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Signal width on 11" double D coil?

cadman_us

Member
What is the width of the signal that runs front to back on a 11" double D coil? I will be using it in a Omega 8000.

Thanks in advance,

Joe
 
Honestly, it isn't really an easy thing to state for even a concentric coil because all coils have their own dynamics. Even the Omega's elliptical concentric is different from the round 8" concentric coil.

cadman_us said:
What is the width of the signal that runs front to back on a 11" double D coil?
Search coils do not 'send' or 'project' or 'make' such things as a "knife blade" field from a Double-D coil, or a 'V-Shaped' signal from a Concentric coil. These are too often used to describe what it supposedly projected or sent out from the Transmit winding.

Both Double-D (DD or Wide-scan) coils and Concentric coils simply generate an electromagnetic field.

Due to their design and tuning, there is a Receive winding which works to alert the detector's electronics of any change in the generated EMF (electromagnetic field). This could be from an enhancement of the EMF caused by iron, or the loss of field power caused by a non-ferrous object, along with the generated EMF on the surface of the detected targets which was induced by the loss of the transmitted field power.

The detector's circuitry, in split-second (faster than that) time will convey that information to us via an audio response and maybe a visual display.

Both the DD and Concentric designed search coils will have a larger or stronger electromagnetic field closer to the search coil and, as the coil-to-target distance increases, the functional portion of the EMF will decrease. Some might describe this by drawing a magical 'V' shape or a bowl-shaped 'U' . If you were to compare ALL brands and ALL coils you would note some rather odd-shaped 'widths' that these search coils can respond to.

While the 11" BiAxial DD coil does have a more narrow responsive area, generally down the center of the search coil from front-to-rear, the very nature of a Double-D coil design with the overlapped Transmit and Receive windings can add to some of the challenges to try and determine a possible 'width.' Near proximity coins can produce some very radical, jumpy, and audibly noise responses, but when positioned only 3" to 4" away they sound much better.

Then you have the audio Tone ID interpretation of a target that can make learning a "signal size and shape and effectiveness" more difficult. For example, with the Omega and Gamma I like to use the d4 Audio Tone ID ONLY when I am doing some typical fast coin hunting in likely places like wood-chip and sand-filled playgrounds. Most of the time I like to hunt with either d1 or d2, determined if I want to hear all targets and audibly classify likely iron, or if I want to find everything, or just reject most iron and find everything.

I have had all-around success (and enjoyment) using the d3 or d4 Tone ID with a concentric coil, and with all coils available I get much better target information, and definitely better sizing and shaping by hunting in d1 or d2 Tone ID.

I'll bet that after you have hunted an ample amount with BOTH the stock elliptical concentric coil and the 11" DD coil, you will have some interesting opinions to share. By then you'll have a better idea of what each coil type might, and might not, do for you.

Monte
 
Monte,

Thank you for the information, very detailed as always. I will take your advice and try running in D1 and D2 tones once I get more comfortable with the Omega 8000.

I have the standard 10" concentric and the 5" DD coil (really like the 5" DD). I wanted to try the 11" DD just to get a feel for it.

I guess it will be trial and error for a little while. Hah, isn't it always that way?
 
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