The rod is a three-piece "5" rod with detente buttons for solid positioning, and friction locks to eliminate wiggle. With everything positioned and snug, it feels just like a one-piece rod. The armrest is a padded "U" shaped affair that can be adjusted forward and back on the rod. The main control box is rear mounted and contains most of the circuitry and the batteries. Eight Ms in a slide-in cartridge- or a matching rechargeable cartridge- power the unit. I've got about 40 hours on the original alkaline batteries, and they are still going strong. There is a small stand attached to the underside of the box to help keep the unit out of the din. The main box also has several controls on it.

 

Mounting the box on the rear of the handle under the forearm makes it a tiny bit awkward to get to these

controls, but this is more than made up for by the way the machine balances in your hand. You can support the machine with one finger under the handle, and it hangs in a natural hunting position. The balance is superb. The controls that are on the box are those you typically set and forget, generally during initial setUp. The controls you use most often are mounted on the handle and display pod. The display pod sits atop the rod just above the handle. There is a toggle

switch readily available to your forefinger and a couple of touchpad’s near the bottom of the pod under the LCD display. I have fairly small hands, and had no trouble getting to any of the controls. The search coil looks like the standard 10" coil that has been on all Goldmasters since the introduction of the Goldmaster II. However, this is the new Twin "D" version. The coil is attached to the fiber lower rod with a nylon nut and bolt, so there is no metal nearby to cause any problems.

 

As we go along, you'll see how absolutely simple this machine can be to operate. Several of these controls and "'-' features can be ignored entirely by the novice, and the unit will still perform admirably. Let's start with the controls on

the main box and go from there. All of the controls on the box, with the exception of the Threshold, have a little white triangle next to them. These white triangles are the Recommended Initial Settings (RIS). This simply means that if you are unsure of the conditions you will be hunting in, then the RIS is a good place to start.

 

Likewise, if your one of those folks who just aren't comfortable trying to figure out where to set the knobs, you can set them to the RIS and know that you will be OK for most conditions. The top/forward-most control is the On/Off and Gain control. This turns the unit on and off, and controls the gain of the machine. Gain can also be referred to as power or sensitivity.

It basically controls how much the signal is amplified. The middle knob is the Audio Threshold. This adjusts

the background buzz that you listen to when hunting with a gold machine. It's adjustable because some folks can hear better than others. Also, windy days or other varying noise conditions may warrant adjusting the threshold a little bit higher or lower. Now you know why this knob doesn't have an RIS. The bottom knob is the variable SAT adjustment. A complete explanation of the Variable SAT is well beyond the scope of this detector review. (I devoted an entire chapter to it in my book.) However, here is the short, "nutshell" version. Virtually all modern gold machines have an SAT circuit. This circuit's entire purpose in life is to try to maintain the threshold hum where you set it, smoothing out ground noise in the process. To this end, the SAT circuit will eventually tune out anything, up to and including the neighborhood school bus. What this means is that most modern gold machines are what are known as motion machine ,As long as there is some motion of the searchcoil, you get signals. Stop the coil and the SAT will eventually tune everything out. Now the speed at which the SAT tunes things out is called (Big surprise here!) the SAT speed. The faster the SAT is set, the quicker it runes things out, which in turn reduces the noise you hear from ground minerals. Unfortunately, as you speed up the SAT, you can also lose some depth on targets.

On most machines the SAT speed is preset at the factory. As you might guess, this leads to major compromises. The preset speed is seldom optimal for the current ground conditions. On all Goldmasters since the V/sat, the SAT speed has been adjustable over its entire range. By varying the SAT speed, you can adjust the unit to different amounts or levels of mineralization, smoothing out the ground racket and not giving up any more depth than necessary.

On the GMT the Variable SAT is handled a little differently than on previous

Goldmasters. The lower two thirds of the adjustment range is pretty much the same. However, the upper third of the range gets a little help from some fancy

software footwork.

