Garrett Electronics Xl-500 Sea Hunter
By Andy Sabisch
From Page 30
November, 1992 issue of Lost Treasure

Garrett Electronics was one of the pioneers in the field of underwater metal-detection technology. In the late 1960s, Charles Garrett and his engineers recognized a market for underwater metal detectors and began work on two models called the Shark and the Aquasearch. Despite extensive research and design efforts, the performance of these detectors never reached the level desired by Mr. Garrett and the development project was put on hold temporarily. In 1980, Garrett released the first underwater detector which was capable of being submerged to 200 feet - the XL-500 VLF/TR which quickly became one of their more popular detectors. In 1984, the pulse version of the XL-500 was released and, over the years, this detector has been associated with many of the more successful marine salvage operations around the world.
There are two different types of circuits currently used in underwater metal detectors today - Very Low Frequency (VLF) and Pulse. While VLF-type detectors will function to a limited degree in salt water where high mineralization in the form of black sand may also exist, the pulse circuit has been designed to ignore these conditions and provide maximum depth at all times.
The one draw-back of pulse detectors is, that with the exception of the XL-500, they do not provide any discrimination which requires that the user dig all targets the coil passes over. On many beaches, good targets are buried amongst a large number of trash targets and some form of discrimination is needed to reduce the amount of digging required to effectively huntthe site. The XL-500 Seahunter is a pulse detector which also incorporates a unique discrimination circuit to aid in eliminating many of these "unwanted" targets.
The XL-500's control housing is constructed of thick plastic similar to the type used for underwater cameras and has been certified leak-resistant to 200 feet. One of the first things that becomes apparent is the weight of the detector. While the control housing weighs 3 pounds 13 ounces by itself, ithas been designed to be neutrally buoyant or virtually weightless when used underwater.
The control housing can be secured around the waist with the adjustable nylon belt that comes with the XL-500. The weight of the armrest and the standard 8-inch search coil is only 2 pounds 14 ounces which allows for extended use both on land and in shallow water without fatigue.
There are only three knobs on the face ofthe XL-500 which control the detector's operation. The AUDIO knob, located on the far left, is a 10turn control used to adjust the threshold signal heard while operating the detector. DETECTION DEPTH, which is the large knob in the center of the face, both turns the power on and allows the user to select one of three sensitivity settings at which to conduct the search.
On the far right is the ELIMINATOR control which functions similar to the discrimination control on other "land-based" metal detectors. Above the ELIMINATOR control is a plug which is used for connecting both the waterproof headphones and the ni-cad battery charger. The 8inch searchcoil plugs into the rear of the control housing and comes with 7-1/2 feet of cable which allows the detector to be used easily in ahipmount configuration.
The meter on top of the control housing serves adual function. When the XL-500 is first turned on, it will indicate battery strength, and when the needle drops to the lower end of the section marked BATT, the batteries should be recharged. When the coil passes over a target, the meter will also indicate relative signal strength which can be extremely helpful when pinpointing.
The DETECTION DEPTH control allows the user to selectthe depth at which targets will be located. If you were searching for a wedding band or set of car keys that had been recently lost, the MINIMUM setting would limit the penetration of the detector so that unnecessary digging could be avoided.
On the other hand, if you were hunting a site where many of the targets might be deeply buried, such as an old abandoned beach, the MAXIMUM setting would help ensure you had not missed any targets that the coil may have passed over. The NORMAL setting can be used where extreme detection depth is not needed such as areas where coral or clay may prevent objects from sinking very deeply.
The XL-5OO comes equipped with ni-cad rechargeable batteries which provide approximately 10 hours of use per charge. The charger is included with the detector and, as mentioned previously, plugs into the headphone jack on the face of the control housing.
When the batteries are being charged, a small red light will be visible just above the connection indicating that the charging circuit is working properly. In order to avoid possibly damaging the seals and subsequently flooding the control housing, the factory recommends that users do not attempt to replace the batteries themselves.
A durable nylon carrying bag is also included with the Seahunter and holds the detector, headphones, charger, and even a sand scoop with room to spare.
Garrett recommends that users return the XL-5OO to the factory every 2 to 3 years for recertification, at which time the technicians will inspect it, replace all of the seals, and pressure test it to ensure it will not leak. The cost of service is in the range of $50 to $60 and it will help insure that your detector will not flood and require expensive repairs in the future.
After assembling the XL-500 and quickly reading through the pocketsized instruction manual, I performed an air test to see how it responded to various targts at different settings. Selecting MAXIMUM DETECTION DEPTH and turning the ELIMINATOR control to "0". I slowly increased the AUDIO knob until I just heard a threshold signal. The Seahunteruses Garrett's unique "Treasure Tone" audio circuit which produces a slightly oscillating threshold tone that ensures even faint signals are easily detected.
As I passed various targets beneath the search coil, the detector produced both an audio and visual (on the meter) response at fairly impressive depths. I increased the ELIMINATOR setting to "3" and repeated the test. This time, the tin foil was rejected; however, very small gold rings and a gold necklace were also being ignored. Coins, silver rings, and larger gold items still produced a solid response.
When the ELIMINATOR was increased to "6", pull tabs were rejected, as were most pieces of gold jewelry. There was also a noticeable decrease in detection depth on coins and silver items, but this happens on most detectors as the level of discrimination is increased. The test emphasized an important fact- the ELIMINATOR control will allow treasure huntersto search areas where others have given up due to trash targets; however, in order to avoid missing a valuable ring or coin, it should be increased only as high as needed to reject most of the unwanted items present.
