What is this anomaly??

[DigDog]

I still believe the frequency of 12.5 khz is the best all around. Used by Tesoros and Garrett's mostly.

I tend to like 14khz-15khz personally.
Thats what latest Tesoro’s ran on and 17khz for the Tejon. I think those hit better on the smaller jewelry than coins which is what i primarily hunted anyways. 12khz seemed to be a good balance between coins and jewelry

 

[Odanscoils]

I tend to like 14khz-15khz personally.
Thats what latest Tesoro’s ran on and 17khz for the Tejon. I think those hit better on the smaller jewelry than coins which is what i primarily hunted anyways. 12khz seemed to be a good balance between coins and jewelry

Yup. I'm really liking my new Tejon.

 

[DigDog]

Yup. I'm really liking my new Tejon.

It will go deep.

 

[synthnut]

I don’t know how we got to the stigma that frequencies are for and only related to depth.
Yes typically lower frequencies go deeper but I think we are losing sight as to the different frequencies were not primarily put out for depth rather than the type of hunting you do.
Lower frequencies hit better on higher conductive targets like silver coins deeper and higher frequencies for lower conductive as well as sensitivity to smaller targets like gold. Different soils and mineralization is another aspect.
The smf is supposed to give the best of both worlds hitting more targets but at the expense of depth.
If frequency was primarily designed for depth only than gold prospecting would be done with vlf 4khz to get the small nuggets at 12”.
Actually why even have detectors above 4khz at that point.
Frequency depth is different in different locations but the frequency in vlf or smf should be chosen more focused what works best for the type of hunting you are doing and the depth is going to be what it’s going to be
Personally i don’t use 4khz. Not hunting silver coins either though.
Imagine using 4khz looking for that deep
Quarter at 14” in the meantime went right over and missed those two small gold rings or chains at 4”

I think that different frequencies in some cases are overly exaggerated….Gold chains for a lot of detectors are a tough nut to crack…Small gold rings are easier to detect….You should do some tests on your own in your soil with a small gold ring at different depths, and different frequencies…..I think that you’ll find that you can still hit gold at 4khz, just like you will hit clad and Silver coins at 40 khz….Optimally ? ….No, but you will still hit them….I’ve hunted, and set up for deep Silver in Old NYC parks, and have walked out with gold jewelry too !……Not an every day occurrence, but it happened just the same…

 

[vlad]

MY guess is "silent EMI" , that seems to be Tom's thing. I doubt he will bring it up as criticism since his rep is as an engineer and technician but pretty easy to push the others to uphold their reps as hacks and I'm sure they will accommodate. I have used both detectors and the Legend , in spite of the flies that buzz around it , smells better than the NOXs.

If its silent how do you know its there? Tom is the one of the best on explaining things. (Is the comment on his site?) Could he have been cloned?

 

[vlad]

I tend to like 14khz-15khz personally.
Thats what latest Tesoro’s ran on and 17khz for the Tejon. I think those hit better on the smaller jewelry than coins which is what i primarily hunted anyways. 12khz seemed to be a good balance between coins and jewelry

12 to 15 kHz was a frequency range picked out early by George Payne as being high energy and more responsive over a wide range of conductive targets and still able to handle wet salt and iron mineral. He always said odd frequency harmonics could get you in trouble with 60 cycle emi. (and the Treasure Baron was at 12 kHz and hit the market around '92.) But he also said any frequency was a compromise: below 12 kHz ground mineral or salt had much less effect The silver frequency of 2.75 and iron mineral and salt are non existent, At the same time it was very low energy did not respond to small targets or low conductors well and took a lot of battery energy to fill the Q of the loop. ( I recall seeing a Garrett design that was at 1 kHz) Frequencies above 15 kHz respond better to low conductors but are more affected by mineral and salt. (Troy Galloway chose 19 kHz for all purpose detecting and the air test on a nickel in air is astounding (and Troy designed some circuitry that had the X-5 hitting high conductors at an equal distance but he never told me how it worked) It is amazing how many makers chose 19 kHz for gold detectors. Coincidence? Georgi Chaushev and his Nexus use a Double O loop on many of his units and his coils are fully resonance matched, Its interesting to read about his detectors which are not motion: he is from Bulgaria and lives in the UK. Here is an old interview: http://www.amdtt.it/2015/01/exclusive-interview-georgi-chausev-nexus-metal-detectors/
Garys detectors in the UK is a good site to visit too for tests.

