By Steve Herschbach
Which metal detectors have the most reliable target ID numbers?
Target ID is a function of depth - the deeper the target, the more difficult it is to get a clean target ID as the ground signal interferes. Other items directly adjacent to the desired target can also cause inaccurate numbers. The more conductive the item, the higher the resulting ID number, but also the larger the item the higher the number. Silver is more conductive than gold, so a gold item will give a lower number than the same size silver item. But a very large gold item can give a higher number than a small silver item, so numbers do not identify types of metal. Gold and aluminum read the same and vary in size so to dig one you dig the other. Only mass produced items like coins produce numbers that are more or less the same over the years but a zinc penny will read lower than a copper penny due to the change in composition.
In general iron or ferrous targets produce negative numbers or low numbers. Aluminum, gold, and US nickels produce mid-range numbers. And most other US coins produce high numbers. Other countries coins, like Canadian coins with ferrous content, can read all over the place.
The scale applied varies according to manufacturer so the number produced by each detector will vary according to the scale used. The 0-100 range for non-ferrous targets is most common but there are others. Minelab employs a dual number system on a 2D scale with thousands of possible numbers, but they are now normalizing the results produced to conform more closely to the linear scale used by other manufacturers.
Increasing ground mineralization has a huge effect on the ability to get a good target ID. Ground mineralization is nearly always from iron mineralization, and this tends to make weak targets, whether very small targets or very deep targets, misidentify. The target numbers get dragged lower, and many non-ferrous targets will eventually be identified as iron if buried deep enough. Small non-ferrous readings and iron readings actually overlap. That is why any discrimination at all is particularly risky for gold nugget hunters.
If you want target ID numbers to settle down, lower sensitivity and practice consistent coil control. The target number will often vary depending on how well the target is centered and how fast the coil moves.
Higher sensitivity settings lead to jumpier numbers as the detectors become less stable at higher levels. The interference from the ground signal increases and interference from outside electrical sources also increases, leading to less stable numbers.
Higher frequency detectors are inherently more sensitive and are jumpier. So lean lower frequency for more solid results. Multi frequency detectors act like low frequency detectors and tend to have more solid target numbers due to the ability to analyze a target with different frequencies.
Another issue is the number of target categories, or ID segments, or VDIs, or notches, or bins (all names for the same thing) that a detector offers.
For instance here are the number of possible target id categories or segments each detector below offers:
Fisher CZ-3D = 7
Garrett Ace 250 = 12
Minelab X-Terra 305 = 12
Minelab X-Terra 505 = 19
Minelab X-Terra 705 = 28
Minelab Equinox = 50
Fisher F75 (and many other models) = 99
White's MXT (and many other models) = 190
Minelab CTX 3030 = 1750
Fewer target categories means more possible items get lumped together under a single reading, but that the reading is more stable. Many detectors will tell you the difference between a dime and a quarter. The Fisher CZ assumes you want to dig both so puts them under one segment along with most other coins.
People who use detectors with many target numbers usually just watch the numbers jump around and mentally average the results. Some high end detectors can actually do this averaging for you! But I think there is something to be said for owning a detector that simplifies things and offers less possible numbers to start with. The old Fisher CZ method still appeals to me, especially for coin detecting. So do detectors like the Garrett Ace 250 or Minelab X-Terra 505 for the same reason.
The problem is that as people strive to dig deeper targets or smaller targets the numbers will always get less reliable. But if you want to have a quiet performing metal detecting with solid, reliable target numbers look more for coin type detectors running at lower frequencies under 10 kHz or at multiple frequencies and possibly consider getting a detector with fewer possible target segments. And with any detector no matter what just back that sensitivity setting off and you will get more reliable target numbers.
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Detectors often use tones to identify targets and often use far fewer tones than indicated by the possible visual target id numbers. The X-Terra 705 for instance can use 28 tones, one for each segment. However, most people find this too busy, and so simple tone schemes of two, three, or four tones may be selected. I think it is instructive that many people often end up ignoring screen readings and hunting by ear, using just a few tones. This ends up just being an ultra basic target id system much like the simpler units offer. Reality is that most people do not need or care about huge numbers of target numbers. For many just three ranges suffice, low tone for iron, mid tone for most gold items, and high tone for most US coins. The meter could do the same thing, but for marketing purposes more is better and so we get sold on detectors with hundreds of possible target ID numbers. Perhaps this is a digital representation of an old analog meter with its nearly infinite range of response but the reality is we do not need that level of differentiation to make a simple dig or no dig decision.
