Which detector principle would be best for this particular purpose?

[Davor]

Guess that would tell the difference.
I am very happy with my IGSL recovery speed, because the original layout was not providing what I expected and I had to tweak it. The discrimination blocks in IGSL are the classic Tesoro design, and from what I know now they can be improved ... a lot. Now it is fast, accurate, and does not saturate. I guess my IGSL would surely pass the Monty's board with flying colours, but then again - the other detectors would as well.

[pelanj]

I'm a bit confused now. So it seem as if the iron in the ground is masking good coins and you don't get indication :duh:
I have very limited experience in metal detecting, and it all comes from using my only IGSL so I can not vouch for other detectors. However, I have a very old and rusty knife with brass bolts on the handle, and when I play with it I get a clear indication for the brass bolts - in spite of a large piece of iron they are bolted to.
I did some modifications to my discrimination channels to improve their dynamic range, recovery speed and stuff, but they couldn't be that much better than the rest of the detectors out there, could they???

Yes, that is exactly it - the coins are hidden in discrimination by the iron. I need to setup a test rig - something like Monte's nailboard test - to get some results from comparation.

[pelanj]

A good kit is the TGSL ... but why would you need that when you already have a Tesoro?
Your best bet is still to go for a much smaller coil like the 4" one, or the 5.75" coil that you have already.

I think the Silver uMax is not the best/quickest of all Tesoros. It is fun to use nonetheless.

[pelanj]

If I knew for a Fact there was coins like that out there, I would be diging anything that Twiched. LOL

There are some, but the easy ones are already out. I do not want to dig 100 pieces of iron for 1 coin (estimation). I would like to make my chances better. The coins are not very valuable if at all. I take it as a challenge.

[Davor]

I'm a bit confused now. So it seem as if the iron in the ground is masking good coins and you don't get indication :duh:
I have very limited experience in metal detecting, and it all comes from using my only IGSL so I can not vouch for other detectors. However, I have a very old and rusty knife with brass bolts on the handle, and when I play with it I get a clear indication for the brass bolts - in spite of a large piece of iron they are bolted to.
I did some modifications to my discrimination channels to improve their dynamic range, recovery speed and stuff, but they couldn't be that much better than the rest of the detectors out there, could they???

[Qiaozhi]

Which of the kits available would you recommend for modifying? I need at least the PCB, I can get the other parts myself. Which one could use a manufactured coil?

I do not mind crackle on iron - it is recognizable from a good target with my Tesoro. What I mind is that I get only crackle from iron and no signal from the coin...

A good kit is the TGSL ... but why would you need that when you already have a Tesoro?
Your best bet is still to go for a much smaller coil like the 4" one, or the 5.75" coil that you have already.

[homefire]

If I knew for a Fact there was coins like that out there, I would be diging anything that Twiched. LOL

[pelanj]

You don't need much motion, so don't worry. If you intend to build your own detector just calculate the high pass filters for a lower cutoff and you'll have the best of both worlds, and you'll have less problems with 1/f noise of the non-motion design.

My experience of roaming the trashy field is that I'd be lost without the ferrous discrimination. Point is that many of the ferrous objects have some galvanisation layer that gives some crackly indication in a non-ferrous channel. So like it or not - you'll never be able to delete ferrous objects from your indication, at least in form of a crackly annoyance. On the other hand, when I have a strong Fe indication at least for some short period of time I know for sure that there is a galvanised piece of iron junk. Fast and efficient.

Which of the kits available would you recommend for modifying? I need at least the PCB, I can get the other parts myself. Which one could use a manufactured coil?

I do not mind crackle on iron - it is recognizable from a good target with my Tesoro. What I mind is that I get only crackle from iron and no signal from the coin...

[Davor]

The problem is that a motion detector with 8" coil will not really fit into some of the spaces. A 6" or smaller could do it - but as the space is restricted, I do not know if there is enough space to swing it, so I though a non-motion detector would be easier.

You don't need much motion, so don't worry. If you intend to build your own detector just calculate the high pass filters for a lower cutoff and you'll have the best of both worlds, and you'll have less problems with 1/f noise of the non-motion design.

My experience of roaming the trashy field is that I'd be lost without the ferrous discrimination. Point is that many of the ferrous objects have some galvanisation layer that gives some crackly indication in a non-ferrous channel. So like it or not - you'll never be able to delete ferrous objects from your indication, at least in form of a crackly annoyance. On the other hand, when I have a strong Fe indication at least for some short period of time I know for sure that there is a galvanised piece of iron junk. Fast and efficient.

[pelanj]

You dont want anything different to all of us in europe.

To really help you we need more info.


DO you

Want to build your own machine?
Do you want to buy a new machine?
Are you going to use your existing machine?

etc
S

I could build a detector if simple or from a kit. Preferably using coil from a professional manufacturer (SEF, NEL, Tesoro, etc.)- I do not want to build a coil myself. If not too expensive, I would buy a detector (preferably second hand) just for that as an upgrade of what I already have. I prefer "tesoro style" detectors - take the iron away (or let me know with a low tone) and dig the rest, no display needed, multi-tone optional.

I saw Rutus Jupiter, XP GoldMaxx and C.Scope CS6MX performing really well in iron on youtube. The non-motion C.Scopes could see a coin below nails even better.

[pelanj]

Without searching for my 4" coil and actually making the test, I think from memory that depth is very respectable and should do the job. Your 5.75" coil will certainly be ok.

To test how much your detector suffers from iron masking, try placing a coin under a rusty nail and see if it can be detected. I suspect the problem you're having is more related to the diameter of the coil you're using, as it can "see" more ferrous targets relative to the non-ferrous. That's why you need a smaller coil.

I yet have to try that, but definitely will. I thought the 12x10 DD would separate better lengthwise, but it does not. I kind of expected that the minimum distance where the coin gets detected would be equal to the width of the DD overlap - it is not the case, the diameter of one coil is the minimum distance to register the coin while iron is supressed (minimum disc on the Silver uMax). Even in "all metal", I get a beep only on the nail and not two beeps - nail and coin.

[golfnut]

You dont want anything different to all of us in europe.

To really help you we need more info.


DO you

Want to build your own machine?
Do you want to buy a new machine?
Are you going to use your existing machine?

etc
S

[Qiaozhi]

I have read somewhere that a very old BFO decector was the best one in a similar place - but maybe I just do not remember correctly. I will try the smaller coil I have (5.75"), but I still have such a feeling that my Silver uMax suffers quite a lot with iron masking compared to other detectors. Do you have any idea how deep could the 4" coil get? I would really like to get down to 6", there should not be much below.

Without searching for my 4" coil and actually making the test, I think from memory that depth is very respectable and should do the job. Your 5.75" coil will certainly be ok.

To test how much your detector suffers from iron masking, try placing a coin under a rusty nail and see if it can be detected. I suspect the problem you're having is more related to the diameter of the coil you're using, as it can "see" more ferrous targets relative to the non-ferrous. That's why you need a smaller coil.

[pelanj]

you need something VLF-IB with NOTCH FILTER, yes, maybe King Cobra, with 6'-8' coil.

good luck

What would be the notch filter good for? I thought it was meant to knock out specific targets - as pulltabs, etc. I want to dig all non-ferrous.

[kt315]

small silver and copper coins amongst larger pieces of iron (nails, screws, horseshoes).

you need something VLF-IB with NOTCH FILTER, yes, maybe King Cobra, with 6'-8' coil.

good luck