The whole depth with single frequency VLF detectors thing in my opinion has been nothing but a red herring for decades. I have read a thousand posts from people wanting VLF detectors with "more depth". Yet VLF detectors maxed out for usable depth by at least 1990 if not before. I have not used any single frequency VLF metal detector since 1990 that got more depth on coins than my old Compass Gold Scanner Pro.
The only real improvement we have seen and are still seeing is in the ability to f
Frequency does a number of things. George Payne was one of the engineers who patented many of the basic concepts used in VLF detectors to this day. Here is an excerpt from his article at http://jb-ms.com/Baron/payne.htm (2002):
"The r component acts differently. It is maximum at one particular frequency and decreases if you go up or down in frequency. We call the special frequency at which the r signal is maximum, the target’s “-3db” frequency. It also turns out that at the -3db frequency th