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I have the Fisher F75+. If I have the discrim set at say 30, why do I sometimes get low VDI numbers like 6 or 7?

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A simple thing worth trying is to perform a Factory Reset on the machine, then re-set your discrim etc. You may have some inadvertent notching set up, and it's simplest to reset, rather than figure out how to untangle the notch.

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    • By Relicrecoveryspecialist1
      Steve I plan on going civil war relic hunting this weekend in an area of a lot of action including cannon balls. I’ve read online how to put it in all metal mode, but step by step or whatever, would all metal be better than BP?

    • By Jeff McClendon
      This is less of a comparison and more of a question. It is a real head scratcher for me. I am not in any way trying to put down one detector and hype up another. This is just my experience.
      So, I recently had another try at the F75/T2/F70 platform. I have over 150 hours on these detectors and have now sold them all.......Why?
      My last go at this great group of detectors was with a 2016 F75LTD Special Edition with all of the latest features. After ten outings with it (about 40 hours) I have given up. Selling on Ebay right now with bids. My last work with it was at a city park that has such bad EMI that a Version 4 Omega 8000 and a T2+ were unusable there. This newer F75LTD had no audible issues with EMI at this park which for me anyway was a big improvement. My problem with it was determining a dig or not dig signal. At this park there is an audible signal every 2 or 3 inches, sometimes even closer. I did two field tests with the F75LTD 11"X7"DD and an Equinox 600 11" DD. Settings for the F75 were ground balance 87, Fe3O4 4 to 5 bars, DE mode, discrimination 15, 4 tones, sensitivity 80. Settings for the Nox 600 were ground balance 3, default Park 1 except for a bit of threshold tone set at 6 and sensitivity at 17 (even the Equinox can have EMI issues). I did use the horseshoe button a lot for iron ID.
      The first time I did this field test I did not want to believe the results. They were not pretty and were basically repeated in this second field test. So, I decided to try again. Both times I picked an area about 50 yards long and 2 yards wide, roughly a full sweep in one direction/lane and a return to the beginning in the adjacent lane. I marked the area off so I wouldn't stray or miss any ground. First I used the F75. Tons of signals, 1/4" aluminum shards are everywhere from shredded pop cans...... came up with 41 cents (3 clad dimes, 7 zinc pennies, 4 pre-1982 copper pennies) , a really cool HO scale tractor (I am a model train guy too, so great find, don't even have to weather it!)  a shell casing and some pull tabs, etc. I did hit a really big target that sounded like big iron falsing by itself and did not dig it. There were so many iffy signals (at least to my ears and eyes with numbers and tones all over the place). I was only concentrating on two-way signals with generally consistent numbers and those are the targets I recovered. None were more than 6" deep.
      Next I covered the exact same ground with the Equinox. From the photos you can see that I or the F75LTD or a combination of both missed a lot of legitimate targets. It was easy to make the dig or no dig decision on these targets with the Nox 600. They were solid, two way, stable numbers and audio, no brainers. None were more than 8" deep and most were in the 2" to 4" range. The big iron screw had a clad dime that was 1" away from it and a little deeper than the top of the screw which was 3" below the surface. I heard the clad dime clearly both during sweeps and pinpointing, two separate obvious.targets. Lots of silver mercury dimes and wheat pennies in this area so I dug both targets. I only heard the iron with the F75. Also, there is no way using the Nox 600 that I would have missed the vast majority of the targets that I recoverd earlier with the F75. They were not difficult targets to recover. Also, except for the big iron screw and dime, I did not dig any targets with the Equinox 600 that were in previous F75 plugs or even adjacent to them, like within masking distance unless the F75 with the settings I was using can have masking issues with targets 4" apart...........
      So, I guess I am super spoiled by the Equinox.......or I seriously suck at the F75/T2 platform.
      These were recovered by the F75LTD

      These were recovered in the exact same ground afterwards by the Equinox 600. 1974 Kennedy half dollar, 1983 Washington quarter, 3 clad dimes 9 zinc pennies, 6 pre-1982 Memorial pennies, several pieces of lead and solid aluminum, etc.

