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Depth Difference ?
- Thread starter fsa46
- Start date
Buried Crap NJ
New member
Ah trick question! We all know that larger coils can get deeper targets. But its not always true. The smaller the coil the easier it is to tune better for conditions (threshold) If your threshold is to high and your sesitivity is not stable then the size of the coil doesn't really matter. Lots of variables to concider when selecting a coil to hunt at any giving time.If I can achive a geat stable threshold with an 8 inch coil and your not with a 10 inch coil I will hear deeper targets all day long,bigger isn't always better.Its always conditions that prevail on any hunt. These may change from day to day at the same location for a million reason.Reasons why a 5 inch may even be a better choise some days. I have said it before and I will again an 8 inch coil is a big coil. When used properly its a formidable weapon on the end of a detector.
BCNJ
BCNJ
OldBeechnut
Well-known member
A Base answer to your question without conditions............
Testing different excaliburs to determine best audio setups I found these results thur air test. Only one eight inch in the group and all machines using the same settings. Notice differences in each machine and each being 10 inch.
Testing different excaliburs to determine best audio setups I found these results thur air test. Only one eight inch in the group and all machines using the same settings. Notice differences in each machine and each being 10 inch.
Very good explanation and why a bigger coil is not always the best choice for depth. One of my deepest coil is the old 8 inch coinsearch coil as it has done well and have seen it get deeper coins than the 10 inch BBS coil and one of the best coils for those trying to learn the Sovereigns as it runs so smooth comparing it to the 10 inch coils and bigger.
Critterhunter
New member
There is an old rule of thumb that in bad ground (minerals) a smaller coil can in fact see deeper due to taking in less ground matrix. And I'm not talking about due to masking such as iron, but rather that the machine is soaking up less ground "stew" and so is better able to see a target at depth without it being washed away by the ground signal. But, so far in limited testing of the S-5 and the old 8" BBS coil that old rule of thumb doesn't appear to be true for me on these BBS units, or at the least isn't as true as often perhaps?
Testing in mineralized ground a larger coil is seeing deeper than both of them, at least in the particular minerals the tests were done. And I'm talking some bad minerals here, containing black sand and microscopic iron where all the coils (big or small) were suffering in depth. I'm thinking perhaps, at least in some instances, the old rule of thumb that a smaller coil will punch or see into bad ground better might not be as true for these BBS units due to the unique way they ignore the ground signal.
But that might change at other sites, because prior to my GT I've seen this smaller coil thing to be true at bad sites, where my larger coils on non-Minelab machines got better depth, or at least ID at depth, than larger coils. I remember one site where that little Whites Bullseye 5.3" (which was actually I think around 6.5" in size) got much better ID at depth than the 9.5" coil. Using the larger coil a silver dime (undug) would give a rather bad iffy coin hit, where as the smaller coil ID'd clean, and not due to any masking being present. Just pure ground matrix problems.
I've read of people using the 8" (7.25") Tornado and getting real deep in some soils. I've also read that of the Coinsearch coil, and I'm talking depths that other machines don't seem capable of even using a much larger coil. I'm lining up my ducks in a row right now to buy the Tornado to use as my primary trash coil and also am real curious to see what kind of depth it will do in my soil, which tends to be from light to high mineraliztion depending on the site. Maybe it'll show me something back to the old rule of thumb and punch deeper in some soils than my larger coils (again, without masking being the factor present).
Plus, look at it this way...If a coin is 8" deep and it's got a shallower piece of trash or iron 4" in front of it, along with another piece of trash/iron 4" behind it, then a bigger coil that's DD line is alignment with all three isn't going to see that 8" coil. First metal object hit and the game is over, even if the coin is directly under the center of the coil. So now you stroll in there with a coil slightly smaller than 8" in size and it sees the coin because it's missing the trash, and yet if you went to an even smaller coil that coin at 8" might be out of reach to it. For that reason, even if you have a smaller coil, something between that size and say your other 10" coil might be just the ticket to pop some stuff that is too masked for the larger coil, yet too deep for a real tiny coil.
