I was hunting at a 1920's house that had underground power running right through the back yard to the house. I started with the 7" concentric on the MMK and then switched to the stock 11" DD to cover more ground. I noticed immediately that 11" was WAY more sucseptible to EMI and I could get on the path of the underground power cable AT ALL. My MMK chirped and went nuts.
I switched back to the 7" concentric and was able to hunt right over the power line with hardly a chirp. If you want to hunt a site with heavy EMI, the 7" concentric might be a life saver. Today I found clad, a 1947 nickel, and a 1949 Roosevelt and 1951 Wheatie in the same hole. I also was using 4 Tone in 5khz which I liked quite a bit. That's a nice combination, but it eats battery.
Forgot to mention that I was also hunting with a friends 12 year old son, who was hunting for first time. I marked a few targets for him to dig that I thought would most lilkely be coins. His first target was a 1950 Roosevelt.
-CS
I switched back to the 7" concentric and was able to hunt right over the power line with hardly a chirp. If you want to hunt a site with heavy EMI, the 7" concentric might be a life saver. Today I found clad, a 1947 nickel, and a 1949 Roosevelt and 1951 Wheatie in the same hole. I also was using 4 Tone in 5khz which I liked quite a bit. That's a nice combination, but it eats battery.
Forgot to mention that I was also hunting with a friends 12 year old son, who was hunting for first time. I marked a few targets for him to dig that I thought would most lilkely be coins. His first target was a 1950 Roosevelt.
-CS