By Steve Herschbach
Some random notes, and if you don't know what I am talking about as regards some detail of this machine or that I apologize.
Well, I finally updated my XP Deus with 11" coil to the version 4 update. Then I hauled it and the Nokta Impact with 11" and Teknetics G2 with 11" out for several hours of cross checking coin type targets. The G2 is a Gold Bug Pro variant running at 19 kHz and I put it up against the Deus at 18 kHz and Impact at 20 kHz. I acquired the G2 new recently to use specifically as a benchmark unit because I am very familiar with it and because in my opinion it does 19 kHz as well as it can be done. I spent hours swapping machines as the hunt machine, then cross checking the undug targets with the other two. Lots of settings tried, with the main goal to try and find some deep fringe type target or target in trash where any machine can get a clear and definable edge.
Well good luck with that. All I mainly did was impress myself again with what a little powerhouse the Gold Bug Pro/G2 is for the price. It is fairly mineralized ground but not the worst, 5 bars out of 7 on the G2 Fe3O4 meter, ground balance about 86. The only real "aha" moment was in learning the Impact really likes to upscale shallow small foil when in 5 kHz mode, but shoves the id back down to where it should be at 14 kHz or 20 kHz. All the machines like to upscale deeper aluminum in this ground.
All three seemed to get tricked in much the same way on certain targets, like a deep pull tab reading like a dime. For gold hunting purposes I do not mind machines upscaling low conductive targets, and in fact the Impact 5khz mode may have a benefit in nugget detecting because it does want to push light foil (and therefore small gold) higher. But for coin detecting upscaling aluminum is annoying. Pretty much par for the course however for mid to higher single frequency machines.
I found running the Impact in VLX1 was nice as I could flip over just one click to the Gen(D) mixed mode program for a dramatically different read and better target definition. Target id numbers in my ground are slightly higher in the "expanded ferrous" modes like VLX1 and VLX2 compared to DI3 and DI4.
The Deus V4 Gold Field program does seem to pack some extra punch now, be fun to get it out nugget hunting once the elliptical coil hits the streets. The new Deep mode really seems great while the new Hot mode is, shall I say it, interesting. First time I have used the X-Y screens also.
The G2 is what it is, almost no controls but it gets the job done with what it has, and good solid id. Deus and Impact in the other hand have countless options and programs to try, but by and large there is no magic bullet. Three great machines, I can hunt with any of them. It will take a lot more hours to sort it all out.
I find when running machines that are all hitting the VLF Wall that it is the "other things" that get my notice. The Impact is obviously the heavier of the three (4 lbs 4.7 oz / 1946 grams), although very well balanced, so I give the feel on my arm award to the G2 (3 lbs 1.5 oz / 1404 grams) and the Deus (2 lbs 4.0 oz / 1020 grams with 11" coil and control box). The G2 and Deus are neck and neck in the comfort department FOR ME* but the G2 feels ever so slightly better to me, I am guessing because the coil is lighter on the G2. The G2 slays both the Impact and Deus for speaker volume if run without headphones, but on the other hand it has no volume control so would be too loud for some situations.
Been awhile since I ran a Gold Bug Pro / G2 unit and caught myself when switching from disc mode to all metal when cross checking at one point and forgetting that the "big number" changes from target id in disc mode to ground phase in all metal mode, so I was looking at the ground phase instead of the little speedometer thinking it was target id for a couple goes. That one quirk always had me liking the F75 versus the Bug in all metal. I wish Fisher made a 19 kHz F75!
*On arm comfort is a very subjective subject. In particular it has a great deal to do with the size of a persons hands plus length and thickness of their forearm, and their height. You really can't take any one persons word on this subject as it is like buying hiking boots. What fits one person does not fit another. It is not all about detector weight by a long shot. Balance is very important as is the all important hand grip. I am 5' 11" with forearms on the thinner side and smallish hands. For instance, my forearm really bounces around in the large Impact armrest area. The Deus armrest which may be too small for some fits me better. For me personally, the 3.5 lb Teknetics T2 / Fisher F75 is the most comfortable detector I have ever used. It is superbly balanced and something about the hand grip that narrows to the top as it cants forward really makes my hand happy. I can squeeze the armrest shut to fit my arm. So if you find the F75 to be a great fit for you, my comments apply to you. If you hate the T2/F75 setup then what I have to say is less important.
