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DD coils. Detection width. What's YOUR angle?

Alimo88

New member
Oh how easy it is to be wrong or right. In a previous 5" DD thread some people say the detection width of a DD coil is about 1.5 inches, I thought it was the full width of the coil. So who is correct?
ANSWER:- We all are. Trouble is we are looking at the coil from two different angles. Specifically 90 degrees around.
Here is a great link to explain

http://www.ohiometaldetecting.com/2/post/2009/09/shes-right-you-really-dont-need-an-additional-searchcoil.html

OR

Coils described

Hope you glean some decent information, I sure did
 
yeah.. this is the article used to get a handle on it, its a good one. BTW just found my oldest coin, 1908 if think, still haven't broken into the 1800s.. yet.
 
I like that article too. Written by someone who gets his point across in a simple and easy way. Mine is 1909. maybe the F5 will get me there?
 
I have read this before and find it quite interesting,Alimo88,have you ever tried tilting your coil just a bit to one side? I try this once in awhile in trashy areas and have found pennies among bottle caps,maybe this has merit or maybe not? By the way I run an f4 with 11 in.dd My oldest coin is also a 1909.
 
Actually the width is only about 2 inches wide as the coil is only hot in the area where the two D's overlap each other. The length of the field is the full length of the coil. So it is not a matter of which way "you look at it" as the width is always the width and the length is always the length no matter which way you are looking at it. Another way to say it is that the detection field of the DD is long and skinny.
 
When I have air tested my 11" DD coil with a coin, the detector will respond from the side of the coil as soon as the test coin gets near the edge and not just close to the coil. This occurs quite some distance away from the coil. It would seem the coil pattern is not as narrow as one might think.
 
dgc said:
When I have air tested my 11" DD coil with a coin, the detector will respond from the side of the coil as soon as the test coin gets near the edge and not just close to the coil. This occurs quite some distance away from the coil. It would seem the coil pattern is not as narrow as one might think.


The problem with air test is that they don't really test the detector - the signal from the ground is 100 times stronger than the signal the detector gets back from a target. The true test of any detector or coil is how well it can pick out that tiny signal from a target from the huge signal from the ground. Without the ground present the detector is kind of just idling instead of running at cruising speed. A DD coil does the best job of reducing the signal from the ground in the area where the 2 Ds overlap.


That said, you are right to some degree about the magnetic pattern from coils, they are not as sharp as many think of them. There are some very good 3D graphs of coil magnetic field strengths for all of the white's coils available for the DFX in the "Digging Deeper with the DFX" book that are quite interesting when used to compare concentric and DD coils. However looking at those graphs you can see that the field strength of a DD coil does fall off fairly quickly when moving away where the Ds overlap one another but it is not a sharp edge.
 
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