Tiny Gold Nugget Test with note on TX Boost

[steve herschbach]

Hi,

OK, this is a bench test. An air test if you will.

I have a 0.7 grain gold nugget I use to air test detectors. Not gram mind you, grain. 480 grains per Troy ounce. Very few metal detectors will pick it up at all, even if you roll it around on the coil. So an air test with it serves to indicate what detectors have at least the basic capability to be a prospecting detector. An MXT with a Shooter coil at Max Gain will barely signal on this nugget within 1/4" of the coil.

Same Shooter coil on the Vision. Prospecting Mode (22.5 kHz only), no tweaks except Max RX Gain. Threshold a bit ratty but no worse than MXT at Max Gain. I'm getting a good hit at 2" and whisper at 3".

Now let's engage the TX Boost, raising voltage to the coil from 10V to 30V. Now I'm getting a good hit at 3" and whisper at 4". That is a 50% increase on a tiny nugget by engaging TX Boost.

This is easily better than MXT performance and actually closer to what I'd expect from a GMT. Now ground conditions will certainly have an impact, but my local area south of Anchorage is blessed with low mineral ground - and lots of tiny gold. Standard practice is a GMT and Shooter coil at Max Gain, and rub that coil around in the dirt.

Note that this Shooter coil is several years old. It is not optimized for the Vision and yet handles Max RX Gain and TX Boost. There is still even some performance left on the table by way of All Metal and Disc Gain. Remember that TX Boost will significantly cut battery life, but for what I'm seeing packing a spare battery pack or two will be no problem. Also note that TX Boost applied in the wrong locations can do more harm than good. It is not magic.

I've done this with enough detectors over the years that I know one thing right now - this detector will hit well on small gold where I hunt. Other places with extreme ground conditions I am in no way vouching for but this detector can do well in my area.

Steve Herschbach
Steve's Mining Journal

 

[HumblePie]

Steve,

These are surprising and very interesting results. I wonder what your initial reaction was to this test...

The F-75 will duplicate your results with the "shooter" coil equivalent (3 1/2" X 6" sniper) prior to engaging the TX Boost. It will give this performance either in JE disc mode (set to zero disc for the tiny stuff), or in the all-metal motion mode. With larger pieces of a few grains and more, the 75 in JE disc will also perform equivalently to all-metal motion mode, but even with a disc setting of "12" (effective small iron discrimination). A great advantage working iron infested tailings, or hot rock country.

(a) would you please go into the basic adjustments in the prospecting mode and "engage" audio discrimination (presuming this can still be done with Vision) while keeping the disc level set to zero...and recheck this test for me?

Frankly I'd like you to do the same test on a 2 to 5 grainer with the prospecting audio disc engaged and disc set to small iron elimination. But I fear pushing my luck too far....

Even in an air test, the GB setting plays a sensitive role. As you know, decreasing GB decreases sensitivity generally, but especially with tiny nuggets. (b) did you note where the GB was set prior to testing? I'd prefer to see any air test conducted with GB set to natural ferrite (magnetite), say about GB81 or GB82 on the MXT as a reference GB setting.

We both know only too well that while giving definite indications as you noted above, air testing misrepresents performance in higher mineral conditions. The GBII is an example of a higher frequency unit that yields excellent air results but unfortunately does not fare as well over high mineral conditions for deeper, larger stuff. I've preferred the lower frequency, but high sensitivity of the 75...it will not perform as well on the tiniest stuff, but will outperform the higher frequency dedicated units for depth on larger targets. A trade-off that works for me, especially since the unit provides full target ID along with other capabilities...as you know. First opportunity this spring, (c) would you check in the dirt, note the ground phase and % magnetite (does this unit provide this info on screen?), and lets see how it performs with an equivalent MXT 10" DD elliptical on a 2 to 5 grain nugget.

Now I know I've pushed too far Steve. Anything will be appreciated, but I also know you will do all these types of tests on your own accord as time permits. You will want to know too. Based on what I've just read here today, I'm like a kid at 3AM Christmas Eve.

