I've always been a big fan of Whites metal detectors. I've owned almost all of them since the late 1990s, and most of them have been exceptional, like the XLT, the DFX, or the 6000 Di Pro SL. I'd always had the idea of one day getting a Pulse Induction to dig deeper, revisiting grounds I'd already covered with other metal detectors. I bought a used Whites TDI SL in excellent condition, complete with Whites 12" Dual Field coils and a 14x8" Super Pulse 350.
I tried the 12" Dual Field, which I had read was rather complex in operation. This coil is actually a sort of 2 coils in one, that is, it has two separate copper windings (dual field): the outer winding generates a powerful, conical pulse that penetrates deep into mineralized soil, ideal for detecting large masses and deep coins; the inner winding (smaller, in the center) is focused on maximum sensitivity to small, high- and low-conductivity objects (such as small raw gold nuggets, thin chains, or tiny fragments).
I easily adjusted the ground balance (if you leave it deactivated on GEB OFF, you won't have the "discrimination" with low and high tones in ALL, but you'd have a single fixed tone) to about 4 (lightly mineralized ground). I tried setting the pulse delay to 10ns to use both windings (if you set it to 25ns, the small central winding would "turn off") and pushed the gain to its maximum, that is, 10.
I began detecting targets, checking and digging them all to learn the metal's behavior. Eric Foster, the designer of the TDI, reversed the classic tone found in VLF metal detectors: a low tone detects highly conducting objects (and large, old nails, but the low tone is preceded by a fast, easily recognizable high tone), while a high tone detects other low-conducting objects.
Search results: I found other targets in the same area I've searched and re-searched with the many VLFs I've had and also with the Cscope 4PI at truly remarkable depths, as expected. The TDI SL was stable for most of the search; I only had to re-balance it once in another area of the field, which was also very easy. It's not a light metal like Deus or others, but it's well-balanced in weight; I didn't experience any significant fatigue with the 12 (but I still lift weights at the gym, so maybe I'm not exactly the average seeker).
I then tried the Super Pulse 350 which I already knew was designed for large and deep objects and so it was, no surprises, silent and easy to handle despite its size.
I tried the 12" Dual Field, which I had read was rather complex in operation. This coil is actually a sort of 2 coils in one, that is, it has two separate copper windings (dual field): the outer winding generates a powerful, conical pulse that penetrates deep into mineralized soil, ideal for detecting large masses and deep coins; the inner winding (smaller, in the center) is focused on maximum sensitivity to small, high- and low-conductivity objects (such as small raw gold nuggets, thin chains, or tiny fragments).
I easily adjusted the ground balance (if you leave it deactivated on GEB OFF, you won't have the "discrimination" with low and high tones in ALL, but you'd have a single fixed tone) to about 4 (lightly mineralized ground). I tried setting the pulse delay to 10ns to use both windings (if you set it to 25ns, the small central winding would "turn off") and pushed the gain to its maximum, that is, 10.
I began detecting targets, checking and digging them all to learn the metal's behavior. Eric Foster, the designer of the TDI, reversed the classic tone found in VLF metal detectors: a low tone detects highly conducting objects (and large, old nails, but the low tone is preceded by a fast, easily recognizable high tone), while a high tone detects other low-conducting objects.
Search results: I found other targets in the same area I've searched and re-searched with the many VLFs I've had and also with the Cscope 4PI at truly remarkable depths, as expected. The TDI SL was stable for most of the search; I only had to re-balance it once in another area of the field, which was also very easy. It's not a light metal like Deus or others, but it's well-balanced in weight; I didn't experience any significant fatigue with the 12 (but I still lift weights at the gym, so maybe I'm not exactly the average seeker).
I then tried the Super Pulse 350 which I already knew was designed for large and deep objects and so it was, no surprises, silent and easy to handle despite its size.
