The Fisher GOLD BUG Metal Detector
''The Gold Bug metal detector is designed for depth and sensitivity, and everything that might detract from these two virtues has been sacrificed.''
From Lost Treasure Field Test By Jack Reid
From page 29 of the October 1987 issue of Lost Treasure magazine.
Copyright ©1987, 1999 Lost Treasure, Inc.
The new Fisher Gold Bug metal detector was designed especially for the nugget hunter. The manufacturer considers it a significant improvement over the two Mother Lode series 660 nugget shooters it introduced in 1984, although both were quite successful.
The Gold Bug metal detector I field tested was shipped to me directly from the factory and arrived in a shipping carton designed expressly for that instrument. The cardboard was sufficiently thick to protect the Gold Bug metal detector from even very rough handling, but resilient enough to absorb the shocks for the metal detector.
Assembly was quick and required no tools. Itwas all the easier because the metal detector came with the seerch coil already mounted to the end of the lower section of the pole and the lower end of the coil cable already connected via a watertight connector.
At the lower end of the S-shaped, gold anodized aluminum upper section ofthe pole, there is an easy-to-grasp slip nut which, when loosened slightly, allows the lower section of the pole to slide into the upper section. By reading all of the ''Setting Up'' section of the 24page accompanying instruction book before I started doing anything, I learned that ideally the coil should be parallel to the ground, about two inches above it and about a foot ahead of the operator's feet when searching.
Preparation was easy to achieve during the initial assembly by first making the parallel adjustment to the coil and then sliding the lower section ofthe pole back and forth within the upper section until it felt comfortable. Next allow the snap lock fitting on the lower section to pop into the nearest holes drilled for that purpose in the upper section. Then, hand-tighten the slip nut for further security and stiffness. In less than a couple of minutes, the Gold Bug metal detector can be assembled, adjusted and almost ready-togo.
During my assembly of the detector, the upper end of the coil cable was still not attached to the control box. The Gold Bug metal detector is so sensitive that the lower section of the pole and all of the fittings that hold it to the coil are made of plastic to avoid false signals. All of these precautions can be defeated, however, by a dangling coil cable.
The Gold Bug may be quickly converted from a pole-mounted control box to a hip mount and it takes a 7-foot-long coil cable to permit this. I planned to use the Gold Bug metal detector in the pole-mount configuration, at least at the beginning, so there was a considerable surplus of cable. Following the instructions, I wrapped the cable tightly around the pole, leaving just enough sllck at the lower end to permit parallel adjustment of the coil, and secured the wire to the pole by means of two spring clips suppiled with the metal detector. Then, I connected the cable to the control box. The clips are plastic-covered spring steel, so I installed them above the slip nut in order tokeep metal as faraway fromthe coil as possible. The most critical, yet not difficult part of assembly was routing the cable to avoid false signals, while allowing enough slack to keep the coil parallel to the ground without putting strain on the cable.
The Gold Bug is of the familiar Stype stem with an arm rest that doubles as a detector stand atthe upper end. The control box is placed so thatall ofthe controls except one canbe conveniently operated with thumb, either in left-hand or right-hand operation, when in the pole configuration.
The control box contains acombined Sensitivity and Battery Test knob, a combined Off/On and volume control knob, a three-position Mode selector toggle switch, a Ground Reject control and a spring-loaded retune button. Threshold Oontrol is a small knob mounted on the opposite end of the control box. It could havebeen grouped with the other controls by mounting itat the lower right of the control panel, where the headphone jack is, but because it is rarely used, it was intentionally placed where it would be difficult to turn accidentally while searching. It is also equipped with a fairly stiff shaft, as control knob shafts go, for the same reason.
The Ground Reject control is one of the sighilicant features of the Gold Bug. It consists of an inner knob surrounded by an outer ring. The inner knob is for coarse tuning and is equipped with click stops. The outer ring is a 16-turn fine tuner. This combination of coarse and fine tuning is what makes the Gold Bug metal detector so easy to ground balance even for high mineralization.
The standard coil is coplanar and eliptical in shape, measuring 10'' by 5'', which is found to be the ideal shape for nugget hunting. It let me cover more ground than an 8-inch round coil and still allowed me to poke in among rocks that were quite close together, sometimes even using a motion mode; that wouldn't have been possible with the round coil. A large eliptical coil measuring 14 inches in length is also offered. As far as I know, Fisher is the only company offering an eliptical coil.
The Gold Bug is designed for depth and sensitivity, and everything that might detract from these two virtues has been sacrificed. For example, there is no discrimination. The Fisher engineers felt that discrimination has no place in nugget shooting since the smaller nuggets havearesponsecloseto that of iron. Because the mere presence of such a circuit, even if set to zero, would detract from signal strength, or at least shorten battery life, they simply left it off the Gold Bug metal detector. Similarly, a meter (visual target identification) is not included.