 

With previous versions of the Goldmaster, the rule was that when the ground gets noisy and mean, first you reduce the gain; and if that doesn't get the job done, then you speed up the SAT. This machine is a different animal. You should probably only reduce the gain below the RIS if the machine tells you to, which it will. When overloaded from too much mineralization, the machine will complain with a loud squawk, and the LCD display will inform you of the situation and ask you to reduce the gain. Otherwise, if you are having trouble with noisy ground that doesn't overload, the first knob you should touch is the SAT. Experiment with that upper one third of the SAT range, and I think you will be pleasantly surprised.

As you look at the control box, sitting right above the three knobs is the toggle switch that sets the hunting mode. Flip the switch away from you and you are in Fast Auto Trac. In this mode, the machine does all the ground balancing for you. They aren't kidding when they say fast, either. One to three quick pumps and you're there. Flip the switch the other way and you are in manual ground balancing mode. This uses a refined version of the ultra-high- resolution manual ground balance system found on the GM4. The other toggle switch on the main box is the audio boost/battery test switch. This is a three-position switch, with the battery test position being spring loaded. You'll notice the RIS triangle in the middle position, which is the normal operating mode. Pull the toggle toward you and the unit will perform a battery test, and then return to center when you release it. Push the toggle away from you and the unit enters the Audio Boost mode. Basically, this does just what it sounds like and gives the audio signal a boost, making

faint signals a little easier to hear. Although typically used for checking "iffy" targets, this is another control to experiment with, especially if you aren't using headphones.

On the front of the control box you will find the headphone jack and the connector for the searchcoil cable. The toggle switch that is mounted under the rod like a trigger is the audio iron ID switch. This is a three-position toggle switch, with the "pulled" position being spring loaded. In the middle position, the audio iron identification is off.

If you push the trigger away from you, it will stay there and you are in the Audio 10 mode. In this mode, everything works normally, except that when the unit is at

least 85% or more certain that a target is iron, it will add a little "grunt" sound to the end of the normal target signal. Note that this doesn't reduce depth in any

way. In the pulled position, you are in the Target Analysis Mode. In this mode three things happen. First, the unit stops tracking. Second, the "grunt" sound replaces the target signal once the 85% range is reached. Third, and this is the fun part,

every pass over the target is analyzed and added to the previous passes for as long as the trigger is held.

If done properly, this can really work well for identifying trash targets. Just remember to swing well to the sides of the target so that the machine gets to see plenty of ground also. The "plus" and "minus" touch pads on the display pod are the manual ground balance controls. The "plus" pad works the same as turning a ground balance knob up, which would be clockwise on most machines, and vice versa for the "minus" pad. When you switch out of manual mode into Fast Auto Trac, the unit remembers your manual setting. The next time you flip back into manual mode, the ground balance is right where you left it. This can be handy for quickly checking various types of positive and negative "hot rocks. "

 

The Grab button is a feature unique to this detector~ and I want to take just a minute to explain it to you. It can be a real time and sanity saver. A tracking unit works by taking samples of the soil by means of the return signal. It analyzes the signal to determine what type and how much mineral is in the ground that the

search coil is passing over. This process happens several times a second. The unit then makes a judgment call based on its programming as to how it should set its ground balance. The Grab button essentially tells the machine that you want it to take the last sample it got and to make that the unit's ground balance.

