Hank and Rainy-day: When I say that today's standard vlf (mf, etc...) discriminators have closed the gap on depth, I realize this is a loaded statement. Because there's infinate types of "discriminators" and there's infinate types of pulse machines. So I was speaking rather broadly with the following evolutionary basis:
Back when pulse machines first came out for beach users (mid 1980s?), it was a given, back then, that ..... yes: You could go deeper with the beach pulses than the then-current breed of discriminators people were swinging on the beaches in those days. Eg.: 6000's, etc.... And ...... consider for the moment, that TODAY however, if you put a WOT coil on the sovereign, that you can get up to 14 to 16" on coins. Maybe even 18" on a quarter or half. Then you can see that that closely mimicks the depth of most of the beach pulse machines.
However, I realize that not many people can get accustomed to the warbly fishy performance of a Sov/Wot combo. And I realize there's some pulse machines (especially some of the high-powered nugget machines), that can, in fact, exceed 18" on coins. I've heard that Minelab's pulse nugget machine, for example, can get a nickel at nearly 2 ft. ! But seriously now, can you imagine the insanity you'd go through, to try to use that type setup on the beach. Or dry sand where teensy staples and pinheads and such exist?
Thus yes, it's an over-generalized statement. But when you start to consider that depths up to nearly a foot (or 14" with the CTX and big-coil-combo) are attainable, you see that the depth differences gap has been much closed, in the last 25 yrs. or so.