Coil choise

[Geo]

Hi.
I want to hear your opinion about who is the best dimension of a coil, so to detect at more depth a coin 20mm or bigger.

Regards

[WM6]

Hi.
I want to hear your opinion about who is the best dimension of a coil, so to detect at more depth a coin 20mm or bigger.

Regards

"20mm or bigger" How bigger Geo?

Here we can apply simple formula:

1mm (dia of coin) = 1cm (dia of coil)

Mean to 20mm coin suit better 20cm coil in soil. Approximative of course.

[Geo]

Hi WM6.
I want to look for some Old coins at depth about 40cm+...
Because i found some coins in the same terrain and at lower depth, i want to use the coil that will give the best depth. Coins are 20mm and 22mm.
But i am afraid that it is not possible to detect the coins at this depth especially on winter where the terrain is "heavy"

Regards

[geminis74]

Hello, Geo
the only detector that gets it (which I have had) is the NEXUS standard, 1 € approximately 38-40 centimeters.
the problem is:
1 - money detector
2 - very difficult work of ceramic sites (uncomfortable, many signs)
3 - the currency has to be completely flat up (hard match)
conclusion
Is it worth it?

[WM6]

Hi WM6.
I want to look for some Old coins at depth about 40cm+...
Because i found some coins in the same terrain and at lower depth, i want to use the coil that will give the best depth. Coins are 20mm and 22mm.
But i am afraid that it is not possible to detect the coins at this depth especially on winter where the terrain is "heavy"

Regards

Geo if you cannot detect coins at such deep by your TDI, than you cannot detect by no other detector. But maybe you need some bigger, about 11", coil (which coil you get with TDI?). Use only Whites coil.

Read manual, visit TDI forums and practice how to use e.g. single tone coin hunting mode and other TDI features. Here something from reg (on Au forum):

"In reality, most of us are still learning about the best ways to use the detector and all the features it has. The one with the most knowledge and experience that posts on this forum is Eric Foster. He is the man who designed the GS 5 and assisted with the design of the TDI.

The person with the most experience with the single tone feature is me and even I don't have all the answers as to the best way to use it. I am the one to first install it on a PI and first to try to use the single tone for coin hunting. This feature is very new and was first installed on my GS 5 about in March of this year. At the time, I wasn't sure just what I would find but I thought the idea of only hearing one tone had real benefits. As it turns out, the feature added a whole new dimension to the detector. Fortunately, at the last minute, White's decided to add it to the TDI. So, the fact the concept is so new, there hasn't been extensive time to fully investigate this feature even by me.

Getting back to the Whites forum, a really good post is the one on Civil War Relic Settings. It is a good place to start regardless of what you will be hunting. The exception would be if you were to try to coin hunt with the TDI. Then I would use what I call the single tone Coin hunting mode used to find high conductive coins such as silver dimes and copper pennies. This mode does deviate from the normal settings in the fact, the ground balance is reduced from the normal setting of 9 or so down to around 5 or so. The exact final setting is more of an operator preference, but the fundamental setting is to minimize signals from buried ferrous junk such as nails, bottle caps, etc.

If I were to add to the post mentioned, I would add the importance of a nice smooth sweep speed and technique. Avoid rapid or jerky motions. Don't be afraid of keeping the coil low to the ground for maximum depth. Also, try to keep the coil level above the ground. If you encounter a really strong signal, raise the coil and pass over the object again to see if the signal changes. With practice you can become quite proficient at determining what is what."

[Geo]

Hello, Geo
the only detector that gets it (which I have had) is the NEXUS standard, 1 € approximately 38-40 centimeters.
the problem is:
1 - money detector
2 - very difficult work of ceramic sites (uncomfortable, many signs)
3 - the currency has to be completely flat up (hard match)
conclusion
Is it worth it?

Hi.
You wrote the problem..... Ceramics. Also at heavy terrain Nexus can't take these great depths. I am interesting more for the TDI..
Regards

[Geo]

Geo if you cannot detect coins at such deep by your TDI, than you cannot detect by no other detector. But maybe you need some bigger, about 11", coil (which coil you get with TDI?). Use only Whites coil.

Read manual, visit TDI forums and practice how to use e.g. single tone coin hunting mode and other TDI features. Here something from reg (on Au forum):

"In reality, most of us are still learning about the best ways to use the detector and all the features it has. The one with the most knowledge and experience that posts on this forum is Eric Foster. He is the man who designed the GS 5 and assisted with the design of the TDI.

The person with the most experience with the single tone feature is me and even I don't have all the answers as to the best way to use it. I am the one to first install it on a PI and first to try to use the single tone for coin hunting. This feature is very new and was first installed on my GS 5 about in March of this year. At the time, I wasn't sure just what I would find but I thought the idea of only hearing one tone had real benefits. As it turns out, the feature added a whole new dimension to the detector. Fortunately, at the last minute, White's decided to add it to the TDI. So, the fact the concept is so new, there hasn't been extensive time to fully investigate this feature even by me.

Getting back to the Whites forum, a really good post is the one on Civil War Relic Settings. It is a good place to start regardless of what you will be hunting. The exception would be if you were to try to coin hunt with the TDI. Then I would use what I call the single tone Coin hunting mode used to find high conductive coins such as silver dimes and copper pennies. This mode does deviate from the normal settings in the fact, the ground balance is reduced from the normal setting of 9 or so down to around 5 or so. The exact final setting is more of an operator preference, but the fundamental setting is to minimize signals from buried ferrous junk such as nails, bottle caps, etc.

