By Steve Herschbach
Snow on the ground so time for a little bench testing. Fisher F75 SE version 7.0A (2013) with 5" round DD coil, Nokta FORS Gold with 5" semi-round DD coil, and White's V3i with 4" x 6" DD coil.
The table shows VDI numbers on some standard items. The little allen wrench is like a small nail - a ferrous item. The BIC ballpoint is my standard simulated small nugget. The ring is my 14K plain gold band, around 7 grams.
The VDI range on the Nokta runs from 1 - 99 with 40 and under generally ferrous. The F75 runs from 1 - 99 with 15 and under generally ferrous. The White's V3i runs from -95 to +95 with negative numbers generally ferrous. I say generally because in all three cases gold can run well into the ferrous range. Like by 10 - 20 VDI numbers into it!
A few big lessons. The Nokta FORS VDI 1 - 99 range is skewed with high conductors bunched on the high end of the scale with most of the scale devoted to ferrous and low conductive items. This is ideal for relic hunters and prospectors. Silver coin hunters however usually prefer the scale to devote more room on the high end to possibly get a better handle on what is silver and what is not.
The ferrous range of the Nokta actually runs all the way down into the ferrous ground range itself which is why there are 40 numbers devoted to it. The ID Mask setting defaults to 10 and if set lower allows ground signals to sound off. Since non-ferrous starts at 40 and I arbitrarily end low conductors at zinc penny on the upper end you have 40 - 82 or a spread of 42 points for low conductors. This really is no more than an average spread due to the large ferrous range.
What I was happy to see is the simulated nugget (BIC ballpoint) nailing at 44 as a non-ferrous target.
Contrast this to the F75 1 - 99 range. There are only 15 points in the ferrous range with the extreme low end represented on the Nokta scale truncated roughly in the middle. However, this leaves 16 up to 62 at zinc penny for a low conductor spread of 46 or slightly better than that on the Nokta FORS and leaves room for a little better definition for high conductive coins also. There is a ten point VDI spread between a dime and a quarter versus only 3 points on the Nokta.
What disturbs me on this particular F75 is that having tried multiple coils I am getting the same result on the simulated nugget test. It wants to nail at a solid 1 which is well under the ferrous 8 reading for the allen wrench. This is not shocking but it is not good either. I can get the ballpoint to break in at 16 occasionally but it should be there hard and solid, not rarely. I had Keith Southern test his updated F75 and it seems to do better. I need to test this again when and if I ever get an upgraded F75 but it does confirm my suspicion that at least some Fisher units are not properly aligned at this critical break point.
The White's V3i slays both of them with White's standard spread of 190 VDI points with half that devoted to ground and ferrous. A full 95 points is devoted to non-ferrous, giving a nice spread across the whole range. The V3i is a three frequency unit and the 22.5 kHz frequency employed allows it to easily nail the ballpoint test with a solid VDI of 3. White's even allows the 22.5 kHz frequency to use a native VDI range that skews and expands the low conductive range that delivers a VDI of 10 on the ballpoint, a very nice cushion between it and a ferrous reading. you have from 1 all the way up to 55 for zinc penny slightly beating both the Nokta and F75 for VDI resolution on low conductors and still room left for very good definition in the high conductor range.
These detectors can employ a dual tone mode that delivers a low tone on ferrous targets and a higher tone on non-ferrous targets. The break point on the Nokta and F75 is preset at the factory VDI breaks of 13 and 40. The V3i you can customize not only the VDI break point but the tones.
The F75 dual tone mode is pretty straight forward, with the volume being weaker or louder depending on the strength of the signal. In other words, a modulated audio. The Nokta Boost or DI2 mode uses a VCO (voltage controlled oscillator) audio where both volume and tone increases with signal strength. Anyone that uses a Fisher Gold Bug is familiar with VCO audio. It is rather unique and some people like it, others do not. Again, the V3i allows the tones to be customized any way you want, with either VCO, modulated, or even unmodulated options.
Things get more interesting in Nokta DI3 or F75 three tone options. The low tone break for ferrous is the same but a third higher tone is added. On the Nokta zinc pennies and higher or from 80 on up delivers the third high tone. On the F75 it breaks above zinc penny so those pennies fall into the middle tone low conductive range.
Zinc penny is also where Indian head pennies and some other old coins can fall. If you hunt strictly by ear and dig high tones only you are going to pretty much dig all coins but nickels. With the F75 it is geared more towards silver hunters so zinc pennies, Indian heads and possibly other coins would get passed up as low conductors. But wait! The F75 also has a four tone option that puts that zinc range into into own fourth tone - problem fixed. You can chose a tone option that focuses more on silver only or one that breaks out that penny range. Jewelry Hunter would probably prefer the 3 tone mode and dig just mid-tones. The bottom line is the Fisher has more tone options for the coin hunters than what the FORS offers.
Of note is that the Nokta DI2 dual tone mode uses VCO audio, but the DI3 three tone option defaults to a more normal modulated audio. DI3 favors a faster sweep speed than DI2 which benefits from going slower. A generality would be that DI2 is more powerful but DI3 better behaved.
