Metal Detecting Articles
njminerals.org is mainly about [what else?] mineral collecting,
but Metal Detecting is somewhat related, so here goes...
The "coin detector" series from Tesoro includes the Silver uMax, Golden uMax, DeLeon, and Cortes. There are a couple of coil options available for these. Of the ones available, the 11-inch round widescan seems to be underappreciated. There also isn't that much information on the Net about it.
I decided to put one through its paces to see how it really performs.
Now that this coil is hooked up on the Silver uMax, it hasn't come off since. Yep, it's a good one.
Air Tests, Field Shape...
Detector used: Silver uMax
Sensitivity: turned all the way up
Air test results (dime): about the same as the 8" donut coil.
The widescan or DD coil is supposed to cover a bigger area with each sweep. The 11" widescan seems to do this. However, it is a common assumption that the field is equally deep all across a widescan coil. I have found that the best depth is right in the center of the coil. That may not be so with other brands, but it is true on the Tesoros I have tried.
Think of the field, then, not as a straight-across "windshield wiper", but instead as one with a slight bow in the center. It will certainly give you a better chance of detecting a target when you're sweeping a large area, but I would still overlap sweeps by two or three inches.
There is a diagram floating around on the net that shows the field from a widescan coil, with the deepest-seeking portions of the field located at the "toe" and "heel" of the coil. Well, that diagram does not describe the Tesoro widescan coils. Once you come to appreciate the bowed field, with its deepest portion at the center, you will like the ease of pinpointing. In fact, this coil pinpoints surprisingly well by the criss-cross method, especially considering it's a big solid profile.
This coil is great because it doesn't get hung up on stubble and brush the way the spoked coils do. It also has a little weight to it, which makes it all the better in this environment.
Although the 11" widescan gets about the same air-test depth as the donut coil (losing, at most, perhaps 1/4 to 1/2 inch of depth vs. the donut), the widescan should have better performance in mineralized soil. That is because the widescan field "sees" considerably less gound mineralization and also experiences less masking from shallow targets that might be nearby.
As far as the deepest possible targets that can be recovered with the coil, only time will tell. However, with this coil on a Silver uMax, I found an Indian head cent at 6 inches, and it gave a smooth, repeatable signal. The coin was partly tipped, meaning it didn't give the optimal signal strength. I also found a button, slightly larger than a penny, that was even more severely canted. Depth was about 6.5 inches. This signal was smooth but rather faint, since the button was on edge.
On another outing in a field that has been plowed within the past ten years or so, I found a corroded Large Cent at 6 inches. It gave a very nice, solid, smooth signal... not an overload, but not faint, either. It was solid. It would have been no problem had the coin been 7 or 8 inches deep.
In between these good finds, I of course dug plenty of aluminum junk, various whatsits, and miscellaneous modern rubbish at depths ranging from zero to ten inches. It was a learning process. The discrimination works quite well wth this coil. Based on the quality of the tone, you will also be able to know when you've swung the coil over something large, as opposed to a quarter or perhaps a button.
The large widescan is going to be good for finding larger objects at depth... mason jar lids, axe heads, beer cans, plow shares, etc.
Based on the evidence, the 11" round widescan should be able to find dime and penny-sized coins at 7 inches without too much trouble, unless for some reason you have really iron-rich soil. It should also find quarter-sized coins at 8 inches without much trouble; in all-metal mode, the depth would of course be even more. The performance is pretty good for a coil having a street price of around 90 bucks, and made for a detector having a street price of only around 240.
If you want the most awesome depth possible from a widescan on a beep-dig type of machine, get a Tejon and then buy yourself a 12x10 widescan. Otherwise, this 11" one on a Silver uMax does fairly well. I do not know how it will perform on a Golden uMax, DeLeon, or Cortes, but I have read that different coils can alter the tones somewhat on the Golden.
In summary, the 11-inch widescan coil is a great choice if you want to cover more ground. Its depth on coins is about the same as the standard 8-inch round coil, at least on the Silver uMax that was tried. Its depth on larger objects is even better. It is the best coil I have tried for brush and stubble. It is built tank-solid like the "Hot Head" coils of the late 1980's, but you should still get a scuff cover to protect it from the many rocks you'll be scraping when you hunt plowed fields.
This is an enjoyable coil to use, and if you're after bigger objects it will get more depth than the 8-inch standard coil. As I mentioned before, that extra mass is really helpful for dealing with weeds and stubble. For its intended purpose, this coil is a winner.
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