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GPX 4500 compared to GMT for small gold


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Doug,

Now that you own a GPX 4500 and a GMT (Great Metal Detector!). You'll find both have their places to be used. I have hunting buddies that bring both detectors into the fields. They find the targets with the 4500 (mono coil) and use the VLF to see if it worthy of digging! Seems like a waste of time to me, just dig it with the first detector! But, it works for them. Now, I use a GPX 4000 and I find 2.4 grain pickers fairly common. My buddies that swing the GPX 4500 consistantly find these small pickers and they use the 11" Commander Mono. After all the ducks are picked off the top of a patch, I like to use a bigger coil (12x15) and set my detector for a deep slow search. This setting isn't the best for shallow small pickers, which can produce some skunk days, when your buddies are pulling shallow dinks out right behind you! This doesn't bother me when I know there are bigger nuggets they miss with the shallower settings of their detectors. When you get back down to your local gold producing area (Greaterville) use your new detector in the same places that your VLF has produced for you...you'll find gold you left with the VLF. Looking forward to hunting with you this Winter!

LuckyLundy

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Hi Luckylundy

Thanks for the good info. was wondering about this one. Don't have a 4500 but do have a GMT

and won't part with it. When I get out to the G fields I do about the same as you but with a TDI

for depth, Maybe when I grow up I'll get a 4500!!

Thanks

Herb

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Aloha everyone,

Glad that LuckyLundy jumped in on this one as a very happy owner of the GMT I would only consider paying for a 4500 if I won it big here in Vegas! Dont think that it will happen soon tho. :grrr01:

I still say that once you get your ears "trained" to the GMT sounds you should be able to find just about any size gold. Just my :twocents: :twocents: !

Other than that I wont touch this topic with a 50 foot pole.

Will be interesting to see what pops up tho and am looking forward to the many posts on this subject.

Aloha and be safe out there,

Stan aka Kaimi

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Hi All, I ran my own test today, I dug a 4 inch hole ,filled it in after placing a half gramer in it. First I tried the 4500 w/the stock coil. I tried to set it the best that I could using different settings. The best that I could do,was to faintly hear the nugget. I then tried the GMT, I got a good signal . It was like an old friend talking to me . I am sure that I will do better with the 4500 when I run it for a while ,but for now I will search for the small ones with the Gmt and go back over the area with the 4500. Thanks to all that replyed. Doug :icon_mrgreen: :icon_mrgreen:

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I have never found anything smaller than a 1/2DWT in Greaterville with a 4500. I have with a GB2. But then again I doubt I know how to run it. I use the GB2 most of the time. I haven't been down there since someone claimed up most of the ground. Hated to see that happen cause it always gave me gold just about every trip.

Happy Hunting, AL. C

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Silver doug you said a half gramer at 4 inches?with the 4500 and you did not hear it ,If those are the facts you are giving ,Then the machine was not tuned or set properly,I can hear 6 gr at 6 inches at one location.Do not mean to kick the hornets nest but it seemed off to me. I also use a vlf .But not to double check the 4500.Just for different gold :twocents:

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The composition of the nugget may be the reason Doug can barely get a signal...I watched Reg cause great amazement and some disappointment when he bet a 3000 user that the 3000 would not detect his "invisible nugget"...I believe the nugget was from the Greaterville area and given to Reg by Mr John B.

Fred

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Hi Fred,

You are right, the "invisible" nuggets were given to me by John B and I want to thank him once again for them. They make testing modifications to PI's much easier to do when trying to detect the really small stuff. Now, John B is the guy who has the interesting stories about invisible nuggets and PI's. Hopefully, he will chime in with a few of them.

The fact is, the detection of small gold by a PI is difficult because of the design of the detector and the signal response from the gold. Small gold generates a very short signal time wise. A PI works on the principle of generating a strong signal into the coil, shutting it off quickly and then waiting for a brief time before looking for a signal. What happens on small gold is the signal from the gold is gone before the PI is even checked for a signal.

Now, the exception is the guy who claims he can detect microscopic gold with his SD. He actually has a following that believes the same. Unfortunately, he only posts on another forum.

Now, I would like to thank doug for the honest post. Some people wouldn't do that. What Fred says is true, there are reasons similar size gold can respond differently on your PI. So, a weak signal from the nugget you tested might change to a stronger signal from a similar size nugget from another area. At the other extreme, the signal could get worse also. What makes things confusing is your GMT will generate a stronger response on all the nuggets mentioned simply because it works on a different principle.

One other thing to keep in mind and that is the signal strength from small gold can vary with the type of coil used on the PI. Someone said that a comparison chart or at least information was posted on the AZ outback forum but I never found it. If anyone has a link to the comparison I would appreciate a link.

Reg

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Hi Rich,

Thanks for the link. The charts make sense and basically coincide with what will happen or depth of detection as plotted by Eric Foster many years ago. Eric's chart looked at max depth based upon the coil diameter versus the size of object and what happens when the coil size is varied. So, Eric's charts look at the results rather than the field strengh.

I have uploaded that chart for people to see. In short it points out if the maximum depth a target can be detected is equal to the radius of the coil used, then there will be a depth loss if a larger coil were to try to detect the same object. It also points out that if the detection range is greater than the radius of the coil, then the increase of depth of detection can be estimated from the chart by simply looking at the vertical line passing through the target depth and where it intersects the larger coil size.

My testing indicates this chart is quite close and can be used as a good reference in most ground conditions. Obviously, there will be variations or anomalies, but the chart works in most cases.