Don't use it in a calculation or average it with other numbers and make a determination. Just set the ground balance of the unit to precisely match the little piece of ground currently under the coil. Now! It's like instant ground balance, and it works in both tracking and manual mode. In Fast Auto Trac, it's a quick way to get the machine back on track if it got pulled too far off by a large iron target or patch of extreme mineralization. In Manual mode, it's a slick shortcut to getting ground balanced. The pod has an LCD display that constantly shows a couple of numbers and a bar graph. These numbers were originally included to help in the unit's development. Later on a decision was made to leave them in~ They definitely have their uses, and I'm sure that as time goes by and more folks use this machine, even more uses will be found for these readouts. The left number is labeled Ground Balance (Type of Mineral). This number is on a scale of 1-100. Higher numbers indicate more negative or "colder" ground, such as black sand. Lower numbers indicate positive ground, such as salt or alkali. This scale corresponds to the ground balance range, and the number shown will tell you roughly where the unit is ground balanced. The number on the right, again on a scale of 1-100, is labeled Follow Black Sand (Amount of Mineral). It will not only let you follow a stringer of black sand hidden in a wash, but it will also let you find old hard-to-see fine tailings piles from drywashers. Pumping the coil up and down may be more accurate than sweeping side to side for these chores. The bar graph is the Iron ID bar graph. This is always functioning and is independent from the Audio Iron ID modes. If you use the bar graph in combination with the Audio Iron ID or Target Analyzer mode, you can get a very accurate idea of what is under the ground.

I would like to pass along a few tips on using the machine in the field, and finally some overall impressions.

First of all, if you are like most of us and use a cup or other container to separate your targets, I would suggest that you put the GMT into manual mode before you lay it on the ground and begin. This will eliminate any problems with the unit tracking into jewelry, shoes, or some mineralization in the ground that could affect your ability to hear a tiny target in the cup. I liked the Target Analyzer mode best for checking possible iron targets. Since the Iron ID mode doesn't suspend tracking, what happens is that the GMT tracks so fast that you quickly find yourself 'way out of ground balance as it tries to track into a piece of iron. This isn't a problem if you swing well to the sides of the target (18" or so), but the terrain doesn't always allow that. I personally think that the Analyzer mode is more accurate, and when you are done and release the trigger, you are right back in business. I must admit that I was most comfortable running the Gain and SAT just below the point where the threshold gets a little jumpy. I'm sure that this is due to my being spoiled rotten by my old Goldmaster V/sat with its super-smooth threshold. However, when I did some testing with small nuggets, the higher gain and SAT levels had no trouble nailing the tiny targets.

It was a real pleasure to just hunt and not have to worry about constantly groundbalancing...lt used to be a source of pride to know that I could perform the tracking machines with a good manual machine. However, because the GMT tends to track into the "colder," more negative ground, it eliminates the biggest complaint against tracking machines that only know how to track neutral. This unit hunts like a pro. And with the ultra-high-resolution 4000: 1 manual ground balance available with the flip of a switch, the best of both worlds is now available in one machine. In Fast Auto Trac, this machine will actually identify a marginal nugget under a negative "hot rock." Anyone can do it with a manual unit by pre-tuning to the rock, but not coming at it with neutral ground balance. At least I can't, and I like to think I know my way around a ground balance knob. I guess my ego will have to take a vacation around the GMT! I can hear everyone saying, "Don't you have anything negative to say about the GMT?" I wish that the Fast Auto TraciManual toggle switch were on the pod instead of the main box

In my opinion, one of the strongest features of this machine is its versatility. This

is a machine for virtually every skill level. An absolute beginner can turn this

machine on, put a couple of knobs and switches on their R/S marks, adjust the

threshold to his liking, and begin hunting very effectively. An advanced hunter has

full control over the Gain and SA7; access to the ultra-high-resolution manual ground balance, a Grab button that delivers instant ground balance in auto or

manual mode, and a full readout of mineral type and amount.

Add to this two different iron ID/target checking modes, an iron ID graph, and an audio boost, and you have a machine that will satisfy the most demanding nugget hunter. I have said it before, but I have to say it one more time: White's, you've done it again! Best of luck nugget hunting. Golden dreams!

 

About the Author

Larry Sallee is an avid prospector and author of two electronic prospecting books, Zip Zip and Zip Zip - The Advanced Course. He and his wife, Sue, own and operate Venture West, a metal detector and prospecting store, in Lake Havasu City, Arizona.