Merf
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- Jan 7, 2007
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A must read for F-75 & F-70 users
This is from Tom Dankowski's forum. [Thanks Gates21]
This works.
COMPILATION #1
Posted by: NASA-Tom (IP Logged)
Date: November 10, 2008 06:07PM
F-75 Peak Performance - Disc '6' & mandatory 'monotone' relic hunting justification
When the F-75 is placed on a Disc setting of '6' and 'monotone'; This set-up config allows (under MOST circumstances) the best iron see-thru ability..... in locating non-ferrous targets in areas that are loaded with ferrous (usually nails) environments. The older the site....... the more nails will be present; subsequently, the more good targets will be masked. Most detectors will 'shut-down' under these scenarios. The F-75 (& T-2) are the only detectors currently available on the market that begins to tackle this type of (extremely common) scenario.... with some 'unmasking' success.
.... With F-75 Disc on '6' and 'monotone',,,,,,.....,,,,,, the moment you invoke a different tone option; Say 2-tone, 3-tone, 4-tone, etc.... the ‘audio’ portion of the Disc, ....even though Disc is set on '6'...... will instantly become a Disc setting of '15'. What does this mean? = Any target that is between a Disc level of "6 thru 15" will now audibly report as a "Low Tone" (iron tone). BIG PROBLEM for a multiplicity of reasonings. Now, any target that is ABOVE a "15" (VDI reading)... MIGHT report a higher tone,,,, (tone freq depending on what tone option is invoked). -------Most folks do not dig iron. And most folks WILL miss masked non-ferrous targets when multitones are selected. Said differently via utilization of a "extremely common occurrence" example;
----- Recently, I recovered a badly masked Barber dime. When I (first) detected this severely handicapped dime, the F-75 was in 'monotone', Disc '6', 'PF' and Sens on '99'. In monotone, the dime AUDIBLY sounded good. (( I was going to dig this target )). The VDI was terrible - would/could NOT lock on to anything close to resembling a highly conductive piece of silver. I then invoked 2-tone..... leaving ALL other settings alone. Now.... the dime was constantly audibly reporting as low-tone (iron-tone).....even as I rotated my body around target. The VDI was jumping all over the board…. mostly in the iron ID range. I made the decision to NOT recover the target, primarily due to low iron-tone..... and walked away. Several hours later, I decided to go back and recover this target (and MANY other similar responding targets)..... with F-75 back in 'monotone'. Results = One 2" nail, two 1/2" long nails..... and one 1893 'O' Barber dime. Yep; MOSTLY iron, but certainly not ALL iron. The 2-tone mode did not lie. Justification = The composite of the 4 targets (3 nails & one dime) were higher in conductivity than any one of the nails individually...... but TOTAL conductive composite was HIGHER than any nail (or combination of nails) would have cumulatively registered. Because I (and the detector) knew that the detected target (suspected co-locate/composite of multiple targets under coil) were higher than the conductivity of most nails... yet STILL ID'd in the 'Fe/iron' range...... this target was needing recovery. Good thing! Selecting any other tone option..... and the detector would audibly report the composite as "low-tone/iron-tone". Yes, the F-75 will still unmask more non-ferrous targets than other detectors if 2-tone or multiple tones are selected; however, a substantially greater level of unmasking performance can be ascertained when unit is placed in 'monotone'. ((( The T-2 with a Disc setting of '21' is the exact same thing as all of the info above ))). Having the ability to adjust how MUCH iron you choose to discriminate….is a major attribute. Small iron items….. such as nails…… will Disc out at a fairly low iron Disc range.
This is Approx 10% of F-75's capabilities.
In addendum:
#1 On both the T-2 & F-75..... running a higher Sens gain in the trash (especially iron) presents a MUCH enhanced resolution on non-ferrous targets amongst iron. This is a paradoxical contradiction; what is....... but should NEVER be. Next time you find a non-ferrous target amongst high iron trash concentration (with high Sens settings)....... drop the Sens and see what happens. The non-ferrous target audio resolution will decrease.......possibly even disappear completely (depends how badly masked the non-Fe target is). The more masking... the HIGHER the Sens needs to be on the T-2/F-75. ((( This is not a typo )))!
