GaryD's Mucky Fingers
Welcome to the classroom page..
I hope these little classroom lessons will help some.
I understand not all will agree with every thing in this classroom.
I don’t confess to be an expert on the xlt or the dfx I just write
what I have experienced and learnt from others
like most things you read on the web there
is always another point of view
Class 1 Pre-amp Gain
Class 2 AC adjustments
Class 3 Transmit Frequencies
Class 4 DC Phase
Class 5 VDI Sensitivity
Class 6 How I set up the ACs
| CLASS 1 Pre-Amp Gain : |
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First let’s look at "Pre-Amp Gain: This is the first circuit the ground target hit’s. This selects the intensity of the received signal when receiving a signal from the coil. This is the front end of the receiver. This adjustment affects all other receiver functions. The higher the number setting, the Higher the receiver front end sensitivity. The more sensitive the detector is to detected items. (This doesn’t mean you can turn the pre-amp up to 15) Rule to remember: Every time a pre amp adjustment is made, you "must re-ground balance the detector". Pull trigger once to return to detecting mode, press Enter to re-ground balance. The factory setting is #2. I would start one number at a time, re-balancing each time a adjustment is made. Use the detector, how does it act? Is it smooth, or are you now getting a lot of false targets signals as you sweep the coil? If you’re getting a lot of false signals, back off a number, re-ground balance, and try again. If that took care of it, that’s all the gain the unit can use in that area, with the settings you have. If it stays smooth, keep bumping it up, re-ground balancing each time, until unstableness occurs. Back off a number, and you have the maximum pre amp setting for that time of use. Notice I said "that time of use" because if you’re operating at maximum pre amp setting this will change from area to area, time to time. If you only had one adjustment to choose from, the pre amp is the one to adjust first. The pre amp adjustment has a affect on all other receiver adjustments, and we will touch on this as we go-along. This is why it is important to full understand the adjustment, and what it does. |
| CLASS 2 A.C. SENSITIVITY : |
A.C. Sensitivity is a control in the circuitry that controls the sensitivity of the final signal after the discrimination circuit. It acts somewhat like the Pre-amp control, but only having a affect on the "Discriminate motion mode" after the signal has been processed by the detector. This adjustment along with the Pre-amp and the VDI adjustment is what will adjust the gain of the detector while searching in the motion mode. These adjustments have a direct affect on detection depth, and sensitivity, (more so the A.C. Sens., and the Pre-amp, than the VDI). It (AC Sens.), also has a direct affect on the units stability. Adjusting to far out of whack for existing settings, and ground conditions, the unit becomes unstable. It really becomes a happy medium between the adjustments of the Pre-amp, and the A.C. Sens. With the VDI Sens. Also interjecting it’s self into the equation. Users of the XLT in areas of the country with low mineralization will be able to run with high AC, and Pre-amp settings. Of course it’s just the other way around with mineralized ground, less is needed. (Note on mineralization, The XLT has the ability to sample the ground mineralization, and report it back to the user for reference. More on that later.) I would first adjust the Pre-amp for highest stable gain, then adjust the AC the same. One does not need to re-ground balance after AC Sens. adjustments like you do with Pre-amp adjustments. D.C. Sensitivity The D.C. Sens. is just like the A.C. Sens. but It only controls the detector in the non-discriminating modes. These modes do not require motion of the coil. This is also the adjustment to set the final gain in the Mixed-Mode lower signal setting. Again, adjust this as high as you can with out the detector being unstable in the All Metal Channel. This includes Pin-Point mode sensitivity. I have found that one can adjust this setting very high with out a lot of ill affects, but it does have a great affect on the Pin Pointing mode with it cranked pass #30. High settings will make the V.C.O. Audio a little hard to handle also. If I have it on, I turn off V.C.O. when I crank up the D.C. gain. There is no need to re-ground balance when changing this setting. |
| CLASS 3 Transmit Frequency: |
Transmit Frequency I have listed below the available frequencies that the XLT user has the ability to set the detector to. #4 is the factory default setting. It is also the frequency that the factory recommends you use for best performance. Under most conditions you normally wouldn’t need to make changes here. One exception would be if you were detecting near another detector, and interference was encountered from one another. When making changes just move enough to stop the interference. Another exception is, there are times when outside electrical interference causes problems. Under or over ground power lines and railway lines can give you problems One can shift frequencies to try to eliminate the interference. I have noticed that the dfx is a little more sensitive to power lines then the xlt. 1 = 6027.5 Hz 2 = 6204.7 3 = 6392.7 4 = 6592.5 Hz 5 = 6805.2 6 = 7032.0 7 = 7274.5 Hz Transmit Boost This adjustment selects the strength of the transmitted signal from the coil. One has only the option of turning the boost ON or OFF. ON is the factory default setting? This is where you would leave it for most all detecting. I haven’t needed to change this adjustment on land. Hunting very mineralized ground, and/or some salt-water beach’s, may require you to turn it off. If your having problems ground balancing or getting no depth, try setting the Boost to OFF. You will need to re-ground balance each time you change this setting. After doing this and you notice that it has helped, you may want to increase the pre-amp gain one number at a time until it becomes unstable, and back off one number. Again, don’t forget to re-ground balance for each change. |
