My GM1000 Methodology - Manual Versus Auto Sensitivity

[Steve Herschbach]

I am just back from a little detector outing and while I was at it I reflected on how once again I seem to do things a bit differently than other people. I am usually shy of talking about my specific settings because I am the last person to claim I know what's best when it comes to other people and how they detect. Ground conditions vary as do people's personal styles and preferences. Therefore I will include my usual caveat here that I am not claiming what I am doing is "the best" way of doing things. On the other hand I do seem to be able to make detectors deliver for me and I am willing to share how I do things in case it may help somebody else. Hopefully that proves to be the case with this post.

For me the key is knowing my detector and how it reacts on my ground. I then let the detector tell me what to do when it comes to balancing sensitivity and ground responses. The task at hand has a lot to do with it. The Minelab Gold Monster 1000 is from my perspective two different detectors in one package. There are two basic tasks I usually expect to perform with it:

1. I have an acre of ground I want to detect from end to end. This for me requires using the larger of the two coils included with the GM1000, a blunt tipped 10" DD elliptical. Due to the GM1000 being a very high gain detector in more ways than one, my basic goal here is stability. I want the machine to be well behaved so that I can cover ground relatively quickly without having to deal with spurious false signals that require analysis. I am going to sacrifice a little theoretical "hots" in order to efficiently cover large areas, areas that may or may not contain gold.

2. I have a 20 foot by 20 foot area that I already know has small gold in it. My goal here is not to cover ground but to clean out the gold. This will at minimum mean running the Gold Monster as hot as possible, and may very well include going to the smaller of the two coils, a 5" round DD. However, I can find gold down around the 1/10th grain (480 grains per Troy ounce) region with the 10" coil and it will hit the larger bits at greater depth in milder ground so I am generally going to stick with the 10" coil unless I really am trying to get the very last flyspecks.

What follows is predicated on the moderately mineralized ground of northern Nevada, where alkali (salt) ground is as much or more a consideration as small hot rocks. Even small depressions like a hoof print will collect water during a rain, and when almost but not completely dried the small damp spot may create a positive signal if the Gold Monster is running at high sensitivity levels. Once again I will warn that the specific settings I mention will vary under different ground conditions.

Under the first scenario where I am trying to cover large areas I have found both manual sensitivity and auto sensitivity to be useful. Deciding between the two is as simple as knowing how variable the ground is. If the ground is relatively homogenous with minimal variation then manual sensitivity can work very well. If the ground gets too variable requiring constant burdensome adjustments of the sensitivity control to keep up, then going to auto sensitivity is more efficient.

What does that mean in actual practice? Let's go over that but first I need to discuss the power up procedure. Much has been made of the necessity to hold the coil in the air as opposed to on the ground when the detector is first powered up. I will admit I am perhaps less stringent as regards that procedure. If I have any nearby electrical power sources, like a power line, cell tower, another detectorist nearby, etc. then I will raise the coil off the ground and point it directly at the tower or other person. This gives the GM1000 the best chance of "seeing" the interference during the few seconds frequency scan so possible interference can be eliminated or at least reduced as much as possible.

However, in the interest of being completely honest, I have not found the Gold Monster at 45 kHz to be particularly sensitive to electrical interference and while in the middle of nowhere Nevada I often just turn the machine on and go about my business will no ill effects noted. The raise coil and point at nearest electrical source is a very good habit to develop, but in my experience at least it is not as critical for me as it appears to be for others.

I am always going to use the deep seeking all metal mode whenever possible. This is not just because this mode goes deeper, but also because the coil is more forgiving about reporting items that are not centered well under the coil. The discrimination mode has the net effect of reducing the overall size of the detection area under the coil. This means that when running in the iron discrimination mode more care should be used to overlap sweeps. When my goal is covering ground that little bit of extra ground coverage per sweep does add up and all metal mode helps reduce the chance a nugget will be missed on any given sweep.

The Gold Monster is noteworthy in that Minelab finally seems to have realized that the speaker actually needs to be loud enough to hear! I am quite enthralled by the boosted audio and the way the smallest targets pop even with my admittedly poor hearing. In fact, the Gold Monster bangs out so loud without headphones that I will often run a notch down from the maximum volume setting - it's so loud that in quiet locations it can be too loud. The volume control is also a secondary sensitivity control in a way, and so I usually run it full out. I do this as much to help create a forced threshold sound as to enhance my ability to hear small targets. More on that later.

