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View Full Version : AT Gold and GMT

03-11-2012, 06:48 AM
For awhile I was sold on the Garret AT Gold now I am reconsidering the Whites GMT based upon its higher frequency for very fine gold. Not looking for coins, not exactly hoping for nugget success but I know of some pl;aces that has very fine gold traces. Friend of mine has a claim and we have been doing some talking, he sluices and knows nothing about Md's, me I don't want to get financially burdened with highbanking and such as my day job pays well. Just a weekend electronic detecting for me.

Steve Herschbach
03-11-2012, 09:08 AM
Detectors do not react to what I call very fine gold or traces of very fine gold. A gold pan is a better tool for that job.

03-13-2012, 06:20 PM
For the sake of a topic continuation I would like to add that I have just purchased the Whites GMT from Alaska Mining and Diving, this MD has simple yet revolutionary software from what I have learned in just a few hours that makes it almost automatic. Well I love gadgets, I have the hottest latest smartphone, yet I can only understand a fraction of it, the GMT can be left in the "auto" mode or can be manually ground balanced, it doesn't have to be twiddled with every ten feet, I like it and I'm just itchin for an early breakup and thaw. Thanks Rick!

silver dog doug
03-14-2012, 10:04 AM
I have 2 GMT's. One is a back up, along with my ML GPX 4500. To be honest, I use the gmt more than the 4500. If your looking for nuggets that weigh less than a tenth of a gram, it will find them. I found 5 nuggets last Sunday, weighing .06 Dwt. in all. Just my two cents. Good luck. Doug

04-07-2012, 05:32 PM
I just bought one (GMT),,,, hoping that it is all that I have read about it. I have been reading all I could get about most of the VLF and a few PI units specifically for nuggets. Hope I made the right choice :cool:

04-13-2012, 10:10 AM
as usual I have buyers remorse,,,,, I keep thinking the GBPro is more advanced because it's newer,,,, anyone have both can you tell me if I should have swung the other way?

Steve Herschbach
04-13-2012, 10:53 AM
The GP Pro is a general purpose detector so a good choice if you want to look for gold nuggets, coins, relics, and jewelry. If you are strictly into prospecting the GMT will easily hit smaller gold than the GB Pro. The GMT is a single purpose prospecting detector.

04-13-2012, 07:52 PM
The GP Pro is a general purpose detector so a good choice if you want to look for gold nuggets, coins, relics, and jewelry. If you are strictly into prospecting the GMT will easily hit smaller gold than the GB Pro. The GMT is a single purpose prospecting detector.
that is the exact reasoning I used to get the GMT,,,,, thanks for your help,,, it calmed my nerves a bit,,, but a little gold nugget would surly do a better job,,,,lol

07-25-2012, 12:16 AM
I had the privilege to detect with Doug at Ganes Creek (week 1) and can attest to his great ability to find both the tiniest nugget to a beautiful piece that looked like the head of a lion.

Aloha Doug and Mahalo (THANK YOU) for the time we spent together. The Amakua (Gardian) of Ganes Creek treated us vey well and I will remember the trip forever.



08-14-2012, 03:56 PM
If a person is searching in a medium mineralized goldfield where tiny gold is not a goal, with mainly a lot of 'iron trash' and/or 'bad hotrocks' about, then what is a better choice, the GB Pro or GMT or AT Gold or F75.??

Steve Herschbach
08-14-2012, 07:26 PM

08-16-2012, 11:03 AM
Thank you Steve, in your link above, I understand what you are saying that all modern VLF's are high quality & about equal in performance except for kHz for smaller gold, and luck & the detector operator(person) is the main difference.

BUT I thought some VLF's in the goldfields were better than other VLF's at visually IDing(indentifying TID numbers) for 'iron trash' and 'hotrocks' while hunting for gold nuggets, this is what I wanted to know. Because on the F75 which have TID numbers for 'iron trash' and 'hotrocks' in true All Metal, where the X-Terra 705 has no TID numbers in true All Metal(Prospecting Mode has only Iron Mask). The AT Gold has a detailed iron resolution TID and the GB Pro has 3 or 4 sources of TID information. The GMT has an iron feature.

So which VLF has the best TID(Target ID being the visual numbers) capability to indentify 'iron trash' and 'hotrocks' in low to mildly mineralized goldfields.??

Steve Herschbach
08-16-2012, 02:33 PM
Actually, all the units at Ganes Creek are being used because they do well at sorting ferrous trash from non-ferrous items in a moderate ground condition, with no emphasis on small gold. If there was a BEST unit everyone at Ganes would use it. Historically the White's MXT has been the favorite but many detectors introduced since it came out offer similar performance. I linked to that post specifically to highlight no one unit being clearly superior in this regard.