Finally, a picture often says it all. Below we have a shot of the White's M6 meter. I like it because the decal below illustrates a lot. You see the possible numerical range of -95 to 95 laid out in the middle. Over it is the simplified iron/gold/silver range. Note the slants where they overlap to indicate the readings really do overlap. Then you get the probable target icons. -95 is noted as "hot rock" because many do read there.
The M6 can generate 7 tones depending on the target category. I have added red lines to the image to show where these tones sit in relation to the scale. It breaks down as follows:
-95 = 57 Hz (Very Low) Hot Rock
-94 to -6 = 128 Hz (Low) Iron Junk
-5 to 7 = 145 Hz (Med Low) Gold Earrings, Chains - Foil
8 to 26 = 182 Hz (Medium) Women's Gold Rings/Nickel - Small Pull Tabs
27 to 49 = 259 Hz (Med Hi) Men's Gold Rings - Large Pull Tabs
50 to 70 = 411 Hz (High) Zinc Penny/Indian Head Penny - Screw Caps
71 to 95 = 900 Hz (Very High) Copper Penny/Dime/Quarter/Dollar
Note that the screen reading of +14 is noted as being a nickel or ring but it can also be the "beaver tail" part of an aluminum pull tab or the aluminum ring that holds an eraser on a pencil, among other things.
The best book ever written on the subject of discrimination is "Taking A Closer Look At Metal Detector Discrimination" by Robert C. Brockett. It is out of print but if you find a copy grab it, assuming the topic interests you.
Always remember - when in doubt, dig it out! Your eyes are the best target ID method available.
By Steve Herschbach
The White's Goldmaster 24K is a new 48 kHz gold nugget detector released in the fall of 2018. Production models started shipping in September and White's forwarded one to me to check out. What follows are my thoughts after a couple days of detecting for gold on several northern Nevada nugget patches.
The Goldmaster 24K marks a break with the past as White's moves from the older metal box designs of the past to newer plastic cases. The Goldmaster 24K physical design is the latest in the evolution of the MX series. The control box itself is derived directly from that used on the White's MX5. The control pod / display originated with the TreasurePro and later used in the MX Sport and MX7 designs. Basically the Goldmaster 24K is in the same housing and rod design as the White's MX7.
Manufacturers face a difficult design choice these days. In general users want metal detectors to be as light as possible. However, weight is not everything - balance matters every bit as much. The problem is that a metal detector search coil is basically a weight on the end of a long stick. Coils can only be made so light due to engineering constraints requiring a certain amount of copper wire and a reasonably robust coil housing. The coil then has a lot to do with determining the final ergonomics of the detector. If the coil weight is not balanced at the other end with some kind of offsetting weight, the detector is nose heavy. This in turn creates torque everytime the detector changes directions which puts stress on the operators arm.
The detector can be made as light as possible, or can be perfectly balanced, but it is almost impossible to do both in one detector. Any detector that weighs less than 3 pounds is almost certain to be nose heavy because enough weight does not exist to balance the weight of the coil. In order to have enough weight to work with it appears the minimum is about 3.5 lbs for detectors that are well balanced. The extra weight is almost always in the form of a battery box located under the elbow. White's has gone this route is the MX series designs with a battery box holding 8 AA batteries under the elbow acting as a balancing weight. This results not only in a well balanced detector but a detector with enough batteries to operate for multiple days between charges or battery changes.
White's Goldmaster 24K metal detector for gold prospecting
Another big choice manufacturers have to make these days is whether to use a straight rod or a "S" rod design. Users tend to be evenly split as to which they prefer, and so this is a choice the manufacturer cannot possibly win. About half the people are going to be unhappy whichever way you go. Industrial type users like beach hunters and prospectors tends to prefer straight rods. Coin, jewelry, and relic hunters seem more inclined to "S" rods. I have used many detectors with either setup and have been happy with both or unhappy with both. The deciding factor for me has been more about the exact size, shape, and angle of the hand grip than the actual rod design. I do not have over-sized hands, and so I tend to prefer a smaller diameter grip. Other people like a larger grip.
