The Fisher Gold Bug
By Jack Reid
From Page 29
October, 1987 issue of Lost Treasure

The new Fisher Gold Bug was designed especially for the nugget hunter. The manufac-turer considers it a significant improve-ment over the two Mother Lode series 660 nugget shooters it introduced in 1984, although both were quite success-ful.
The Gold Bug I field tested was shipped to me directly from the factory and arrived in a shipping carton de-signed expressly for that instrument. The cardboard was sufficiently thick to protect the Gold Bug from even very rough handling, but resilient enough to absorb the shocks for the detector.
Assembly was quick and required no tools. It was all the easier because the de-tector came with the search 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 of the pole, there is an easy-to-grasp slip nut which, when loosened slightly, al-lows the lower section of the pole to slide into the upper section. By reading all of the "Setting Up" section of the 24-page 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 operators 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 of the 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 se-curity and stiffness. In less than a couple of minutes, the Gold Bug can be as-sembled, adjusted and almost ready-to-go.
During my assembly of the detector, the upper end of the coil cable was still not attached to the control box. The Gold Bug 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 con-verted 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 in the pole-mount con-figuration, 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 slack at the lower end to permit parallel adjustment of the coil, and secured the wire to the pole by means of two spring clips sup-plied with the 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 to keep metal as faraway from the coil as possible. The most critical, yet not difficult part of assembly was rout-ing the cable to avoid false signals, while allowing enough slack to keep the coil parallel to the ground without put-ting strain on the cable.
The Gold Bug is of the familiar S -type stem with an arm rest that doubles as a detector stand at the upper end. The control box is placed so that all of the controls except one can be conveniently operated with thumb, either in left-hand or right-hand operation, when in the pole configuration.
The control box contains a combined 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 Control is a small knob mounted on the opposite end of the control box. It could have been grouped with the other controls by mounting it at the lower right of the control panel, where the headphone jack is, but be-cause it is rarely used, it was intention-ally 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 significant 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 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, some-times even using a motion mode; that wouldnt have been possible with the round coil. A large eliptical coil measur-ing 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 nug-gets have a response close to 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. 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 automatic retuning; 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 Auto-Tune, but was more prone to false sig-nals 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 isnt possible, although they require very little motion. No Motion, in my experience, produced the strongest re-sponse of the three modes, but it re-quired 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 Auto-Tune 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 thats free of any targets, set mode to Auto-Tune, Sens to 7 and Ground Re-ject to 5(midpoint). Turn on the detector and set Volume at 10 (unless youre wearing earphones). With the search coil held waist high, adjust the Thresh-old control on the back of the control box to produce an acceptable back-ground hum. Now, lower the coil to an inch or two above the ground. One of three things will happen: 1) The hum will remain steady all the way down; this means that the detector is ground bal-anced. 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 return to original, again as the Auto-Tuning takes over. But just because Auto-Tune restores the original hum doesnt mean the detector is ground balanced; Auto-Tune is automatic retuning, not automatic 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 tun-ing, 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 de-creases when the coil is lowered with the coarse tithing 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 feature 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 be-cause, being a silent search mode, theres no background hum to use as a guide. The ideals to tune out the effects of ground mineralization, 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 ground and adjusting the coarse tuner to the last position where the Gold Bug responds to the ground with a beep when the coil is in the lower position. Then, use the fine tuner to adjust the detector to just eliminate the beep, pressing in the Retune button for a couple of seconds just before each time the loop is low-ered.
It took a little bit of practice, but before long I was able to ground balance in all three modes quickly, using just my thumb to make the necessary adjust-ments. This came in very handy in the field because the amount of mineraliza-tion in auriferous areas is apt to change very quickly and frequent rebalancing is more the rule than the exception. Rais-ing the coil about a foot while searching very quickly let me know whether or not the Gold Bug was still ground balanced.
The first target I tried the Gold Bug on was the gas pipe leading into my home. Its a black iron pipe slightly over 1" in diameter with 18" of soil and a layer of 2" common bricks above that. The Gold Bug 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 detector and goes a long way in identifying junk items, especially useful since the Gold Bug 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 dis-crimination, the Gold Bug 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 fer-rous metal from those indicating the coins.
The gold ores signal was distinct, yet lower in pitch than the others. Cer-tainly, the Gold Bug does not have audio discrimination as it is defined by the metal detector trade; the circuit simply isnt there. But, it does have audible dis-crimination, thanks to its variable pitch response. Audible discrimination ac-complishes much the same as audio discrimination, but without the accom-panying 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. Ive 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 vi-sions of 10- and 12-ounce nuggets, I didnt realistically expect much. A days searching yielded three small nuggets, all less than half a penny-weight. They were all quite deep, as small nuggets go, however, and proba-bly had been missed by other detectors. One of them was unidentifiable from the other soil that Id scooped up, so I tried a trick shown on page 18 of Fishers 24-page instruction book, which accompa-nies each Gold Bug. With the 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 fail on top of the coiL When the nugget hit it, the detector beeped, but I still couldnt 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 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 Id 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, on the other hand, made accurate ground balancing a cinch.
I knew from experience that miner-alization changed rapidly and that fre-quent rebalancing was a necessity. The Gold Bugs variable pitch audio was a big help here. One time, the signal strength and pitch gradually increased, but it didnt sound right for gold. How-ever, a scoop of soil contained what appeared to be, at first, a dozen or more pin-head sized nuggets. They looked great in sunlight, but passing my hand across them the shadow test re-vealed them to be exactly what the de-tector indicated: a pocket of iron 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 I sued a stiff plastic cup to scoop out signaling soil, passed the detector over each scoop and if it still in-dicated 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 nug-gets of a little more than 1/10 gram each; altogether, they weighed 3/4 gram. In my view, the real test of the nugget-hunting detector is not how large a nugget it signals, but that it will consis-tently detect very small nuggets in high mineralization. The Gold Bug per-formed very well in this respect.
I also took the Gold Bug to a saltwa-ter beach which is famous for its mag-netic black sand. It was too early in the year to expect a bountiful harvest of coins and rings; I arrived early on a cold and windy day and there were few other people present. My purpose was to find out if I could balance the Gold Bug 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 dol-lar) 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 theyd been there for some time and had probably been mis-sed by other detectors searching this well-hunted beach. It goes without say-ing that I 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 particu-larly liked the Gold Bugs ease of ground balancing in heavy mineraliza-tion, the eliptical coil and the variable frequency audio response, which was most helpful in distinguishing gold nuggets from hot rocks and other tar-gets.
Its ease of ground balancing also made it a more than acceptable saltwater beach hunter, although it wasnt de-signed for that purpose. I think that with a little more practice, the Gold Bugs variable frequency audio would have enabled me to distinguish between the usual beach junk and the real goodies, certainly more easily than with a general purpose detector in the All Metals mode.
For more information, contact; Fisher Research Laboratory, 1005 I St., Los Banos, CA 93635, Phone (209) 826-3292.

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