crown caps, maybe a solution?

[saika]

Howdy, everyone! Merry Christmas and Happy Holidays to all!

I can't believe that I can still get out to hunt at this time of year. It is great.

I went out to a park here and decided to Castanza my hunting technique. Nope, I wasn't going to look for coins and rings but pull tabs and bottle caps. What an adventure, I did really well indeed.

I did notice something neat and was wondering if other users could see if this duplicates for them. After detecting a questionable signal that is right on the border of breaking up and doesn't give you a perfect signal but still interesting. Pinpoint the target in disc mode. Mark the spot and pinpoint it in AM mode and see if the spot moves. I found that in every case where it did pinpoint differently but consistantly it was a crown cap. The pinpoint was out by about 1.5" to 2" with the 5.75 coil. The only penny that I found was the same spot in both modes as were the square tabs.

 

[JHM]

I'll give it a try hope it works for chopped up cans as well.

 

[rentasquid]

I guess that its his, or, at least he's the main one that I've heard touting it. And it sounds similar to what you are doing.
In all-metal, pinpoint a target. Note its position on the ground. Back up and sweep forward until the target is about half way to three-forths of the way between the transmitting and receiving coils(with the old brown-donut coils, or with the 7" concentric, the sweep point is right under the Tesoro decal). At this point, if your target is trash, you probably wont get much of a good signal. Sweeping the target over the center of your coil will give you a good beep, but moving it out to the edge, the target will again disappear, or become very erratic. This doesnt happen with a coin. It remains a good stable target to the edge. Give it a try. It really works. He calls it "edge-pass rejection". I dont know if this is his discovery or just common knowledge, but it works, or at least has worked for me.
This past spring, I did some detecting in the eastern Oregon Goldfields. As I was scanning around the hillside, I used this technique, because of the dense trash. I had a target that I pinpointed that sounded much like the rest of the trash, but upon using this technique, I could tell it behaved different, by not disappearing, like all the can lids and misc. rusty items did. I dug it and it turned out to be a chinese coin from the 1700's.
[attachment 43474 chinese2.jpg]

Give it a try and see if it works for you.(you might have to try to find that spot, if you are using different coils than the ones I mentioned)

J.

 

[saika]

Thanks guys, more ammo in the belt

 

[rentasquid]

it is a little more detailed(as only Monte can do). This is some good stuff. And, if you want, you can find the whole link if you type Edge Pass Rejection and exact words into the search engine on this site. Enjoy...

PROBLEM TARGETS and "QUICK-OUT": A good, old-fashioned TR-Discrimination type detector will easily reject a bottle cap, rusty or not. Other very low-conductive trash can be rejected very cleanly with a TR- Disc. model because that circuitry design is what I refer to as a "true, progressive" discriminate design. Nails, old iron bottle openers, hair pins, and perhaps the most annoying of all, the crimp-style bottle cap, can all be rejected quite easily.

The more modern motion discriminators, however, have some difficulty with a lot of rusty iron just, but the biggest headache for many coin-hunters is that blasted, annoying bottle cap! I am NOT referring to the taller, higher-conductive aluminum screw caps, but to the older pry-off and current twist-off bottle caps with the scalloped, crimp-on edge. Often you will get a rather good-sounding audio signal from a bottle cap in the discriminate mode. If the response is from what appears to be a fairly shallow target, say surface to 3" or so, then try the All Metal mode test for Narrow vs Wide signal. Generally, the rusty bottle caps will produce a wider signal than a coin-type target. If you still question the target, pinpoint the target more precisely and then use a technique I have referred to as "Quick-Out." This is where the operator uses a short but quick sweep across the well centered target and notes the audio response.

Give a more "brisk" sweep across the target dead-center. (Note: It should be a SHORT and brisk sweep to avoid covering multiple targets.) Quite often, a bottle cap or other problem target with magnetic properties will be "kicked-out" with this quick-sweep technique. It works best on targets that are within the typically shallow range, perhaps from surface to 3" or so, depending on the mineralization.

As stated, it will often, but not always, audibly reject these problem targets, but it only takes a couple of quick passes to try and "classify" the target this way. Although the audio response might still be there, those with metered units might note that the ID is now reporting "iron" or at least "jumpy or unstable."

EDGE PASS REJECTION: Like ATC and "Quick-Out", I coined another term to refer to techniques I've used since the early '80s with motion discriminators. Edge Pass Rejection, or EPR, can be used with "Quick-Out" techniques, if necessary, for really challenging situations.

Lay a couple of coins and a couple of bottle caps on the ground, spaced far enough apart so as not to interfere with a coil's sweep. Use a newer crimp-style (crown-type) bottle cap, and older one, and one that is rusty. Then, sweep the coil over the coins, dead-center, at about a 2"-3" height. Note the good audio signal. Continue to sweep over the target coin as you draw the search coil back towards you and note any audio change. You'll see that most of the time a coin will continue to signal well until its position is just in from the edge of the coil (perhaps an inch or so). Now, advance the coil and note that the same is true in from the back edge of the search coil. A coin-type target in a typical coin and trash target range will respond well when it is just in from the outer edge of the coil by about an inch or so.

Repeat this test with the various bottle caps on the ground. Dead center, with a slow, comfortable sweep, you will probably get a good audio response. However, you will note that as you back the coil off while sweeping and get near the "edge" where the coin still sounded off well, the problem trash item will usually be rejected! Advance the coil while crossing the junk target and you will note that the same result occurs from the back edge of the coil. Where the coin was still responding the trash is often rejected!

On some really difficult targets, like a few pesky bottle caps, combining "Quick-Out" and "EPR" will "classify" them as undesirable ferrous trash targets. Please remember .... the sweeps across the targets in question should be brisk and short so as not to cover additional near-by targets. In some sites, (such as drive-in theaters or picnic grounds or fairgrounds) these techniques are very helpful, especially when using a smaller coil, such as a 4" to 7" size, to handle the trash problem.

Once again, those who use any form of metered ID will benefit from this technique as it will tend to make the "jumpy" or "bouncy" target readout register and lock-on as an iron object. Perhaps a bit jumpy when you try "Quick-Out" directly over the target, but on the more problem bottle caps you use that together with "EPR" and these two techniques will almost always provide the operator with an accurate or proper classification of the junk target. Coin targets, on the other hand, will not produce the lock-on iron reading.

 

[SkiWhiz]

Great advise, do you suppose it would work with a Cibola with the 9X8 concentric coil. Thanks! Steve.

 

[rentasquid]

read the post above, where I reposted Monte's article and do what it says. You might have to play around a bit, but it should work.

J.

 

[saika]

I just tried this EPR technique with bothe the stock 9x8 and the 5,75 coils. I compared it to a mercury dime in both cases.

The effect is very noticeable on the 5.75 for both new and rusty caps. There was at least a 1.5" to 2" quiet zone anywhere around the edge of the coil when responding to the crown caps.

On the 9x8 it was a little more subtle, with the exclusion zone needing to be determined from around the inner coil, not the outer edge. It is there but not as easy to see, for me anyways.

Yes it does work on my Vaquero so it should work on your Cibola also.

MAny thanks for reminding me about this Squid, I used to use it years ago but forgot about it.