That's what I heard too. But if you pop out 2 scoop full beside each other, 1 ft wide hole, and then pop in the atx iron check. You would get the PI depth with essentially the 'vlf' iron check.
Steve, I anticipated that you (and others reading) would say something like this. Eg.: a) "dig out a scoop or two, then scan again." Or b) well shucks, at least the top 4" eliminates 1/3 or so your potential iron"
Sure, it's an improvement over utterly zero ability to tell iron. But the fact still remains: if you want to get the super deep stuff with the ATX , you'd be going after the whispers. And as such, as those deeper depths, you'll have no disc.. And having to stop and dig half way to each one, is precious md'ing time lost, in my book. If all you cared about knowing iron vs non-iron, is the top 4 or 5", then heck, why even have a deepseeking machine TO BEGIN WITH ? Doh! So knowing that deeper targets is the goal of most of us, then kiss iron-ability goodbye.
There was a certain excavation done years ago, beneath the Santa Cruz beach boardwalk, where the spoils-sand, from 10 to 15 ft. down, was dumped out on to the beach. Several of us showed up to work these tailings. Old coins (silver, etc...) was being found. One guy drove 50 miles to be there, and had brought his beach pulse. Afterall, he reasoned: "This is the beach, and this machine goes deep, and I won't miss tinsel fine chains, and will effortlessly see through any minerals, etc....". But after 20 minutes, the guy drove 50 miles back home, to get his standard machine. Because while he was busy digging nails till the cows came home, the rest of us were getting one coin after another. See ?
Yes I realize "that's just one example". And yes I realize that other spots won't necessarily be iron-ridden. But just saying, since the depth of each is about the same these days (pulse vs VLF / MF), then .... at least having the ability to knock out iron allows you into such spots. Ie.: nothing lost.
The rare exception, in my opinion, is if the sand is truly so nasty with minerals, that you have no choice. I have not seen too many beaches like that in my area. Once in awhile, the sand at a gully-wash outflow will turn gun-powder black. Or up by the cut you'd have to lower your sens. But those are isolated zones, that you can merely move out of. I suppose if the entire beach were jet black, then you'd need a pulse. But if not, I'd much prefer to pass hair-pins, nails, etc.....