Blank Planet said:
FBS will never be deeper than BBS if you read Bruce Candy's blog on detector tech on the minelab site.
Having owned three top Minelabs and now a GT I tend to agree with that opinion in my soil. I'm sure I'm totally off base and wrong and it all depends on your soil but my pet theory is that the lower 1.5 to 25khz of BBS frequencies are reflecting or "glaring" off my minerals less in the ground matrix, as they say the higher frequencies tend to in general have more problems with penetrating some minerals. A friend who is using a top Minelab and Pro Coil has been having me check his undug targets before digging. Thus far I've been able to easily see any super deeper or severly masked coins with the 12x10 on my GT that he has had me check...And just as well as his machine has from us comparing notes on the target quality. I believe the 12x10 is helping the GT keep up in terms of depth and separation with the excellent abilities in those respects of the Pro Coil and the faster processor of his machine. Separation's real weapon is just how sharp the detection field is. A slow machine can do just as well as a fast machine so long as you keep your sweep speed slow. If the coil can't see the coin while also not lighting up nearby trash than no amount of processing can make up for that. The coil's field in effect "bursts" with the first target it hits and can't reach the deeper coin below it. That's why I feel these Minelab's using the Pro Coil or a 12x10 are able to "unmask" coins that even the fastest machines on the market are missing.
Really, these FBS and BBS machines are so maxed out in terms of depth when taking in the laws of physics concerncing VLF technology that I think any of them (Xcal, GT, SE Pro, Etrac, Old Explorers) will beat the others out in depth based on who's using the bigger coil. Of course there are limits to gains in coil size increases showing more depth, and that depends on how mineralized your soil is. In my soil the 15x12 got less depth than my stock 10" coil, but the 12x10 does get deeper....So I would assume for my soil that the coil size limit to show gains in depth is about 12 or 13" in coil size. Any bigger than that and the target gets washed out or degraded by the soil matrix the detector is also taking in along with the target's signal. Even though I could run the 15x12 at very high sensitivity settings it tended to give it's better deep target signal with sensitivity set much lower than what was max stable. I believe that's due to running the coil too "hot" sucking in too much ground signal or "glare" and thus the target gets washed away or degraded by that.
Anyway, I really do believe that...That it's the coil on these FBS and BBS machines that makes the difference. Otherwise would have they bothered with the expense and time to manufacturer the 11" Pro Coil and not just use the old 10" coils? Besides weight, the Pro Coil is a big step up in separation and depth over the older coils. That's where much of the gain in those aspects is coming from IMHO.
It appears the new Minelab is using an 11" Pro Coil. For that reason I doubt it has any more depth than the current models using the Pro Coil, unless somehow they are generating a stronger voltage (maybe one of the reasons for the big battery besides GPS being power hungry?) to the TX winding in the coil to create a bigger field. Only problem with that is that it has issues with ground glare and is why it's fixed at a certain strength and can't be raised on most detectors. There is an amp out for the Sovereign that puts more voltage to the coil to force it deeper, but many people said they couldn't use it in their even moderately mineralized soil because of the ground glare it created.
