excess of 4 inches. In the locations I am accustomed to searching, these deeper rascals will frequently prove to be silver coins.
Now lets move on to the manner in which the Mark 1 can be pro-grammed to find nickels and, we hope, small gold rings, while at the same time rejecting pull-tabs and screw caps.
Well aware that VLF/TR discriminating-type detectors tend to reject nickels and small gold rings when adjusted to eliminate pull-tabs in the discriminate mode, the elec-tronics experts in the Teknetics labo-ratory in Lebanon, Oregon have come up with an exclusive feature called Target Select that can solve the problem.
Programming the Target Select circuitry is accomplished with ad-justments of two controls, the Power knob and the knob located directly below it marked TGT Set (Target Select). It is a simple adjustment process that should be completed af-ter the detector has been properly tuned and ground balanced. Heres how.
With the indicator of the Power knob placed at the on position, hold the toggle switch to the right and slowly turn the discrimination con-trol (GB Disc) until the needle reaches the desired level of discrimi-nation on the dial. When coinshoot-ing, I prefer using enough discrimi-nation to knock out both pull-tabs and aluminum screw caps, so lets adjust the Mark 1 accordingly. In this case, turn the GB Disc knob un-til the needle reaches the S-Caps por-tion of the dial, which is around 60. When so adjusted, the detector will ignore much of the trash you will likely encounter.
To program the instrument for finding nickels while ignoring those pesky pull-tabs and screw caps, move the Power switch clockwise to the setting marked Target Select. Again holding the toggle switch to the right, adjust the Target Select control until the needle settles on the portion of the dial marked Nickel. Release the toggle switch and you are ready to begin searching.
To be on the safe side, lets make another air check using a nickel, a screw cap and a pull-tab. If the ad-justments were performed properly, you should now be able to hear a solid beep from the coin, but not from the two trash items. If a minor glitch exists, gentle adjustments of the TGT Set and GB Disc knobs may be necessary.
The instruction booklet suggests an interesting experiment that illus-trates the effectiveness of the Target Select component in action. Leaving all the other controls set as before, turn the GB Disc knob all the way to the left to the zero discrimination level, then repeat the air checks with the same objects used before. At this point, with no discrimination, you should receive audio signals from all of the targets except the nickel.
Now turn the GB Disc knob in a clockwise direction to the maximum discrimination setting, then perform the air tests again. This time, the only object that should produce a re-sponse will be the nickel. Notice the depth thats achieved. My air checks produce a readily recognizable signal at 6 inches. Quite impressive.
I was anxious to learn more about this amazing feature, so I checked with Roy Van Epps of the Teknetics engineering staff for details. Ex-pressed in laymans terms, heres an explanation of what happens.
The Target Select component can be set so the Mark 1 will accept any other specific type of targets which possess a rejection factor that is lower than the level of discrimination you have programmed into the in-strument. At the maximum level of discrimination you would normally not receive an audio signal from any metal target. By bringing the Target Select circuitry into play, however, you can instruct the detector to select certain objects to be accepted or re-jected over and above what the dis-criminate control alone is capable of doing.
In other words, you can use as much or as little discrimination as you wish during your search opera-tions. You can then tell the Target Se-lect component to pick out and re-spond to any single type of target you wish thats below the established dis-crimination level. I think that Roy Van Epps put it nicely, when he ex-plained that you can consider Target Select as being like a little window which enables you to see only certain targets.
Well that little window ac-counted for a lot of nickels during my field-testing activities. The har-vest of five-cent pieces was particu-larly impressive when I was hunting in parks and school yards that were popular search grounds. Obviously, the other coinshooters had adjusted their detectors to reject pull-tabs and thus had missed the nickels which I found.
Even more impressive was the number of older silver dimes, quar-ters and wheat pennies I recovered during my field-test period with the Mark 1. The bulk of these deeper coin discoveries is attributed to the manner in which the Audio Target Identification feature is able to alert the operator to the presence of a de-sirable target. I found this to be ex-tremely helpful in those areas that were well littered with pull-tabs and other junk.