I went into all that detail to be sure the reader understands that weight and balance is very much a personal preference item. Getting a detector to fit right for everyone is like making a pair of boots that fits everyone. You can't do it. Therefore when I say that the MX physical design as employed in the Goldmaster 24K is a very good fit for me don't take that as meaning it will be great for you. Yet it is a very good fit for me and quite comfortable on my arm, with just enough forward weight to keep my elbow in the arm cup without having to use the arm strap. The design is also lighter than the White's GMT by nearly half a pound, so the Goldmaster 24K is both well balanced and lighter than what came before. The Goldmaster 24K with 10" elliptical coil and with batteries installed weighs 3 lbs 7 oz (3.4 lbs) or 1562 grams on my digital postal scale.
The Goldmaster 24K has an IP54 rated enclosure that has a high level of protection against dust particles, and a fair amount of protection against water. The coils are waterproof but the detector itself is not submersible so keep that display pod out of the water. The "S" rod is a three piece design with excellent quality twist locks that create a firm, wobble free rod assembly when fully engaged. The armrest position is not adjustable but it is well placed.
The 24K is powered by eight AA batteries in a battery holder that pops out of the rear of the battery box. The 24K is supplied with eight alkaline AA batteries but rechargeable batteries may be substituted for use in the battery holder. The 24K can get up to 40 hours operation using high quality alkaline batteries and while using headphones (external speakers use more power). The Goldmaster 24K does have a speaker built into the rear of the display pod, and there is a female 1/4" headphone jack directly above the battery door. White's thoughtfully includes a small plastic plug to insert into this hole when not in use.
White's 24K battery holder and headphone jack location
The Goldmaster 24K comes with a 5.5" x 10" DD coil as the stock coil. A 6.5" round concentric coil is available as an option. Scuff covers for the coil are not included with the detector or when you buy an accessory coil - they are separate optional items.
The 5.5" x 10" DD search coil weighs 14.5 oz or 412 grams. The coil is 1" thick. The 6.5" round concentric coil is 3/4" thick and weighs 13.1 oz or 370 grams. Therefore the 24K when outfitted with the 6" concentric weighs in at 3 lbs 5 oz (3.3 lbs). White's possibly has a 13.5" x 8" DD available soon that weighs 1 lb 8 oz or 682 grams. Finally, a version of the 4" x 6" Shooter DD is in the works also. Neither of these coils is available for sale as of March 2019 so for now the GMK has one accessory coil (the 6" concentric) available for purchase. Do note that all pre-existing coils for other White's Goldmaster or GMT models are not compatible with the Goldmaster 24K. The 24K pumps about 50% more voltage to the coils than previous models, requiring tighter tolerances in the new coils. The coil connector has been changed to prevent confusion.
5.5" x 10" DD search coil and 6.5" round concentric coil for White's Goldmaster 24K
The Goldmaster 24K shares many functions with the White's GMT model but there are differences. The most obvious being that the GMT uses knobs for control adjustments. The 24K uses a sealed touchpad which is more water and dust resistant, but some controls have secondary functions that necessitate having the Quick Guide near at hand when learning the detector.
The 24K like the GMT does of course have a sensitivity control, and like on all hot VLF detectors it is a critical control. The solution to most problems regarding metal detector instability or interference is to reduce the sensitivity.
The 24K features both automatic ground tracking or a fixed ground balance adjusted via a tap of a "ground grab" button - in this case the pinpoint button, which doubles as a ground grab when given a quick tap. Ground tracking can be a great function for variable ground and people new to detecting. Personally I prefer to lock the ground setting (via the "Lock" button) and update it manually via the ground grab function. I did use the ground tracking however, just to try it out. It is lightning quick, taking just a pump or two to track into the ground. Ground grabs are instantaneous.
The White's GMT allowed for a locked ground balance to be tweaked up or down manually via plus or minus buttons on the control pod. The 24K takes a slightly different route by allowing a "ground balance offset" to be dialed into the detector. The ground balance offset is a powerful feature and so deserves some explanation. Prospectors often prefer manual ground balance because they can choose their own setting that for various reason might be different than what a machine will choose using a preset function like ground grab. Ground grab may be set to deliver a very neutral ground balance. The prospector may prefer that the balance be slightly positive to help enhance tiny nugget signals. They may want to choose a ground balance setting halfway between the ground itself and some pesky hot rock, which may mean adjusting either positive or negative from the neutral setting. This might require that the operator first do a ground grab, then hit the plus button a couple times to manually offset the ground balance.
