on beer and soda bottles. I will be working with the AT Pro and Omega and MXT Pro and a couple of other detectors and post the final evaluation results on Saturday, most likely. The first two postings on the ahrps.com Forum were strictly indoor comparisons. I've watched a number of videos attempting to depict what the AT Pro will do with bottle caps, just as I have witnessed and used other detectors with so-called bottle cap identification. Generally, you'll find that some attempts to get better bottle cap ID on direct target sweeps can result in less than wonderful performance on other types of targets.
A couple of examples of detectors that have been a round for a while show some design differences. Take the White's 6000 Di Pro SL or the 6000 Pro XL and renamed XL Pro as well as their XLT. These models, which are basically analog types wand use a four-filter type circuit, do produce a reasonably good "bottle cap reject" response. Naturally, this is usually most effective on bottle caps that are relatively shallow, such as in the upper 3" of the surface, or perhaps to 4" but iffy at that point. Those are typical levels where bottle caps are found.
There are some models which, just by the nature of their design, also handle bottle caps pretty decent, such as the analog-based White's Classic ID or IDX Pro models. They can kick-out or break-up a bit on bottle caps in a somewhat different manner even on a direct sweep.
The Teknetics T2 is another model that features a bottle cap audio circuit in their 3b selection. The main concern I have with iron rejection with the T2 and some other models is that they use a Double-D coil and DD's are generally not that good at discrimination compared with a concentric designed coil. However, and I admit that it took me time to like it, I found the T2 can do a decent job of classifying some bottle caps using the 3b audio. However, it doesn't always get it right, and some desired non-ferrous targets can also produce more inconsistent readouts while being tighter when I use a different audio process choice.
All that said, I will tell you that most of the time, regardless of the make or model detector in hand, I can get the most reliable 'bottle cap' audio and visual classification on the typically shallower caps by employing techniques I have used and taught for about thirty years. depending upon the search coil used and model, and sweep speed I am able to use at a site, I use my "Quick-Out' or "EPR" (Edge Pass Rejection) techniques which will usually produce a low-tone audio if Iron is accepted, or maybe audibly reject the bottle caps if a little iron rejection is used. Also, it will produce an Iron Target ID read-out. Both the rejection or low-Iron tone and visual Iron ID are what we ought to get from those bottle caps.
The AT Pro I was working with the other day did okay in the in-air testing, but I'll do some more in-air and in-ground comparisons this Thursday and Friday.
To conclude I will tell you this. I enjoy using my Omega quite a bit and I don't have any problems classifying or identifying most bottle caps as likely iron targets using the Omega. I won't compare it to any videos because I wasn't present to compare with the same settings and samples, but I can tell you the Omega does quite well.
Oh, if you would like to read and print out a copy of my article on Audio Target Classification, you can view it and download it under Tips & Techniques at the ahrps website. That will explain 'Quick-Out' and 'EPR' techniques.
Monte