The V3i again is unchallenged. You can actually go so far as to independently set a separate tone for every single VDI number, and the tones can be any from 191 tone options. You can make low conductors high tone if you want. Absolutely nothing on the market compares to the V3i for audio and visual customization options.
Well, this all seems pretty easy, right? Just get the V3i and get on with business. Sadly, these are air tests. You might ask, for instance, which detector did best for "depth" in these air tests, as if there actually is such a thing. I only pay passing attention to that but the F75 seemed to be doing very well in that regard. Here is the problem with this entire lesson and all my typing. When you put things in the ground all these nice air tests rapidly decay and fall apart.
In very mild ground or on very shallow targets detectors can be amazing. In my ground unfortunately VDI numbers start breaking down at around 3-4 inches! What you discover is that if you get too focused on cherry picking VDI numbers good finds deplete rapidly. Almost all accessible public areas have been detected for decades. So the easy accurate VDI results have already all been cherry picked away. The best finds these days often come from digging targets that were passed up precisely because they did not give a perfect response.
In my opinion, these days we have to cast a wider net and be willing to dig more trash to make those exceptional finds. What that means is huge numbers of VDI numbers and tones although flashy and fun often is no better than just using a simple two or three tone method and going for it. Styles differ vastly and because really this is about enjoying ourselves there is no right or wrong way to do things - as long as you are enjoying yourself. For me, something simple like the Nokta DI3 tone option for digging all high conductor possible coin signals actually works pretty well in actual practice. If I want coins except nickels just dig high tones and have fun. The F75 allows a special mode that kicks nickels into the high tone range so you can do the same thing and get the nickels also if you choose. The V3i by now you should know the story - set it up any way you want.
Still, tests like these are very valuable to me in setting the baseline for performance in the field from which I can work to discover how much things vary and hopefully why. The theoretical goal if finding a machine that adheres as closely to bench testing results as possible in the field. Sometimes you get textbook results, but then at another location everything goes haywire. But unless you know where you are starting from you will have no idea what is going on.
I will sum this up for now by saying that the Nokta FORS is a machine that appeals to simplicity and leans towards relic hinting and prospecting. That is not to say you can't do well coin detecting with it, it is just that it is not set up with coin detecting specifically in mind. The F75 nicely straddles the middle for all detecting purposes.
The V3i is in theory the perfect detector but the reality is huge numbers of people have discovered more options does not always mean better detecting, and it is not unusual at all for people to abandon the V3i in favor of simpler machines. Unless you spend a vast amount of time with a V3i it is hard to feel like you have mastered the machine. The V3i appeals to my inner detector nerd but it is usually the case where in the field I prefer simpler machines myself. Still, I made the V3i part of all this just to see how it really does do if given a fair chance and at least when bench testing it is impressive to see all the bells and whistles in action.
This is all just stuff I am finding out for myself. I have no real reason in reporting it to you other than just to be sharing some info that is taking at least a little effort to collect. It helps me digest it better trying to put it clearly in a form you can better understand. Hopefully it will help someone in their own choice in a detector. As you may be figuring out if you have not already, there are no best VLF detectors, just lots of really different VLF detectors. They all actually do a good job finding stuff but it is in how they go about it that differs so much. It is mostly a case of finding out what style and type of detector works best for you.
It is good friday unless you had to go to the dentist like me. My appointment wasn't till early afternoon, so I had a couple hours to go walking up a canyon near the old channel workings. I seen pocket gold geology as soon as I made it up the canyon a short ways. there is areas out there where the old timers found a few pockets and once in a while you can still find a pocket. but apparently they didnt know I was coming with my detector 140 years later because they took all the good ones. I did find some scraps they forgot. 6 pieces in 3 small areas. 2.8 dwt before my dentist appointment. luckily at the dentist everything was good. I took along the Fors plus as my bird dog to sniff out those golden birds. Fors plus did a good job and really does well in that kinda geology. Happy Easter
Well it looked like there was a small window of opportunity to get outside today and get on some gold. Headed back to previous detecting site for some swingin. Moved down range 50 yards from last time to see what was there. Hit a good patch of small stuff that was mostly stuck in bedrock left behind by our historic miners. Only bad thing is I think they had a trap shoot there at one time. I never found so many birdshot bb's in such a small area. Only lasted a few hours then it started clouding up and started to sprinkle. It was fun while it lasted. Once again Fors plus operated great in all metal with "dd" coil. Have to not forget concentric for a try next time. Can't wait till next time. 23 pcs. For 2.5 dwt. Nothing big but the color is nice
I have a few videos that I will post a link for here shortly
After a very busy summer and fall, I had a chance to get out for a couple hours between the rain showers. Went to an old spot that I havent been to in awhile. We hit the place pretty hard before, but fors gold always finds a little more just a little deeper. Found 7 more for 2 dwts. Going to be switching to a new detector this season. So it was fun detecting with Fors Gold one last time. It was a good year and a half with the Fors. But it will have to be the backup now.
Hopefully it rains alot more. The ground is still as hard as concrete.