One of the greatest features on the Minelab Gold Monster 1000 is the automatic ground tracking. In my ground at least it is very efficient at effortlessly keeping up not only with ground conditions but in taking the edge off many hot rocks that would be problematic for other detectors. The beauty of this is that it eliminates the need to keep up with and make small adjustments to the ground balance control as would be the case with a detector that lacks an efficient automatic ground balance. I think most companies are equivalent when it comes to many features, but I do think when it comes to automatic ground tracking technology that Minelab has been and continues to be the industry leader. I was a "manual tuning only" diehard for a long time, but my experiences with the Minelab SDC 2300 in particular taught me to let go of that old thought process.

The automatic ground tracking shifts the burden to the sensitivity control as the prime operational control on the GM1000. Minelab has positioned this control close enough to the center of the control panel that it is easily manipulated up or down with a thumb press by either left or right handed individuals.

To summarize, I will raise the coil and point it at the nearest electrical source and then I will power the detector up and wait until it completes the frequency scan. The Gold Monster defaults to the last settings and so my machine will already be in all metal mode, but if not I will switch to that. From there I will go to manual sensitivity setting 7 and do a short walk around sweeping the coil over the ground. For me this means the coil is sliding lightly over the ground or no more than a few millimeters over it.

So far for ground I have been frequenting the magic settings are 6 - 7 - 8. With the Gold Monster at full volume what I am seeking is a very minimal amount of ground feedback. These are very soft sounds that are quite unlike the hard edged pop of a genuine target. These sounds are created by the sensitivity being so high that ground noise is just starting to overcome the ground tracking ability to silence the ground.

The problem with a silent search machine while in manual ground balance mode is that without a threshold you can end up leaving some performance on the table. If a setting of eight generates a little ground feedback, and you decide to go with 7 to make the machine completely silent, there is nothing wrong with that per se. However, if the ground changes and gets milder you may have the ability to run at a higher level of sensitivity, and without a change in the audio to alert you to a change in the ground, you will just leave the setting where it is.

In my case if a setting of 7 is completely silent, I will bump to a setting of 8, and this almost always gives me that little ground feedback I want. If 7 is too noisy, I will drop to a setting of 6 and this will probably do the trick for me. The range between each setting seems about perfect for a person to settle on a range of three settings, too little, too much, and just right. For my areas 6 - 7 - 8 are the magic numbers. For worse ground the range may shift lower, to 5 - 6 - 7.

Try and picture this. At sensitivity 7 I am just scanning along, coil lightly on the ground, with soft ground feedback, waiting for that hard little signal that even the tiniest target will generate. Then all the sudden the machine goes dead quiet. I have entered less mineralized ground. One thumb tap to sensitivity 8, and I get my "false threshold" back.

Or, at a setting of 7 the machine gets noisier. Maybe a little alkali patch or more mineralized ground. A quick tap down to 6 reduces the feedback to my desired minimal level. What I am doing is letting the ground tracking do its job, and then just bumping the sensitivity up or down a notch to ride the ragged edge of best performance for the ground.

"Gee Steve, sensitivity 6 - 7 - 8, aren't you giving up lots of depth running at 6 or 7 or anything less than 10"? My air testing...."

A pox on air tests! They have uses but have little bearing on how to get the best performance out of a detector in the field. I do like to run my detectors hot and that does often mean with some ground noise, but it has to be kept within manageable limits. For the purposes of covering a lot of ground pushing the GM1000 to the edge is good but any farther and everything sounds like a target and knock sensitivity shoots up dramatically, especially at the hyper sensitivity settings of 9 and 10. The reality from what I have seen so far is that the Minelab Gold Monster 1000 at settings of 6 - 7 - 8 will match or exceed most detectors in its class. Let's save manual sensitivity 9 or 10 for my next detecting scenario up next.

Again, a reminder that 6 - 7 - 8 is working well for me in moderate ground. In more mineralized ground it may be 5 - 6 - 7 or even 4 - 5 - 6. If you simply listen to the machine it will tell you where you need to be. Too high, too low - just right. I have actually found gold with the sensitivity as low as 3 when in some nasty salt encrusted ground. People seem so adverse to lowering sensitivity I often wonder how many would just give up before going that low. It just can't find gold set that low, can it? Yes it can. You either tame the ground or go home and even though depth is reduced you can still find gold a low sensitivity settings if that is what it takes to get stable performance in the worst ground.

