An eye opening shut out

My brother and I went to the Cleveland, TN area to do a little relic hunting today. Danieltn, you can find him on youtube and some of the detecting forums, was kind enough to invite us to do a little digging and give my bro. some tips on setting up his new V3i.
I took my F75 LTD and Nautilus DMC-IIb, both great machines. We hit a beautiful field where a running skirmish was fought and started swinging. I used the Nautilus for the first couple of hours and got only iron signals. Even when Daniel would find a good target with his GPX-5000 and call me over to sweep it, nothing. My brother was having similar results with the V3i.

I went back to the car and changed detectors thinking that the F75 would be better able to handle the mineralization. The machine ground balanced around 64 which is where it balances in my test garden but, and this is a big but, the Fe scale was between 1 and 3 depending on which area of the field I was in. The F75 gave me nothing but iron sounds and readings. It did pick up a couple of the bullets that the GPX found but the VDI read between 11 & 13 and I would not have dug them on my own. I tried everything I could think of including adjusting the ground balance, lowering the sensitivity, changing to every mode on the detector, nothing helped.
My brother did find one bullet with the V3i but other than that his story was the same as mine.

Daniel on the other hand was pulling bullet after bullet with the GPX a couple of them from an honest 16". Part of the area I hunted was along the edge of the field and I covered it twice with both the Nautilus and the F75. At the end of the day, Daniel was kind enough to let me take his machine for a spin so I wouldn't leave skunked. I retraced my steps along the edge of the field and literally within the first five feet I dug two bullets, one at 8" and one at 10". I know for a fact that the Nautilus and F75 coils passed directly over both of these bullets. I was inching along and overlapping my sweeps East then West with both detectors.

I thought the red clay in my yard was bad but it's nothing compared to the dirt in this field. According to Daniel it's on par with Culpeper, Va. and even the Minelab FBS machines don't fare too well in this field.
The funny thing is that the field just behind this one, which we could not hunt today, has pretty benign dirt.

Other than buying a PI I have no idea how to successfully hunt a field like this.
If anyone has any ideas, I'm wide open to suggestions as I hope to go back before too long.

Only from reading but the GPX - 5000 is as deep as it gets in bad ground.
I read a post of a hunter who found a bunch of Spainish coins and hunted over the site many time till
he found no more.
Then he brought a GPX to the site were he found another bunch of coins in the 15 inch + range.

and investigate target's....that the discriminator wont signal on....

Some of the better bad ground machine's in North Georgia I have found are The machines that offer a true all metal threshold based mode....and learn how the VDI number's in disc mode will be skewed if you rely on them.....Look for machines that offer the DD coil as option or standard...

Your F-75 will hunt it ....just takes patience and lot's of digging...and yes the good targets once in the disc range will be 11-12 on the vdi in bad dirt.....

The nautilus is a great design with the all metal and disc in unison but the blow back from the ground mask target's...they really need a DD coil design...
the MXT is one of the best bad ground machine's for utilizing all metal and disc in unison and will pull target's at depth once you learn the behavior of the mixed mode...If it''s down there the all metal mode will report if you keep your sweep speed right for the conditions and always achieve proper Ground Balance...However hard this maybe....

if it's an area like a battlefield I have found to just run all metal and check the target's that are tight and sweet sounding in all metal...you know have that round sound to them...

at least dig enough dirt to get the disc to report....

if you done have a all metal threshold based mode get a full range disc.....learn that the iron tones may say iron but have a different sound to them and should be investigated..Weaker and some what rounder sounding than say a nail or iron debris...

Mineral area's are slow go ....especially in an hunted hard area's....the goods are deep and the readings will pull into the iron range quickly...

Bad dirt can be hunted effectively with VLF's but it takes years of hunting it to get proper result's....most people will give up or dismiss the area as hunted out and it is far from it...... ....one good thing though is the area will never be hunted out...

P.I.s are the best for these area's but to get one that disc you have to spend the 5K and they still are not on the same level as a VLF disc ability...I am hoping that will change in the next few year's price wise and technology wise...