Reg

post-449-1249067042_thumb.jpg

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Hi Doug

The bulk of the nuggets you've already found would not be heard by the 4500 :Huh_anim]: . If they are audible to the 4500 they will at best be heard at shallower depths than your GMT will hear them at :angry-smiley-010: . Hunting very course gold and disceminated species at the source is best hunted with your GMT the 3 times deeper beeper :woohoo: !! You will however be shocked at the deep trash in the area your hunting with the 4500 :confused0013: !! Happy Huntin John B.

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Doug,

The stock coil on your GPX 4500 is a 11" Commander DD. Remember, that your DD coil is half Mono. If I'm running my DD coil It's common for me to run it in Mono even with the Iron Reject (Discrimination) Max'ed out! It's and easy flip of the switch back to DD mode. If I get a very faint signal in DD, I'll switch to Mono and it's a much better signal (target) strength. Don't forget to run your Gain as high as you can...this will make them little nuggets talk to your ears. Your VLF has a different sound than the Minelab will make on your targets (gold). You'll have to mess around with your Audio Tone, Signal Peak and Threshold to find the tone you like the best...the Factory Preset (FP) is just your starting point. Them ghost nugget are true! I've found nuggets with my VLF in patches hit by Minelabs, but that's one to their 50 nuggets. Just got back from a long weekend of dredging and the weather in the lower foothills is fantastic this week...NuggetSlayer and I will be out at the patches this week. Keep practicing!!! I do.

LuckyLundy

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Hi Doug

The bulk of the nuggets you've already found would not be heard by the 4500 :Huh_anim]: . If they are audible to the 4500 they will at best be heard at shallower depths than your GMT will hear them at :angry-smiley-010: . Hunting very course gold and disceminated species at the source is best hunted with your GMT the 3 times deeper beeper :woohoo: !! You will however be shocked at the deep trash in the area your hunting with the 4500 :confused0013: !! Happy Huntin John B.

Thanks John, That confirms what I thought. At least I won't spend the rest of my life trying to make the 4500 do what it can't. :grrr01: :grrr01: Doug

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Doug,

The stock coil on your GPX 4500 is a 11" Commander DD. Remember, that your DD coil is half Mono. If I'm running my DD coil It's common for me to run it in Mono even with the Iron Reject (Discrimination) Max'ed out! It's and easy flip of the switch back to DD mode. If I get a very faint signal in DD, I'll switch to Mono and it's a much better signal (target) strength. Don't forget to run your Gain as high as you can...this will make them little nuggets talk to your ears. Your VLF has a different sound than the Minelab will make on your targets (gold). You'll have to mess around with your Audio Tone, Signal Peak and Threshold to find the tone you like the best...the Factory Preset (FP) is just your starting point. Them ghost nugget are true! I've found nuggets with my VLF in patches hit by Minelabs, but that's one to their 50 nuggets. Just got back from a long weekend of dredging and the weather in the lower foothills is fantastic this week...NuggetSlayer and I will be out at the patches this week. Keep practicing!!! I do.

LuckyLundy

Good to hear from you Lucky.I tried the DD in Mono and it is louder. I am going to Greaterville next weekend and will do some pacticing, I might even find a nugget or two, if the Gold Gods are with me. Dredging sounds cool to me, much better than fighting the heat. Hope that you need help carrying the gold down the Mountain. Happy hunting. Doug :icon_mrgreen:

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Hi Guys,

Not a this versus that thing for me. I own both the GPX-4500 and GMT. Just got back from a trip, in fact, where I used both.

My GPX is a great unit. But this location, while it does have some larger nuggets, is just chock full of little gold. I mean to the tune of over an ounce per yard in some places. Bottom line is I can go over a spot with the GPX and pull out some nice nuggets. Then I can take the GMT with a small coil and scrub the ground and get all kinds of little stuff. I can hit tiny stuff weighing 1/10th grain or less. Seems silly until you drop thirty or forty 2 grain and 1/2 grain and 1 grain nuggets in your vial in a short period of time. They can add up pretty quick.

But after some fun detecting we just set up a highbanker. That little spot got us 2.25 oz of nice gold out of about two yards shoveled.

Anyway, I've just got to have both. Gold Bug 2 is great also.

Steve Herschbach

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Anecdotally, I "once" found a .2 grammer with a 16" NFM coil on my GP. Actually, I only detected a marginally suspicious ee - ew whisper, then came back later with my GB2 and recovered the little nugget. I consider this an anomaly that should be taken for what it is worth -- certainly not a general rule. On a different note, certain birdshot (#4s and up) induce a "warbly" reaction in my GP when rigged with a 14" NFE. My GB2, of course, will positively scream at birdshot down to the smallest #9s. But the one grammers and up found in 10" or deeper are pretty much beyond the capability of a VLF, whereas the GPs and SDs have not much trouble at all. Each is a specialized tool for a special purpose. There is a place for each in my equipment inventory.

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Hi Guys,

Not a this versus that thing for me. I own both the GPX-4500 and GMT. Just got back from a trip, in fact, where I used both.

My GPX is a great unit. But this location, while it does have some larger nuggets, is just chock full of little gold. I mean to the tune of over an ounce per yard in some places. Bottom line is I can go over a spot with the GPX and pull out some nice nuggets. Then I can take the GMT with a small coil and scrub the ground and get all kinds of little stuff. I can hit tiny stuff weighing 1/10th grain or less. Seems silly until you drop thirty or forty 2 grain and 1/2 grain and 1 grain nuggets in your vial in a short period of time. They can add up pretty quick.

But after some fun detecting we just set up a highbanker. That little spot got us 2.25 oz of nice gold out of about two yards shoveled.

Anyway, I've just got to have both. Gold Bug 2 is great also.

Steve Herschbach

Steeve, It sounds like you have a great patch. If I had the GPS reading it would be a great place to start. :laught16::laught16::laught16: Only kidding, thanks for your help. Happy hunting. Doug

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