The 24K has a "Follow The Black Sand" mode like on the GMT but it is now called Ground Scan. Ground Scan is enabled by pushing and holding the ground balance "Lock" button. While in Ground Scan the "Up" and "Down" buttons create a ground balance offset. This offset is retained when you leave Ground Scan mode and will be applied both when doing a ground grab and even while in ground tracking mode.
The Ground Scan / Follow The Black Sand thing is intended to allow a prospector to locate and trace shallow magnetic sand deposits that might indicate potential gold concentrations. This is a rarely used function, but including the offset ability means this function may be accessed much more often just to create these ground balance offsets. With the GMT you could ground grab and then manually tweak the setting, but the tweak had to be applied every time the ground grab is performed. Now the offset can be dialed in and automatically applied. The real zinger however is that this also allows the 24K ground tracking function to be directly tweaked - very, very rare indeed. Almost every detector I have ever used has a preset ground tracking circuit that puts the ground balance where it wants, end of story. With the White's Goldmaster 24K you can create a tracking offset to deal with hot rocks in a way that simply can't be done with most other ground tracking systems. Really cool White's!
White's Goldmaster 24K with 13.5" x 8" DD coil (prototype lacking decal)
The 24K has the volume control the GMT lacks which is quite handy for those who want to run without headphones but not necessarily at full volume. There are 8 levels of volume plus two boost settings, Boost 1 (b1) and Boost 2 (b2) that kick in when you adjust the volume control above 8.
The GMT features a Variable Self Adjusting Threshold (V/SAT) control that governs the rate at which the audio resets itself when passing over a target or ground variations. The GMT has a knob that runs from 1 to 10 and on the Goldmaster 24K the SAT setting has been simplified to three settings - off, medium, and fast. The default setting of medium is all most people will ever need. However, in extreme low mineral ground the off setting can enhance weak signals, although the detector may need very careful coil control and slower coil sweeps to allow the circuit to keep up. Conversely, extreme high mineral variable ground may require the fast setting to smooth out variations in the ground signal.
The threshold control itself is interesting. Normally on an old school threshold based all metal detector the all metal mode and threshold are one and the same. The Goldmaster 24K like some newer digital models appears to employ what is referred to as a "reference threshold". The threshold may be adjusted, but appears to be disconnected from the all metal channel and is instead layered on in parallel. The SAT control above does directly affect the all metal channel as described above. Yet it does what it does whether the threshold is present or not. Reference thresholds often exist for the sole purpose of nulling or going silent when passing over items that have been discriminated out, but this does not happen when the Iron Cancel (see below) is engaged. While bench testing in all metal with the SAT set at zero I thought I might just be able to hear a waver in the threshold. I would be interested in hearing from other nugget hunting experts on this matter, because in my opinion the threshold as it exists on the Goldmaster 24K is not coupled to the all metal channel in the manner one would observe on the GMT for instance. The only effect seems to be with threshold completely off the 24K will no longer give any ground feedback at all if out of ground balance. Based purely on what I am observing in actual use I would say the 24K is a silent search detector with a reference threshold added as opposed to a true threshold based all metal circuit like on the GMT. The difference is subtle but there for my ear at least and if there is a connection there between threshold and all metal channel, it is too minimal for me to discern while in actual use.
Now we get into the real meat of where the GMT and Goldmaster 24K part ways. The GMT has an iron (ferrous) probability meter as does the Goldmaster 24K. The GMT meter is merely a bar graph - far left means 10% chance of ferrous and far right means 90% chance of ferrous. Somewhere in the middle means 50% chance of ferrous. The Goldmaster 24K puts a blacked out block at the top of the screen with similar positioning, but the actual percentage numbers display out as a "target id" number. This is not a target id number as thought of on coin detectors, but instead intended to be a display of the odds that an item is non-ferrous.