Detectors either work in a pure all metal mode, or results can be filtered (discriminated) via audio or visual target id numbers, commonly referred to as VDI (Visual Discrimination Indicator) numbers. Pure all metal is not filtered except for ground response and so offers best depth. This is as opposed to filtered discrimination modes, which lose depth. Even a discrimination mode set to accept all targets still loses depth due to the filtering so it is important to beware the so-called "All Metal" mode offered on some units as it is sometimes not a true all metal mode but a discrimination mode set to accept all targets. The X-Terra 705 has what is called "All Metal" when in fact it is the notch disc mode set to accept all targets. The X-Terra 705 Prospecting Mode is the true All Metal mode.

Usually you have to choose between the All Metal mode and the Discrimination mode. You choose either max depth, or give up some depth for some discrimination ability. Many units do offer alternatives however. Most offer all metal audio combined with metered discrimination, where the audio gets full depth, and the meter kicks in if the target is in reach. Some units run in "mixed mode" where you get audio discrimination as far as it will go and full audio all metal depth at the same time. A rare few pipe one audio response (the all metal) into one ear, and the other response (the filtered discrimination) into the other ear. This ability to see or hear the results of both the all metal channel and discrimination channel at the same time can be very desirable compared to having to choose one over the other. If nothing else it eliminates lots of switching back and forth.

The GMT and X-Terra 705 in Prospect Mode, and AT Gold in All Metal mode all also offer iron discrimination ability to help identify iron targets while in all metal. None of these methods offer a target id except to try and identify a ferrous target as such. The GMT uses both a probability meter and audio "grunt" response. These methods are distinct and separate from target id type discrimination and may or may not be user adjustable.

The whole concept could be expanded on in detail on the pros and cons of the different methods but the fact is no one method has a clear edge, with many users preferring one system over another. All suffer from exactly the same problems:

1. As mineralization increases, target identification of any sort becomes less reliable

2. As depth increases, target identification of any sort becomes less reliable

3. As target size decreases, target identification of any sort becomes less reliable

4. Combine items 1 through 3 above and any use of discrimination is likely to cause small gold nuggets or large very deep nuggets to be mis-identified and rejected as ferrous

I know very well the desire to have one unit or another identified as clearly "the best" but I can rarely draw that distinction. There are too many very good, very competitive detector models all so very close that small differences in actual ground mineralization, hot rocks, and size and shape of both gold and trash all combine to give one unit or the other a slight edge at some locations and a slight deficit at other locations. Very often it simply boils down to user preference. Unfortunately that means just trying them to see what works best for you.

For me it is fairly simple. I do not like to be forced to choose either/or. For instance, the Gold Bug 2 requires me to hunt in all metal for max performance, then flip a switch to get an iron id check. This leads to lots of switching and even worn out switches! Better to have a unit that gives me both indications at once so I get the full performance possible combined with target information when it is available. What I have found is none of the systems are 100% reliable, so whatever system is employed, I only pass on a target if it is a very high probability of being ferrous. That is when I am not doing what is best - digging it all.

So you asked "If a person is searching in a medium mineralized goldfield where tiny gold is not a goal, with mainly a lot of 'iron trash' and/or 'bad hotrocks' about, then what is a better choice, the GB Pro or GMT or AT Gold or F75.??" and "So which VLF has the best TID(Target ID being the visual numbers) capability to indentify 'iron trash' and 'hotrocks' in low to mildly mineralized goldfields.??"

My answer - none is clearly superior in this particular area. All can identify ferrous items or hotrocks visually while in all metal mode. All can be fooled. Other features better define the units, such as the GMT small gold capability or AT Gold being submersible.

The GMT has one of the most straight forward systems in the "Probability Meter" in that it is telling you right up front all you are getting is a best guess. It never goes below 10% on gold and never above 90% on iron, admitting there is always a chance it is wrong. The "iron grunt" audio kicks in at 80% or more. I am not saying this system is superior, just refreshing honest. You only get 100% id when an item is in your hand.

The X-Terra 705 although it has no visual id does have an adjustable "iron mask" setting in Prospect Mode which allows you to set the audio rejection point from less to more aggressive.

I am using the F75 mainly because I like the weight and balance. There are many units I could use that would do just as well. I do like having a separate all metal audio and visual target id (personal preference) and I find it harder for me to concentrate on mixed audio modes. This way my ear need simply try and hear a target. Then I work the target and if I get no target id or anything less than a solid ferrous target id I dig it. When I first got the machine I made the mistake of digging only solid non-ferrous readings, and that cost me some gold for sure.

I should point out that Ganes Creek wizard Dave Rankin hunts the pushes after everyone else with his White's MXT and constantly bangs out nuggets everyone missed. He is an example of a person who has truly mastered the machine and how the Relic "Mixed Mode" actually works by giving an all metal third tone on targets deeper than the two tones generated by the filtered discrimination circuit. Most people only hear and respond to the two primary tones and miss the deep nuggets.