    • By Steve Herschbach
      I am a big fan of the Fisher F75 from a different perspective than most. I am a prospector and have done very well finding gold nuggets with the F75. The very powerful all metal mode combined with the simultaneous on screen target id numbers have allowed me to quickly and efficiently hunt trashy tailing piles in search of large gold nuggets. The light weight and superb balance make the F75 a pleasure to use for long hours in rough terrain. It also was my detector of choice for my one and only trip to the UK that I have done so far, and it served me well there.

      I spent a month in 2013 metal detecting on Jack Wade Creek near Chicken, Alaska. I kept my great results there quiet pending a return trip there in 2014. That trip has now been made but that is another story already told in detail on my website. Now I can finally reveal the details of the 2013 expedition.

      I started out early one morning with my big gun pulse induction metal detector, but got onto a tailing pile that had ferrous trash scattered down one side, and I was just not in the mood for it that morning. I went back to my truck and got out my trusty F75. I run the F75 in all metal because it has instant target response; there are no worries about recovery times in all metal. The coil picks up every variation not only in targets but in the ground allowing me to monitor what is going on at all times. Knowing what the ground is doing is important in keeping the ground balance properly adjusted for maximum results.

      The key thing I like about the F75 in all metal however is that the meter always runs in discrimination mode and places a nice, large target number on screen while in all metal. The audio alerts me to a potential target, which I then analyze more carefully while watching the target numbers. All metal goes deeper than discrimination modes, so no on screen number means a very deep target beyond discrimination range. This alone makes running in all metal desired when prospecting because running in discrimination mode would miss all those extra deep signals.

      In all metal I dig them until a target number shows up. Deep targets or small targets in mineralized ground will often read ferrous, so I watch the numbers and if they even once jump to non-ferrous, I dig. Only targets that give a 100% strong ferrous reading over multiple sweeps can be safely passed. Though I will throw in my caveat that no discrimination system is 100% accurate and there is always a risk of passing a good target. When in doubt, dig it out!

      I do often employ pulse induction detectors and do very often just dig everything. I advocate that when time and conditions allow. The reality is this is not always practical for many reasons. Maybe it is just limited time and overwhelming amounts of junk. Better to increase the odds by using discrimination than bogging down digging 100 nails in a small area. In my case it often boils down to fatigue or flat out not being in the mood to dig junk.

      So it was on this particular morning, and therefore my F75 came out and I got to work sorting through the trash working my way up the side of the tailing pile. I crested the top and got a strong reading and looked down. There was a shallow dig hole with leaves in it, obviously from some hunter there in prior years. I figured the guy had recovered a trash item and kicked it back in the hole so I cussed him quietly under my breath. I hate it when people do that!

      Then the target numbers caught my eye. They were all over the place. A crumpled piece of flat steel might give numbers like that though. Still, I was curious and figured I would retrieve the trash this person left in the field. I gave the old dig hole a big scoop, and out pops a big gold nugget!!

      I seem to have a talent for finding ugly gold nuggets, and this one was perhaps the ugliest I have ever found. It looked more like a rock burnt in a fire than a gold nugget when I dug it up, though the glint of gold is unmistakable. This gold however was very pale and in fact later analysis revealed it to be roughly half gold and half silver and other metals.

      It is a little known fact that gold alloys tend to have very poor conductivity ratings. Gold is very conductive, and silver is a superb conductor. You would think adding silver to gold would improve the conductivity, but in fact just the opposite happens, and the conductivity lowers dramatically. Gold/silver alloys are closer to lead in conductivity than that of the pure component metals, explaining why bullets read identically to most gold nuggets.