As was demonstrated during the simulated air checks, the Mark 1 will sing out sweetly with a high-pitched signal when a coin is detected while the undesirable targets produce much lower sounds. To illustrate how ben-eficial AT! can be, Id like to share with you one of the sessions that im-pressed me the most during my field-testing activities. First, a bit of back-ground information.
The incident occurred after a local schoolteacher asked if I would be willing to show his students how a metal detector operates. I enjoy in-troducing other persons to the hobby, and readily agreed. We started with a classroom demonstration. I demon-strated how the detector operated, let the students hear the sounds pro-duced by various objects and an-swered questions. We then moved outside to a nearby lawn for which I had obtained permission to search.
I cautioned the lads and lassies to not be concerned if we heard any sounds other than the high-pitched signals I had demonstrated in the classroom.
As expected, I picked up a lot of the low tones associated with junk targets. But then I heard what I was listening fora high-pitched beep. I swept the loop over the target area in two directions and was pleased to hear a positive response each way. The needle of the meter indicated either a penny or a dime at a depth of four inches. Everyone had an opportunity to hear the signal and observe the readings before I at-tempted to recover the target. Using my probe, I managed to touch the target. I used my coin gun to carefully remove a circular plug from the lawn. And there she was, a pretty little Mercury dime.
Employing the same search-and-recovery procedure, I located two more coins, which surprisingly also proved to be silver dimesa Roosevelt and another Mercury. This marked the first time I have ever managed to recover three silver dimes in a row and I assure you I was delighted with the detectors per-formance. I wound up my allotted one-hour search mission by finding one more coin, a Memorial penny, and ended with a deep appreciation of the capabilities of the Mark 1.
The same procedure I employed during the show-and-tell session with the students produced such excellent results throughout my entire test period, Id like to go over it in more de-tail.
Start by adjusting the detector to operate in the GB Discriminate mode using sufficient discrimination to eliminate responses from screw caps. Program the Target Select to accept nickels.
Begin searching by sweeping the loop over the lawn or ground surface at a slow speed, making certain to overlap each sweep so as to not miss the deeper targets. Ignore any audro signals other than a high-pitched
When you receive such a response, pass the search coil back over the spot in the reverse direction. If the signal comes through both ways, you have a target worth investigating.
After receiving the audio alert, check the meter to determine the probable target identification. If a coin is indicated, press the toggle switch to the left and move the loop back over the area so the needle will show the approximate target depth.
Locating the presence of coins at shallow depths (say up to three inches under the ground surface) is a cinch. Just keep alert for a high-pitched signal, use the meter to de-termine target identification and depth, then carefully remove the coin from the ground. Yet, I did encounter a problem on shallow coins.
Pinpointing a surface coin with a 7/4-inch loop can be a challenge if the target is standing on edge in a turf consisting of thick Bermuda grass overlaying ground containing an abundance of small stones and gravel. I encountered such a spot along the banks of the Kings River in Californias San Joaquin Valley and really had to work to make some re-coveries. Because of their vertical positions, the coins were tough to touch with a probe, and the multitude of pebbles compounded the problem. Yet, this would be true with any search coil this size.
The Mark 1 definitely proved its coin-sniffing prowess during those occasions when I was privileged to be able to search older parks and lawns. Such locations are the honey holesmost likely to harbor the deeper targets that frequently prove to be more desirable coins.
Success in these search areas de-pends upon the operators. ability to recognize the signals generated by deeper coins and his or her expertise in recovering targets without damag-ing the turf. Pinpointing a deeper tar-
get is quite easy with the Mark 1, and the coin gun I am currently field-testing- makes an ideal recovery de-vice.
The 14-cell nickel-cadmium re-chargeable battery system thats pro-vided as standard equipment is an-other well-appreciated feature. Battery condition can be quickly checked by turning the Power switch to the Batt position and observing the meter. Should you get careless and forget, the detectoPwill alert you to weak batteries by means of a loud audio signal. To restore the cells to full power, simply plug the charger into a socket at the rear of the control housing.
Priced at $749.99, the Teknetics Mark 1 comes with a limited lifetime warranty that applies as long as the original purchaser owns the detector. For additional information, see your local dealer or contact Teknetics, Inc., 300 Market Drive, Lebanon, Oregon 97355.