That said, DD coils are great in that you can largely get over masking issues by gridding from a few angles even with a big coil, due to the wiper blade still DD line that runs the length of the coil. My new "rule" is to only grid at 45 degree angles to landmarks such as wood lines or sidewalks or such. Most people parallel this stuff, while some will 90 degree grid to those landmarks, but it runs against human nature to grid at odd diagonal angles. Even when you decide to do so if you don't keep it constantly in your mind to make that effort before you know it your back to paralleling or going 90 degrees to the landmarks. A friend and I recently have been doing this at a small patch of grass we gridding hard a while back and it's like we never hunted it before, and often you'll find if you work your way around the coin it's a complete null from the "normal" angles most people use. That's why it hasn't been found yet.
Testing in mineralized ground a larger coil is seeing deeper than both of them, at least in the particular minerals the tests were done. And I'm talking some bad minerals here, containing black sand and microscopic iron where all the coils (big or small) were suffering in depth. I'm thinking perhaps, at least in some instances, the old rule of thumb that a smaller coil will punch or see into bad ground better might not be as true for these BBS units due to the unique way they ignore the ground signal.
But that might change at other sites, because prior to my GT I've seen this smaller coil thing to be true at bad sites, where my larger coils on non-Minelab machines got better depth, or at least ID at depth, than larger coils. I remember one site where that little Whites Bullseye 5.3" (which was actually I think around 6.5" in size) got much better ID at depth than the 9.5" coil. Using the larger coil a silver dime (undug) would give a rather bad iffy coin hit, where as the smaller coil ID'd clean, and not due to any masking being present. Just pure ground matrix problems.
I've read of people using the 8" (7.25") Tornado and getting real deep in some soils. I've also read that of the Coinsearch coil, and I'm talking depths that other machines don't seem capable of even using a much larger coil. I'm lining up my ducks in a row right now to buy the Tornado to use as my primary trash coil and also am real curious to see what kind of depth it will do in my soil, which tends to be from light to high mineraliztion depending on the site. Maybe it'll show me something back to the old rule of thumb and punch deeper in some soils than my larger coils (again, without masking being the factor present).
Plus, look at it this way...If a coin is 8" deep and it's got a shallower piece of trash or iron 4" in front of it, along with another piece of trash/iron 4" behind it, then a bigger coil that's DD line is alignment with all three isn't going to see that 8" coil. First metal object hit and the game is over, even if the coin is directly under the center of the coil. So now you stroll in there with a coil slightly smaller than 8" in size and it sees the coin because it's missing the trash, and yet if you went to an even smaller coil that coin at 8" might be out of reach to it. For that reason, even if you have a smaller coil, something between that size and say your other 10" coil might be just the ticket to pop some stuff that is too masked for the larger coil, yet too deep for a real tiny coil.
That said, DD coils are great in that you can largely get over masking issues by gridding from a few angles even with a big coil, due to the wiper blade still DD line that runs the length of the coil. My new "rule" is to only grid at 45 degree angles to landmarks such as wood lines or sidewalks or such. Most people parallel this stuff, while some will 90 degree grid to those landmarks, but it runs against human nature to grid at odd diagonal angles. Even when you decide to do so if you don't keep it constantly in your mind to make that effort before you know it your back to paralleling or going 90 degrees to the landmarks. A friend and I recently have been doing this at a small patch of grass we gridding hard a while back and it's like we never hunted it before, and often you'll find if you work your way around the coin it's a complete null from the "normal" angles most people use. That's why it hasn't been found yet.
In the field the 10 inch Tornado is a couple inches deeper than the smaller 7 1/4'' 800 Tornado coil in ideal conditions.Moist sand is where the larger Tornado has worked best for me,I found silver dimes at depths of 12 inches plus.In thrashy parks with high mineral ground the 800 coil will be very close to depth,because the sensitivity can run higher.The smaller Tornado coil is very stable and hits harder on smaller targets,which equals a faster sweep speed,two successful seasons in comp hunts confirms this.My choice for my park hunting is the 800 coil,with beach hunting the 1000 coil probably would be a better choice.Both the 800 & 1000 Tornado's are great coils.HH Ron