Over on PA a new Impact user is asking for help because they can't get it to go deeper than a few inches and the only thing that I could come up with was to use a concentric coil, because I have not used one out in the field/beach,
And a dealer was really trying to sell me one today but not without making ***hole comments about my machine and the CTX when I asked him how it compared to mine,
anyways here is that link to PA if anyone has word of wisdom to help out,
Sure impact is allrounder but not depper than at max impact does well on hot grounds as well as garret at max operating frequency give nokta high end but on the other hand it fail in dapth test against garret at max but both achine are good in every point of view the biggest point of both machine is nokta runs on three frequncy 7khz 14khz 20 khz so its all rounder but nokta enginear forgot what garret just make an all terrain waterproof metal detector with 13.6 khz submersible upto 10 feet at last my thaught is sure nokta is used for gold prospective but at max with all terrain can be also allrounder i dnt know y nokta made a great product but did a small mistake that is waterproof i am sure in future they also gonna make impact waterproof then the sell of their product will be higher no other detector can compare with it then
By Steve Herschbach
I had somebody ask me to test a couple gold nuggets on my Nokta Impact - preferably a 1 gram nugget and a 2 gram nugget. The person wanted to know the VDI number for each in the DI2 mode and Deep mode.
This by accident may be very informative possibly for people who do not know exactly how VDI numbers are generated. The short story is they are a combination of the target conductivity and the size of the target. In other words, silver is more conductive than lead, so two identical items, one made of lead and the other silver, the silver item will have a much higher VDI number.
For two items made of silver (or lead, gold, whatever) where one item is larger than the other, the larger item will generally have higher VDI numbers.
The Nokta Impact is unique as far as I know in that it has two different target id (VDI) number scales that are used in the various modes. The Impact VDI scale runs from 0 - 99 but as I said there are two different ways the scale is divided. One set of modes uses 0 - 15 as ferrous, all else non-ferrous. The other modes use 0 - 40 as ferrous, all else non-ferrous, expanding the ferrous range.
I did not want to sort nuggets all night so came up with a 0.90 gram nugget and a 2.03 gram nugget, both from the same Nevada location, and both of similar shape although one is obviously larger than the other. Here are the results...
The 0.90 gram nugget using the DI2 0 - 15 equals ferrous scale has a VDI number of 37. The same nugget in the Deep 0 - 40 equals ferrous scale reads 63.
The 2.03 gram nugget using the DI2 0 - 15 equals ferrous scale has a VDI number of 32. The same nugget in the Deep 0 - 40 equals ferrous scale reads 56.
Here we have a smaller gold item giving a higher VDI number than a larger gold item. How do we explain these results?
Gold nuggets are not pure gold. These nuggets are probably around 85% - 90% gold. The rest is mostly silver. Here is a strange fact. Silver is more conductive than gold. You would think adding silver to gold would raise the VDI number. However, reality is pure metals conduct electricity better than alloys, and so adding silver to gold actually lowers the conductivity and therefore the VDI numbers. In this case the size, shape, and most importantly, alloy composition of the larger nugget is causing it to read lower than the smaller nugget.
This is a great example of why if you are looking for gold nuggets you at a minimum dig all non-ferrous targets. And because weak nugget signals (very small nuggets or large nuggets deep) in mineralized ground can read as ferrous, the only truly safe approach is to dig everything.
Here is a photo of a large variety of gold nuggets and some coins I tested with the White's DFX, which uses the same -95 to 95 scale as many White's detectors. Again, you can see that size and VDI numbers do not correlate due to shape and purity differences. In general the paler gold has higher silver content. Click on photo for larger version.
By Mike Dawson
Editors Note - this thread was split off from a previously existing topic.
I already knew your comments were for your own personal use but if you did not want people to comment on them why post them in the first place? That Aussie guy on youtube also had a sdc 2300 so he was no dunce with Minelabs but it just did not work for him or just had too high expectations.I also respect his right to express his feelings publically as we live in a free society- in Australia anyway. I would quickly have criticised the Impact on any forum if it did not meet my expectations,but there is nothing to criticise except the headphone jack which protrudes too far out from the main housing and can be easily stepped on and the cord is too long.Maybe Minelab could have made the GM 1000 easier to use on goldfields just like my Impact.In my experience there is no smoke without fire.There has not been one post on how the Impact performs on goldfields except mine on any forum and I feel that is a real shame as that is where it excels. I am sure the Impact not only works for me but for plenty of other people too.I found it a little heavy to start with but after a few days with my new arm muscles it seemed light and very well balanced for me anyway and I am getting on, so it would also suit other novices and retirees.There is certainly a lot of resistance towards the Impact in Australia. eg. no Impact tests in the world or Australia in 2 months on goldfields since it came out, but when the GM 1000 came out there were posts about it in goldfields that week.