TDI Coils

I hear a lot on other forums that the stock 12" coil that comes with the TDI SL is not the best coil. I find it hard to understand their statements, because the 12" coil is all I've ever used. It has good depth, or better said it hits well on all my test garden targets (that have been in the ground an undisturbed for over 7 years now). The only time I notice an issue is in the trashy areas, it takes quite a bit of extra work to swing and rotate around some targets to locate them prior to digging.
I guess before asking my question I should indicate they type of hunting I do.
First off I use my SL to hunt for the missed coins and relics in some of the worst ground conditions for my area. These areas are littered the coal waste "after burnt", these sites are all but impossible to hunt with the traditional VLF machine. I have found many coins in these areas, see next paragraph.
Secondly I plant to make one trip to the beach each year.

Second hunting trip:
Went to an old school where the coal cinder waste has been dumped for years and hunted for 1 ½ hours. This area has been grid hunted for years and I was sure there were no goodies left to be found. Well wrong again.
GB to a little over 8, pulse 10, gain 10 and off I went; very first signal was a wheat penny at 4-5 inches and perfectly vertical. You can see the scratch I made with my shovel. Wow, was I off on my pin pointing skills. Couldn’t believe how I could have missed that one because it gave a very good, consistent audio response from every direction. One thing I noticed, it didn’t give a double beep like a VLF machine would on a vertical coin.

Thought I had the sound nailed down, but was I wrong. Started digging nails, three to be exact, all sounded fairly good but I could tell there was something wrong, but I’m learning, so I dug anything that sounded remotely good.
A few minutes later, not more than 10’ from the penny, another signal that sounded different, not sure what sounded different, still learning. Wow, a silver dime and not quite 5” deep. Now I am wondering how I could have missed that one, not a clue yet.
Well anyway, the next two targets were nails, then another perfectly vertical copper penny. Had a very good hunt, for an area that basically dried up over a year ago. Wonder what I'll find once I have a little time on this machine?

Question 1:
When it comes to ground coverage is the entire coil used or only the one in the center?

If the 12" is not the best for my type hunting what is?




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Mark g
I'm not an expert but I did borrow a tdi sl that had the small DF coil on it for about a month. I really liked the Sl. Now I'm working on getting my own Tdi I think I'll get the 12 in mono as my stock coil. Most people say use the mono for relics and coins and the DF coils are better for small gold and are really sensitive. I'll send you a PM on a coil and a message abut it. Did you go w the sl? Im trying to decide between the pro or that. I hear pros and cons for both.

I bought the sl for the weight difference. But afterwards I learned you can attach the pro to your belt.

Mark the dual field coil was developed to be sensative to small gold--as this was what the TDI's were originally developed for.Some very knowledgeable people have determined that a mono coil is better for coins and relics and they recommend the Razorback or Miner john coils which were developed for the TDI series. Hope this helps. Keep up your good reports.

Just passing through so I thought I would give you a quick tip or two in case you weren't already aware. The Miner John Razorback folded mono coils are excellent and run about $200 depending on the size. I have one that I think is about 7x11. The TDI SL can give the bigger TDI a run for it's money with a good battery like the RNB plus it drains at a stable pace. The TDI SL is basically a TDI without the giant battery and a few other lights. There is also a guy on mytreasurespot that sells an 18v battery will give the TDI SL more depth. For coins (no nickels or gold) the real kicker is to make sure you try out Reg Sniff's high conductor tuning. It will ignore nails but find silver in the nails. If you haven't run the machine before with this tuning setup you are in for some fun. I need to get back to work changing a ceiling fan.

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Edited 1 time(s). Last edit at 06/07/2015 05:21PM by TabWhisperer.