Whites TDI Classroom

Hello friends!

I've been using several VLF detectors but it appears that the depth is crucial for the Roman coins on my fields, which are my primary targets.

It'll be very useful for me( I believe for many other members too) to get opinion from experienced users about TDI on Roman sites, which are quite iron-contaminated areas.I wonder if the TDI will be fine for detecting bronze Roman coins( no doubt about silver ) ?
I reckon that the bronze is not as high conductive as silver and gold, but I need to know if the TDI will sound the same ( with high pitch tone), or at least similarly as for high conductive metals?
Any guidance or the maximum depth for small( 10-15 mm), medium (15-25 mm ) or large bronze coins(over 25 mm) will be additional help for a potential buyer of a TDI. Suggestions about additional deep coils are also welcome.

Thanks in advance and HH

The lack of replies is likely because this is a new area for TDI users, most of whom are in the USA or Australia. It is a certainty that the Romans never reached the American shores, in fact there is scant evidence that they even ventured to the east coast of Ireland. There are only a handful of TDI users in England and I do not know of anyone who has used a TDI for this purpose. That is not to say that it wouldn't excell at finding such coins, but one would need to run some tests to see what the responses are. Sad to say that I do not have any Roman coins now, even though in the early days pulse induction detectors were used to great effect on archaelogical sites to find ancient coins. Many Roman sites have strongly mineralised ground, so the GB feature would be very useful. Also such sites are often littered with small iron i.e. sandal nails, which although ancient, are of little interest. The response from bronze coins would depend on their diameter and thickness. Larger bronze coins would almost certainly give a low tone, while the small coins would likely give a high. Silver usually gives a low tone unless very thin and small. Gold depends very much on the purity, as well as size and thickness. I searched a Roman site (with full permission) many years ago and was frustrated by all the nails, as the straight PI I was using had no discrimination. However, a larger than normal signal got my attention, and it turned out to be a nice iron Roman door key. I suspect that sandal nails, being very small would give high tones, so by switching to the high conductor mode would bring in the larger bronze and most silver coins, as well as eliminating any ground response. Why not buy a few coins on ebay and see if a Whites dealer has a TDI that you could test them on?

Eric.

I have a tdi and a handful of Roman coins I purchased on eBay. I will try to test them this week to see what sort of signals result(high/low).

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White's IDX Pro, White's TDI SL



Edited 1 time(s). Last edit at 10/14/2011 04:07PM by dbsmokey.

Yes the TDI will find the small Roman bronzes in mineralised ground, All of a batch of 47 I have tested you will get with the machine set to low conductors as set for standard nugget hunting.
A lot of small hammered silver coins can come in at this range also.
The only issue is a lot of small Iron must be dug and can delay your search time and you will have to go over the same ground again in high conductor setting for any targets ring pull and above conductivity readings.

There is an alternative you could try....

I have yet to try a small DD coil on the TDI but I have a standard Minelab GPX5000 DD coil which works well on mineralised pasture using this method.

So, the theory is, stick a small DD coil on and search in normal pulse mode (not GB mode). If you can work your site this way (perhaps with lower sensitivity settings) discrimination on small iron is not such an issue, signals are smoother and you won't hide as many non ferrous targets behind iron. I would advise you practice this method on the beach wet sand areas to get a feel for different target behavour so you can suss out iron signals from good non ferrous ones.

I've added a pic of some Roman coins tested, found recently with another detector, All but the largest coin read as low conductor.



Good hunting

Terry.



Edited 1 time(s). Last edit at 10/15/2011 01:02AM by Terrytorment.

Thank you friends for your time given to this topic. I have already found dozens of Roman coins with my VLF detectors, mostly the coins were on depth between 10-20 cm( 4-8 inches), and mostly on a meadow and cultivating fields. The problem I am sometimes facing with is that, in one particular field where I found most of the coins, the ground is so mineralized and so condensed( compressed) that my VLF machine barely detects a large bronze coin (20 + mm diameter) on 5 inches on the dry soil. Yesterday I was beeping around,dug out 2 coins and 2 beautiful large finger rings(one of them was the deepest target, over 8 inches), but the soil was very wet due to heavy rains in past several days.I believe that you also noticed increased detector's depth on a wet soil.
I don't own a TDI so I can't run any test, but I would highly appreciate everybody's efforts in presenting one on this topic.
What I also need to know is whether the TDI will be deeper than common VLF detectors on large bronze and silver( over 20mm) and discriminating small iron at the same time? Also, I would like to know what was your deepest findings with TDI equipped with 12'' coil ? Just as a comparison, my VLF brand machine with 12x15'' butterfly coil detected a large Roman bread frying-pan (iron, diameter around 11+ inches) on 80+ cm with a quite strong audio signal.
Greetings and happy hunting

Depends on the ground. What is the number you achieve ground balance? You will loose depth on all high conductive coins with normal thickness. The lower the GB the more depth is lost. Good news is small low conductive coins such as hammered will ring thru loud and clear. You can manipulate the GB control to a point were some small ferrous targets will shift tones.

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Geo






Eurotek Pro ( coming soon)

In the closet:
Blisstool
TDI
Sov.GT
Headhunter Wader
Vista Smart

Quote
LOTR
Thank you friends for your time given to this topic. I have already found dozens of Roman coins with my VLF detectors, mostly the coins were on depth between 10-20 cm( 4-8 inches), and mostly on a meadow and cultivating fields. The problem I am sometimes facing with is that, in one particular field where I found most of the coins, the ground is so mineralized and so condensed( compressed) that my VLF machine barely detects a large bronze coin (20 + mm diameter) on 5 inches on the dry soil. Yesterday I was beeping around,dug out 2 coins and 2 beautiful large finger rings(one of them was the deepest target, over 8 inches), but the soil was very wet due to heavy rains in past several days.I believe that you also noticed increased detector's depth on a wet soil.
I don't own a TDI so I can't run any test, but I would highly appreciate everybody's efforts in presenting one on this topic.
What I also need to know is whether the TDI will be deeper than common VLF detectors on large bronze and silver( over 20mm) and discriminating small iron at the same time? Also, I would like to know what was your deepest findings with TDI equipped with 12'' coil ? Just as a comparison, my VLF brand machine with 12x15'' butterfly coil detected a large Roman bread frying-pan (iron, diameter around 11+ inches) on 80+ cm with a quite strong audio signal.
Greetings and happy hunting

Hi LOTR,

Did you manage to get the answers to your questions re TDI/VLF? I am interested in this information myself. Just posted a message asking if there is anyone within the UK working farmland with the TDI.
Richard

well, the answers/tips given above are quite useful but i think that the best way is to test tdi pro/sl on the roman field and get the right overview of how it performs.so far no perfect detector, only the one that fits to your needs

cheers