 

[DigDog]

12 to 15 kHz was a frequency range picked out early by George Payne as being high energy and more responsive over a wide range of conductive targets and still able to handle wet salt and iron mineral. He always said odd frequency harmonics could get you in trouble with 60 cycle emi. (and the Treasure Baron was at 12 kHz and hit the market around '92.) But he also said any frequency was a compromise: below 12 kHz ground mineral or salt had much less effect The silver frequency of 2.75 and iron mineral and salt are non existent, At the same time it was very low energy did not respond to small targets or low conductors well and took a lot of battery energy to fill the Q of the loop. ( I recall seeing a Garrett design that was at 1 kHz) Frequencies above 15 kHz respond better to low conductors but are more affected by mineral and salt. (Troy Galloway chose 19 kHz for all purpose detecting and the air test on a nickel in air is astounding (and Troy designed some circuitry that had the X-5 hitting high conductors at an equal distance but he never told me how it worked) It is amazing how many makers chose 19 kHz for gold detectors. Coincidence? Georgi Chaushev and his Nexus use a Double O loop on many of his units and his coils are fully resonance matched, Its interesting to read about his detectors which are not motion: he is from Bulgaria and lives in the UK. Here is an old interview: http://www.amdtt.it/2015/01/exclusive-interview-georgi-chausev-nexus-metal-detectors/
Garys detectors in the UK is a good site to visit too for tests.

So your opinion if you were to choose between using multi, 15khz, or 20 khz single frequencies that are available on the legend for gold jewelry which one do you think would work best in bery little to no mineralization soil?

 

[vlad]

So your opinion if you were to choose between using multi, 15khz, or 20 khz single frequencies that are available on the legend for gold jewelry which one do you think would work best in bery little to no mineralization soil?

It depends on how much battery power is put in individual frequencies of a multi, or in a single. No one says what the actual transmitter power output is in whatever it is measured in of each radio frequency. And the FCC classifies metal detectors as non emitters, so it is low. (A P.I. has 10x to 20x the power of a VLF but it can do this because it is a intermittent transmitter and can still have a "reasonable" battery life. If a VLF could transmit at the same level the battery life would be short because they transmit constantly.) The only thing you can do is personally test some targets in your area and tabulate the results. In wet salt I would think a multi would be deeper. But, in 1972 Technos Inc. in Maitland, Fla. had some NASA engineers get together and make a TR-IB high frequency unit with target i.d. on a meter called a P.R.G. or Phase Readout Gradiometer for hunting the beaches there for Spanish gold coins and it would hit a quarter at 12 inches in light to moderate minerals, and there was not a motion circuit or ground cancel circuit. (George Payne patented motion in 1977.) When the mineral increased though depth decreased, and it would not work it black sand (and from friends in Hawaii neither will a multi.) If you can get a signal in a single I would tend to think a multi format would do the same: but I'm not sure the reverse is true. (My go to detector is a CZ, but a close friend has very high praise for the Legend and has one and a similar competitor's model) and one is on my to buy list. NM is doing things right and offering a lot of features for the money.
I cannot say much more except to do tests on targets, and make sure its ground balanced: if you can, add a little positive offset.
(Do they have concentric loops?)

 

[DigDog]

It depends on how much battery power is put in individual frequencies of a multi, or in a single. No one says what the actual transmitter power output is in whatever it is measured in of each radio frequency. And the FCC classifies metal detectors as non emitters, so it is low. (A P.I. has 10x to 20x the power of a VLF but it can do this because it is a intermittent transmitter and can still have a "reasonable" battery life. If a VLF could transmit at the same level the battery life would be short because they transmit constantly.) The only thing you can do is personally test some targets in your area and tabulate the results. In wet salt I would think a multi would be deeper. But, in 1972 Technos Inc. in Maitland, Fla. had some NASA engineers get together and make a TR-IB high frequency unit with target i.d. on a meter called a P.R.G. or Phase Readout Gradiometer for hunting the beaches there for Spanish gold coins and it would hit a quarter at 12 inches in light to moderate minerals, and there was not a motion circuit or ground cancel circuit. (George Payne patented motion in 1977.) When the mineral increased though depth decreased, and it would not work it black sand (and from friends in Hawaii neither will a multi.) If you can get a signal in a single I would tend to think a multi format would do the same: but I'm not sure the reverse is true. (My go to detector is a CZ, but a close friend has very high praise for the Legend and has one and a similar competitor's model) and one is on my to buy list. NM is doing things right and offering a lot of features for the money.
I cannot say much more except to do tests on targets, and make sure its ground balanced: if you can, add a little positive offset.
(Do they have concentric loops?)