Keith






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Thanks Keith, I did try the all metal mode on the F75 but I will admit that I lack the years of experience using it that you referred to. I have put in a fair amount of time with it but evidently not enough. It is relatively easy for me to discern a ferrous targets sound from a non ferrous one even using the single tone on the f75 in disc. but the all metal side is a different story.
I love the dual mode of the DMC. The V3i can somewhat imitate it but I like the Nautilus better.
All of the detectors mentioned above hunt the areas I am normally in well so I can't see sinking the money into a PI right now. I would like to have one at some point especially if someone cracks the key to really discriminating with them. The depth alone is impressive enough to warrant having one. The GPX with the battery mounted on my belt was incredibly easy to swing. Light and well balanced with a pleasant threshold and clear, easy to understand target signal (at least on bullets.)

I can't help but wonder, being a dual frequency machine, if the CZ-3D would have performed better than the others today. Any thoughts on this?

Chris

In North Georgia (red clay)...........both the CZ and F75 were nearly 'on-par' as far as mineralized dirt performance is concerned. Some areas the CZ would slightly trump......and other areas the F75 would slightly trump. If mineralization was moderate.....the CZ would trump.

And still..........no matter how well you can get a VLF unit to perform............it is the PI that FAR surpasses the performance of ANY VLF unit......in bad dirt. I utilized a Minelab SD-2200 in North Georgia (Lake Oconee area).......where a CZ would bell-tone overload with the ground.....((with the coil about 4" above the gorund)).........and the PI unit was completely unaffected. No ID capabilities were a major problem.....and serious amount of 'learning-curve' was required.

I have been reading through this thread and about the GPX-5000. As I understand it it is a PI unit? Anyway I Googled it and saw
this YouTube video [www.youtube.com]

Absolutely amazing tho say the least! A small Roman coin at 17" WOW! I am unfamiliar with PI units and have never even seen one.
Aren't they mostly used for water hunting? Being in Nebraska makes me a flatlander. Is the biggest downside of PI units price and
poor discrimination? I just keep thinking with the way computers are doubling in performance about every 18 months SOMEONE
would make a breakthrough in metal detector design/concept.

If you have the time......could you perhaps give us a explanation as to why it is so difficult to develop effective discrimination in PI technology. I, and assume others, have wondered about that.

2 different operating systems.
VLF transmits and receives at the same time.
So this allows adding on a conductivity range we know as discrimination.

Pulse transmits and then shuts off and uses the coil to "listen" for a generated
response from the object.
Since the ground signal decays much faster than a metal object,
this method allows for sort of eliminating the ground response from having
a large detrimental effect on useable depth.
Pulse units can have a sort of ground balance also to help over sudden
ranges of ground mineral changes.
From what I have read, Pulse can transmit a lot more current than a VLF.

There is also a delay feature and it can be set to knock out objects
starting with low conductors.
I think this is used on the Sea Hunter supposedly to knock out stuff
like foil but still retain higher conductors like gold rings.

Perhaps the better pulse detectors can sort of tell the difference between
higher and lower non-ferrous conductors.
The Bugaboo though is the iron.
So far they haven't been able to differentiate it from the non-ferrous items
at least to maximum depth.

This is just general knowledge and since I haven't used a pulse,
I really don't know much about them except for what I have read over
the years.
I thought however I would respond and perhaps Tom can go into more
detail and correct any errors I may have made with this post.

George Paine actually made a discriminating pulse many years ago
but it would only work about 4 inches deep, after that, it was all-metal.

Really I think a meter could be added to a pulse and at least provide
a visual type of disc. but once the GB is moved, likely the whole
set of readings would be skewed and the delay would have
to be taken into account.
Eric Foster has mentioned that a meter could be possible on pulse.
It would likely take a true on board computer to calculate all the
variables and hopefully come up with the correct reading.

A true discriminating pulse and/or with a VID is the holy grail
of metal detecting.
But if it was an easily accomplished task, it would have been
one long ago.
I have my doubts with the ecomony in the shape it is in,
we will see any company sinking R&D into developing it.

There is the legend of a discriminating pulse detector
called the Pulse Devil but that is another story.......

I seriously doubt Dave Emery will ever finish the Pulse Devil.

More on PI's shortly.

Thank you. Excellent explanation.