Which Frequency Is Running In Each Mode?

[Geotech]

1 hour ago, Magic12 said:

I have a Therory That Detecting a Hoard of coins is like detecting Chains in the Beach

 

Correct, lots of small eddy loops don't produce as strong a signal as one big eddy loop.

[jasong]

On 4/27/2022 at 11:07 PM, Geotech said:

I used 220 US silver quarters (3 lbs) placed in a small plastic tub and buried 24" from the top of the tub to the surface of the ground. This was when I lived in NC and the soil was fairly mild.

Would clad quarters be a sufficient substitute or will they hit deeper than silver? Were they in rolls, or randomly placed in the plastic container?

I'm just kinda curious if the GPZ and this 17" concentric X Coil I have could hit it. It's the deepest setup I've ever run by a good margin.

But I totally get the idea about many small eddy loops != one large loop too and the difficulty of the test. I'm just kinda curious.

[Geotech]

Clad will work. Randomly dumped.

I dug this up in 2008 so I haven't tried any detectors since then. It's very possible that a newer model might succeed.

 

[jasong]

Thanks, I'll give it a try this summer when I move to a bigger yard I can tear up, easier to just take a big scoop out with my backhoe in this crazy concrete-like clay soil we have here. It's mild ferrous, but all ridden with varying degrees of alkali to greater or lesser extents.

[EL NINO77]

I decided to write something about this topic... it's been a few days since I found time to test several detectors that I currently have with me on several types of coins, because I was wondering if the detectors Minelab Equinox800, CTX3030, xp ORX, and Rutus ATREX when using a multi-frequency,, or a single frequency from 4khz to 40 khz to compare the range response for a given type of coin..

Simply after the last experiences in detection in the field... I was interested... to which type of coin will the given detector respond best... and at what multi-frequency or 1 frequency... from 4khz to 54 khz...

 ......so I checked these detectors in a simple Airtest.. for various coins....

I was surprised by one fact during the tests... namely that the large 40mm... . a 4-ducat  gold coin - the size of a silver dollar... had a significantly greater range than a silver dollar, by 7-8 cm... more..  37cm Silver Dollar vs. 45cm a Gold 4-Ducat coin..!!!

This means that the current detectors are frequency or multi-frequency dependent ..around 4Khz, which is more optimized for higher medium conductive large gold coins...but not for highly conductive Silver dollar type coins..

....... the picture N.1 shows the relative range of detectors for different types of gold and silver coins using a low-weighted multifrequency..or 1f frequency 4khz...!!!

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for comparison... I will give a test of the same detector at 1 frequency of 17.4 Khz.. Here you can see how the use of a high frequency is associated with an increased or decreased range on various high-conductive, medium-conductive and low-conductive coins...

 

[GB_Amateur]

If my eyes are reliable, the large silver coin is a 99.9% purity silver 1 ozt 'round' from the USA.  It's difficult to get a higher intrinsic conductivity than that (and it would be in a lab at some weird temperature).

Do you know the purity of your large gold coin?

So I'm understanding correctly, the top photo shows air test max distances for 4 kHz fixed frequency?

[EL NINO77]

19 hours ago, GB_Amateur said:

If my eyes are reliable, the large silver coin is a 99.9% purity silver 1 ozt 'round' from the USA.  It's difficult to get a higher intrinsic conductivity than that (and it would be in a lab at some weird temperature).

Do you know the purity of your large gold coin?

So I'm understanding correctly, the top photo shows air test max distances for 4 kHz fixed frequency?

..GB_Amateur.....

Yes .. you are right... I used 2 large silver coins in the test... namely 1 Silver dollar/investment coin/ with high purity silver 999/1000.. and for comparison also a large 37mm Spanish Silver coin 5 pesetas 1891.. of purity 900/1000..for verification..to check the results of the test..for highly conductive coins..but what is important is the results of the test range for these highly conductive coins were practically the same...

The next highly conductive coin in the test was a rough larger Roman AS coin... because I was interested in how the range of such a coin would change depending on the used frequency or the use of a differently weighted multi-frequency.