      This ugly nugget is a detectorists worst nightmare, because the 50-50 alloy mix and rock content give it a much lower conductivity reading than would be the norm. I surmise what happened is this earlier operator got a poor signal and gave a dig to get the coil closer to the target. The signal did not improve, as would be expected with most gold nuggets, so the operator decided it was trash and moved on. The rest of the hill being covered with junk no doubt contributed to this decision.

      It was my insistence on investigating everything except 100% ferrous readings that made the difference. The readings on this target were not solid as one would expect from a pretty strong signal but all over the place. Most people would say that indicates a trash target but I have seen many gold nuggets do the same thing in mineralized ground. The result is I dug a shallow 2.33 ounce gold nugget that somebody else walked away from. Sadly for them one more scoop would have revealed the nugget for what it was. Hopefully this is a reminder to the reader that far too often detectorists look for excuses not to dig. How many good finds get left behind because we do not want to take that extra minute or two to dig a target?

      This nugget is far from a premium find, but I have already sold it for over twice the cost of a new Fisher F75. That detector was a real money maker for me as that was far from the only gold I ever found with it.

      Unfortunately I say was. I made a huge change in my life in 2013 and moved from Alaska to Reno, Nevada. The move resulted in a desire for me to weed down my detector collection. I was pretty excited to do some coin detecting in Nevada where the potential finds were much better than those possible around Anchorage, Alaska.

      Almost all my detecting with the F75 had previously taken place in rural locations far from possible electrical magnetic interference. In Reno, EMI raised its ugly head. I found much to my dismay that the F75 did not like my new location, and in fact when turned on to hunt the yard at my new home I could not get it to settle down at all. No matter what I did the machine chirped and beeped and numbers flew all over the screen. Unfortunately I experienced what many urban hunters have found out – the F75 is a very sensitive high gain detector that does not get along well with electrical interference. I ended up selling my F75 in 2013 for this sole reason.

      Fast forward to the fall of 2014. I am contacted by the good folks at Fisher wanting to know if I am interested in trying out a new version of the F75 they are preparing for market. I of course say sure as I am always game to go metal detecting with different units. A new F75 is sent my way along with a list of the possible improvements. One immediately gets my attention – improved resistance to electrical interference.

      All the focus was on a new mode or “process”, as Fisher likes to call them. The new FA process is intended to better pull non-ferrous items out of trashy or mineralized ground. It does indeed work as advertised as I found out in an accidental situation I came across.

      I went to a local park and did a simple hunt for non-ferrous targets, comparing the DE default mode to the new FA fast mode. I did not really care what I found as long as it was non-ferrous. I should note the ground here is very difficult, reading 1 on the Fe meter, the second highest reading you can obtain. Hunting in this park is very much like nugget detecting, and the best detectors get very limited depth and highly inaccurate target numbers as a result of the high mineralization.

      One spot really summed it all up for me. I found three targets I could cover in a single wide swing that all read as ferrous in DE mode, but when I switched to FA mode all three switched to non-ferrous. FA mode is very fast with short, machine gun type reports in the audio. I was running in two tone mode, with ferrous giving low tones and non-ferrous high tones. In DE mode I could sweep and get three low tones in a row. Simply switch to FA mode and now there were three high tone reports in a row. This was an extremely dramatic result seen in person. In this case all three targets proved to be nothing more than aluminum targets, but they could just as well have been small hammered coins in the UK or small gold nuggets in Alaska.

      I hate to oversell things and I have to note that the difference in going to FA mode is not going to be earth shaking. Most targets read the same in DE and FA modes. But FA provides a tipping point, a little push that takes targets previously ignored and lights them up. By shortening the audio response on targets it also attenuates responses to a degree and so depth and signals on the tiniest targets may be impacted. Depth however is not useful if a target is misidentified or ignored completely due to target masking from nearby objects. FA mode is another tool in the toolbox that can help produce targets in specific situations previously overlooked by others.