Thanks. These new digital detectors are a little different than what i was use to like a tesoro with a manual gb knob you can turn. Not sure how to get the same results with a digital since they basically auto gb themselves lol.
This was actually a confusing concept for me as i have asked but few understood what i was trying to say.
A manual gb analog detector like a Tesoro for example with a gb knob, you pump the coil and listen and adjust the knob accordingly more positive or negative, but in my soil no matter where the knob is or where, how much i turn it, dojesn’t change anything. So I assume that i have no mineralization hence why no change and it then doesn’t matter where it is at. Again this is my assumption as it is the same way with all the analog manual gb detectors. If i am wrong and the gb is actually not set correctly then it is a problem.
But now with the new digital detectors and auto gb, or even preset just let it do its thing. However the manual feature is there and acts the same as an analog with manual gb. So how do you add a little positive offset when there is no basis for a starting position.
No concentric that I’m aware of but they just this week introduced two more new DD options.
Concentric seems to be heading towards being obsolete as everyone is dealing with some sort of mineralization.

 

[vlad]

Thanks. These new digital detectors are a little different than what i was use to like a tesoro with a manual gb knob you can turn. Not sure how to get the same results with a digital since they basically auto gb themselves lol.
This was actually a confusing concept for me as i have asked but few understood what i was trying to say.
A manual gb analog detector like a Tesoro for example with a gb knob, you pump the coil and listen and adjust the knob accordingly more positive or negative, but in my soil no matter where the knob is or where, how much i turn it, dojesn’t change anything. So I assume that i have no mineralization hence why no change and it then doesn’t matter where it is at. Again this is my assumption as it is the same way with all the analog manual gb detectors. If i am wrong and the gb is actually not set correctly then it is a problem.
But now with the new digital detectors and auto gb, or even preset just let it do its thing. However the manual feature is there and acts the same as an analog with manual gb. So how do you add a little positive offset when there is no basis for a starting position.
No concentric that I’m aware of but they just this week introduced two more new DD options.
Concentric seems to be heading towards being obsolete as everyone is dealing with some sort of mineralization.

