By Mark Gillespie
A few things I've learned about coal waste hunting.
I started inquiring about some old locations I hunt. Most of the locations are old, shut down schools where coal was used as a heating source for decades. Before the EPA was birthed most people did what ever pleased them when it came to disposing of waste, regardless of what it was and these old school sites are no exception. The burnt coal waste was spread over many acres of school property which created some extremely harsh ground conditions. Grass and weeds find it hard to get a start and most areas are void of any vegetation. Most of the school grounds look like Martian landscapes with small BB size or smaller pieces of coal waste everywhere. This material attracts to a magnet with little effort and can reduce depth of all VLF detectors by well over half. In fact until recently maximum detection depth was actually 2-3”. Any target deeper would give a solid iron audio report if any sound at all. After many years of hunting these areas, all but completely unsuccessfully, I finally purchase a White’s TDI SL.
It turned out the SL opened up these old sites and many nice coins, relics and gold jewelry were unearthed, but not without many trials and numerous adjustments.
Case in point: one particular area had been, in my opinion hunted out with many different VLF machines (ranging in cost from $250 - $2000) over a 10 year period and I was certain there were no good targets left.
Now I’m going to fast forward 2 years of hunting experience and mention a couple very important and rewarding hunting trips that might help someone.
Settings: sensitivity 6, ground balance 7 ½, pulse delay 10 and conductivity set to high and used the stock 12” dual field coil
First was an old school site where both coal waste and nails are very abundant. I had been hunting about 15 minutes and all the SL was giving were very short audio reports, which sounded more like chatter or EMI and not targets. This prompted me to increase the time delay to about 15 , which increases the time before a transmitted signal is analyzed, thinking the small pieces of coal waste were the short reports (partial masking) I was hearing. Continued hunting another 5 minutes and noticed the short audio chatter continued but not to the same magnitude. Stopping and increased the delay to around 17 and off I went hunting again. Suddenly I noticed the machine was running very quiet, to quiet.
A minute or two later and a very loud low tone, which on the SL means a high conductor, I stopped and reduced the delay to 10 and found my definite answer. The coal waste was causing the ground chatter and false audio reports. Increased the delay back to 17 and recovered a wheat penny around 4” deep. Now to be honest I had to stop for a moment and think about what just happened. Decided to start over I returned to where I began hunting and discovered I had passed right over many good targets. After digging a few more wheat pennies and a silver dime I decided to start checking these targets before digging and discovered if I decreased the delay most of these targets became the short sounding audio reports I had heard earlier. The PI was just the trick to discovering some nice coins deeper than 4” in these barren areas. From this site I learned the time delay helps with eliminating small metallic pieces from interfering with coins and other relics.
I must admit, at times, I tend to over think some of my hunting trips but the thought came to mind. What if there was gold jewelry in the area where I was hunting coins (conductivity high)? Yes I could have been hunting with a setting of all but the area is so polluted with targets I chose only high.
So another trip to the same site with only two setting changes pulse delay 15 and conductivity set to low. In addition to this I change, I opted for the smaller 7 /12” dual field coil. Again the delay settings helped with the coal waste problem mentioned above and allowed me to hunt with a little sanity.
Less than 15 minutes later came my first ring, not gold but gold plated, but that helped motivate me to keep going. Dug a couple beer pull tabs and finally a nice gold class ring came to light. What a very rewarding hunt it turned out to be.
Mark Gillespie 2017
By Steve Herschbach
White's quietly instituted a summer sale (ends in August) that resulted in some steep price drops for some models. The TDI SL was dropped from MSRP $1299.95 to $1099.95 which in turn created a Minimum Advertised Price (MAP) of only $989.
As ground balancing PI (GBPI) detectors go the TDI SL is no powerhouse, but this price reduction puts it firmly in VLF country as far as the hit it will put on your pocketbook. If you have a VLF and places it refuses to work due to intense ground and hot rocks, this presents an affordable potential solution.
just a short video from a few weeks ago, in the video I quickly sweep over an area to clean off the surface targets so I can work the area later with the GMT, good example of using two cheaper gold detectors to your advantage.
oh' don't watch it if your sensitive to swearing or dogs feeding themselfs.
Enjoy, I'll post up another video later on.
Just thought I'd share the settings I use when I'm out hunting for gold in Australia.
First setting: General gold detecting
Set pulse delay to 10' Ground balance in ALL as best as you can' between the high and low tone.
Flick into LOW and sweep the coil if your getting ground noises which I generally do just turn the GB up half a notch' so from 9 go to 9.5, if need be you can go a full notch without any huge loss on depth or sensitivity' this should now allow you to use full gain.
Dig all high tone responces and listen carefully.
Just note that running Low you will only find gold up to about 7-10grams
If you still continue to get strange sounds that you can't ignore by advancing the GB setting, try the the GB process all over again but at 12 pulse delay.
Second setting: large deep items
When Using HIGH set pulse delay at 15-20' ground balance in ALL as best as possible' it will actually be a lot smoother because of the pulse delay setting' flick into HIGH, to remove any ground noise you now "reduce" the GB setting a little say from 6 go to 5.
In High you will only detect targets the machine thinks are high conductive and any gold over about 7 grams, don't be concerned about loosing small gold you won't detect it anyway so in this setting run big coils and Use full Gain if possible.
Dig all repeatable low tone responces if it turns out to be ground noise reduce the GB setting more up to about 2 notches from the original GB setting or do the GB process again but at a higher pulse delay.
This setting will go deep expect big holes.
Set the frequency correctly if you can't, use the machine away from EMI but generally the TDI doesn't suffer that bad.
Iv found heaps of gold with the first setting so it does work well' but I'm yet to find a massive nugget with the second setting but the deep items I'm digging up shows one will be gold hopefully soon.
Hope it helps.
By Rivers rat
Hi got a custom coil for whites TDI hand made in France by a top engineer ,i bought if for my deepstar but never used it.
So whats more well this coil is the dog on the beach,less noises more stable and 2 to 4 inches deeper ,also a better ID of ferrous targets by a double bio easier to hear.
The engineer is Alexandre Tartare owner of MANTA METAL DETECTORS
Just with the Minelab PI coils being used on the TDI's. I've heard that once you get over about 14" with some coils the TDI's struggle to run them regardless of pulse delay settings etc? Was wondering if anyone has had any success with a larger coil on a TDI? Most, in Australia at least, seem to have success with smaller coils on the TDI series like NF Sadie & 12" x 7", 14" x 7/9" etc. Only ever heard of one being used with a 16" Coiltek but never seen or heard back any results with it, although I see one bloke said he tried one & then sold it going back to a Coiltek Blitz 14" x 9" which runs fine at 10uS. They seem to do well on small gold with the smaller coils here @ 10uS.Was wondering if this is why Miner John/Razorback are making coils specific to the TDI & Minelabs I.e. they have a 14" round for the TDI but it's not compatible with the Minelab PI's. They do however have other coils specifically for the Minelabs.