      The new F75 also expands on the available audio options in ways many people will appreciate. These additions and the new FA mode will tend to get all the attention, but for me they pale in comparison to the new ability of the F75 to engage and disengage the new Digital Shielding Technology (DST). The version of the F75 I received had DST engaged at all times, and the difference in my ability to use the F75 at my home was as dramatic as it gets. My previous F75 was basically non-functional. My new F75 ran just fine, with only minimal EMI discernible at higher gain levels.

      I noted no downside to this. Given the situation, how could there be? Other field testers however were concerned that in low EMI situations perhaps there was an edge lost by having DST engaged, and so Fisher decided to add the ability to engage or disengage the feature as desired. It does not get any better than that. Use it if you need it; leave it off if you do not.

      All I know is this. What difference is there between a detector you can use and one you cannot use? All the difference in the world, and in my opinion I struck gold a second time with the F75 seeing it run with the new Digital Shielding Technology. That one feature alone means I can use the F75 in urban areas where I could not use it before, and vastly improves the reasons for my owning the detector once again. I am very confident a great many people will agree with me when they get a chance to try out the new, improved F75. Everything else in my opinion is just icing on the cake.

    • By Steve Herschbach
      People often forget about factory reset functions since it is still a rare feature. I am a proponent of resetting newer generation digital metal detectors on a regular basis, especially if settings get changed around a lot. The more setting changes are made, the more chance of a programming bug slipping in and messing with the operator. This is the procedure for the many F75 variants out there.
      From the F75 Owner's Manual page 10:
      RESET function
      The F75’s microprocessor saves all settings which you input, even after the power is turned off. If you wish to reset the settings to the factory preset, follow this process:
      Turn detector off. Press-and-hold the red MENU button and push-forward-and-hold the TOGGLE SWITCH. Turn the detector on, while you are still holding the controls. Release the MENU button and TOGGLE SWITCH. See the F symbol. When the F disappears, the detector is reset. Note: some latest F75 versions may show five pairs of number instead before displaying the F - the ten digit serial number. All settings have now been returned to factory defaults.
      Fisher F75 Metal Detector
    • By Herbert
      Hi all,
      I'm new here. I really like this site with all the great advice. I read Steve's detector reviews. Excellent stuff...
      I'm new to metal detecting and would really like to get into it. I'm foremost interested in nugget hunting, but also general detecting in the parks and on the beach. After reading all the reviews here I'm thinking of getting a Fisher F75 LTD.
      I'm a fairly tech savvy person, and learn pretty quick.
      I'd rather spend more in the beginning and have a good machine to grow into. 
      But I read some opinions that the F75 might be too much machine for a beginner. 
      So I'm asking the experts here if I'm better off with a Fisher Gold Bug Pro or a Fisher F19.
      I would welcome some input.
    • By Steve Herschbach
      Once upon a time all metal detectors went beep, and you dug up a metal object. Then a simple form of discrimination was developed based roughly on the conductivity scale. The main feature of this scale is that ferrous (iron or steel) items read lower on the scale than non-ferrous items. In a perfect world all ferrous readings could be set as a negative number, and all non-ferrous items set as a positive number.
      The reality is not so perfect however. Some steel items, especially items with a hole like a steel washer, will read up in the middle or high end of the scale, and show up right where only non-ferrous readings should appear. Thin sheet steel (bottle caps, flat section of rusted cans or roofing material) can show up in the mid range, and hardened steel items like bolts or ax heads can read way up in the silver range. These types of targets can trouble coin hunters in particular.
      Gold reads much lower on the discrimination scale normally due to a fairly low conductivity for gold. The gold range overlaps entirely with the lead and aluminum ranges, and these items are arranged on the scale based more on size than anything. Small gold, aluminum, and lead reads very low, and larger gold, aluminum, and lead tends to read in the low to middle portion of the scale.
      Those who chase these low end targets run into another problem with ferrous. Very small gold, lead, aluminum, and other small non-ferrous low conductors actually overlap with small ferrous items and so the clean ferrous to non-ferrous "breakpoint" does not actually exist,. The breakpoint is more of a "breakzone" i.e. a fuzzy zone where items overlap. The ground itself contains ferrous materials in the form of iron minerals. Ground minerals can act to confuse the detector further, enhancing the chance that a small non-ferrous reading will be interpreted as ferrous. Another way to say that is that in highly mineralized ground the overlap between ferrous and non-ferrous targets gets larger. The ground mineralization is critical to how this all works and so air testing is not recommended for testing the ferrous/non-ferrous overlap region on any particular detector.
      Note that this does not apply just to very small items. The deeper an item is, the smaller it appears to a detector. In other words a deep large item can sound just like a shallow small item. When you bury items of any size in highly iron mineralized ground, the deeper they are, the more chance the ground mineral signal will overlap and cause the item to read as ferrous right at the edge of detection range.