The Gold Bug offers three search modes: Auto-Tune, No Motion and Motion. Auto-Tune is a motion mode featuring automaticretuning; it operates with threshold hum. Motion is, as the name says, a motion mode which has silent search; it seemed to me to have slightly better response than AutoTune, but was more prone to false signals from mineralization and hot rocks. No Motion operates with a threshold hum and is used mainly for pinpointing. No motion is also good in rocky terrain where using either of the motion modes isn't possible, although they require very little motion. No Motion, in my experience, produced the strongest response of the three modes, but it required frequent retuning and ground balancing.
The best results are obtained if the Gold Bug is ground balanced for the mode being used. I found that AutoTune is the best place to start, because once ground balanced in that mode, any subsequent adjustments required for one of the other two were minor.
To adjust for Auto-Tune, find an area that's free of any targets, set mode to Auto-Tune, Sens to 7 and Ground Reject to 5 (midpoint). Turn on the metal detector and set Volume at 10 (unless you're wearing earphones). With the search coil held waist high, adjust the Threshold control on the back of the control box to produce an acceptable background hum. Now, lower the coil to an inch or two above the ground. Gne of three things will happen: 1) The hum will remain steady all the way down; this means that the metal detector is ground balanced. 2) The hum will fade and then return to normal as the Auto-Tune circuit takes over. 3) The hum will grow louder and then retum to original, again as the Auto-Tuning takes over. Butjust because Auto-Tune restores the original hum doesn't mean the metal detector is ground balanced; Auto-Tune is automatic retuning, notautomatic ground balancing. The goal is to produce a steady hum as the coil is being lowered and raised. This is all-important and easily done, thanks to the 16-turn fine tuning.
If the hum increases when the coil is lowered, turn the center knob of the Ground Reject control, the coarse tuning, one or two clicks counterclockwise, raise the coil about a foot and lower it again. There will be one position where the tone barely increases. The outer knob, which is the fine tuner, is then used to produce a smooth hum as the loop is lowered. The 16-turn feature of the fine tuner permits a very precise job of ground balancing. If the hum decreases when the coilis lowered with the corse tuning set at 5, use the same procedure, but turn the coarse tuner clockwise.
Ground balancing in the No-Motion mode is done much the same way. The main difference is that the automatic tuning featre is inoperative, making it necessary to push in the Retune button for a couple of seconds between each attempt at ground balancing.
Ground balancing in the Motion mode is somewhat more difficult because, being a silent search mode, there's no background hum to use as a guide. The idea is to tune out the effects of ground mineralzation, but not to the point where small or deep nuggets are also being tuned out. This is done by lowering the coil from about 10 inches above the ground to about an inch above groundand adjusting the coarse tuner to the last position where the Gold Bug metal detector responds to the ground with abeep when the coil is in the lower position. Then, use the fine tuner to adjust the metal detector to just eliminate the beep, pressing in the Rettine button for a couple of seconds just before each time the loop is lowered.
It took a little bit of practice, but before long l was able toground balance in all threemodes quickly, usingjustmy thumb to make the necessary adjustments. This came in very handy in the field because the amount of mineralization in auriferous areas is apt to change very quickly and frequentrebalancing is more the rule than the exception. Raising the coil about a foot while searching very quickly let me know whether or not the Gold Bug metal detector was still ground balanced.
The first target I tried the Gold Bug on was the gas pipe leading into my home. It'sablack iron pipe slightly over 1'' in diameter with 18'' of soil and a layer of 2'' common bricks above that. The Gold Bug metal detector sounded off with a lusty squeal. The instrument has a variable pitch audio, either through the speaker or headphones, and ferrous metal targets have a notably higher pitched response than do non-ferrous ones. This feature is intentionally built into the metal detector arrl goes a long way in identifying junk items, eepecially useful since the Gold Bug metal detector has no discriminator or visual target identification meter.
My test bed was my next target-a collection of goodies and garbage. Fif teen items are buried two feet apart and at various depths. These include various ferrous metal fasteners, bottle caps, pull tabs, coins and a two-ounce Troy piece of gold ore still in its quartz matrix buried at 11 inches. Since there is discrimination, the Gold Bug metal detector sounded off on all of them. The ferrous metal samples produced the highest pitched signals, and I was soon able to easily distinguish the signals indicating ferrous metal from those indicating the coins.