That's all I can think of for the moment, it will be interesting to discover the....possibilities. Thankyou, and only when you have the time Steve.

Jim.

 

[steve herschbach]

Hi Jim,

I do not think you'd be getting ahead per se going from an F75 to the Vision if all we were talking about was a tiny gold nugget. I've tested the F75 in that regard and it does very well. I prefer the Vision for it's multi-frequency operation with option to run in any one of the three frequencies, the ability to create custom tone patterns, and because I can notch anything, even high coin range. The analyze screen is really something. Almost all my detectors are dig-it-all type units and so with the Vision I'm looking for just the opposite. While I'll go find gold nuggets with it jewelry is really my reason for getting the unit.

I guess what I'm saying is guessing at what you are doing the F75 is a very good unit for you. It is good at what it does. But when I get a chance I'll try and do a few more tests with the Vision.

Steve Herschbach

 

[steve herschbach]

Hi Jim,

Put the Vision in Coin & Jewelry Mode (reject iron, accept non-ferrous). Disc Sens at 80, tried TX Boost On and RX Gain 15 and unit overloaded with my older Shooter coil. Backed RX Gain down to 10, now stable. 0.7 grain nugget basically had to be rubbed on bottom of coil to be detected. A 3 grain nugget has a hard hit at 3 inches. Tried TX Boost OFF and RX Gain of 15 and got about the same result. Air test of course.

Steve Herschbach

 

[HumblePie]

Thanks Steve, I'll respond more appropriately later today. Was out tonight, it's now very late here. Bedtime.

Jim.

 

[HumblePie]

Steve,

Thanks again for providing this supportive data. This unit's small gold performance does surprise.

It will be interesting to discover Visions performance over dirt. My unit will signal solidly on 2-3 grainers in fairly high mineral ground here at three inches. That performance is achieved in all-metal motion or JE disc mode with a small iron discrimination setting, either the sniper or 11" DD coil. That represents approximately a 25% depth reduction from air testing.

On a larger nickel size (real nickel composition pre-1981 Canada nickels) target, freshly buried at 10 inches, my unit will easily provide a strong, two-way repeatable signal with a few inches air space to spare between the coil and the ground surface. That represents approximately a 10% depth reduction from air testing. Mind, in the spring when soil conditions are "wet" that signal depth is mitigated but still a diggable signal. Our iron oxide/hydroxide/ferromagnesium silicate configuration here is such that excessive moisture increases the soil's resistance to detection depth. All is not black and white as we all realize, but depends upon conditions at any given time. Your remark below...

"The analyze screen is really something."

Yes, there may be some advantage to be learned here, but I doubt very much that it will exist in terms of distinguishing gold from bit/pieces of aluminum debris that occupy similar conductivities. Rather, I suspect there may be some improvement with differentiating (a) wheaties from silver dimes...you note the dime hit hardest with the 2.5 frequency, while the wheatie hit hardest with the 7.5 frequency...in an air test. Ground conditions will ultimately determine both accuracy and repeatability (precision) in that regard. (b) hopefully...with larger rusty iron. We note the small iron illustration depicts the rusty nail hitting on the 7.5 frequency hardest. I'd like to see a larger rusty iron target, for example, a 6-8" X 1" or so rusty drill bit tested to see which frequency hits hardest. As you know, large iron is the big headache when searching for larger ores/nuggets over here in silver country. Such iron will frequently read into the higher conductivities. While audio/visual clues are often present, sometimes they are not...depending on a number of factors. Hence, a frequency indicator might be useful there.

Steve, I won't presume upon your time further here, but should you conduct that iron test, I would be most grateful if you would post back the result. All the very best to you, we'll look forward to further discussion sometime down the road.

Jim.

 

[B.T]

For max sens down here in Oz I use the MXT with the 5.3 eclipse. In quiet ground it beats the shooter no probs for small gold!
The 5.3 is my top choice on the MXT when the ground is quiet and lowly mineralised.
The Vision sounds pretty good though and Im hanging out for one to land here.