      Fisher F75 metal detector
      The early model discrimination detectors usually had a knob that adjusted all the discrimination. Everything below the knob setting was ignored, and everything above the setting accepted. The discrimination pioneers rapidly discovered that the dividing line between ferrous and non-ferrous is "fuzzy". The knobs could be set to reject nearly all ferrous readings, but then some good non-ferrous targets would get missed. The solution was to use a little bit lower discrimination setting, which meant more ferrous trash was dug, but more non-ferrous items were revealed.
      Managing the ferrous to non-ferrous breakpoint is critical. There is no setting that rejects all ferrous while detecting all non-ferrous, and the more mineralized the ground is, the less reliable the settings become. As a rule of thumb, the more aggressive the iron rejection, the more chance of non-ferrous items being misidentified.
      Detector technology advanced, and tone schemes were developed that divide the discrimination scale up into segments or "bins" where all numbers within a specific range make a specific tone. These tone schemes are often preset at the factory. The ranges can be arbitrary and arranged in many ways, but all share one common factor. Where is the setting that divides low ferrous tones from the higher non-ferrous tones? This is the "ferrous breakpoint". Everything below this point will give a "ferrous tone" and everything higher a "non-ferrous tone".
      The detector engineers are well aware of the overlap between ferrous and non-ferrous items. In choosing one setting to define what is in reality a zone the engineers have to make a hard choice. If the setting is too low, the operator will get many non-ferrous readings that turn out to be ferrous. That really irritates people. Or they can set the breakpoint higher. That way less ferrous gets dug. Some good non-ferrous items will also be missed, but only in the rarest cases does anyone ever know what they are missing. The odds are there will be more complaints if the ferrous breakpoint is too low than too high. The goal is not to find every non-ferrous item, but to keep from digging too much trash identified as good.
      This diagram is shows the common discrimination range employed in nearly all metal detectors. This particular model (Garrett) sets 40 as the point where ferrous items separate from non-ferrous items. Yet the chart reveals the overlap zone runs from about 35 to 45, a solid ten point spread. Small gold can identify as ferrous, especially in iron mineralized ground. Many detectors identify this zone on the meter via overlapping diagonal lines.

