A
Anonymous
Guest
Hi,
I've been constructing a DD coil for my GQ, and while testing the overlap positions discovered that different positions will cause different target responses. I'm using flat wound coils to mimic a PCB coil I'm working on.
With 40% overlap, range and stability suffers and it's not possible to go below 10us reject.
With 25% overlap it becomes highly sensitive to very small nuggets, even more so than the mono, while maintaining a good range on larger nuggets, but it also responds positive to magnetic hot rocks that the mono nulls out.
With about 10% overlap, all the hot rocks in my collection cause a nulling of the threshold when directly under the coil centre, while still responding to medium nuggets. On two types of hot rock (Andesite and ?)it will see the nugget under the rock.
The different types of hot rock require differing levels of overlap to null them out, and as the level is changed to remove the worst offenders (ones that cause positive responses with the mono) there is a corresponding loss of sensitivity to smaller nuggets.
It appears then, that to achieve the greatest return, a coil should be tailored for each locality to deal with the worst mineralisation encountered, and the expected median gold size.
Cheers
Kev.
I've been constructing a DD coil for my GQ, and while testing the overlap positions discovered that different positions will cause different target responses. I'm using flat wound coils to mimic a PCB coil I'm working on.
With 40% overlap, range and stability suffers and it's not possible to go below 10us reject.
With 25% overlap it becomes highly sensitive to very small nuggets, even more so than the mono, while maintaining a good range on larger nuggets, but it also responds positive to magnetic hot rocks that the mono nulls out.
With about 10% overlap, all the hot rocks in my collection cause a nulling of the threshold when directly under the coil centre, while still responding to medium nuggets. On two types of hot rock (Andesite and ?)it will see the nugget under the rock.
The different types of hot rock require differing levels of overlap to null them out, and as the level is changed to remove the worst offenders (ones that cause positive responses with the mono) there is a corresponding loss of sensitivity to smaller nuggets.
It appears then, that to achieve the greatest return, a coil should be tailored for each locality to deal with the worst mineralisation encountered, and the expected median gold size.
Cheers
Kev.