Hi, Tim!
Here is the info (straight from Tesoro's site) that explains how the "concentric" and "widescan" designs work and how they differ.
The URL is at the bottom, if you decide to go there and check it out!
I'm almost positive ShortStack was referring to the 12" X 10" coil, a feller would need training wheels on a 12" X 18", LOL!!
P.S. I printed it here rather than just posting the URL, because I think it can help others also!
There are two main types of searchcoils currently on the market – the concentric and the widescan.
The concentric coil uses two round antennas, one inside the other. This coil is used on most detectors that are designed for coin, jewelry, and relic hunting. Concentric coils discriminate very well and pinpoint very easily because the strongest signal is always in the center of the coil.
Widescan coils use two D-shaped antennas that are placed back to back. Because of this configuration, they are also called “double-d” coils. The widescan coil is less affected by mineralization than the concentric, so it is generally used for gold prospecting or relic hunting in bad ground. Pinpointing is done with the heel or toe of the coil. After determining the type of coil that is best for your type of hunting, the next thing to consider is the size.
There are many different sizes of coils available and each one may fine tune your hunting but only if you get the correct size. Larger coils go deeper than smaller coils but only on larger targets. When using a large coil, you may lose sensitivity to small targets. A large coil is also more susceptible to masking. Masking happens in the discriminate mode when a good target and junk target are both under the coil at the same time. If the targets are close enough together, the bad target will be discriminated out, and at the same time, the detector will not be able to pick up the good target. Masking is very common in junky playgrounds and in-and-around old house sites. Smaller coils will concentrate the signal and make the detector more sensitive to the little targets. Unfortunately, smaller coils tend to lose depth when compared to their larger cousins. Being that these coils don‘t have as wide a search pattern, they are also less likely to mask targets in trashy hunting situations.
The 9x8 and the 12x10 are spoked coils that use Sinusoidal Technology. This technology creates a detection bubble that works from the center of the coil to beyond its edges. These coils produce an infinite number of electromagnetic flux lines, which surround the coil and penetrate deep into the ground. As targets pass through the bubble, they start interfering with or breaking the flux lines. The detector reads the interruption of flux lines and a signal is produced. When you saturate the ground with these flux lines, you're guaranteed better sensitivity to smaller targets and more depth on larger targets.
The Clean Sweep (18" by 3.6") uses widescan technology to provide tip-to-tip sensitivity. A wider detecting sweep means less time over unproductive ground and more time finding the goodies you want. The widescan design resists changes in mineralization.
Another style, the Printed Spiral, is made only by Tesoro for use with pulse induction circuitry. It offers good sensitivity to a broader range of target sizes and improved sensitivity to less conductive targets such as fine gold chains.
Knowing where you are going to hunt and what you are hunting for will go a long way in helping you choose the right coil for your needs. A larger coil is needed when hunting in a clean area or when hunting for relics that may tend to be deeper. A small coil will help find the smaller targets such as gold nuggets or fine jewelry or can be used when coin & jewelry hunting extremely trashy sites.
All searchcoils are electrostatically shielded and waterproof. See your nearest Authorized Tesoro Dealer for more information.
Long Cable = (LC) - Approx. 8 foot length, Short Cable = (SC) - Approx. 3.5 foot length
Coils–Standard (µMax models) Cable Price Scuff
3x18" Widescan (COIL-3x18W-LW-LITE; includes lower pole & scuff) (LC) $199 $16
3x18" Widescan (COIL-3x18W-SW-LITE; includes lower pole & scuff) (SC) $199 $16
4" Round Concentric (COIL-4RC-SW) (SC) $89 $6
5.75" Round Concentric (COIL-5.75C-SW; includes scuff) (SC) $99 $8
7" Round Widescan (COIL-7RW-SW) (SC) $89 $8
8" Round Concentric (COIL-RC-LB) (LC) $99 $8
8" Round Concentric (COIL-RC-SB) (SC) $99 $8
8½" Round Widescan (COIL-8.5RW-LW) (LC) $89 $8
9" x 8" Concentric (COIL-9x8C-LW) (LC) $139 $12
9" x 8" Concentric (COIL-9x8C-SW) (SC) $139 $12
11" Round Widescan (COIL-11RW-LW) (LC) $99 $14
12" x 10" Concentric (COIL-12x10C-SW) (SC) $159 $22.95
9 x 8 white scuffs may or may not be textured and need to match the surface of your coil. 9 x 8 black scuffs are also available.
Your local dealer will be better able to get a price for you, of course.
Or you can browse their page here:
http://www.tesoro.com/product/coils/
Hope this helps!
Regards
SkyPilot
