I've used all of the coils currently available for the X-Terra. In regard to the three 9-inch concentrics, I see little (if any) difference between their detection depth capability. As well, each frequency of coil is capable of detecting silver, copper, gold and other metal targets.
[attachment 129552 07fallfindsoldstuff.jpg]
All three frequencies will even hit on iron and other "less desirable" targets. This is a picture of some of the "non-coin" items I dug while learning the sounds of the different coils.
[attachment 129554 non-coinX-Terraitems.jpg]
I don't live near any "gold fields". But I'm convinced that the higher frequency would be a better choice for "raw gold" than either the 7.5 or the 3 kHz. Im just a guy who likes to find old coins at old sites. And I will continue to make my coil choice based on the mineralization of a particular site, what the audio response sounds like for particular targets and whether target separation is of concern. Not on whether or not that frequency of coil will "detect" that target. I am convinced that for coins, relics and most gold jewelry, any of them will "beep" when the coil passes over the targets. It is how they "beep" that helps to make my decision. The DD coils separate better. But the concentrics go deeper in my moderate soil conditions. The 18.75 seems to be a bit more sensitive than the other two in that it requires a bit lower Sensitivity to operate smoothly. As such, the audio response on small pieces of gold jewelry is more pronounced using the 18.75 kHz than with the 3 kHz. The 3 kHz coil allows me to "hear" the broken sounds produced by most pieces of aluminum and iron better than the 18.75 kHz. And the 7.5 kHz stock coil is a good "compromise" for those who don't feel the need to buy more coils.
Coils are simply another "tool" for the job. It is up to the individual to determine which "tool" works for them and make the effort to become proficient at using it. JMHO HH Randy
[attachment 129552 07fallfindsoldstuff.jpg]
All three frequencies will even hit on iron and other "less desirable" targets. This is a picture of some of the "non-coin" items I dug while learning the sounds of the different coils.
[attachment 129554 non-coinX-Terraitems.jpg]
I don't live near any "gold fields". But I'm convinced that the higher frequency would be a better choice for "raw gold" than either the 7.5 or the 3 kHz. Im just a guy who likes to find old coins at old sites. And I will continue to make my coil choice based on the mineralization of a particular site, what the audio response sounds like for particular targets and whether target separation is of concern. Not on whether or not that frequency of coil will "detect" that target. I am convinced that for coins, relics and most gold jewelry, any of them will "beep" when the coil passes over the targets. It is how they "beep" that helps to make my decision. The DD coils separate better. But the concentrics go deeper in my moderate soil conditions. The 18.75 seems to be a bit more sensitive than the other two in that it requires a bit lower Sensitivity to operate smoothly. As such, the audio response on small pieces of gold jewelry is more pronounced using the 18.75 kHz than with the 3 kHz. The 3 kHz coil allows me to "hear" the broken sounds produced by most pieces of aluminum and iron better than the 18.75 kHz. And the 7.5 kHz stock coil is a good "compromise" for those who don't feel the need to buy more coils.
Coils are simply another "tool" for the job. It is up to the individual to determine which "tool" works for them and make the effort to become proficient at using it. JMHO HH Randy
Thanks Digger! It really helps me with my X-Terra 70 coil choice. I really appreciate your 'Posts' and your expertise. Thanks.