Fishers Nugget Shooting Mother Lode 660
By Jim Martin
From Page 37
January, 1985 issue of Lost Treasure

Nugget shooting! Few expres-sions in the treasure hunting vocabulary spark a greater degree of excitement than this term alluding to the search t& raw gold with a metal detector. Just thinking about the pos-sibility of finding a golden nugget or two with a buzz box is enough to trigger dreams of riches.
One way of helping to turn such dreams into realities is to start out searching with an instrument that is designed expressly to detect gold.
The Fisher-built Mother Lode 660 is such a device.
As the name Mother Lode implies, this is a specialized instrument de-signed for modern gold prospectors.
Its a quality built unit, blessed with the features and circuitry that the Fisher engineering staff feels are es-sential for achieving success at elec-tronic gold prospecting. Key ele-ments include the Mother Lodes VLF (Very Low Frequency) search capabilities, a super-sensitive ground balance control system and three loop options1-inch, 8-inch and 3/2 inch. This trio of Electro-Static-Insulated search coils is designed to provide the versatility needed to con-tend with varying search conditions in the field.
Fashioned with the weekend pros-pector in mind, the Mother Lode 660 has all the components required for this highly specialized phase of trea-sure hunting, but without frills. By eliminating the non-essentials, the manufacturer has managed to hold the weight of the detector down to 4/2 pounds. Weight is a key factor to consider when you are using a metal detector all day longa standard practice among dedicated nugget shooters. By limiting the weight and distributing it along the well-balanced, adjustable stem, the de-signers have reduced much of the arm fatigue associated with heavier detector models.
The Mother Lode I was assigned to evaluate (Prototype #4) was essen-tially an improved version of that proven workhorse, the Fisher Model 441. The design engineers have re- tamed the features which made the 441 popular, while adding some re-finements to make the Mother Lode more suitable for nugget shooting.
But will this machine really find gold? Thats almost the standard question asked about nugget shoot-ing. And yes, Ive asked that ques-tion many times myself.
To ascertain how well the Mother Lode 660 responds to gold, I con-ducted a series of air tests using a pair of small gold nuggets as targets.
Starting out with the eight-inch search coil that is standard equip-ment, I was able to obtain what I consider a discernable reading on a 2/2 pennyweight (DWT) nugget at 3/2 inches. A check with a larger 7/2 pennyweight nugget produced an audio tone at 5/2 inches.
Switching to the smaller 3 ~/2 search coil (which is available as an option), I obtained a recognizable audio signal on the smaller nugget at three inches and on the larger at 4/2 inches. I prefer a smaller loop when probing into crevices and tight cor-ners and the slight loss in signal depth did not concern me.
Air checks with the larger li-inch coil, also an option, produced re-sponses from the larger nugget at 61/2 inches and response on the smaller chunk at four inches. This increased range could prove advantageous in some search situations, but the larger loop is apt to make for weary arm muscles if you use it very long.
Keep in mind that these are merely rough air check distances and do not necessarily represent depth readings in the field. I am certain that some-one with more sensitive hearing than mine may be able to obtain better results on a similar series of air checks. And, of course, the larger the nugget being used as a target, the greater the depth range you can ex-pect. An itty-bitty nugget is going to be extremely tough to pick up.
For example, a one-half penny-weight golden tidbit is nothing really earth-shaking, but I sure get a thrill if I spot one in the bottom of my gold pan. Yet I almost had to rub a nugget this size on the Mother Lodes search coil in order to get a response during an air check in the VLF Normal mode. Switching to the VLF Maxi-mum mode, I did get a signal at one inch, but it really wasnt a response that was readily apparent.
A few simple air tests like these will serve to convince an interested layman that the Mother Lode 660 has the capability of finding gold. More dedicated metal detecting enthusiasts will undoubtedly want to know more about the machine, particularly how well suited it is for nugget shooting operations in the fieldwhich are a far greater challenge than obtaining readings in an air check.
I had several questions of my own that I wanted answered. Did the Mother Lode tend to drift? Is it easy to ground balance? What is its sensi-tivity under poor conditions? How much is required in the way of ad-justments?

