Gold Mountain Gmt 1650
By Andy Sabisch
From Page 36
April, 1990 issue of Lost Treasure

The most recent addition to the new line of Gold Mountain metal detectors is the GMT 1650. Having recently started using both the King Cobra and the Thunderstick from Gold Mountain, with a good deal of success, I was looking forward to trying out this new detector.


The GMT 1650 is a silent search, slow motion discriminator with a non-motion, all-metal mode and manual ground balance.

Similar to the other detectors in the Gold Mountain line, the GMT 1650 is mounted on a modified S-shaped rod, and at 3 1/8 pounds, is both lightweight and well-balanced. The armrest incorporates a built-in stand, which keeps the detector upright and away from the ground when recovering a target. The stand is wide enough to prevent the detector from tipping over, even when hunting on uneven ground or on a hill. The shaft breaks down into three pieces for convenience of taking on trips or into remote sites.

The control housing is held securely on the shaft with two sets of spring clips. These allow easy removal for hip-mount configuration or shallow water searching. The 8-inch searchcoil comes with six feet of cable, eliminating the need for an extension.

The searchcoil is less than 3/4 of an inch thick and makes hunting in both overgrown areas, as well as in the water, quite easy. The loop is attached to the plastic isolator shaft with a nylon screw and wing nut, which eliminates the interference normally experienced with metal screws or shafts near the searchcoil. The coil has a decal that marks the precise target center for accurate pinpointing, even on deeper targets.

The knobs on the GMT 1650 are Sensitivity, Discriminate Adjustment, and Ground Adjustment. The toggle switches are Mode Select and Discriminate Range High/Low Select. The headphone jack will accept any standard 1/4-inch headphone plug.

The GMT 1650 is powered by eight penlight batteries, which are included. The batteries are in two plastic holders in the compartment on the rear of the detector, and are changed by removing the access door, disconnecting the batteries, and sliding the holders out. The expected battery life is about 20 to 25 hours with carbon batteries; around 30 hours with alkaline batteries. As with all detectors, the use of headphones will generally add 5 to l0 hours to the expected life of the batteries. Nicad batteries can be used with no effect on the performance of the detector; however, at present, the factory does not offer this as an option.


The GMT 1650 comes securely packaged with a detailed instruction manual. The detector is quite simple to assemble; however, one point not addressed in the manual is to ensure that the searchcoil cable is wrapped tightly around the shaft to avoid false signals. With the high sensitivity of the GMT 1650, a loose searchcoil cable may cause false or erratic operation.

The Discriminate circuit on the GMT 1650 is rather unique. Unlike most metal detectors, where the discriminate control is a single turn knob ranging from no discrimination to full discrimination, the GMT 1650 has two separate ranges of discrimination. The Discriminate knob allows for settings from 0 to 7 on both the low and high ranges.

As with any detector, you want to use only enough discrimination to reject most trash items. These two ranges allow for a more precise setting of the discriminate level, resulting in more good finds in high trash areas.

I turned the GMT 1650 on by rotating the Sensitivity knob clockwise, which also activates the automatic battery test feature. The condition of the batteries is indicated by the length of the tone heard. New batteries will produce a tone lasting approximately two seconds. When the tone lasts for less than one second, batteries should be replaced. With new batteries, the Sensitivity knob cannot be turned above the 2:00 oclock position without hearing chattering from the speaker or headphones. This is normal and the GMT 1650 will provide exceptional depth around the 1:00 to 2:00 oclock settings. As the batteries begin to loose strength, the Sensitivity knob can be turned toward the MAX setting with no chattering. This feature was designed to allow the user to operate at maximum sensitivity, and compensate for any loss due to weak batteries.

Setting the Discriminate Adjustment knob to 4, the Mode switch to DISC, the Discriminate Range toggle switch to LOW, and the Sensitivity level to 1:00 oclock, I proceeded to see how the GMT 1650 responded to various objects in an air test. The depth on coin, jewelry, and relic targets was impressive, and it was one of the few detectors I have tested that would even respond to a thin gold chain or small earrings.

