I understand what discrimination does, Ted. I also understand what notch does. What I don't understand is what the difference is, aside from the fact that notch lets you apply discrimination in three "windows". The manual doesn't say anything about any other difference. Where did we get this idea that it is in fact simply audio elimination? And why is one better than the other? If I don't hear iron, then hasn't it been discriminated out?
The idea that notch is only audio elimination (or more correctly audio and target ID blocking) is covered in Andy Sabisch's book on the Deus which is endorsed by XP and it gets applied AFTER discrimination is applied. Discrimination applies a digital signal processing to the raw target signal.
You ask why one is better than the other, well I thought I explained it several different ways. For one thing you keep looking at it as if you only have a piece of iron underneath your coil - what is important is how the that iron affects your ability to pick up a desired target, not really whether or not you hear that iron. Discrimination helps with this, because it affects how the target ID is determined if you have multiple targets underneath the coil. Also, if you apply too much discrimination you will LOSE DEPTH CAPABILITY even for targets that have conductivities ABOVE the discrimination breakpoint. This is not true for notch. If you set DISC to 40 with no notch you set NOTCH from 00 to 40 with no disc, your detector will behave differently in each case. In the first case, you are applying heavy signal processing filtering. Digital filters and signal processing are not perfect, plus you affect the response of the detector because applying such filtering bogs down the microprocessor that is doing all the computations. The affects depth so a deep high conductor target, say a dime that registers a target ID of 93, but is a week signal because its deep may not be heard when you apply disc all the way to 40, even when the target ID of the dime is well above the disc breakpoint. Conversely, if you have no discrimination applied and simply notch all the way to 40, there is no signal processing applied only audio and target ID blocking, the dime signal will be unaffected. Yes, in both cases you will not hear iron nor get an iron ID, but the way the detector is responding to the desired higher conductor is way different. Try it yourself, but hopefully we can get a youtube expert to post a video demonstrating this. There are secondary effects to be considered also such as how the iron masks a desired target and how the deus processes a composite iron/coin target (iron can drag down the composite target ID, the degree to which this effect is seen can be mitigated through use of discrimination BUT NOT notch which will have NO effect on this blended target ID But using notch can help filter undesired audio and target ID artifacts without affecting how the signal is processed by the Deus. The key is deftly using both Discrimination AND notch in concert with each other to better bring out the desired target signal.
Target>Coil>Signal Detection>Signal Processing (Discrimination, Reactivity, Silencer filters are applied here depending on user settings)>Ferrous/Non Ferrous, depth estimate from signal strength for the horseshoe indication is generated as well as Audio and Target ID's from the processed signal>Notch (if applicable) is then applied here to block undesired tones and associated target IDs from being seen and heard>Display and Headphones respond.
Andy's book has further detailed explanations of the differences between notch and disc and makes a big point at his bootcamp sessions that notch DOES NOT EQUAL discrimination. Feel free to check out Andy's book instead of the paltry instruction manual if you want the details you are looking for or run some tests. Please don't just take my word on it, by all means. I'm all for skepticism, but I think it is perhaps going a little too far at this point so I think I am going move on.
