First, here is the discrimination scale of the T-2:
0-9 = Rock/Ferrite Range
10-39 = Metallic Iron Range
40-54 = Foil Range
55-59 = Nickel Range
60-74 = Pull-Tab Range
75-79 = Screwcap/Zinc Range
80-99 = High Coin/ Silver Range
and typical target I.D. points:
Foil or Gum Wrapper = 40-55
U.S. Nickel Coin = 57-59
Aluminum Pull-Tab = 60-75
Aluminum Screw Cap = 70-80
Zinc Penny = 77-79
Copper Penny or Clad/Silver Dime = 82-85
Clad/Silver Quarter = 88-90
50 Cent Coin = Typically 92+-
SIlver Dollar = Typically 94+-
Silver Eagle Coin = Typically 95+-
For this test, I used a 3 inch long old rusty square nail and a U.S. Dime. I first placed the dime under the nail at about the half way point of the nail.
Disc. set to 40 resulted in a strong signal on the dime, though the VDI was pulled down into the screwcap range. I raised the disc. on up to 59, just below pulltab range, and continued to get a similar signal. Once the disc. was increased into the pulltab range, the machine would no longer signal on the dime. Removing the dime at each different setting, the detector showed a clean rejection of the nail alone. This was sweeping the coil directly against the long axis of the nail. Turning 90 degrees to the nail and sweeping along the long axis resulted in no signal on the dime at any of the above settings.
Next, I did the same thing and same settings with the dime placed approx. one inch away from the nail. This time the dime signal bounced between the iron range and the screwcap range at all settings, and gave no signal when sweeping along the axis of the nail.
Last, I separated the dime and nail to about 2 inches, but this time the dime target was pulled into the other direction on the VDI, bouncing between the screwcap and quarter range (dime averaging at center) with a strong separation of the nail and dime using the toe of the coil once the nail and dime were separated by 1 1/2 inches or more, effectively allowing for good target separation sweeping either axis at this point.
I think the effect of the nail is acting as usual, appearing to the detector as the usual dumbbell shape because of the larger fields at either end of the nail which are stronger than the signal from the dime, therefore hiding the dime "in between". When sweeping the coil over the nail against it's long axis, the signal is always strong, even when the nail is directly over the dime. The T-2 acts alot like a Tesoro machine in this regard, but exhibits an almost opposite reaction in the different sweep directions when using a concentric coil on the Tesoro as opposed to a double-D on the T-2. The T-2 also signals stonger on the dime in relation to the nail at a higher discrimination setting than is possible on the Tesoro Compadre with a 5.75 inch coil or a Conquistador with 9 inch coil.
I also tried the 3 and 4 tone audio options, and running at zero discrimination, the nail gave the signature low tone while the dime would break through with a higher tone at various angles and sweep directions, most notably those described above that gave a good single tone signal. I think based on what I've seen here, if hunting in a high iron environment, I would opt for the 3 or 4 tone I.D. option. The "3b" tone option was added to the newest version of the T-2 which supposedly offsets the sampling point to help in dealing with steel bottle caps. Still need to do some experimenting with that one.
Remember too that this was just a cursory discrimination air-test, and not in-the-ground results that can vary depending on mineralization levels.
Ralph