Does it have a stat mode (no motion hunting mode? And an adjustable threshold? Does the manual GB show numbers?
I hope concentrics do not head for obsolescence. They are deeper, they discriminate better and more accurately, have a symmetric search field and the coil has no dead spots, and are much quieter: 60 cycle can really be a problem for DD's and concentrics are much quieter. As to seeing less mineral that's almost a trick statement: it is because DD's see less ground. I strongly suspect a DD and a concentric that see the same amount of ground see the same amount of mineral. (the mineral is there)
A problem with designing them is the receive winding needs less turns in it yet many makers give an equal number.
(below is George Payne from the now deceased J Bird's old site that is gone)
There is a difference between the standard round and DD loops. On the coils I designed for Discovery I don’t recall a problem with excessive phase shift between the two coil configurations. When I first started designing coils for Discovery I decided to pick a particular frequency of operation and inductance for the Transmit and Receive coils. In addition the “Q” of the Transmit must be control within a certain range. For those who don’t know......the coil’s Q is the ratio of the coil’s inductance to its resistance at a given frequency. Whenever the coils change in size the turns are modified to return the inductance to the standard value. This tends to maintain winding resistance and more importantly, the Q of both the Transmit and Receive coils. So, its important to have standard coil values to target the design to. Normally this would be the coils, inductance, resistance and effective Q. It these values are maintained the resultant coil phase will be maintained over all coil designs regardless of the coils size and shape.
The DD coils can get you if you are not careful. As you know the Receive is generally the same size as the Transmit on these coils. Coupling that with the tendency to keep the Receive turns constant can result in a serious change in the coils output phase. Therefore, the Receive turns must be reduced considerably to lower the inductance back to the standard value. From a practical standpoint the inductance does not have to be exactly equal to the target inductances. As I said the tendency is to keep the turns the same as you change from one coil design to another. This tends to keep the sensitivity the same across many designs. However, that should not be the consideration. In this case its more important to control the phase across many designs. It’s better to look at it this way. For example, suppose that we build two Receive coils where one coil has twice the diameter of the other. But we keep the turns the same in both coils. For this example the larger coil would have an inductance that was twice the smaller coil. These coils would not have the same output phase. The larger Receive would easily have more sensitivity than the smaller coil because of the greater turns and coil area. However, this would not be a good design. The turns on the larger coil must be cut by .707 times. This would make both coils have the same inductance. Ideally we would also need to change the Receive wire size to keep the Receive resistance constant. Remember the coil Q is the ratio of its inductance to resistance at a given frequency. If we keep the inductance and resistance constant then the Q would also be constant. However, I don’t generally change the wire size on the Receive because if you maintain the inductance constant the resistance tends to not change as well. As I said, math calculations show that the wire size should be changed and to what size. But from a practical standpoint the Receive wire size can be left the same. When we reduce the Receive turns on the larger coil the coils characteristics approach the characteristics of the smaller coil. However, the larger coil will still has more sensitivity than the smaller one because of its greater area. The key here is not to get so concerned about the coil’s sensitivity that you forget about the overall design.
All that being said the DD coils do have the worst phase shift away from the target value. However, it can be control within acceptable limits as outline above. I don’t recall the exact phase tolerance on the Discovery DD coils but I think it’s below 0.5 degrees. We always calibrate the fixed ground phase trimmer to be +0.5 degrees. The phase of most soils do not go below -0.5 degrees. Therefore, we have a total difference here of 1 degree.

 

[DigDog]

Does it have a stat mode (no motion hunting mode? And an adjustable threshold? Does the manual GB show numbers?
I hope concentrics do not head for obsolescence. They are deeper, they discriminate better and more accurately, have a symmetric search field and the coil has no dead spots, and are much quieter: 60 cycle can really be a problem for DD's and concentrics are much quieter. As to seeing less mineral that's almost a trick statement: it is because DD's see less ground. I strongly suspect a DD and a concentric that see the same amount of ground see the same amount of mineral. (the mineral is there)
A problem with designing them is the receive winding needs less turns in it yet many makers give an equal number.
(below is George Payne from the now deceased J Bird's old site that is gone)
There is a difference between the standard round and DD loops. On the coils I designed for Discovery I don’t recall a problem with excessive phase shift between the two coil configurations. When I first started designing coils for Discovery I decided to pick a particular frequency of operation and inductance for the Transmit and Receive coils. In addition the “Q” of the Transmit must be control within a certain range. For those who don’t know......the coil’s Q is the ratio of the coil’s inductance to its resistance at a given frequency. Whenever the coils change in size the turns are modified to return the inductance to the standard value. This tends to maintain winding resistance and more importantly, the Q of both the Transmit and Receive coils. So, its important to have standard coil values to target the design to. Normally this would be the coils, inductance, resistance and effective Q. It these values are maintained the resultant coil phase will be maintained over all coil designs regardless of the coils size and shape.
The DD coils can get you if you are not careful. As you know the Receive is generally the same size as the Transmit on these coils. Coupling that with the tendency to keep the Receive turns constant can result in a serious change in the coils output phase. Therefore, the Receive turns must be reduced considerably to lower the inductance back to the standard value. From a practical standpoint the inductance does not have to be exactly equal to the target inductances. As I said the tendency is to keep the turns the same as you change from one coil design to another. This tends to keep the sensitivity the same across many designs. However, that should not be the consideration. In this case its more important to control the phase across many designs. It’s better to look at it this way. For example, suppose that we build two Receive coils where one coil has twice the diameter of the other. But we keep the turns the same in both coils. For this example the larger coil would have an inductance that was twice the smaller coil. These coils would not have the same output phase. The larger Receive would easily have more sensitivity than the smaller coil because of the greater turns and coil area. However, this would not be a good design. The turns on the larger coil must be cut by .707 times. This would make both coils have the same inductance. Ideally we would also need to change the Receive wire size to keep the Receive resistance constant. Remember the coil Q is the ratio of its inductance to resistance at a given frequency. If we keep the inductance and resistance constant then the Q would also be constant. However, I don’t generally change the wire size on the Receive because if you maintain the inductance constant the resistance tends to not change as well. As I said, math calculations show that the wire size should be changed and to what size. But from a practical standpoint the Receive wire size can be left the same. When we reduce the Receive turns on the larger coil the coils characteristics approach the characteristics of the smaller coil. However, the larger coil will still has more sensitivity than the smaller one because of its greater area. The key here is not to get so concerned about the coil’s sensitivity that you forget about the overall design.
All that being said the DD coils do have the worst phase shift away from the target value. However, it can be control within acceptable limits as outline above. I don’t recall the exact phase tolerance on the Discovery DD coils but I think it’s below 0.5 degrees. We always calibrate the fixed ground phase trimmer to be +0.5 degrees. The phase of most soils do not go below -0.5 degrees. Therefore, we have a total difference here of 1 degree.

