does the coil signal go down in a cone or strait down?

[martygene]

been wondering if the signal from any of the minelab coils goes strait down of does it go down in a cone shape? so if I am using the stock 11" coil is it still 11" diameter at 10" down or is it say 5" diameter at 11" depth? this is something I need to know so I know how much to overlap each swing.
if it does go in a cone shape maybe that is why people are finding more with the 17" coil, not because of depth but because it's cone at 10" depth is around 10" diameter.
or is this something we have to ask Minelab directly to get an answer to?

 

[GKMan]

The DD coils transmit a line down the middle, it is not cone shaped like the concentric coils. that said I still overlap

 

[Altamaha]

Concentric coils have a cone shaped pattern which gets narrower as the depth increases and DD coils have a blade shaped pattern the width of the narrow strip from the front to the rear edge of the coil. The with of the pattern is the width of the coil (front to rear) at all depths.

 

[CT Todd]

Here they are from minelab