Which detector principle would be best for this particular purpose?

[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 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...

[homefire]

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

[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.

[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???

[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.

[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]

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.

[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.