Vlad unfortunately i had sold all those detectors years ago sad to say. Due to health problems I didn’t think at the time i would ever get back to doing it.
When I finally did the first thing i did was search for a new Tesoro and thats when I realized they along with others had gone out of business.
Now its all the “new” technology but on the positive side they are alot lighter something i had always desired in the older models. The Tesoro’s some of them were not that heavy although. Couple of my favorites was the sovereign on land and excal at the beach but were on the heavy side. Both had DD coils and we’re pretty deep. Couple of the tesoro i had were with concentric coils and were very deep.
Another thing maybe you can confirm is that from my understanding a DD coil “sees” in the ground in a U shape only about an inch or so wide and not sure if depth is relative to size/width of the coil.
And the concentric “sees” the ground in a V shape, as wide at the top as the coil and tapers down to a point at a depth relative to the coil size as well. So dd is a thin U and the concentric a V.
Understood both go as deep as the size of the coil but the concentric sees more wider area at the top and only a small point at the deepest part whereas the dd is more even top to bottom but field of view is only an inch wide but sees alot more area at the deepest part.

 

[vlad]

Vlad unfortunately i had sold all those detectors years ago sad to say. Due to health problems I didn’t think at the time i would ever get back to doing it.
When I finally did the first thing i did was search for a new Tesoro and thats when I realized they along with others had gone out of business.
Now its all the “new” technology but on the positive side they are alot lighter something i had always desired in the older models. The Tesoro’s some of them were not that heavy although. Couple of my favorites was the sovereign on land and excal at the beach but were on the heavy side. Both had DD coils and we’re pretty deep. Couple of the tesoro i had were with concentric coils and were very deep.
Another thing maybe you can confirm is that from my understanding a DD coil “sees” in the ground in a U shape only about an inch or so wide and not sure if depth is relative to size/width of the coil.
And the concentric “sees” the ground in a V shape, as wide at the top as the coil and tapers down to a point at a depth relative to the coil size as well. So dd is a thin U and the concentric a V.
Understood both go as deep as the size of the coil but the concentric sees more wider area at the top and only a small point at the deepest part whereas the dd is more even top to bottom but field of view is only an inch wide but sees alot more area at the deepest part.

Coil diameter does not necessarily mean it equates to the depth: and target size also must be factored in. A 3 foot manhole cover will be detected deeper than a 1/2 dime. Yet an ultra deep large loop will not hit a tiny gold nugget. And the better the resonance match generally enhances the depth. Georgi Chausev's loops are 100% resonance matched, and his Double O coil is maybe the deepest of all: his coils are handmade and he throws away 30% that do not meet the standard. You have the right idea: the DD is like a windshield wiper and hits from front to rear, and supposedly a little wider at the bottom, but not as deep. The DD also has more problems with steel washers and bottlecaps too, and this is from them being round and alloys. Concentrics handle them much better and they read lower on i.d. than DD's do. The F-75 is a great detector but the standard 11" DD is awful discriminating BC's. Put on the 10" concentric and its a different detector. (If you know someone using an F-75 w/DD let me know--I can tell you how to i.d. BC's 99% of the time.) If you like the analog types look at the Deeptech line. I CANNOT recommend Richard at backwoods enough. If you answer the questions I had above on the Legend I think I can help: but I do not have one yet. Check out Gary below on detecting tips. His video on frequencies is an eye opener (to me also.) https://www.youtube.com/@metal_detecting

And you can see the Double O loop below. (And Richard knows the Legend too.)
"est quod id est"

 

[vlad]

So your opinion if you were to choose between using multi, 15khz, or 20 khz single frequencies that are available on the legend for gold jewelry which one do you think would work best in bery little to no mineralization soil?