| CLASS 4 DC Phase: |
The DC Phase is one of the options on the XLT that very rarely gets used. I think That's a shame as it can enhance your operation of your detecting unlike any current production units can,(exclude new DFX,). The most important function I use it for, is to tell me the condition of the hunted ground mineralization. Knowing what the mineralization of the ground you are hunting in, will give you a heads up advantage with you initial adjustments for that area. How many of you have set your XLT up HOT for peak performance in one area, to move to a different site, and wonder if the adjustments you previously used will work ?? I will tell you how just go to DC Phase. Go to "Pro Options", Display, DC Phase. Just turn it on. You can leave it on all the time if you so desire, it has no affect on the detectors performance. Pull the Pin Point switch. Notice in the upper Rt. hand corner a set of numbers appeared. This is your DC Phase reference numbers. How to use: When not over any metal, lay coil firmly, flat on the ground. Engage pinpoint switch. Observe DC Phase numbers. When they settle down, and stop moving, that's the DC Phase reading of the ground mineralization. These reading are only relational to the XLT as a reference. Remembering or make a note, any other site you hunt in with the same DC Phase readings, and you can use the same settings used on the previous site. Interpreting numbers to mineralization : White's said that numbers from -40 to -50, should be considered neutral ground. As we move toward the end of the scale to -95, that should be considered very mineralized, (-) negative conductive, magnetic soil. Going the other way from -30 toward the + numbers should be considered (+) positive conductivity soil. One should be able to see the advantage in knowing what the mineralization of the soil is. If you have a real hot program you want to use, and it was set up on - 50 ground, going to ground like - 50 should work the same. If the ground reads - 8o, that should tell you your going to need some adjusting to your gain controls. DC Phase Target IDing. There is another function of the DC Phase, and that is using it to ID targets. It's very complex, and some users find it difficult to do. When locating a target with pinpoint, move coil off to the side, clear out of detecting range of target. Release pin point trigger. Leaving coil flat to the ground, pull pin point trigger, and slide coil over the target still holding the pin point trigger engaged. Holding pin point on, centre over target, place coil firmly, flat on ground, exactly centred on target. Read DC Phase reading. From what I have been told and read by successful users of DC Phase target ID is that any (+) positive reading number would be a good target. It's very critical that the coil be placed precisely over the target, and held firmly flat on ground to get a good reading. I must admit although I have tried the DC targeting it’s not for me but is dose work. Never leave anything unturned, it's something to look at. A quote from the XLT manual, “The relationship between D.C. Phase, Ground Balance, V.D.I. number, and Discrimination is complex. Results are not always repeatable in varied ground conditions. Ground and target responses can distort the detection field of the loop in a number of ways, by bending, reflecting, absorbing, and thus altering the phase, and amplitude the detector Measures. This in turn produces inconsistencies in the relationships of these features. |
| CLASS 5 V.D.I. Sensitivity: |
This adjustment controls the strength of the target signal needed to activate the display on the screen. Increasing it will make the display respond with more indications, but the reliability of the display starts to get poorer. Contrary adjustments, the display will be less sensitive, but the result will be more reliable. Setting the V.D.I. numbers a little higher will improve the response of the display to deep items, but there is a trade off. As the sensitivity increases the chances of making the detector, and the display unstable also increases. The V.D.I. Sensitivity, the A.C. Sensitivity, and the Pre-amp gain have a bearing on one another. The detector likes a happy medium between these controls. The detectors display, and some of the audio modes are also associated. The V.D.I. adjustments could have an affect on the audio sensitivity. Like all gain, and sensitivity adjustments set too high for the given soil conditions, the detector, and/or the display will become unstable. ICONS: The Icons are designed for average use in the US. Matching targets normally found in the US. Turning the ICON display "Off" will result in a faster speed up of the display. VISUAL DISCRIMINATION: When turned "ON" all Rejected V.D.I. numbers will not be displayed. If your not interested in the rejected target information, turn it On. This will also speed up the remaining display speed. Other words when it’s on, all the discriminated out items will not show up on the display. In the default mode, all information is displayed whether or not it’s discriminated out in the audio response. The disadvantage to using this is that rejected targets will not appear visually for you to interpret, and to investigate further. |
