also sometimes just called a 'D-D,' is the same coil. The name was derived from the fact that the Transmit winding and Receive winding inside the coil housing somewhat resemble the letter 'D' and a backwards letter 'D'. They are positioned such that the somewhat straight sides of the 'letter' overlap.
Those overlaped sections form a long and narrow responsive area that extends from near the front of the coil directly back through the center to a spot near the rear of the coil. The reference to 'widescan' comes from the fact that this hot, responsive area from front-to-rear scans a wide swath as the coil is swept from side-to-side.
This unique design, developed by Don Dykstra, a co-founder of Compass Electronics, has it's strength in the fact that it can provide <EM>coverage</EM> on the sided-to-side sweep. This is due to the inner coil's placement and the generated electromagnetic field. The title of "D-D" was derived from the two coil's appearance and not the developer's initials. (Just a little Sunday morning trivia <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt="
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The trade-offs that we see with the use of this coil type compared with the more conventional "concentric" wound coil is that the widescan coils tend to not detect as deeply (comparing similar physical-sized coils), often do not discriminate quite as well, and might not be quite as 'hot' or responsive to smaller targets. While possibly more theory than function, the widescan design is supposed to handle highly mineralized ground better than a concentric, but it really all depends upon the coil's overall design and size.
The spoked design of this new large coil will help to eliminate some of that 'sucking' sensation, if used for beach hunting, and for that use as well as hunting wide-open spaces where coverage is called for this Double-D might be handy.
It will be interesting to read and hear the reports from both Tej
