I notice that people ask about depth on every forum and about every detector. Frankly, I don't think that depth is a major concern when comparing any detector that isn't an entry level model. Most decent detectors will get all the depth that most people will ever need.
The real question is how is the seperation? How well will it unmask targets? Will it give you a hint that there is something good mixed in there with the trash and iron? Most will give you a good TID on a good target that isn't masked by trash or iron... and that is where the difference lies. Plus, there is the human factor involved in using the detector so much that it is like an extension of your arm and brain. I think there are some people who can out hunt many people using their 15- 20 year old machine because they know everything it does. I know people who can swing a Tejon and find minnieballs well over 12" deep that I cannot hear. There are people who use a Sovereign who can dig really deep targets that I would never notice using the same machine, with the same settings, and swinging at the same speed.
In my opinion, when you get over 8" deep on a lot of targets, most of what a detector tells a new user goes out the window. However, experience with most any good detector will make good finds not only deep but shallow. I find many good targets in the 4" range that have had a coil passed over them more than once but were left in the ground because the detector wasn't understood or the user was just digging targets that had a high probibility of being good according to the TID/VDI and tone... I love "hunted out" sites. There are always some really good targets there.
Most places that are worth hunting are so because of extended human acticity... which means many times more trash and iron than coins and buttons and other goodies. All this trash and iron makes the issue of depth a non issue until the junk that is masking the goodies is removed or until someone comes along who knows their machine so well that they can hear the little hints of that their machine gives of a good target in the trash.
If depth is the issue just buy a PI detector and dig everything or maybe a Tejon and run it in all metal VCO... or a SovereignGT and run it in all metal pinpoint... you'll dig deep but you'll also spend most of your energy digging and toting around iron and trash.
Depth is not the issue... seperation, unmasking, and TID is much more important and the E-TRAC is unparalled in this respect... plus it will go DEEP, like most other good machines if you are willing to deal with some falsing and noise. You can get depth without becoming unstable but you can usually get deeper with unstability BUT... until you really know your machine, running it on the edge of insanity will be unproductive because you wont know the falses and chatter from the good things the machine is telling you.
anyway....
Julien
and BTW thanks for the VLF explanation, pity were talking FBS here