Cache Test

[Qiaozhi]

Here is a photo of the first round of detectors I tried. All failed. I had high hopes for that 24" coil on the 6000/pro.

White's 6000/di Pro with 15" coil
White's 6000/di Pro with 24" Magnum "cache" coil
Fisher Gemini 3
Discovery TF900
Minelab 2200/d with 18" mono coil
Garrett GTI2500 with Bloodhound attachment
Teknetics T2

I spoke with Georgi Chaushev (the Nexus designer) today. He has performed some further tests on a similar 1Kg cache of coins in undisturbed soil using the new Nexus Ultima with dual 20" search coils. Hopefully the test results will be published soon on either Gary's Detecting website http://www.garysdetecting.co.uk/ and/or at www.nexusdetectors.com.
Georgi claims that the cache is easily detected with the new Ultima.

[Carl-NC]

Hey Carl-NC this is the two detectors I would give a shot. The sierra madre by Whites with largest coil available and the X-200 by Compass with 16 in. coil. If these don't pan out try the industrial metal locators made by Whites and Fisher. They seem to be super sensitive to any type metal.

Those are 2 detectors I don't have.

[Carl-NC]

I spoke with Georgi Chaushev (the Nexus designer) today. He has performed some further tests on a similar 1Kg cache of coins in undisturbed soil using the new Nexus Ultima with dual 20" search coils. Hopefully the test results will be published soon on either Gary's Detecting website http://www.garysdetecting.co.uk/ and/or at www.nexusdetectors.com.
Georgi claims that the cache is easily detected with the new Ultima.

I have no doubt that a detector can be made to detect this cache, and I think I read that one of Georgi's Nexus could already do so, at least to some extent.

I am in the process of getting my PI running with a 1m loop. I had planned to do this with my SMT prototype, but decided not to hack it up because I wanted to bring it to the beach. So I pulled out an old thru-hole prototype, which has problems and I am still debugging. Hopefully will get it going in a week or two.

- Carl

[Unregistered]

Hoard containers

With reference to the comments on the containers used for U.K. hoards there were in fact three main types of container.....money bags, wooden boxes and coarse-ware pots.
Of 1600 hoards (this number has now been well surpassed) over 500 were in clay pots,the most common container used, six in glass vessels, six in silver and the remainder in bronze, lead and later on pewter and tin containers. Plus a few in stone urns, mortars and even the centre hole of a quern stone.
Not many got detected intact....normally if a detectorist made the find it was only because the container had been hit by a plough and some coins brought to the surface. The bulk of the hoard would be found as more powerful machines were brought in and the soil removed in layers until no more signals were received.
Re the suggestion of the Compass X-200 I did not find it to be super deep with the large coil. As with most non P.I.'s the extra mineralisation, (width and depth), counters the extra depth the larger coil should be producing.
How about a test on a less deep hoard target between the Whites with the 15" and the same machine with the 24".

Brian

[Joe(TX)]

Re: Gary's Cache Test

Carl, if you are having a problem with your P.I. with a large coil? I may have a remedy. Now if you have an original Garrett Seahunter P.I., I was told that the old BFO Coils such as the 12 by 24 or 24 by 24 would work on it with the proper connector. I know that Gary would not use a P.I. in the U.K. because of all the iron but I'm curious to see what a Seahunter P.I. could do with the 24 by 24 inch coil.

[Carl-NC]

Maybe... they have about the same inductance as the coils for my Seahunter MkII. Might try this.

[Unregistered]

This test doesn't make sense because I have found single coins at 12in. Of course they weren't in containers either. Could the fact that the side cubby hole is under undisturbed ground be the cause of lack of detection. The density of the soil around most caches is different than undisturbed ground no matter how long they have been buried. Maybe this is something worth looking into. Heck Cael just cut you a forked stick of witch hazel and tie a silver necklace on it and you will probably have no trouble finding it. Just kidding by the way but they are effective for finding water.

[Qiaozhi]

Magnetic Field Intensity

Hi Carl,

While you're in the mood for digging holes and burying stuff , how about putting a sensor in the "cubby hole" and measuring the magnetic field intensity. I think it would be interesting to see how the field varies in the area of undisturbed soil when compared to the bottom of the hole.

As we've probably all experienced, if you recover a deeply buried coin and then replace it at the bottom of the hole, quite often the detector cannot "see" the coin. So the question is whether this is caused by some sort of halo effect, or is there something else going on? Does the density of the soil affect the magnetic field in some way? Commonsense would probably indicate that a coin lying at the bottom of an open hole should be more easily detected than one buried in soil. However, the opposite appears to be true.

My suggestion would be to measure the magnetic field for these four cases:
1. The "cubby hole" - without soil.
2. The "cubby hole" - with soil.
3. The bottom of the hole - without soil.
4. The bottom of the hole - with soil.

What do you think?