With the 8-inch loop (included with the detector), I was still able to detect a small vial containing just a few grains of gold nuggets at approximately 3 to 4 inches. The GMT 1650 produced a clear, repeatable signal on all of the targets, even at the maximum detection depth.

I took the GMT 1650 to my test garden to see how it worked in the mineralized red clay so common to this area of the south. The Ground Adjustment knob is a 10-turn ground balance control which allows one to precisely adjust out the effects of mineralized ground.

To set the ground balance correctly, turn the Ground Adjustment knob clockwise until a slight resistance is felt (which is the end of its adjustment range), and then turn the knob two turns counterclockwise. Hold the searchcoil straight out in front of you at waist level, press the Discriminate Mode toggle switch all the way to the right and then release it, allowing it to return to the middle position. Lower the searchcoil to the ground and listen to the threshold tone. If the tone increases, you have overcompensated for the amount of mineralization; if the tone decreases, you have under compensated.

If the tone changes, raise the loop, press and hold the Mode toggle switch to the right, and turn the Ground Adjustment knob in the required direction to adjust for the mineralization level (clockwise (+) if the tone decreased, counterclockwise (-) if it increased). Release the Mode toggle switch and lower the searchcoil to the ground. Repeat this process until there is no change in the tone as the searchcoil is raised or lowered to the ground.

One tip not mentioned in the instruction manual is to tune the GMT 1650 slightly positive when ground-balancing, which will result in smoother operation and an increase in detection depth. This is achieved by turning the Ground Adjustment knob clockwise (+) about one-half turn after proper ground balance has been achieved so that the threshold tone increases slightly as the loop is lowered to the ground.

The importance of properly compensating for the mineralization in the ground cannot be overemphasized. By taking an extra minute to precisely set the ground balance level, the more sensitive and stable the GMT 1650 will be in the field. Also, if the sensitivity level is changed, the ground balance setting should be checked and, if required, adjusted.

The GMT 1650 responded with a clear signal to all the items buried in the test garden, and I was able to raise the loop a few inches off the ground and still pick up most of the objects.


When I take a new detector out for a field test, I take it to areas that have been heavily hunted, or are either highly mineralized or high in trash, to get a more accurate indication of how it will perform.

The first site I took the GMT 1650 to was a Civil War site that had been the scene of a light skirmish between Union and Confederate forces during the battle of Kennesaw Mountain in June, 1864. With three treasure hunting clubs in the Atlanta area, and probably well over 200 active relic hunters, finding a nearby site that has not been heavily hunted is virtually impossible. I had personally hunted this site on and off for several months, and the number of finds had nearly dropped to zero. Another problem was the old trash dump in the area that had been plowed over, leaving small pieces of iron everywhere, so I felt the site would be a good test of the depth and trash rejection capabilities of the GMT 1650.

After arriving at the site, I set the Discriminate range toggle switch to the LOW setting, the Discriminate Adjustment knob to 3.5, Sensitivity Level to 1:00 oclock, and quickly ground-balanced the detector. With the discriminate at this setting, the small pieces of iron, and any nails, would be rejected, yet the larger iron objects, such as gun parts or shell fragments, would still be detected.

The S-shaped armrest and the light weight of the GMT 1650 made searching in the overgrown areas extremely easy. Almost immediately I received a solid signal near the base of a large tree. Switching to the all-metal mode, I pinpointed the target and started to recover it. At approximately 7 inches, I found an eagle coat button in excellent condition the prospects were looking up for this site.

As I continued through the under-growth, I received another signal which turned out to be a fired .58 caliber minnie ball at 6 inches. Having hunted this site before with a number of other detectors, I noticed that the GMT 1650 was not bothered by small pieces of iron.