The gold ore's signal was distinct, yet lower in pitch than the others. Certainly, the Gold Bug does nothave audio discrimination as it is defined by the metal detector trade; the circuit simply isn't there. But, itdoes have audible discrimination, thanks to its variable pitch response. Audible discrimination accomplishes much the same as audio discrimination, but without the accompanying loss of signal strength. Later on, in the field where I dug everything, I discovered that these relationships of sound to target composition generally held true, even in the highly mineralized soils characteristic of nugget-bearing areas.
I had the opportunity to take the Gold Bug to a claim in northern Arizona within sight of route I-10. This is a very regularly prospected area. I've seen legions of nugget shooters, dry washers and dry panners working the area during the annual Quartzsite Pow Pow. Most everyone came away with some stones of gold, but nothing really sensational. Although my mind was filled with visions of 10- and 12-ounce nuggets, I didn't realistically expect much. A day's searching yielded three small nuggets, all less than half a pennyweight. They were all quite deep, as small nuggets go, however, and probably had been missed by other detectors. One of them was unidentifiable from the other soil that I'd scooped up, so I tried a trick shown on page 18 of Fisher's 24page instruction book, which accompanies each Gold Bug. With the metal detector in Auto-Tune mode, I held it so that the coil was flat on the ground, then I slowly let a handful of the soil containing the nugget fall on top of the coil. When the nugget hit it, the metal detector beeped, but I still couldn't tell which was the nugget. I used my index finger to move around the pieces of dirt on top of the coil, and when I moved the nugget, the metal detector beeped again - and there it was.
Later on, I took the Gold Bug to a claim in Plumas County, Calif., where I have permission to search. I had hunted nuggets on the claim before, but never with any degree of success. The soil is so mineralized that it was difficult to ground balance the detectors I'd used. I could produce a hum that barely increased or decreased when the coil was lowered from waist level to ground, but rarely one that held steady. The 16-turn stacked Ground Reject adjustment on the Gold Bug metal detector, on the other hand, made accurate ground balancing a cinch.
I knew from experience that mineralization changed rapidly and that frequent rebalancing was a necessity. The Gold Bug's variable pitch audio was a big help here. One time, the signal strength and pitch gradually increased, but it didn't sound right for gold. However, a scoop of soil contained what appeared tobe, at first, a dozen or more pin-head sized nuggets. They looked great in sunlight. but passing my hand across them - the shadow test - revealed them to be exactly what the detector indicated. apocketofiron pyrites. Working further up the wash produced periodic faint indications of what I was then able to recognize as indications of gold, but there was still snow on the ground and the earth was saturated with water.
Attempting to isolate small nuggets proved futile, so l sued a stiff plastic cup to scoop out signaling soil, passed the detectorovereach scoop and if it still indicated gold, I dumped it into a bucket. I took the bucket home, spread out the dirt on a large piece of vinyl and let the sun dry it out for several days. At first I used the method described earlier of dropping suspected nuggets of top of the coil and then I panned out the rest of the soil. This yielded five very small nuggets ofa littlemore than 1/10 gram each; altogether, they weighed 3/4 gram. In my view, the real test of the nugget hunting metal detector is not how large a nugget it signals, but that it will consistently detect very small nuggets in high mineralization. The Gold Bug performed very well in this respect.
I also took the Gold Bug to a saltwater beach which is famous for its magnetic black sand. It was too early in the year to expect a bountiful harvest of coins and rings; I arrived early on acold and windy day and there were few other people present. My purpose was to find out if l could balance the Gold Bug metal detector to the black sand. I used the Motion mode and was able to get good balance with Sens at 6.
Two hours of sweeping produced three clad coins, four pennies, and a 1981 Mexican 10-Peso coin (nickel/ copper and about the size of a half dollar) - all of them at least four inches below ground level. The depths, coin dates and presence of a Mexican coin long before the start of the tourist season indicated that they'd been there for some time and had probably been missed by other metal detectors searching this well-hunted beach. It goes without saying that l also retrieved my share of junk.
All in all, I found the Gold Bug to be a superior nugget shooter and well worth the $499.96 price tag. I particularly liked the Gold Bug's ease of ground balancing in heavy mineralization, the eliptical coil and the variable frequency audio response, which was most helpful in distinguishing gold nuggets from hot rocks and other targets.
Its ease of ground balancing also made it a more than acceptable saltwater beach hunter, although it wasn't designed for that purpose. I think that with a little more practice, the Gold Bug's variable frequency audio would have enabled me to distinguish between the usuul beach junk and the real goodies, certainly more easily than with a general purpose metal detector in the All Metals mode.
For more information, contact; Fisher Research Laboratory 10051 St., Los Banos, CA 93635, Phone (209) 826-3292.
Copyright ©1996-2003 LostTreasure, Inc.