White's Goldmaster 24K controls and display screen
If you look at the display above there is a colored bar at the top of the 24K LCD meter - red on left, wide yellow middle, and dark gray on right. The three colors taper one into the other to indicate overlap. The red on the right indicates the probable ferrous range, and dark gray indicates items reading too high to probably be gold, but more likely a copper, brass, or silver item (high conductors) or certain ferrous items that "wrap around" and "read high". These include hardened steel items like large bolts, almost any washers, ax heads, etc. In theory this scale could be used for coin detecting but the coins with few exceptions like a nickel tend to bunch up all on the right. The intent really is to be more of a ferrous/non-ferrous meter but I do think I could make do with this for some general detecting scenarios. In air tests a nickel read 88, zinc penny 95, dime 96, and quarter 97.
The Goldmaster 24K has an Audio Mode button that engages and disengages something analogous to the "Iron Grunt" feature on the GMT. Engaging the Audio Mode replaces the normal VCO type "zippy" audio with a simple high or low beep. Any meter reading below 50 will deliver the low "ferrous" beep and anything 50 or higher a high "non-ferrous" beep. Since the gold probability range runs much lower this is helping the operator concentrate only on the high probability targets - anything with over a 50% chance of being non-ferrous. This "over 50% equals non-ferrous" audio mode could be useful for direct hunting in some situations. However, when pushing the detector hard in all metal mode and then switching the Audio ID mode on I found that I would have to reduce sensitivity or encounter quite a few false signals in mineralized ground. That being the case I was more prone to using this as a ferrous check by engaging the button for a quick audio reading, then back again to all metal mode.
The Audio Mode as I described it above acts much like the Iron Grunt feature on the GMT, but on the GMT the ferrous audio alert only kicks in when there is an 85% or greater chance of the item being ferrous. It is not a certainty on how the percentages correlate, but the 24K audio ferrous tone does kick in at readings of 50 and below (greater than 50% chance of being ferrous). Borderline gold targets can read lower than this however, down into the 40s and even lower. A 30% chance of gold is still pretty good odds. So what to do now except read the numbers?
White's has addressed this with another control, the Iron Cancel button. Engaging Iron Cancel activates an adjustable iron rejection setting. The default is for anything reading 15 or lower to simply not beep. This corresponds to the solid red area on the bar graph display at the top of the meter. Borderline or mixed content items will break up or give erratic readings. The best part however is that the setting can be adjusted from 0 all the way up to 62. This allows the operator to completely block out a chosen range of low end readings that is either more conservative or more aggressive than the Audio Mode preset. As noted before, the threshold, if any is used, will not blank over rejected items - they are simply ignored.
I noted above that highly conductive items and some steel items can read at the very high end of the scale, typically 95 and above. If the goal really is gold it is very unlikely that readings this high will be gold and so White's also offers the ability to block out this high end range. Tapping the "lock" button while in the ferrous adjustment mode will automatically block all readings of 94 and higher, which is where most iron high end false signals will occur.
Other controls on the Goldmaster 24K - a pinpoint function, frequency shift to help avoid electrical interference or for running two 24Ks close together, a backlight for the meter for low light conditions, and finally, a factory reset.
White's Goldmaster 24K with stock 10" x 5.5" DD coil
Now for the part everyone has been waiting for - how does the Goldmaster 24K at finding gold? When I test nugget detectors I tend to concentrate on smaller gold. First, because it is more plentiful and easier to find in limited time frames for testing purposes. Realistically small gold also challenges the detector the most. A metal detector must be tuned as hot as possible to find very small bits of gold. Yet this also causes problems with mineralized ground and hot rocks. It is not so much the small gold sensitivity that matters but how the metal detector handles the ground while tuned up for tiny gold. This is why air tests are minimally useful for nugget hunters. They can reveal theoretical information about how small or how deep a detector can find gold under perfect conditions. Air tests give no indication however of how the detector will handle bad ground and hot rocks when tuned to the max. A detector can air test extremely well and fail completely in the field. Therefore when you see my metal detector test reports, pay attention to the smallest nuggets I find, not the larger ones.
The 10" DD coil is a good all around nugget hunting coil, with DD coils having the advantage for handling difficult ground. It was the 6.5" round concentric that wowed me however and after I got it on the detector I really did not want to take it off. The 10" DD will be a better choice for really bad ground, but lacks that magic edge on the tiniest bits of gold. I also appreciate that concentric coils are easier to pinpoint with, and generally have better ferrous identification performance compared to DD coils. One nice thing about the 24K being well balanced is the 13.5" x 8" coil is less nose heavy than would be the case for an unbalanced detector. This is the coil to use for covering ground in search of larger gold nuggets.