The detector ran completely silent except when the loop went over a good target.

Searching near an old barbed wire fence produced four more dropped minnie balls from between 6 and 9 inches deep. Near one of the fence posts, I received a solid signal over a larger area than I had been getting from the bullets. I switched to all-metal pinpoint mode, centered the target, and began to dig. At 7 or 8 inches, I checked the hole and found that the target was further down, so I continued. At l0 inches l hit a large tree root and excavated underneath it in order to get to the target. Finally, at over 14 inches, I found an old axe head that appeared to be from the Civil War period.

The next site I took the GMT 1650 to was a lakeshore in the north Georgia mountains. The beach was less than 100x40. After setting and ground-balancing the detector and making a few sweeps across the sand, I began to get some chattering due to mineralization. I lowered the Sensitivity level to 2:00 oclock, rechecked the ground balance adjustment, and started to hunt. The detector ran completely silent from then on.

After moving less than five feet, I received my first signal which turned out to be a quarter at almost 7 inches. Continuing to search the sandy area of the beach, I recovered coins at depths ranging from 1 to 8 inches.

The only trash items I found were occasional pull tabs and screw caps which I had to recover if I wanted to find all the gold rings and chains. I intentionally passed the searchcoil over bobby pins lying on the sand to see if the GMT 1650 would respond to them, but it didnt even crackle or chatter.

After about an hour searching the beach, I decided to try hunting the shallow water. I quickly unsnapped the control housing from the armrest, hung it around my neck, and walked into the water. The ultra-thin design of the Striker searchcoil proved to be extremely easy to move through the water. It did not give the positive buoyancy that most other loops do, making them hard to hold under water.

Almost immediately I received a loud signal and recovered two quarters and a penny in one scoop. After making one pass parallel to the beach, I had found eighteen coins, one Avon ring, and two pull tabs. Moving out to waist-deep water, I began another pass back to the other end of the beach. The first two signals resulted in a dime and a penny. The next signal was a faint one, two or three scoops down. Lifting the scoop out of the water, I caught the glint of a 14-karat wedding band, partially covered with sand. Quickly putting the ring in my pocket, I continued to search, recovering several more coins.

About halfway across the beach, I received a loud signal that was in the first scoop of sand I picked up. As the sand sifted out of the scoop, I saw a beautiful 10-karat ladies college ring. I had found two rings in less than 10 minutes!

Before leaving, I checked to see what I had found at the beach. In addition to the two gold rings, I had 73 coins, four pieces of costume jewelry, three fishing sinkers (despite the no fishing signs), two Matchbox-type cars, a few pull tabs and screw caps; and, most importantly, no bobby pins, barrettes, or nails. .

My hunting partner, Gerry Jones, lives in a house built in the 1 800s, and was interested in trying the GMT 1650 out in his yard to see if there was anything left (we had both hunted it fairly thoroughly).

Near the path, I received a signal and switched to the all-metal mode to pinpoint it. I found a .22 caliber shell casing at3 inches. After searching the rest of the path, I started along the low wall at the front of the yard. The first signal I received was solid and repeatable in the discriminate mode, but when I switched to the all-metal mode to pinpoint it, it was very faint.

After removing the plug, I checked the hole and found that the signal was still there, but off to one side. As I carefully scraped dirt from the side of the hole, I saw a coin, almost on edge, over 6 inches down. Removing the coin from the hole, I saw that it was an 1888 Indian head penny in VF condition.

Less than five feet away I received another solid signal that produced 1918 wheat penny down 7 inches. Gerry and I were both amazed that we had missed these coins in the past, considering the small size of the yard and quality of the detectors we had used.

We went to see Steve Bakke, in Douglasville, who is the local Gold Mountain dealer. After showing him the coins we had just found, he suggested we all go across the street to a small park by the railroad tracks. Steve said he had seen at least 30 treasure hunters searching the park over the last few years and he wanted to see if the GMT 1650 could find anything they might have missed.

