Coal waste

[Mark-VA]

In the area where I live the old schools burned coal for heat. During the years of coal use they disposed of the coal waste on the school property. This waste will easily attract to a magnet and has almost completely shut down the hopes of ever finding metal targets over 2" deep. I have a couple areas that was used by adults to play ball for over 75 years (other ball fields where no waste was disposed of have produced many nice coins, rings and relics). We have yet to find the kind of treasures that should be there. I have experimented with the soil in this area for more than 5 years now and can say it is impossible to detect a clad dime at more than 2-3" deep in these areas. There has been more than 8 different metal detectors (Tesoro Vaquero, Tejon, Lobo, Garrett Ace 250 and AT Pro, Whites DFX and V3i, Minelab Explorer SE and Etrac) used in attempts of locating buried targets in these areas. As a final attempt I recovered a sandwich back of the material and sent it to Dave J. at 1st Texas for analysis and the following is his statement. Since this material attracts to a magnet the typical VLF machines are useless and only a PI machine might produce results. He did suggest borrowing a Whites TDI or some other PI machine in hopes of penetrating the soil in these areas. I would also like to add that there is very little grass growing in these vast areas I call the bad lands.

[mikebg]

I think a conventional PI machine can not to handle. You need PI operating with an induction balanced search head and gain control for preamp to avoid saturation. A TWIN LOOP machine will cope with problem. How deep are suggesting the desired targets?

[Mark-VA]

I have done some experimental diggings and the 4-6" range will be the limit for these areas. I might add, the sink rate in this soil is extremely slow.
One day I'll have the opportunity to try a PI machine and just see what comes up.

[Tepco]

Try PI and something will come out. From my own experience under similar conditions (coal waste) any VLF machine is more or less useless. First try some ordinary PI, monocoil will work just fine, considering depth (4-6in) and target size (coin, ring) only negotiate detector settings somewhat. Some more advanced machines will go try this soil very well, but first try some old,cheap, simple or DIY one, just to figure out it is worth trying at all, more or less ignoring technical aspects or testing detector maximum performance at this point.


Some 3y ago i tried DIYChance detector design, present on this forum, with some small modifications, under very similar conditions, it worked surprisingly well, despite i was bit disappointed with its performance in some other situations. Chance can be considered as advanced detector design however, despite it is simple and cheap to build.

[grungymike]

Gain control for preamp? I'm wondering about a panel mounted 1M pot in the negative feedback loop. What are the potential pros and cons?

[Mark-VA]

Not very likely I'll ever be able to buy a used PI. Very expensive for an experiment.
But I've read where they can really produce under this type of soil conditions.
I'll keep looking for a used unit for sale, Who knows I might even find one at an estate, yard sale.
I've also notice a few regular detectors at pawn shops.
But I don't know enough about them to tell if they are working correctly.

[TH Jim]

See the Surf PI Pro thread, unlike the 1.2 version the pro has adjustable gain/sensetivity making it useful for difficult conditions like highly trashy areas and EMF noisy environments.

Regards, Jim

[Mark-VA]

At sometime in the future I'll have an opportunity to try a PI in these locations.
I can only imagine the amount of non-feo targets I know are just beneath the ground in these areas.
I've actually buried a dime at 4" deep and can't get a half way decent audio response.

[bernte_one]

http://www.youtube.com/watch?v=3RFWNjv2yso
this is my modified baracuda
maybe you search something like that

regards

[Mark-VA]

Thanks, very interesting machine.

[Mark-VA]

Bad Lands Picture

Here is a picture of a small area in my bad lands coal waste.
Most of these small items attract easily to a magnet.
Very little grass grows in these areas.
Impossible to detect past 4 inches in depth.
I've actually buried coins at 4" and the detector would not sound off when passing the coil over the buried coin.