Watch this video on frequencies and target response. Its eye opening. (but he does not address multis)

 

[JCR TX]

Nokta has indicated they are seriously considering Concentric coils for The Legend. They have received very positive & enthusiastic response for the 2 they have available for the older Kruzer & Anfibio line of detectors. I have both the 7" & 9". They are great.

 

[DigDog]

Nokta has indicated they are seriously considering Concentric coils for The Legend. They have received very positive & enthusiastic response for the 2 they have available for the older Kruzer & Anfibio line of detectors. I have both the 7" & 9". They are great.

I would probably get one. I really liked some of the stock concentric coils Tesoro had.

 

[DigDog]

Coil diameter does not necessarily mean it equates to the depth: and target size also must be factored in. A 3 foot manhole cover will be detected deeper than a 1/2 dime. Yet an ultra deep large loop will not hit a tiny gold nugget. And the better the resonance match generally enhances the depth. Georgi Chausev's loops are 100% resonance matched, and his Double O coil is maybe the deepest of all: his coils are handmade and he throws away 30% that do not meet the standard. You have the right idea: the DD is like a windshield wiper and hits from front to rear, and supposedly a little wider at the bottom, but not as deep. The DD also has more problems with steel washers and bottlecaps too, and this is from them being round and alloys. Concentrics handle them much better and they read lower on i.d. than DD's do. The F-75 is a great detector but the standard 11" DD is awful discriminating BC's. Put on the 10" concentric and its a different detector. (If you know someone using an F-75 w/DD let me know--I can tell you how to i.d. BC's 99% of the time.) If you like the analog types look at the Deeptech line. I CANNOT recommend Richard at backwoods enough. If you answer the questions I had above on the Legend I think I can help: but I do not have one yet. Check out Gary below on detecting tips. His video on frequencies is an eye opener (to me also.) https://www.youtube.com/@metal_detecting

And you can see the Double O loop below. (And Richard knows the Legend too.)
"est quod id est"

Vlad the thing is depth is not as important to me anymore.25 years ago i would dig deep holes but with my health i have no interest in digging past 10”-12”
Fortunately for me my soil is very sandy and loose. I don’t even use a shovel anymore lol.. Whatever i can easily dig out with a Lesche tool or sand scoop is good enough. Most of my soil is so loose after i cut through any grass i can actually use my hands to dig. Ive fixed and replaced sprinklers in my yard with just my hands.
For me anyway a coil over 10” is just to big. Most of my detecting is small areas around parks, houses, etc where there is alot of trash anyway. The beach would be the only exception.and even there not looking to go very deep.
Would a concentric really benefit me anymore not so sure. Better discrimination but what about separation if you are looking in shallow trashy areas or just shallow for that matter. I like a nice 6x9,small with decent coverage imo. A good combination of both.
The 9x8 concentric Tesoro had was a good size that seemed very deep.
A F-75 with a concentric is very interesting. I always pondered on the F75 but never got one.
Kind of spoiled now with the legend If I want to run in multi i can if i want a single vlf i also can.

 

[DigDog]

Watch this video on frequencies and target response. Its eye opening. (but he does not address multis)

Ive seen his frequency comparison videos before. Very interesting and informative

 

[DigDog]

Watch this video on frequencies and target response. Its eye opening. (but he does not address multis)

The multi is a mystery as the information on the exact frequencies they use and how is proprietary. Would love to see that.

 

[vlad]

The multi is a mystery as the information on the exact frequencies they use and how is proprietary. Would love to see that.

Since multi has been out since 89 (and Fisher invented it) I think its not proprietary and is understood. Besides ML and Fisher, Whites, NM and Garret use it,
Ask NASA Tom, or Ty Brooks who wrote the Tek Talk column for WET for many years.

 

[sprchng]

Getting back on track with the OP , has anyone tried to replicate the anomaly and been successful?