The Mother Lode is a VLF detec-tor designed to transmit at an operat-ing frequency of 4.5 kHz. Because it operates in the very low frequency range, the Mother Lode can be ground balanced to compensate for the irritating noises caused by exces-sive mineralization in the soil. Natu-ral gold has a habit of hiding in heav-ily mineralized areas, and if you plan to search for nuggets at locations where gold is most likely to be found, you should equip yourself with a metal detector capable of coping with the excess noise problem. The Mother Lode can be ground balanced by means of a two-stacked knob located at the lower left side of the control panel. Marked Ground Reject, the bottom portion is a single-turn knob calibrated from 0 to 10. Use this to make the initial ground balancing adjustment. The upper segment is a ten-turn knob for fine-tuning that may be. required by changing soil conditions in the search area. This two-stacked con-trol takes a bit of getting used to, but is really not difficult to master after you become better acquainted with the machine.
The first stage of the ground bal-ancing process is no problem. It calls for the same type of up-and-down movement of the loop, together with the necessary left- or right-hand turning of the control, procedure thats required when ground balanc-ing any VLF metal detector that re-quires manual adjustment. You need to practice with varying soil condi-tions in order to master using the top knob to fine-tune the instrument.
Simply reading about how to operate this control is not going to cut the mustard. You must get out in the field and learn how to do it yourself. You must also accept the fact that changing ground mineralizations may call for a frequent adjustment.
Audio responses from small gold nuggets are often very faint. Conse-quently, it is essential that a detector be tuned to a gnats eyelash when it comes to establishing the proper au-dio threshold sound. This critical ad-justment is performed with a ten-turn knob at the upper left-hand side of the control panel marked Thning. The multi-turn knob allows a wide degree of latitude when fine-tuning the detector. Use it wisely.
Dont look for a retuning control, however. If the Mother Lode starts to drift away. from the original thresh-old point, theres no handy little switch or button to make it behave.
To compensate for the lack of a re-. tune control, the manufacturer sug-gests that you maintain the estab-lished threshold sound level by using the upper segment of the two-stacked ground balance control. When the rascal starts to -wander due to a change in mineral content of the soil, a slight adjustment to the left or right will help restore the original sound level. But you are advised not to touch the tuner in the process. That will change the established setting and as a result you will have to go through the entire ground balancing process in order to get back in busi-ness.
Sounds confusing? It is. But who ever told you that nugget shooting was going to be easy?
The Mother Lode also does not have the discrimination level control found on conventional VLF/TR DISC type detectors. It operates in the VLF (All Metal) mode exclu-sively and does not have the ability to eliminate responses from un-wanted metal objects. There is no way to program the detector to dis-tinguish treasures from trash. If your quest is for gold, you will have to in-vestigate ev4ry audio signal.
Perhaps I have been negligent by not starting out with a mention of the first control you should be concerned withthe Power/Volume switch in the upper right-hand corner. Click this on to activate the circuitry, then continue turning in a clockwise di-rection to increase the sound inten-sity. The same switch must also be turned on in order to operate the Bat-tery Test push-button, which causes the little LED light to glow when the cells are sufficiently juiced.
Power is provided by 12 1.5 AA batteries, which are housed in twin six-packs inside the control box. You can replace the batteries by removing the front cover, which is secured in place by a pair of knobs.
Backing up the standard VLF Normal search mode is a secondary mode which the manufacturer calls VLF-Max. The mode selection switch is incorporated into the sensi-tivity knob at the bottom right-hand corner of the control panel. When the knob is flush with the face of the panel, the detector is in the VLF Normal mode. If pulled out, the knob switches the instrument into the VLF Max mode. This is another control you must learn to operate through actual experience.
The sensitivity control is provided to enable the operator to cope with the challenges that occur in highly mineralized search locations. Soil conditions in these areas can vary so widely that it is difficult to make any meaningful statements about them except that they can be miserable to work in. That is .why a sensitivity control is incorporated into the de-sign of a metal detector. Its a control that you must learn how to master through actual field experience in the area you are searching,
Evaluating the performance of the sensitivity control, as well as the VLF Maximum mode, is difficult to do during an air check. Such tests are performed under ideal conditions, with no unpredictable soils to cause trouble. However; it is possible to obtain a feel for both the sensitivity and VLF Max by passing a gold nug-get across the face of the loop.
Decrease the sensitivity setting, for example, and you will lose an au-dio response from the nugget in both modes. Use a high-sensitivity setting during your air tests and you will re-ceive positive responses in both VLF Normal and VLF Max. But in these situations you do not have to contend with heavily mineralized soils.
Move outside in the field to con-duct your tests and heaven only knows what you will encounter. Ground conditions vary so widely that written reports and instructions can only offer guidelines. You must figure out each situation yourself. I dont mean to sound so iffy in making this statement, but thats the way things are in the field of elec-tronic prospecting.
The promotional-minded folks at the Fisher Research Laboratory scored an impressive coup by having Woody Woodworth, a well-respected name in electronic prospecting, pre-pare the operating manual for the Mother Lode 660. Woody writes with authority based on endless hours in the field, while explaining how to operate the detector and de-scribing some of his nugget shooting experiences. His sage remarks, to-gether with practical tips on how to obtain the best performance from the Mother Lode, make the operating manual a valuable how-to guide from which every weekend prospec-tor can benefit.
Woodworths well-written 24-page manual is convincing proof that nug-get shooting can pay off. So are the exhibits of beautiful nuggets he sometimes displays at gold shows throughout the western states. The cover photo on the August issue of Lost Treasure depicts some of the golden goodies Woody has found. Dreams are born of these.
Although designed for modern ar-gonauts, the Mother Lode 660 offers no guarantee to success at locating gold. No metal detector on the mar-ket today can make such an assur-ance.
Gold is where you find it, as the saying goes. If you select a search lo-cation where nuggets are not present, or where they lie beyond the depth range of your detector, you are not going to find any. If you are fortu-nate enough to find a spot where nuggets are present, theres still no guarantee you will find any.
Nugget shooting can be hard work, even at the most promising of loca-tions. I think Woody summed up the situation quite well when he wrote in a recent letter, The two controls manufacturers fail to add to a detec-tor when it comes to nuggets are the Persistence Knob and the Luck Knob.
To this I can only add a hearty Amen!

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