If I were to add to the post mentioned, I would add the importance of a nice smooth sweep speed and technique. Avoid rapid or jerky motions. Don't be afraid of keeping the coil low to the ground for maximum depth. Also, try to keep the coil level above the ground. If you encounter a really strong signal, raise the coil and pass over the object again to see if the signal changes. With practice you can become quite proficient at determining what is what."

Hi WM6.

At my TDI, i use the 12" coil. But when i use the Ground balance, the depth is about 20... 30 % down. I use it at 17.5us delay and the GB at 5....6 so to reject some iron objects. So i need more depth, this is the reason that i ask for the best coil size for detect a coin 20mm.
Is there some formula to calculate it????

[Reg]

Hi Geo,

I have attached a chart posted several years ago by Eric Foster showing what one might expect for depth when using different coil sizes. It takes some time to figure out, but I have found it to be reasonably accurate.

Unfortunately, ground conditions can distort the final results, especially if working areas where the ground is bad.

Now, with that said, the general concept is if you are getting less but close to half of the diameter in depth, then increasing the coil size will not help that much.

As an example, lets say you are using the 12" factory coil on the TDI and only can detect the coins at 7", then making a larger coil may only gain 1" to 2" max and that doesn't take into account if you have trash in the area that can affect the results.

The depth loss because of the ground balance can vary depending upon the coin's material and conductivity. If your coins are silver or copper content meaning they are highly conductive, then advancing the ground balance will help quite a bit and can add as much depth as increasing the coil size.

Sometimes increasing the GB setting will make it easier to tell iron objects also because they will have a tendency to double blip or change tones as the coil passes over them, while a silver or copper coin will not do the same thing.

Like you I will turn the GB down to 5 or so to reduce the amount of iron trash I will have to dig, but once an area has been hunted out, I will then increase the GB to above 9 to maybe 10 or so and this will add a couple of inches more of depth which is about all I might expect if I increased coil size.

If I get a good signal at the higher GB and I can't tell if it is clearly copper or silver, I will then reduce the GB and listen carefully for a smooth very weak signal. In the single tone mode, silver and copper will give the smooth tone, but a lot of the iron junk will stutter or have a sharp edge to the signal. Unfortunately, some wire or nail objects can still sound good. So, some of the time I can use this technique which sort of tells me the buried object is probably a coin but not always.

This technique is not foolproof but it does help. It also takes more time and more practice to use it effectively.

Reg

[Geo]

Hi Reg.
Thank you for the info .
I agree that with higher GB i have better depth but there is problem with the iron objects. When i say iron i mean rust iron objects, especially objects of rusted steel . I am looking more for copper and silver, so especially for the rusted steel i must turn the GB to 1 so to reject it. But if the signal is low... i can't understand if it is copper, silver or rusted steel because if i will put the GB=1 i will lose all of them. So if the signal is very low i must dig.....

Regards

[ivconic]

Forget all other models and coils....BS!

If you exactly want to dig coins at 35-40 cm depths than buy XP Gold Max Power (default coil 22cm, but you can ask for a bit larger...some 28cm..as i remember) and go to dig those coins.
All other stories, about other coils and models are.......never mind!

[WM6]

. So if the signal is very low i must dig.....

Hi Geo,
Take an assistant with you and he should dig.

[Reg]

Hi Geo,

You are right, there is no way to ignore all the iron junk and turning the GB down to 1 helps a lot, but like you said, there is a serious depth loss on detecting good targets at this setting.

Now, as I said, I turn the GB up to a higher number, maybe 10 and listen carefully to the signal from the buried object. I have learned a few tricks that let me know more about at least some of the buried objects at this higher GB setting. It certainly isn't foolproof but it does help reduce the junk I dig.

Now, coins are smaller targets always smaller than the coil, so sweeping slowly over a target tells me a lot. A very wide target will almost always be iron junk. A coin will almost always give a very smooth rising signal from any direction. I piece of iron junk may give a good signal one way, but may stutter, shut off, or be an abrupt signal when passing over the object from another direction.

Large iron objects can change signals by raising or lowering the coil and passing over the object again.

All of my suggestions take time to learn so don't expect it to be easy right away. These techniques are much easier to learn if you are very familiar with using a PI that has no disc feature at all. If all you have ever used is a VLF with a good discrimination feature, then using my techniques will be difficult to learn at first because they are a step backwards or feel like a step backwards.

Where I live, no VLF will detect many of the coins deep because the ground is so bad. That is why I now use the PI. In mild ground, the VLF will probably do better, but I don't have that option where I hunt, so if I want to detect the older deeper coins I have to use what works and that is using a PI. That is why I am always trying different things.

Nothing is perfect and my techniques work better in some places than others, but when nothing else works, a person has to try something.

Reg

[Geo]

Hi Reg.
I am familiarized with both vlf and PI technology.
I use a XLT, GTI2500 and a Minelab Sovereign but when there are ceramics or the ground is "bad" i have not good results. Also i use a Superscan with 1x1 coil and a Delta Pulse with 20.... 55cm coil. But PI have bigger problem at old ceramics, so TDI is a very good solution if i will gain some depth more!!!. Also i saw that some "soft" rusted iron objects makes a switched sound on TDI when i have the Gbat 5..... 6, so i understand then and i don't dig.

I will try your tricks, and i hope they will work good for me

Regards

[Geo]

Hi Geo,
Take an assistant with you and he should dig.

Yes, but i must stay at terrain until he will dig, and now is winter