FIELD TEST

Metal Detector Field Test & Review - The Garrett AT Pro
By Chris Gholson
From Page 56
March, 2011 issue of Lost Treasure

Anyone that has been involved with metal detecting for any length of time will have undoubtedly heard the name Garrett.

Garrett has done wonderful things for the industry in four decades by supplying quality detectors and through their efforts to help promote the hobby. Their products have been responsible for finding millions of dollars worth of ancient coins, relics, jewelry and gold nuggets, and are revered by treasure seekers.

In addition to the hand-held products, Garrett produces a range of detectors for use in security screening, crime scene investigation and for military de-mining operations. One of the newest additions to their consumer line is a detector known as the AT Pro.

The AT Pro (ATP) is a VLF detector, which operates at approximately 15 kHz and is outfitted with a waterproof 8.5" x 11" elliptical Double-D coil. The machine weighs in at roughly 3.2 pounds and is powered by four AA batteries. It features an updated panel with an LCD screen and all pushbutton controls.

But what really sets this machine apart is its versatility. It is a true multi-purpose detector that has the ability to locate all types of buried treasure-coins, relics or gold. And with its unique All-Terrain design, this machine can be used just about anywhere.

The entire detector can be submerged under water to a depth of 10 feet! With this level of weatherproofing, the ATP is an excellent choice for streams, ponds, or in shallow water.

The ATP includes Garrett’s exclusive Target ID technology and patented discrimination features. It offers six detection modes, which can be adjusted using the MODE button-three STANDARD and three PRO.

The Standard detection modes include: Custom, Coins and Zero. The Pro modes also include: Custom, Coins and Zero.

The difference between the Standard and Pro modes has to do primarily with a target’s audio response. In all three Standard modes, the detector provides a full-strength binary audio response regardless of the target’s size or distance from the coil. In other words, while hunting in any of the Standard modes, the detector will make a beep when passed over a metal target. The pitch will vary depending on the conductive properties of the target, but it will be just a beep.

The Standard modes offer quieter, more stable operation and may be a good place for new users to start while familiarizing themselves with the detector.

However, to truly unlock the power of the ATP, the user will want to explore the Pro modes. The benefits of these modes include the ability to hear and determine a target’s approximate size and depth via the Proportional Audio and Tone Roll Audio.

Pro mode also offers faster recovery speeds for separating targets that are in close proximity. The advanced audio features of Pro mode are intended for skilled users who wish to hear the signature of targets versus the simpler target response provided in Standard. Basically, the Pro mode will allow you to hear targets as they really are.

For example, if there is a coin near the surface, the detector will produce a loud signal response. If we take that coin and bury it at six inches, the signal produced will be weaker, thereby telling the operator that the target is a reasonable distance away from the coil. Whereas in the Standard mode, the detector will give the same type of signal response whether the coin is near the surface deeper.

As mentioned, there are six operating modes to choose from. The ZERO Mode is essentially an All-Metal mode. There will be no discrimination and all metals will be detected. This is a good option for relatively clean, trash-free ground.

The COINS mode can be used to find most types of coins and jewelry, while eliminating many trash targets like iron and foil. In this mode, the discrimination level has been preset to 35 and one notch that is associated with foil has been excluded. Pull-tabs have not been eliminated because they have properties similar to small coins and jewelry. This mode will be a good choice for those that like to hunt parks, playgrounds, or perhaps along the beach.

The CUSTOM mode has been left open for the user to customize. The factory preset for this mode is the same as ZERO. Any changes or adjustments made in CUSTOM will be retained after the detector has been switched off. Changes made to the ZERO or COINS modes will not be retained.

The Digital Target ID system found on the ATP provides a specific value to help the user identify targets more accurately. Unknown targets are identified in the LCD with a number. This number is a representation of the target’s conductive properties. Numbers closer to 1 are the most ferrous; numbers closer to 99 are the most conductive. The Digital target ID number can be used in conjunction with the Target ID Cursor, which is found just beneath the Target ID Legend.

The Target ID Cursor will move along the Target ID Legend and settle on the place that best represents the target found. Ferrous targets show up on the left half, non-ferrous targets that are lower in conductivity will show in the middle, and highly conductive targets will show on the right half. The Digital Target ID is more precise than the Target ID Cursor, however, when used together, it is fairly easy for the operator to get a general idea of what type of target has been detected.

Another way for the operator to quickly determine the probable identity of a target is by listening to the audio tone. The ATP is equipped with a Tone ID feature that produces three distinct tones based on a target’s composition and conductivity. Low tones indicate ferrous items, such as nails, wire, boot tacks, etc. Medium tones indicate small or thin non-ferrous items. Including gold nuggets, foil, small jewelry, and some hammered coins. High tones indicate non-ferrous targets with medium to high conductivity, such as most coins and larger jewelry.

The ATP can be ground balanced manually and automatically. Ground balancing is a crucial part of detecting and must be done every time the machine is turned on. Sometimes, if conditions are severe, it may be required several times a day. Persons that do not take the time to ground balance will leave good targets behind.

The automatic ground balance procedure is quick and was my preferred method. To balance, simply find a clean piece of ground free of metallic targets. Push and hold the GND BAL button while pumping the search coil towards the ground. If the machine is out of balance you will hear a noise when the coil is lowered or pulled away from the ground. Continue to hold the button until there is very little change in audio when the coil is moved. In some cases, the manual setting may achieve a more precise balance, but it is not recommended for new users.

