Not exactly the case from what I've read...The BBS/FBS frequencies do in fact do more (again, from what I've read...but I have read opposing views on this) than just put out two frequencies. In fact, the very reason why they don't have a conventional ground balance is due to the digital "filtering" that BBS/FBS allows to be possible. Don't confuse this digital "filter" with how conventional ground balance on other detectors work...Where in fact when you ground balance they in effect set up a filter to "ignore" the ground signal. Thus, a target at depth or in mineralization has to break through that filter in order for the detector to see it. That's why ID suffers at depth on other detectors, while BBS/FBS machines are known for accurate ID even at extreme depths and/or in bad mineralization. I've always understood that the multifrequency of BBS/FBS is what made it's unique way to ignore the ground possible. If in fact they are running on only 2 frequencies and that eliminates the need for a conventional ground balance, then why do the Whites or some Fishers using 2 or 3 frequencies still require a ground balance? Something more has to be going on here in terms of the multifrequency aspects of BBS/FBS, but as said I have read differing opinions on the true nature of BBS/FBS and just how many frequencies it uses, so please somebody fill me/us in with any in depth gory details you can muster up.
What I've read in places is that the Minelabs may in fact key in on a few frequencies to process the signal, but it's the interaction of the compilation of frequencies spectrums that interact with the target that gives the sum accumulation of target response...and then effects the final outcome of what part of the spectrum the machine is paying attention to.