I agree with what Cybersage said. Funny, I really stayed away from Minelabs for years due to all the too positive posts on the forums. I wanted to try to get those results with other machines. My ground mineralization, which isn't terrible though, had other ideas.
Another guy that posts here mntnflyr4fun, also had the same experience as us, going from a V3i to an E-Trac and starting to find deeper coins in hunted out spots. (He just needed a nudge from someone :angelic: )
In non mineralized ground I think the V3i/VX3 might go deeper, as it also has that Tx mode.
Just a point regarding the V3i/VX3 and E-Trac/FBS machines - I see a few notable differences between them and FBS machines that might explain some of the performance differences:
1 - The Ground Balance on the E-Trac does seem to work differently. It seems more like a ground removal than ground balance.
2 - The V3i seems to run it's 3 frequencies separately, the E-Trac and Fisher CZ's (another depth monster, maybe even deeper than E-Tracs in certain grounds) both combine their frequencies. There has been some debate on this, but I will go along with what Tom D said regarding his observations.
3 - The E-Trac (and CZ's) are putting their energy across 2 frequencies, not 3, that sharing of energy might limit the White's machines some. Whites has even said for maximum depth use a single frequency.
4 - FBS technology sure is doing something with time domain. For example, I agree the E-Trac does better in iron than the V3i, but why? The V3i is noticeably faster! It must be something to do with FBS.
Albert