The ATP has eight sensitivity settings shown on the LCD. I recommend using the highest sensitivity setting, as this will allow smaller and deeper targets to be found. However, the level used will ultimately be determined by the conditions present in the area. High settings can be used when hunting ground with low mineralization and electromagnetic interference (EMI). Lower settings may be required if the ground mineralization is severe, or there are high levels of EMI.

If you find the detector is behaving erratically, try re-ground balancing. If this does not alleviate the problem, try lowering the sensitivity. If this still does not solve the problem, you may need to adjust the frequency. The ATP has the ability to slightly alter its operating frequency to help combat noise caused by power-lines, other metal detectors, electric fences, etc. There are four slightly different frequencies to choose from. These adjustments are small and will not affect detection performance.

As far as discrimination goes, the ATP has plenty of it. It features a high-resolution iron discrimination adjustment called IRON DISC. This feature is adjustable from 0 to 39. Low settings offer less iron discrimination, while high settings will eliminate more iron. The user should never apply more discrimination than is necessary; otherwise the detector may mask a good target that is in close proximity to a bit of iron.

In addition to the high-res Iron Discrimination, there are also 12 "notches" available This is called Notch Discrimination and can be used to eliminate trash targets. Any combination of these can be switched on or off. We will not discuss them in detail simply because I feel they should be used with caution.

Turning off a notch in the wrong place could cost the user a nice piece of gold. I found this when passing a nugget across the coil and intentionally hitting the ELIMINATE button. When I ran the nugget across again there was no target response - the nugget had been eliminated!

For gold prospecting, I would recommend that none of the notches be eliminated. Instead, I found myself relying more on the IRON DISC. With this I could run at fairly high levels (25-30) with very little risk of ignoring a nugget.

In order to test the gold finding capabilities of the ATP, I took it deep into the mountains of central Arizona. I chose this area because I had found gold there in the past, and because much of the ground was shallow with little trash. I started off in a mid-sized wash that meandered through the hills for nearly a mile with exposed bedrock full of cracks.

I opted to start in the Pro Zero mode first. I increased the Sensitivity to its maximum level and began the ground balance procedure. I quickly discovered this setting was too high and could not cope with the abundant black sands and hot rocks. After dropping the sensitivity to four and re-ground balancing, the ATP ran smoothly. EMI was not a problem, so there was no need to adjust the Frequency.

My first target came within five minutes. It produced a medium pitched signal and a Target ID of 40. My excitement grew when I increased the IRON DISC to a 25 and the target still rang true. Fortunately, I didn’t have to dig much of a hole before discovering it was only a .22 bullet. At least I knew all was working well with the unit.

The next two targets I found were a bit out of the ordinary for a remote location. I swung the coil upwards towards the bank and got a loud, high-pitched signal. While attempting to pinpoint it, I picked up an equally strong signal about five inches away. Neither was affected by the IRON DISC and both gave high Target IDs, ranging from 75-80.

The ATP told me they were coins, but I had a hard time believing there were coins this far from town. After digging them out I found the ATP had not lied. One was a 1976 penny and the other a 1981 dime.

I walked nearly a quarter mile more of the wash and only passed over the occasional target that was obviously iron. These signals gave a low Target ID, usually in the 20’s, and would only trigger a broken signal or no signal at all. I dug a few of them just to be safe and found all were nails or fragments of iron.

I was considering moving to new spot when I received a mellow, but definite signal from a piece of bedrock. It was not strong and I believe if I had been swinging the coil any faster I would have missed it. It gave a medium pitched tone with a Target ID that wavered between 35-40 and was not affected by the discriminator. Things were looking positive, but I knew it could be another bullet.

The rock was fractured and it was difficult to determine which crack the signal was coming from, so I made use of the PINPOINT feature. This allowed me to stop the coil directly above the target without losing it.

I chipped away until there was nothing left but broken bedrock and sand. Finally, I spotted the source - it was indeed a nugget! Although the piece weighed nearly one gram, and had only been concealed by an inch or so of material, it did not give the strong signal I would have expected. The only explanation I came up with was that it must have been turned on edge.

I found the ATP a pleasant machine to hunt with. Some of its strong points were: easy operation, light weight, automatic ground balance, highly versatile, and extremely weatherproof. The ATP is a true All-Terrain detector that can be used on land, in the water, in the mud, or even snow.

I did not have the opportunity to test it underwater, but have been reassured the entire detector can be taken up to 10 feet deep, providing the supplied headphones are not submerged. Optional waterproof headphones are available.

The biggest con in my opinion was the lack of a Threshold. The threshold is a constant background "hum" emitted by the detector. The ATP is a silent search machine, which means no sound will be heard unless a target is found. I know there are hunters that prefer silent search detectors, but I am not one. The humming of a threshold can be annoying, but that hum is packed with valuable info.

Often a small, or a deep nugget, will not produce a clear, distinct signal. Many will only trigger a slight waver in the threshold and a silent search machine could miss them. I don’t mind the extra noise and, if Garrett decides to release an updated model, I hope they consider the addition of an adjustable threshold.

I would also ask for an adaptor that would allow different brands of headphones to be used, and a backlight in the LCD would have been a nice addition.

The new AT Pro is a unique detector with something to offer every hunter. It can be used for all types of detecting and can be taken just about anywhere.

At only $699.95, it offers versatility and performance at a reasonable price. It comes with a full 2-Year Warranty and is made right here in the USA. For more information, visit www.garrett.com, or call them at (972) 494-6151. Don’t forget to mention that you read about it in Lost Treasure Magazine!

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