I'm not a fan of the Concentric coil. Your deepest point is in the dead center of the coil. With the double D, the coverage is uniform from the tip of the coil straight to the back of the coil.
Yes the concentric is a little deeper but you will have to overlap your swings 3 to 4x to get the same coverage consistency as you do with one pass of the DD. That's why most higher end machines come with a DD. Uniform coverage.
For me, the DD is the way to go... Hands down!
The Iron discrimination is there so if you don't want to hear the iron tones.
Some hunters like to hear the iron so you can check around the iron edges to look for hidden targets that may lay next or a little beneath the edge. Most experienced hunters will hunt in all metal just for that reason. The DD can come into play here, as you can use the tip of the DD to edge around those iron targets for good targets that might be masked.
Question: Do you think my machine with dd coil can get better depth on coins then my machine with 8 inch concentric coil ? Also, don't you get better depth by setting disc to zero?
Better depth? Depends on where you are hunting. Think of it this way. Say you have a Mercury dime at 7 inches laying next to a small piece of iron. That particular concentric will only get that depth at the center of the coil. So, if you have to put half of the coil over the iron target to get the 7 inches in the center of the coil is going to hitting the iron mostly. Now with a double D, all you have to do is have just the tip of the coil over the coin and none over the iron.. I hope that made sense. Now some higher end machines are made to see the higher conductive signal(depending on the size) vs the iron, but in most lower end units, that is usually not the case.
Zero Discrimination? You will get better depth by having the least amount of discrimination, BUT I don't recommend zero discrimination. The reason is something called "Iron Wrap". It's where low iron targets will sometimes hit in the high conductive range, in essence wrapping around the scale and hitting in the first notch or two of the top of the scale.
Think of the scale of targets as on a clock face. Iron targets hitting at 1:00 o'clock and good targets(silver) hitting at 11:00 o'clock. Having some discrimination will sometimes take care of that.
The good thing about at least being able to hear some of the iron is you can then inch around the edges of the iron signal with the DD listening for those hidden or masked targets.
Again, the Concentric will be deeper, but you will have to go slow and really concentrate to get the center of the coil over every square inch of ground to utilize the 2 or 3 inches you will gain when using it. To grid a property it will require more swings to do. Yes, with a concentric you will get better depth, but you will get a more uniform coverage with the DD.
People worry way to much about depth, when most good targets start at 5 inches and down to 9. Most are just masked, depending on area.
Concentrating on or around iron targets and using a coil/machine that can separate and recover quicker can make the difference in thinking it is hunted out and finding the goodies that others missed! Swing speed is also a large part of this equation.
Question: Is the center of the coil on con coils the only area that reads?
NO! As you get further out from the center, the detection field lessens. The center is the only area that reads the deepest. The outer edge is drastically reduced. However, the DD is made to hit the same depth from tip to tip. It is usually just a 2 or 3 inches less depending on size, machine, and soil conditions.
ON SMALLER TARGETS: Think of a cone(concentric) going straight into the ground compared to a knife blade(Double D coil).
Another thing is when going over a target with a DD you won't recieved a signal until it gets closer to the center line that divides the coil in half. On the concentric you will begin to hear as it hits the outer edges of the coil(depending on depth of target) and it will get louder as it reaches the center. It can be confusing when swinging over a target and takes longer time to figure exactly where the target is located.
If using concentric, you won't know if it's at 9 o'clock or 5 o'clock position of the coil or wherever.. On the DD it's only on that line that divides the coil
It makes it a lot easier to pinpoint also with out using the pinpoint button. You just use the wiggle back method.. I will discuss that in a separate blog.