      The ferrous/non-ferrous overlap region
      What this means is that any detector that employs a preset tone scheme with no ability to adjust the "ferrous tone breakpoint" is assured to be missing at least some items due to an overly aggressive setting dialed in at the factory. This was eventually recognized, and now quite a few detectors allow the point where ferrous tones flip to non-ferrous tones to be adjusted. Some models are now even allowing for multiple volume controls for each separate tone, are at least the ferrous tone. This is most often called a "ferrous volume" setting.
      The Fisher F75 is an earlier tone based model and as such the tone schemes are preset at the factory. You can choose between the schemes, but the tone settings of where the tones occur cannot be adjusted. The F75 employs a target id scale that ranges from 1 to 99 with the 0 - 15 range defined as ferrous. From the F75 Users Manual page 20:
      1. 1-7 iron
      2. 8-15 iron
      3. 16-20 foil
      4. 21-25 foil
      5. 26-30 nickel
      6. 31-35 nickel
      7. 36-45 tab
      8. 46-55 tab
      9. 56-60 zinc
      10. 61-65 zinc
      and from page 25:
      Most iron objects 4-12
      foil from gum wrapper 16-25
      U.S. nickel (5¢ coin) typically 30
      aluminum pull-tab 33-55
      aluminum screw cap 60 - 70
      zinc penny (dated after 1982) typically 60
      aluminum soda pop can most often 63-69,
      but can vary widely
      copper penny, clad dime typically 70
      U.S. quarter (25¢ coin), clad typically 80
      50¢ coin, modern clad typically 86
      old silver dollar coin typically 90
      US silver Eagle $1 coin typically 91
      The implication is that non-ferrous items will only read 16 and above. Any readings of 15 and lower are deemed ferrous.
      The F75 has several preset tone schemes, the basics being monotone, two tone, three tone, four tone, and Delta Pitch (separate tone for each target id number i.e. multitone).
      The quirk is simple. The two, three, and four tone schemes all have a non-adjustable factory preset low tone for ferrous at 15 and below. The tone schemes override any other discriminations settings. In other words, if you have manually set the discrimination for ferrous to be a lower setting, switching to any two, three, or four tone scheme will automatically change the low tone setting to be at 15 and lower.
      The problem is that with time it was revealed that the F75 will detect some non-ferrous items at much lower settings than 16. Tom Dankowski finally put it all together and determined that a reading of 7 or higher would reveal additional non-ferrous items that are rejected when the setting is at 15. Tom's recommendation for the F75 while hunting ferrous is therefore to not use the tones, but to use the monotone setting and adjust the discrimination manually to 6. That way items 7 and higher signal as a non-ferrous target instead of delivering a low ferrous tone via the tone schemes. Again, going to a tone setting will automatically override a manual discrimination setting if one has been set.
      Tom wrote this all up as a great article in the 2009 Fisher Labs World Treasure News on page 11.
      I actually had the chance to see this in person in my own use of the F75. Early on I trusted the tone settings and two tone is quite handy for those simply wanting to dig all non-ferrous. Yet on my trip to England with the F75 I encountered a mystery. A gold coin was found and another F75 newbie was telling me about how he tested it with his F75 and it gave a nice ferrous tone. He was quite upset and worried his detector was defective. He did not have the coin however and so I could not see what he was describing and at the time I have to admit I was clueless. I know now that he was using tones, and that the gold coin was reading lower than 16 and so being identified as ferrous!
      My early use of the F75 was more for gold nuggets, and I usually used all metal mode. Yet my favorite feature on the F75 was full time target id while in all metal mode. My method was to acquire all targets, then dig any that flickered even once above my mental ferrous breakpoint. Unfortunately I leaned too much on the user manual initially and tended to pass on targets reading under 16. My early writing on the subject reflected that. After I discovered on my own that gold was reading lower I started adjusting my mental settings lower. Then I bumped into Tom's writing on the subject and it all came together.
      The bottom line in that non-ferrous items can read as low as 7 on the F75 yet the ferrous tone break is set at 15. This is just fine for most Park coin detecting, but problematic for those hunting low conductors of any sort or coins in dense ferrous. Either use monotone and decide where you want the setting to be (6 as Tom recommends or maybe somewhere in between 6 and 15 if 6 has you digging too much trash) or hunt in all metal and use the target id numbers to decide when to dig keeping in mind non-ferrous can read lower than 16, especially in high mineral ground.
      This is not a flaw in the F75 but just a function of any detector using a preset tone scheme. There are many detectors like this on the market. They tend to be less expensive models, or older models, as most new detectors now feature an adjustable tone break for the ferrous/non-ferrous overlap zone.
      Another take on the subject.
      And down the rabbit hole - Tune Out Nails - You Will Miss Gold!
      Fisher F75 Information Page
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