My wife and I had made plans to spend a week on the island of Cozumel located off the Yucatan peninsula in Mexico and decided to bring the XL-500 along to see what othertourists might have left behind. Despite receiving a few inquisitive looks from the customs inspector at the airport, he didn't ask us anyquestions about the detector and we were soon heading for our hotel.
The XL-500 Seahunter has been designed for serious beachhunters and treasure divers that need a high-quality piece of equipment that is not affected by changing ground conditions.
After changing clothes, we went down to the heach to "scout-out" the area. The hotel beach was located in a man-made lagoon and was fairly small; however, there were a numher of guests laying on the sand and swimming in the water. Deciding to wait until the crowd thinned out a little, we took a walk along the beach and spent some time relaxing around the hotel pool.
After dinner we took the XL-500 back to the beach and while Rosanne began reading a book, I waded into the water. In order to ensure I didn't miss any of the jewelry that I hoped to find, I set the DETECTION DEPTH to MAXIMUM and turned the ELIMINATOR control. As the sun dropped below the horizon, we decided to head back to our room and try out in the water again the following day.
Early the next day I went down to the beach and rented a SCUBA tank so that I could work in the deeper water at the mouth of the lagoon. I removed the lower fiberglass rod from the arm rest assembly which would allow me to lay on the sandy bottom and sweep the search coil within arm's length in front of me. Turning the ELIMINATOR control ftllly counter clockwise and placing the DETECTION DEPTH to MAXIMUM, I began searching along the seawall in about 10 feet of water.
Having used a number of other underwater detectors over the years, one of the biggest problems I have found is that while the volume is adequate above water, when underwater the bubbles from the regulator often "drown out" the audio signals when a target is detected.
The combination of the volume level and the quality headphones on the XL-500 eliminates this problem and I was able to hear even faint changes in the audio threshold quite clearly. After 30 minutes I had only found two coins and a rusted key chain so I turned around and began swimming back into the swimming area. A few minutes passed when a faint change signal caught my attention. I used my hand to fan some of the sand away and rechecked the hole.
The signal had moved and was now a few inches away from its original resting spot. I spent several minutes searching for the target and finally found a small 14 KT gold stud earring. I could hardly believe that a target that small could be detected so I passed it under the search coil and was surprised to hear a noticeable audio change. Over the next 30 minutes I was able to find two more gold earrings along with several more coins, and as I began to bead to the surface, I was looking forward to hunting the beach further before returning home.
Another site that we took the XL500 to was a freshwater spring in central florida frequented by scuba divers and swimmers alike. Most of the swimming took place on one side of the spring and divers used the middle for certification and practice.
Since I was going to be diving this site, I used the optional Scubamate attachment which quickly converts the detector to allow for one-hand operation. After checking my gear, I put the regulator in my mouth and dropped to the bottom of the swimming area which was about 15 feet deep. After 10 minutes, all I had found were pull tabs so I increased the ELMINATOR control to "5-1/2" to reject the bothersome targets.
I realized that I would miss most of the smaller gold items; however, with a limited air supply, I decided to try and find some coins and hopefully a large class ring while ignoringthe pull tabs. A little over an hour later, I checked my pressure gauge and with only 400 PSI remaining, headed back to shore. Unfortunately as I went through my "goody bag," all I had were 38 coins, a junk ring with a skeleton's face on it, and several large screw caps.
While the XL-500 had rejected most of the trash targets present, it didn't appear as if the clientele that frequented the swimming area had worn much jewelry to lose.
Switching tanks, I decided to try searching the bottom of the spring underneath where the divers practiced. The water in the spring was extremely clear, and I was surprised to see that my depth gauge read just over 75 feet when I reached the bottom.
Checking the dive tables I figured thatto avoid any decompressionstops I could only spend about 25 minutes on the bottom. Setting the timer on my watch, I turned the XL-5OO on, selected NORMAL detection depth, and began searching.
Almost immediately I received a loud signal and brushing an inch of sand away revealed a 2 pound diver's weight. A short distance away another signal revealed a nice diver's knife - also just under the surface. All too quickly my time was up and I began swimming towards the surface.
In addition to the weight and knife, I had found an old mask, several sets of keys, the buckle from a weight belt, and a small bandful of coins. The Seahunter had worked flawlessly at that depth and the Scubamate handle had made searching with it quite convenient.
The XL-5OO Seahunter has been designed for serious beachhunters and treasure divers that need a highquality piece of equipment that is not affected by changing ground conditions. It has proven itself to be extremely versatile both on dry land and beneath the water, with ease of operation and overall performance being its two strongest features.
An optional 13-inch search coil is available, and while it is not as sensitive to small targets as the 8-inch coil, it will detect larger targets at deeper depths and allow the user to cover more ground with each pass. The larger coil lists for $99.95. If you are planning on using the XL500 for diving, you should consider purchasing the Scubamate attachment which sells for $79.95.
If you are interested in trying your hand at water hunting, stop by your local Garrett dealer and have him demonstrate the XL-5OO Seahunter before you decide on your next detector. For the name of your nearest dealer and a copy of the new 1992 Buyers Guide, contact Garrett Electronics at 2814 National Drive, Oarland, TX 75041-2397, or call them at (8OO) 5274011 and mention that you read about the XL-5OO Seahunter in Lost Treasure.
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