 

[steve herschbach]

Hi B.T.

Not knocking the MXT. If a person was looking at the MXT and the Vision with solely prospecting in mind I'd advise them to get the MXT. It's the better prospecting unit of the two and costs half what the Vision does. I'm just glad the Vision is in roughly the same ballpark as the MXT on small gold..

My personal situation is that if I am going to hunt large gold nuggets or am going to be in particularly bad ground I'm going to use my GPX-4500. If I am chasing the tiniest bits or have lots of iron trash around I'll switch to my GMT. Between the two I found I really did not use my MXT anymore for prospecting. And so I sold it and have been using a DFX for in town jewelry hunting. But now I'm looking for the Vision to be my only "do-it-all" machine and it's main use also will be in town jewelry detecting. So my DFX is now gone. The fact the Vision does as well as it does on gold was a welcome surprise and so I've decided to give it a go nugget hunting also just to see what it can do.

Here in Alaska I get a lot of people who want a machine they can coin hunt with and then take to Hawaii and maybe beach hunt and go do a little prospecting. Just one detector, and do everything. The MXT has fit the bill and loads of gold has been found here with the MXT. But some people (like me) want stuff like more tones or notch discrimination or even a backlight, which the MXT lacks. I'm feeling comfortable now that the Vision will be able to offer people those extra bells and whistles and still do well enough on gold nuggets to satisfy most people. But for down and dirty serious prospecting I'll always recommend dedicated prospecting detectors.

Steve Herschbach

 

[B.T]

That's fair enough Steve. I swing a 45 in the bad ground too. The Vision does look real impressive, shame about the dollar exchange rate though.
Have a good one over there and good luck.

 

[steve herschbach]

Hi B.T.

I do think the 5.3 will be great on the Vision but I'm going to wait for an optimized version.

Check out http://www.findmall.com/read.php?66,928025,929118#msg-929118 as it is related.

Spring is coming here and winter on the way where you are. I hunt of course in summer. Is it better hunting down under in the winter?

Steve Herschbach

 

[B.T]

n/t

 

[nlhawk]

Steve, you wrote:

If a person was looking at the MXT and the Vision with solely prospecting in mind I'd advise them to get the MXT. It's the better prospecting unit of the two and costs half what the Vision does. I'm just glad the Vision is in roughly the same ballpark as the MXT on small gold..

what is it that makes the MXT better suited for prospecting than the Vision? I tried to look the posts over, but did not see this answered.... having said that I'm half blind so I may have simply missed it....

as a side note: I look forward to your posts, they are very helpful and insightful.

Thanks
Lee

 

[steve herschbach]

Hi Lee,

If all you want is prospecting capability then when comparing the MXT and Vision I have to favor the MXT. It is based directly on the GMT and has good gold sensitivity combined with a superior ground tracking system. It costs half what a Vision does and is easier to operate being a good old knobs based unit. The question to be asked is simple. If all we are talking about is prospecting, why would a person want a Vision instead of an MXT? I really can't think of anything. Maybe the 3 frequency operation in certain hot rock locations?

What makes the Vision attractive is the fact it comes close to the MXT but offers lots of features for other types of detecting. If you don't care about those features, you don't need it.

None of which says the MXT is some kind of perfect prospecting machine. It is a great do-it-all strong on gold, but no match for dedicated units like the GMT or TDI.

Just my opinion.

Steve Herschbach

 

[nlhawk]

Well your opinion is quite valued. I should have included in the post that my interest is pure curiosity.
Currently I own the TDI and the GM4B. Since 1995 my whole focus has been exclusively on prospecting. Last year for the first time I broke down and purchased the DFX just to get a feel for the other side of detecting. I liked the DFX so much that when the Vision came out I got it. Proud acquisition on March 20. After reading your post I was just as I say curious about how the older MXT would be better at prospecting. Obviously if it's based on the GMT that kind of tells the story right there....

Thanks for the rapid reply. I love this sport both sides, but truthfully mostly prospecting....
Lee