So what about auto sensitivity? Simple really. If you are finding that you are having to bump the sensitivity up and down too often (you will know when that is for you) then it is time for Auto sensitivity. Auto sensitivity is different than manual in that you can trust it to keep the detector at the optimum level even if running silent. In general Auto is the silent running mode whereas Auto+ usually introduces a slight amount of ground feedback at full volume. As I mentioned earlier the volume control acts as a secondary sensitivity filter and running it lower can reduce or eliminate slight ground noise while still allowing targets to sound off loud and clear. Auto+ works best for me in most places but if need be I can drop to simple Auto for more difficult variable ground where Auto+ may get too noisy.

OK, we have been hunting as described above and get a target. What next? If you are digging everything, a good practice, then just recover that target. If it is faint, either bumping the manual sensitivity up two points or dropping out of Auto into a high manual setting can aid greatly in pinpointing and recovering the target.

What about trash? Too much and I don't want to dig them all? I am hunting in all metal mode and I rely on the meter to make a dig or no dig decision. In some ways it is a probability thing. If a few sweeps over the target from various directions produce a series of "hard left" ferrous meter responses, the target is likely ferrous. My goal is to try and coax a non-ferrous response with the meter kicking to the right. Just one non-ferrous response raises the odds you have a non-ferrous target. Even then I might pass in a trashy area, but two or more non-ferrous responses and you had better just dig it. Small nuggets in mineralized soil are fighting the ferrous content of the soil itself and in bad ground the ferrous ground response often wins. If you are looking for gold look for reasons to dig targets, not reasons to walk away. The amount of trash will help determine just how aggressive or lax you decide to be in these dig or no-dig decisions.

Running is disc mode should be reserved for situations where there is no other option. It may be needed to eliminate a certain hot rock response. Or there may be multiple trash targets per swing - you can't analyze them all. The iron discrimination mode can be a real lifesaver in these instances.

However, consider the borderline nugget that will read ferrous seven out of ten swings. That means you only have a 30% chance on a single pass over the target of having the machine give an audio non-ferrous report while in iron discrimination mode. The odds are even worse if you are not perfectly over the target, a bit too high, or swinging a little too fast. If the detector decides ferrous on that first pass, you get no sound and go right by, never knowing it was there. This is where detectors with a ferrous tone have the advantage in alerting you to every target so you can double or triple check. With a silent rejection system you get just one chance at the target and if the detector is wrong, the nugget is missed.

Minelab Gold Monster 1000 Iron Discrimination Mode Versus All Metal Mode

All metal is more forgiving in multiple ways, but mostly by alerting you to every target, allowing you to stop, get the coil lower if need be, slow the sweep, change the angle, etc. all with the goal of trying to coax a non-ferrous response from the target. I highly recommend that if you use discrimination you use it sparingly and conservatively, and only go to full blown iron disc mode it you must. We all have a different threshold for when that will be but rest assured hot rocks or thick trash will pretty much force the issue.

That sure sounds complicated! In practice, hunting at sensitivity 6, I am going to get a signal. If it is faint, I will bump the sensitivity a couple notches now that I am on target. Too hot for general hunting but fine for spot checks. The target response will enhance, giving much surer results on the discrimination meter, and allowing for easier pinpointing and recovery. Target in pouch, sensitivity back down two notches and I am on my way again.

For extreme ground JP has a bit more complicated method for getting back into the hunt as described here. For me personally hunting in moderate ground simply going back to my base sensitivity setting and swinging away is working fine. Again however, I am discussing just general detecting at this point, not getting the best and finest edge on the performance. Which leads me to....

...that 20 foot by 20 foot spot I want to clean out. The 5" coil has an edge on the really tiny gold and in more mineralized ground in particular it "sees" less ground and is the coil of choice for cleanup duty. In moderate ground I run the Monster at manual sensitivity 10 and much like running my GPZ 7000 fully maxed out with Steve's Insanely Hot Settings I tame the machine strictly through coil control. This means moving at a crawl, and because at sensitivity 9 and especially 10 some knock sensitivity is introduced, I employ my magical ability to keep a coil 1 mm off the ground while never touching anything. In severe ground sensitivity 9 or 10 may not be attainable at all, and as always I defer to JP and his operating procedures for dealing with really bad ground. But for my milder ground I can crank the GM1000 all the way up and even with the 10" coil hit gold down to around 1/10th grain and with the 5" coil smaller yet. Again, extreme coil control is the answer here but the catch is that you are never going to cover much ground in a day doing this. If covering ground is the goal, stick with more stable settings. But if you want to chase flyspecks (they do add up) then be very patient while working the coil and the Minelab Gold Monster is pretty amazing in what it can do.