For medium to milder ground and the smaller gold however I really do like that little concentric. In particular there is a lot of grass growing in some desert areas, and the 24K with 6" coil was perfect for mowing through the grass to keep the coil on the ground. This is another area where an "S" shaft has the advantage. A straight shaft detector wants to roll to the side when forcing the coil against resistance, where a balanced "S" shaft being in line with your arm does not produce that kind of rollover torque.
The 10" x 5.5" DD coil was a little more prone to false signals when bumped hard than the concentric coil, to the point where I could run higher sensitivity with the concentric on this particular ground. The ground in lots of Nevada is rather mild, often with alkali (salt) content, and it may or may not have bad hot rocks. This particular location had two types of hot rocks to deal with. The bottom line is I was able to run the concentric at full sensitivity of 10, and in audio boost 2 (b2) while in all metal mode and SAT set at medium (default). Even with the machine maxed out like this the detector ran well, and as I said before falsed less than the DD coil would if I attempted the same settings.
White's new XGB ground balancing system really does seem to do a good job finding a setting that works well with both hot rocks and the ground by tracking multiple ground balance points. I liked to engage tracking, run over a mix of ground and hot rocks, and then lock the setting. I was scrubbing and pretty much digging everything. The Goldmaster 24K with the little concentric is hot as a pistol and as usual if you give me a hot detector I was able to find some really tiny gold. The eight nuggets below weigh a total of 8.3 grains (not grams - 480 grains per Troy ounce). The largest nugget is 1.8 grains and the smallest are in that under 1/10th gain range. Now, none of these were super deep because you can't find tiny gold super deep, but they were all good zippy targets - and I was not using headphones!
Gold nuggets found by Steve with new White's Goldmaster 24K - smallest under 1/10th grain
The proof is in the pudding and there is no doubt the Goldmaster 24K can find the gold, and some really small gold at that. I am not going to try and convince anyone that there is some kind of magic breakthrough here - at the end of the day the 24K is a hot 48 kHz single frequency metal detector just like the GMT in many regards. Some oldtimers may still prefer the GMT for its threshold being tightly connected to the all metal channel while the threshold connection on the 24K is much weaker. Although the Goldmaster 24K can be run hot and noisy, all it's design features point to a detector that is intended to be set up as quiet as possible, and this may even mean running without a threshold. I did not see any evidence that this would really hurt the performance at all. This kind of quiet hunting tends to appeal more to people new to nugget detecting, especially those who cross over from coin detecting. Add this to the lighter weight and lower cost package and White's has done a great job producing an alternative to the admittedly long in the tooth GMT.
White's Goldmaster 24K Data & User Reviews
White's Goldmaster 24K Quick Start Guide
White's Goldmaster 24K Advanced User Guide
White's Goldmaster 24K & GMT Compared
Little gold nugget on coil fresh out of the ground
This will be where I will post information. I will try and answer any questions I can about detector. Other folks who have experience with detector and wish to join in, by all means do so.
Should have detector today sometime. Thought I would get this thread started to save time later. I will only be using Tarsacci on turf, not salt water/sand application.
I may do some testing on freshwater beach due to lower minerals present.
For refererence - Quick start guide
Tarsacci MDT 8000 Data & Reviews
By Steve Herschbach
Update January 2019 - I started reviewing detectors on the internet over twenty years ago. At the time it seemed I was providing a service since good information was hard to find. I enjoyed reviewing machines in detail for those who were interested. The internet was more friendly back in those days.
Times have changed, and these days everyone with a video camera is a metal detector expert. In particular there is a trend where industry insiders like me are considered tainted sources of information, not to be trusted. Personally, I don’t need people questioning my integrity. I was doing this for fun and that sucked all the fun out of it. I am therefore no longer accepting invitations to test or review metal detecting equipment.
That said, my thanks to those of you who have expressed your appreciation for my efforts over the years. You can find my collected detector reports here. The focus on this website going forward will be individual user reviews as part of the new Metal Detector Database with User Reviews. Check it out!