[Joe(TX)]

Re: Gary's Cache Test

Carl, I bet that an Arado 120b or 130 can find that cache! Problem is that not very many are here in the states. I know of only one collector of these machines. Maybe I can convince him to duplicate Gary's Cache test and report on the resulsts?? Joe

[Carl-NC]

While you're in the mood for digging holes and burying stuff , how about putting a sensor in the "cubby hole" and measuring the magnetic field intensity. I think it would be interesting to see how the field varies in the area of undisturbed soil when compared to the bottom of the hole.

I agree that measuring the field strength under various conditions would be a Useful Thing to do, but I would have to build such a device, and dig another hole. Maybe I'll give it a shot when I bury my next cache target.

As we've probably all experienced, if you recover a deeply buried coin and then replace it at the bottom of the hole, quite often the detector cannot "see" the coin. So the question is whether this is caused by some sort of halo effect, or is there something else going on? Does the density of the soil affect the magnetic field in some way? Commonsense would probably indicate that a coin lying at the bottom of an open hole should be more easily detected than one buried in soil. However, the opposite appears to be true.

I've had the opposite occur... as I dig down the target response gets stronger, even though the coil is still at surface level. I noticed it just yesterday digging coins out of the surf.

- Carl

[Carl-NC]

Carl, I bet that an Arado 120b or 130 can find that cache! Problem is that not very many are here in the states. I know of only one collector of these machines. Maybe I can convince him to duplicate Gary's Cache test and report on the resulsts?? Joe

I happen to own a 120b, so I can try it.

[Unregistered]

Cashe test

Here is the cache... 3 pound of 90% silver coins.

Hello Carl.
The cashe you show on the picture is a little bit incorrect for the test (forgive me for saying this) in two regards.

1. The coins you show on the picture are in very good condition and very likely will be in good electrical contact.
In a hoard burrien for long time (centuries) in the ground all og the coins are covered by thin layer of oxide which isolates them from one another. For this reason they can not be picked up as one big piece of metal.
2. The test published in garysdetecting is for 1 kg. of mixed coins, only few of them are silver and also relatively small in size (the silver ones).
3. The quantity in your test seem to be about 400 grams higher than garysdetecting test.

Please accept my appologies for trying to set the record straigt. Nothing personal.

Please visit also my test page in www.nexusdetectors.com
I have now accurate immages from a properly conducted tests and some description as well.

Best regards.
Georgi Chaushev

P.S. I will explane soon in my web site the real nature of a hoard under ground. What kind of signals the hoards can cause for any detector and how they can be detected more efficiently.

[Unregistered]

Hole is covered. I'm seriously concerned that when the grass recovers, I may never be able to find my coins again. I need to add some method of marking the spot.

You can hammer a piece of wood and leave it to stick a bit higher than the surface.

Cheers.
Georgi Chaushev

[Unregistered]

Hi Carl,

While you're in the mood for digging holes and burying stuff , how about putting a sensor in the "cubby hole" and measuring the magnetic field intensity. I think it would be interesting to see how the field varies in the area of undisturbed soil when compared to the bottom of the hole.

As we've probably all experienced, if you recover a deeply buried coin and then replace it at the bottom of the hole, quite often the detector cannot "see" the coin. So the question is whether this is caused by some sort of halo effect, or is there something else going on? Does the density of the soil affect the magnetic field in some way? Commonsense would probably indicate that a coin lying at the bottom of an open hole should be more easily detected than one buried in soil. However, the opposite appears to be true.

My suggestion would be to measure the magnetic field for these four cases:
1. The "cubby hole" - without soil.
2. The "cubby hole" - with soil.
3. The bottom of the hole - without soil.
4. The bottom of the hole - with soil.

What do you think?

Hello Qiaozhi.

The reason that a recovered coin gets dificult to detect on the bottom of the same hole is due to the folowing factors;

1. The opened once hole creates a signal with opposite polarity (phase shift) to the signal from the coin, which is equals worse (more mineralized) ground conditions.
2. Detectors with search coils not tuned in resonance are not capable to register the difference between the coin and the disturbed soil under significant depth (equal or even less to the depth on which the coin was recovered).
3. It could be also genuine mistake of the registered recovery depth. Assumption that the depth was more than in reality.

Best regards.
Georgi Chaushev

[Carl-NC]

Hello Carl.
The cashe you show on the picture is a little bit incorrect for the test (forgive me for saying this) in two regards.

1. The coins you show on the picture are in very good condition and very likely will be in good electrical contact.
In a hoard burrien for long time (centuries) in the ground all og the coins are covered by thin layer of oxide which isolates them from one another. For this reason they can not be picked up as one big piece of metal.
2. The test published in garysdetecting is for 1 kg. of mixed coins, only few of them are silver and also relatively small in size (the silver ones).
3. The quantity in your test seem to be about 400 grams higher than garysdetecting test.

I completely agree, and somewhere I had already mentioned points 2 & 3. So I have more coins (1.36kg vs 1kg), they are all-silver (higher conductivity), and they have no corrosion... yet nothing can detect them.

- Carl