It is easy to get pat answers on the internet. All the units have forums specific to them so if you ask on the Gold Bug forum what unit is best guess what answer you get. Or dealers push the brand they sell. Me, I am currently using (in alphabetical order):

Fisher F75 Special Edition - My "Ganes Creek unit" for large nuggets in trashy areas

Fisher Gold Bug 2 - My "go to" unit for tiny gold

Fisher Gold Bug Pro - Jewelry detecting

Minelab CTX 3030 - Jewelry, silver coins

Minelab GPX 5000 - Gold nuggets in mineralized ground

White's DFX with Bigfoot coil - Jewelry hunting in turf

I am not brand centric and do most any type of detecting so I always have several detectors for different uses, and am always fine-tuning the selection. Right now I need a new salt water unit for Hawaii, a place that has always given any detector I have used in the surf a tough time. I have yet to ever decide on a "best" unit for Hawaii. They all seem to come up short one way or another and so I am forced to consider lots of "second best" units with none getting the "best" label. Such is the decision often faced with detectors and so I often sound evasive when being asked to pick a "best" unit. There rarely is such a beast; it usually boils down to considering pros and cons and making compromises.

08-20-2012, 03:26 PM
I don't think the F75 should be in that group of MD's,,,, I like the iron grunt ID on the GMT,,

Steve Herschbach
08-20-2012, 04:30 PM
Hi grouser,

His group or mine? His group was with the very important caveat "where tiny gold is not a goal". And if tiny gold is not the goal then the F75 is a very capable detector.

That other group of metal detectors are my own - I am not telling anyone to use what I do, I am simply telling you what I am using and why. Since my F75 SE has found over a half pound of nuggets for me I think I will have to stick with it a bit longer.

Now, after that defense of the F75 I do think you have a point about it compared to the Gold Bug Pro, AT Gold, and GMT. It is a nearly $1000 detector and so sticks out as more expensive, and the extra you are paying for is not for prospecting. The other units are $700 more or less, so in a better bang for buck range.

The GMT is a superb nugget detector, the most popular dedicated nugget detector sold in Alaska. Hot on small gold, easy to use, and a bargain for the price. You can certainly make a case for it being a good choice out of the detectors he asked about. Unlike the AT Pro, F75, and Gold Bug Pro it is pure nugget detector.

Got the Bug
08-20-2012, 05:10 PM
Steve' are the Fisher Gold bug 2's " Which I bought 1 @ A.M.D. " and the GMT's on the same level, or is one better then the other for differant reason's / feature's ?

Steve Herschbach
08-20-2012, 05:32 PM
The Gold Bug 2 was designed for Fisher by then lead engineeer Dave Johnson. The GMT was designed for White's over 10 years later with Dave Johnson as lead engineer. So the detectors are more similar then you think. Both are designed to find tiny gold nuggets in mineralized soil.

The GB2 runs at 71 kHz and the GMT at 48 kHz. With its higher operating frequency the GB2 has just the slightest of edges on the detection of the tiniest gold flakes, pieces weighing 1/10th of a grain or less. But at the price of a very significant reduction in depth on larger nuggets. The GMT has a far better balance of sensitivity on small nuggets while retaining the ability to hit larger gold at depth in minerailzed ground. Further, the GB2 is a purely manual tune machine while the GMT offer both manual and automatic ground balancing.

The bottom line is two-fold. For the Kenai Peninsula with its low mineralization and small gold, the GB2 affords a small advantage to those willing to learn it, especially when paired with the 6" coil. However, at AMDS we have found that many people are not willing to make the effort, often because they may only detect once or twice a year. The GMT is a better choice for those wanting more turn on and go ability and for this reason is the more popular of the two.

In more mineralized ground and on larger nuggets the GMT can have a significant advantage over the Gold Bug 2 for depth. The GMT also offers on-the-fly iron discrimination where on the GB2 you have to switch back and forth between the two settings.

The GB2 is "old school" in that it is one of the remaining analog designs on the market, whereas the GMT represents newer microprocessor based designs. The GB2 is near the end of its life as it is getting hard for Fisher to find the analog components required to make the unit. I have two myself just in case that happens.

Both are excellent units when used properly and with die-hard fans in both camps.

Got the Bug
08-21-2012, 03:50 PM
Thanks Steve, I am more then happy with my GB2 but I have heard alot of good about the GMT also. But nobody could explain it to me to where it made much sense, until now. Wanting to pick up another machine just didn't need two that were that close to each other. I think I would like to look into a serious big nugget / depth mach. any suggestion's. Best bang for the buck type machine. Any body else out there that has some time on different machine's if you have a minute drop your 2 cent's in. Appreciate it, Ken " Got the Bug "