| Getting the best from your ACs: |
This is how I set the ACs up when I’m on site. I only use a pre-amp of 3 to start with turning it up to 4 if I can, but I have found 3 to be a good pre-amp in the area i hunt. I don’t believe in high pre-amps of 15. I know some do and if they feel happy using it that fine by me. I would sooner turn the ACs up and with a pre-amp of 3 I’m able to do this. 1. I start by turning ID tone OFF on the program, before I setup on site 2. Load up program and ground balance 3. I would normally sweep the coil for 20 seconds or so to make sure there are is no metal in the area I’m setting up in. Then put the coil on the ground and listen for the hum, if its stable I would up the ACs and repeat what I’ve just done, and so on till the threshold starts to null like it dose when you go over iron, then drop back one number and that the best AC for that area, the most important thing I think is to have a stable threshold (sometimes I will run it in a slightly unstable mode which is when you are running your detector HOT), I would run it this way when I knew there were half cut Hammered coins around (I must admit I do like running my machines hot) but it dose give your ears a bashing. 4. If the threshold is not stable when you start off, then drop down a number at a time till you get it stable. 5. When it’s stable I then go back to the menu and turn ID tone ON |
| I read this on a Whites site sometime ago From My mate Vernon, (The first truth about detecting) |
There are many knowledgeable people on this site that are more than happy to help you with question about the XLT and tricks of the trade. In fact many of us don't have anything to better do, since we can't go detecting yet because of all of the snow. The XLT is one of the finest detectors on the market today and is more than capable of detecting jewellery or anything else for that matter. You have to use less discrimination and understand that you will have to dig a lot more junk items along with the good stuff if you want to find rings and jewellery. Advertisement hype aside, the truth of the matter is, a detector can't tell the difference between a penny or a small piece of copper tubing, a 50 cent piece or a freeze-out plug, a silver dollar or a shredded piece of pop can, a pull-tab or a $5,000 diamond ring. Once you understand that little profound fact, you will have learned the first truth about detecting. A discriminating detector with ID capabilities is a wonderful thing and a great help if you don't take it as gospel. Understand that the detector is only giving you information on what it" thinks the target might be, based on a set of pre-programmed "most likely." The XLT will have no trouble detecting jewellery but you won't find most jewellery hunting in the Coins Program. If you want jewellery, you will need to hunt in the Coins & Jewellery or Jewellery & Beach Program. And if your XLT says it is identifying a piece of foil at three inches... dig it, it may well be a piece of foil, but it might also be a platinum diamond ring! Do some table top tests with your XLT. Put it in the factory reset Coins & Jewellery Program and get yourself a ton of miscellaneous jewellery and anything else you can find like Zippo lighters, keys, spoons, small batteries, small metal toys, anything you have around the house that you might find in the ground and pass them quickly back and forth in front of the coil about 6" to 8" away. What an eye opener that will be. You'll notice there are no neat little icons of a can opener as you pass one in front of the coil, but you should get a good solid beep. Right off hand, I don't know what icon will pop up, but it's not going to be a can opener... and you'll also notice as you pass your grandmother’s 80 year old brooch in front of the coil, an icon of a brooch does not come up, but you will get a good solid beep. So if you're hunting for jewellery, either turn the icons off, or don't pay any attention to them. What you would be looking for is a good, solid, repeatable beep, and some good graphs on the far right hand of the screen. You should notice this in your table top testing; if you take a man's gold wedding band, and pass it in front of the coil, you should get a good solid beep and a good solid set of high graphs after you've passed it quickly by the coil several times. This is what you're looking for when you're hunting for jewellery, or artifacts, as opposed to coin hunting where you could depend a lot more on the icons. I find that by making sure you're accepting nickels, that is, you're detecting with a good response a nickel... then you would be able to detect most of the good jewellery. But there are exceptions. I once detected a very small filigree 14 k gold ring; it registered a -7 on the VDI scale, but had a good solid response, so I dug it. I've dug many cheap rings that registered as foil and some thin gold rings as well. So, what I'm saying is by doing some table top testing, it will help you greatly in realizing that the detector is not infallible, and that if it's a good repeatable solid beep, you'd want There are many to dig it. I hope this has shed some light on the XLT. Vernon (Alaska) |