Couple of ?s ...what is your reasoning on why and how you think some of these rings get so deep , say 9" ? Settling ground , added soil , time , weight ?
Knowing your detector and experience is everything. But going by your vdi explanation, wouldn't you still dig everything ? As a beachhunter, I pretty much dig everything with my Pi. Not as much with my Nox. I mainly go by sound and shape , regardless of any numbers. Like the way you dig zincs. I will always dig short double taps knowing it's probably a Bobbie pin. But have also pulled rings as well on occasion. Because I think the ring is laying flat and I'm picking up both edges. So why not just dig it all based on bouncy vdi and size ?
Lots of questions here... I'll try to answer each of them.
what is your reasoning on why and how you think some of these rings get so deep , say 9" ?
I hunt parks and schools exclusively (except when I travel, then I'll hit a beach). The reason for the depth is soil condition, water, and vibration. Lots of the parks here, are relatively new. Which means the topsoil is brought in, and they're primarily sodded (in the last 20 years). It's not uncommon for city parks to be aerated (using plug method, or disc cutting). Because the parks and schools are well watered, and get a lot of foot traffic (which equates to vibration), it's not uncommon for gold items to sink fairly rapidly, once it's through the root layer (which usually takes about 2 years). Based on the age of the quarters I find at 4" (usually 6-8 years is the most modern), It's reasonable to expect a ring at 8-9" that is 20 years old or less. But remember, this is loamy, sandy soil. I've hit some parks where I dig through the sod layer, and BAM it's hardpan. Nothing sinks below that. It just sits there, so I only ever get 3-4" depth at the most.
Knowing your detector and experience is everything. But going by your vdi explanation, wouldn't you still dig everything ?
VDI isn't everything. If it were, the ACE series, with a bell-tone and VDI would be all anyone needs to be masterful in the field. The truth is, the sounds the signals make, and a few other things, add a whole other layer of detecting prowess. While VDI is part of the equation, for sure, here are other factors I take into consideration when determining whether or not to dig.
1)
Depth reading of the item is part of it (for example, Rebar survey posts ring up at 81, but you can hold the coil over the ground at 4" and it'll still show 1". This indicates a LOT of metal, not a coin. Same holds true iwth a buried can, for example. It does NOT hold true with a bangle (round bracelet), though. see, #2.
2)
Width of object in the ground. Some people use the "X method" to pinpoint an object. Using a DD coil, it's simple enough to identify where an object is, without having to turn your stance to create the X. Just wiggle in from the left, to get the left-most side of the object, wiggle from the right to get the right most side. This shows if the object is WIDE. You can do the same with wiggling back until the object no longer dings from the top of the coil, and move forward with the wiggle until you get the object to the bottom of the coil. This gives the HEIGHT of the object (or length, depending on how you choose to envision this). When coupled with #1, a bangle will show wide and tall, but will give a fairly accurate depth reading (usually off only by a notch or two, not 4-6 notches.
3)
the SOUNDS t when coupled with the VDI, this is probably the most valuable information when considering what to dig. The ATMax has variable sound (meaning the more shallow the object is, the stronger the sound). Also, the high response rate of the signal, means that there's a lot of "chatter" to decipher when moving your coil over the object. I can regularly weed out can slaw, based on the sound (not all of it, though), and DEFINITELY can ID foil wrappers (unless they're folded). It's not perfect, but the sounds an object makes can help ID what it is.
4)
The VDI bounce. Especially useful in schoolyards, some objects have a regular bounce to them on the VDI. They'll bounce around in the 40s 50s 60s, and 70s. Some of these items bounce so regularly and consistently, you can ID them without pulling them out of the ground. Pencil ferruls (the metal tips) have a regular signal bounce to them. They both sound and LOOK the same on the VDI. I can safely ignore those signals, without worry. I still dig a lot of ferruls, though, because once the pencil disintegrates, the ferruls tend to flatten, and then they sound differently (more like a pendant in the ground).
5)
The consistency of sounds based on other signals I've dug in THAT field on THAT DAY. This cannot be understated. I usually dig everything for the first 20 minutes, just to get a feel for where objects are going to ring up. Soil conditions (wet/dry), and even whether or not it's been recently fertilized (changes the mineralization), can change how items ring up in the VDI. On some days quarters will ring up 83-84, and on others, it's 85 solid. I usually dig everything for 20 minutes to get a feel for what the park/school is doing, and then base my decisions later, on that knowledge.
6)
Location, Location, Location. If I'm detecting around a trash can, I'm likely to find 1000 pop tops and not a single gold ring. If I'm detecting along a field edge, I might find a gold ring, so I'll dig pop top signals. I skip trash signals all the time, based on location/proximity to trash cans.
7)
Sound "woooing or booping". When thinking about how I find rings, so often, I do have to say there is a HUGE difference (in my own brain) about signals that "could be rings" vs. signals that definitely are NOT rings. Rings, on the AT Max, all have a sharp boop sound to them. If they've got broken shanks, they're still sharp, just choppy.
They sounds like this:
Boop Boop Boop (when moving the coil slowly back and forth over it).
They do NOT sound like this:
wooo wooo wooo
or this:
Boooooooop boooooop (indicating a much larger solid object, such as a crumpled can.)
These boop vs. wooo sounds are really where the difference is, between someone who knows their machine, and someone who just digs signals. To be clear, there are LOTS of items in the ground, other than rings, that make Boop Boop Boop sounds (like poptabs, or metal caps), but I've never encountered a single ring, EVER that went woooo woooo.
My biggest rule, though, is "if there is any doubt, check it out!" I'll dig it. I find lots of gold thinking it's probably a corroded penny, for example, but I want to be sure. If I cannot safely rule it out, I'm going to dig it up. Sure, I find a lot of trash. But I find a LOT of gold in the dirt, that others miss.
So why not just dig it all based on bouncy vdi and size ?
For a bell tone machine, that's what people would have to do. The ACE series, for example, is a bell tone with a VDI. I used to own an ACE machine. I found gold with it. I found LOTS more trash, though... like 4x-5x the amount of trash. I couldn't tell the difference between trash and good signals, because so many targets sounded and looked like good targets.
Moving the the AT Pro brought a "next level" of ability to weed out trash. took close to 100 hours to figure it out, though. At the 1000 hour mark, I was really great with it. Then I moved to the AT max, and thought I was going to go nuts with the chatter. Little did I realize, on day one, that the chatter was the cat's meow, baby! I'm now able to dig less trash targets than good targets on any given day. This results in less time digging garbage, and more time hunting productively. As a result, I find more gold, now, in fewer hunts, than I did with the AT pro. I certainly recover more clad, too.
Cheers!
Skippy