Now to ... the large 40mm gold coin 4-Dukat 1915..-weight 14 grams.. /size of a Silver Dollar/...this gold coin has a fineness of 0.986/1000 ..which is practically 24k gold...

.....And that's exactly why I was interested in how this large pure gold coin fares against other  2 gold coins - 20mm gold Dukat coin 1915 986/1000- 3.5 gram 24K .. gold and above all against the very old 2000 year -5 gram Celtic coin of the Stater - which is probably a gold alloy with the addition of silver /electrum /..

  ...for completeness..I supplemented this test with various other coins-- in order to get a complete overview.. about ...how big a difference in range the set high and low frequency can make for these types of coins..

Take my test with a margin...,,,but take into account one fact...namely...that for large silver coins or thick copper coins of the Roman AS type...there is still a large margin in the range when using a frequency below 4 khz ..and I expect that the used frequency of the detector working at - 1.5 Khz would be able to significantly reduce the reach of such large and highly conductive coins...
...This would agree with George Payne's measurement results..who determined the optimal frequency for the Silver Dollar coin to be around 900 hertz/0.9khz/

..As for the large 40mm/14gram/24k gold coin, the test showed that the frequency of 4 khz or low-weighted multi-frequency works perfectly for optimal reach on such a large 24k..gold coin...
..
Another interesting result in the test is... a test on an old 2000-year-old gold 5-gram Stater coin - made of a low-conducting gold alloy with an admixture of silver--/electron/where it turns out that the frequencies 13khz - 20khz /or a higher weighted multifrequency work best / ..

[GB_Amateur]

You've done a lot of work and thank you for that.  But could you show these data in a table?  If possible show the composition and diameter (where applicable) for each coin.  It appears that between the two frequencies, some got better ('deeper') some got worse ('shallower') and at least one stayed almost the same.

I can't speak for others but I never would have guessed that a 98.6% purity gold coin that is slightly smaller than a 1 ozt 99.9% silver round would win this competition convincingly, and at both frequencies!

Once again I'm reminded that simple explanations don't capture the entire picture and one needs to be careful making generalizations, at least expecting those generalizations to cover all situations.

Now I wonder if this has anything to do with recovery speed.  Is the phase shift for the silver round later than for the large gold coin?  If so is it possible that the silver round signal is truncated, affecting the reported signal amplitude?  (Just talking off the top of my head, in case you didn't notice.  ?)

[EL NINO77]

17 hours ago, GB_Amateur said:

You've done a lot of work and thank you for that.  But could you show these data in a table?  If possible show the composition and diameter (where applicable) for each coin.  It appears that between the two frequencies, some got better ('deeper') some got worse ('shallower') and at least one stayed almost the same.

I can't speak for others but I never would have guessed that a 98.6% purity gold coin that is slightly smaller than a 1 ozt 99.9% silver round would win this competition convincingly, and at both frequencies!

Once again I'm reminded that simple explanations don't capture the entire picture and one needs to be careful making generalizations, at least expecting those generalizations to cover all situations.

Now I wonder if this has anything to do with recovery speed.  Is the phase shift for the silver round later than for the large gold coin?  If so is it possible that the silver round signal is truncated, affecting the reported signal amplitude?  (Just talking off the top of my head, in case you didn't notice.  ?)

 

....The purpose of this test was to find out how different detectors cope with high-conductivity coin type targets for deep detection... I recently had the opportunity to buy a CTX 3030 with a standard 11" coil and a large 13x17" coil at a very good price after tests on my test field where I have it buried higher a medium-conductive 50 euro cent coin at 37 cm with good results, I was curious how the test detector would cope with the other detectors I currently have with me Equinox, CTX, Atrex and ORX in tests for gold and high-conductivity silver coins... and high-conductivity Roman AS../coin/

Of course, I expected that the range of the CTX *3030 detector would be the greatest right on highly conductive coins... but as it turned out... the greatest range was right on a large 40 mm -14 gram 24 gold coin..

that surprised me a bit and that's why I tested the Equinox similarly on the multi programs Park1 and Park2 ... also on one frequency 4khz, 5khz, 10khz, 15khz, 20khz and 40khz...