Due to the amount of pull tabs, tin foil, and screw caps in the park, we set the discriminate range toggle switch to HIGH and the Discriminate Adjustment knob to 3.5. This setting would reject all of the pull tabs and tin foil and most of the screw caps, while still accepting Indian head pennies.

Due to the ground mineralization and the cinders from the trains, we set the Sensitivity level to 1:00 oclock in order to avoid any chattering. After five minutes we had not received any good signals and I was starting to wonder if everything actually had been found.

Finally, near an old oak tree, we got a solid signal in one direction, but when the loop was swept in the other direction, the signal became broken. Switching to the all-metal mode it appeared to be two separate targets close to each other.

After cutting a plug and removing some dirt, we found a 1944 wheat penny at about 4 -1/2-inches. Checking the hole in the discriminate mode produced no response, but in the all-metal mode the detector indicated that there was still something in the hole. Just off to one side at about 4-inches, we found a large piece of tin foil. The GMT 1650 had picked up the wheat penny which was adjacent to, and deeper than, the trash target.

Near an indentation in the ground, where a tree had been, we received another signal which also broke up in one direction and appeared to be two targets near each other when checking it in the all-metal mode. At 5 inches, we found a 1964 silver dime and a 1948 wheat penny next to a large rusted carriage bolt.

I often take my finds to show to co-workers, and several have expressed an interest in going with me to try treasure hunting. I wanted to see how a true novice would do with the GMT 1650 in areas that had been hunted in the past.

Brent Turner had expressed an interest in Civil War relics, so I took him to an area that was being cleared in the shadow of Kennesaw Mountain. The site had been cleared for about two weeks, there were holes all over, and several other hunters already searching, so I told Brent not to expect too much.

I handed the GMT 1650 to Brent and showed him how to set the discriminate level and adjust the ground balance. I quickly showed him how it responded to various targets and how to pinpoint the target using the all-metal mode, and he headed across the cleared field. As I searched, I kept looking over to see how Brent was doing. After 15 minutes or so, he yelled over, saying he had found a minnie ball at least he was not going to be skunked.

After about 30 minutes, I met a hunter, who is a member of the local club I belong to (the North Georgia Relic Hunters). He said he had been hunting for the last few hours and had found nothing other than a few pieces of rusted metal and barbed wire.

We had talked for about 10 minutes when Brent came walking over with a big grin on his face. In one small area he had found three dropped .58 caliber Confederate minnie balls, one fired Union minnie ball, a shoe grommet, and the internals of a period pocket watch.

Most importantly, he had not dug iron trash and the GMT 1650 had run completely silent. The other hunters in the area shook their heads over his finds and asked for the name of the nearest dealer that carried Gold Mountain.


I found the GMT 1650 to be one of the most sensitive metal detectors available today. The unique dual range discrimination circuitry is extremely useful when setting the discrimination level to reject just the right amount of trash, while accepting all the good targets in the area.

The wide-range ground balance control, combined with its lightweight and optional searchcoils, make the GMT 1650 an extremely versatile metal detector. Even when used by a novice, the GMT 1650 was able to locate valuable targets in areas that had been heavily hunted in the past at depths comparable to, or greater than, metal detectors costing hundreds of dollars more.

Jim Breckenridge, President of Gold Mountain, said that there is a sign over their lead engineers work area that says simply DEPTH and DISCRIMINATION. Based on the performance of the GMT 1650, their goal for more depth and discrimination has been realized with this detector.

If you are in the market for a new metal detector that will provide you with the ability to find valuables in virtually any area, you need to take a look at the GMT 1650 before you make any purchase. At only $399.95, it is one of the best buys available today.

For more information and the name of your nearest Gold Mountain dealer, write: Gold Mountain Technologies, 1630 Falcon #102, DeSoto, TX, 751 15, or call (214)224-3294.

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