I do hope this helps somebody somewhere. Again, all I am doing is telling you what I am doing and what is working for me. If you prefer to do something different by all means - I am not trying to say these settings are the "best settings" as in my opinion there simply is no such thing. The best settings for my wife would probably be Auto sensitivity while in disc mode. "Here honey, swing this closely over the ground, and if it goes beep, dig it up." Different ground and different experience levels mean different settings. Never be afraid to experiment. If you only use settings you find on a website and never experiment yourself you will never truly learn any detector and what works best for your circumstances. Good luck out there and above all, have fun!

More Information On the Minelab Gold Monster 1000 Sensitivity Settings

Photo below: Some gold I just found, 4.9 grams total. The top four nuggets were found with the GPZ 7000 (largest nugget 2.2 grams) and the bottom nine with the Gold Monster 1000 (smallest flake ?? gram) using the methods described above.

[IdahoPeg]

Very interesting and informative write-up Steve. My GM1000 use falls into your "20x20" clean up category....small coil, manual 10 most of the time, deep all metal. You gave me some good pointers for when I use the larger coil! :-)

[Bhogg]

   Fantastic Post Steve,

Great to see some good informative information on the GM1000 It really helps to fully understand the machine.

Thanks Steve

[ophirboy]

Thanks for the information . it's good to get alternate views on how to run this machine rather than get stuck in a rut and forget to experiment with new ideas . 

Cheers PM??

[Steve in Idaho]

Very good info Steve. You should go to work for Minelab and write instruction books for them. The GM 1000 book is short on good instructions..

[Chet]

Hi Steve

Great write up; a lot of great information.

Thank you,

Chet

[mn90403]

I'd have more to say if I had one but I can tell it is a good GET TO KNOW what you are doing instruction that helps all of us with more than just the GM 1000.

Mitchel

[Steve Herschbach]

Thank you everyone for the kind comments. It does help make four hours of two finger typing worthwhile!

It is very often the case when I lay hands on a new Minelab that I scratch my head and wonder what they were thinking about certain things. The initial impression can sometimes be underwhelming. Without fail however as I use them and learn them I become more impressed with the only thing that really counts - the ability of any new Minelab gold detector to put gold in my pocket.

I strongly believe that all detectors have strengths and weaknesses. It seems to be a badge of honor for many people on the internet to focus on the weaknesses. In fact some people do not seem to consider any review of any detector to be legitimate unless it is liberally sprinkled with commentary about how the machine fails in various ways.

That is just so easy. I can tear any detector apart. Pick any detector, and I could tell you how badly it sucks in various ways. Especially if I take the attitude that the only thing of importance is my needs, wishes and desires. The fact that what one person does not like may very well be just the ticket for a lot of other people is lost on the "Debbie Downer" crowd. People betray a small minded provincial attitude when they declare a detector no good when others around the world are able to use the very same detector successfully.

I on the other hand take great pride in the fact that you can hand me almost any decent detector and I will go out and make it perform. I do that not by focusing on what detectors can't do but by determining what they do best and then leveraging whatever strengths they have to my advantage. This does often take some time and effort in using the machine enough to see where it really shines.

I also think it is inappropriate for me to look down on anybodies choice in a detector model. I would rather try to genuinely help that person out with being successful with whatever detector that fits their circumstances in life, unless it is wildly inappropriate for the application. I have noted an unfortunate tendency on some forums for PI owners to basically rain all over VLF owners when they ask for help or advice, the answer often being "you wasted your money - buy a REAL prospecting machine". Oh really. That may be locally true but worldwide VLF detectors have produced and continue to produce tremendous amounts of gold.

Long story short the Minelab Gold Monster is another detector that has grown on me the more I use it and become more familiar with it. I just seems easy for me to find gold with it. Yeah, it's a VLF with the limitations inherent in the technology but there are strengths also in sensitivity to the tiniest gold and in discrimination that can be very useful, and all in a simple, affordable detector. Certainly there are places where it will struggle and it is not for everyone, but for me at least and in Nevada in particular it is a sweet little detector.

[Steve Herschbach]

Picked up by Minelab (with permission) and republished as a Treasure Talk entry.

0.7 gram nugget found with Gold Monster 1000