...How about the multi frequency (MF) detectors ... Do they offer more flexibility in this area?
Absolutely! Single frequency detectors have made many advancements in software to help compensate for mineralized conditions, but they are still single frequency machines that can't stablize like a multi-frequency machine. Here is the scenario you will probably encounter.....
You buy a reputable single frequency machine like the ATP, Racer, Deus or F70. It may work perfect in a new subdivision that has fresh top soil, stable soil, so you set out for your first adventure to find relics. You travel a few hours and are now in your prime location to begin the hunt. You hear beeps, but there are no targets. You ground balance the machine and the false signals seem to go away but a short distance later you encounter it again. (this repeats over and over). To avoid that nonsense, you decrease the sensitivity and now the false signals aren't happening as frequently but they are still happening. You test a planted target to make sure the detector is tuned and OH SNAP, you realize your max depth went from 10" down to 6". ARggh, you cuss at the machine. You post a few rants on the forum, try some suggestions and have the same result. Eventually you stumble onto the forum's beach section where folks deal with mineralization and conductive salt water every day. There, the beach section folks console you and suggest trading it for a machine specifically designed for those unstable ground conditions..... which you trade in your machine and try again, but this time find success!
-OR-
On the other hand, if you had bought an Explorer, E-trac, Equinox, CZ, DFX, (or any other MF-VLF) you would have turned on your machine and swung confidently knowing that if it beeped, it was an honest signal. You knew that as you swung you were still getting great depth. You'd also feel great knowing that if you ever went to a salt water beach, your MF detector would be equally stable on the conductive wet salt water sand that again plagues so many single frequency VLFs.
Visit this link for a list of multi-frequency machines ...
http://metaldetectingforum.com/showthread.php?t=248905