#2 The mandatory "monotone" instructions is primarily for iron nail pits. Long description:
--- If a non-ferrous target is co-located in very close proximity to iron/multi-iron scenario.......,,,,,,,, then......... as you rotate your body around the composite target; the audio will be bouncing between all of the different tones (same with VDI)...with each tone being exceptionally short in duration. You may even encounter a multi-tone audible reporting in ONE sweep of the coil !!! ..... Surely enough to confuse most detectorists into a NON-recovery decision..... as the target is audibly confusing,,, and is not a 'clean' or "solid" repeatable sounding target. ((( Most masked targets are not 'clean' audio targets ))). Each of the multi-tones reporting will be audibly shorter in duration. Kind of a "ratty" sounding/bouncing signal. NOW..... when monotone is selected/invoked,,,,,, this SAME composite target(s) will audibly report a LONGER duration SINGLE-tone audible presentation (instead of several ‘shorter-in-length’ different tones in one sweep of the coil)..... that will less-likely confuse the operator ..... and authorize the operator to make a much better profiling of the composite target audio signature ..... with the end resultant being a more intelligible target-recovery decision from less audible fatigue. Tech Terms; A better signal-to-hull emitter correlation. I'd rather hear ONE "longer" monotone vs. several shorter multi-tones in rapid succession….in a single coil sweep. NOW....... IMAGINE sweeping the coil in a iron nail pit with 2 or 3 or ---- especially 4 tones selected. A hill-billy jug band!!! Try and make non-fatigued intelligent audio decisions under this common scenario! The VDI is extremely "jumpy" in iron pits.... AND SO WOULD BE THE MULTI-TONES!!! ...... At least,,,, in monotone,,,,, as the VDI is presenting extreme variances .... the one monotone will be CONSTANT and STABLE......even as the conductivity of the multi-target scenario varies dramatically ........ even with only one sweep of the coil.
#3 On CZ-3D.... in the 'enhanced' mode; Nearly ALL old coins.... and new coins,,,,, will report as "hi-tone". On the F-75 & T-2, you MUST invoke 4-tone...... which will then cause the OLD coins to audibly report in the 3rd highest tone region (vs. mid-tone)...... and the new coins will remain in THE highest tone. If you select 3-tone on T-2/F-75.... only the NEW coins will report as high-tone.... and SOME of the older coins might report as high tone. Most of the older coins would then audibly report as mid-tone (just like the alum soda tabs).
#4 If you run Disc on 0-4 on the F-75..... all nails will report as good targets in monotone. With F-75 Disc on '6'..... MOST (not all) nails will report as a snap-crackle-pop....tick-click (not a solid audio); which, in turn..... can be ignored. Axe heads, hammers, gun barrels and other large iron targets will give a good audio with Disc on '6' on the F-75. .... But, MOST fields we hunt are not loaded with axe heads, gun barrels and hammers.
#5 The F-75/T-2 have a tendency to "up-average" non-ferrous target ID numbers when near disintegrated iron or bad minerals. VERY common occurence. It is partial 'silent masking' coupled with conductive target response. I have several documented experiences exactly relating to this.
+++ Let's say that you detect a slightly masked silver dime. Normally (without being masked) it would VDI at '71'. But now..... it's slightly masked. It may now VDI at '89'..... a somewhat "up-averaging" VDI common resultant. In both cases, the detector reports "hi-tone". No problems yet.
A slightly corroded buffalo nickel will VDI at '28' in open air...and audibly report as a 'hi-tone'. Now....... with this same nickel in the dirt ... in a natural setting and partially masked..... IT TOO will "up-average" (just like the silver dime) ,,,, to,,, say = VDI '47'. Hmmmmmm, now the nickel 'looks' like a soda tab to the detector...and the unit will now report the slightly masked nickel as a mid-tone. ((( All of this holds true for medium conductivity items...such as relics & gold jewelry ))).
....If you are recovering Mercury dimes at (say) the 11" depth strata...... You may want to ALSO recover the 11" depth strata mid-tones.... as many of these will be the corresponding era Buffalo nickels.
The T-2 & F-75 electronic design architect is notorious for "Up-Averaging" non-ferrous targets in the presence of iron & iron oxides. Not a problem, considering other single freq units would remain completely silent.
ALL detectors have a difficult time ID'ing nickels. CZ's do the best ID job, but are not immune to EASILY mis-ID'ing nickels.
#6 All-Metal mode is the deepest mode; HOWEVER, coin-sized objects will still ID to depths of only 12" or so. The depth at which a target will properly ID in the ID mode..... is the same depth it will properly ID in the AM mode (F-75 & T-2). Yes, targets will audibly report to greater depths in the AM mode...... but the VDI screen will remain blank on the deeper targets. Now,,,,,,, that being said...... IF you are a extremely seasoned hunter...you can take advantage of these greater (no VDI) deeper depths. If you can audibly 'profile' deep/weak targets, you are in for some serious enjoyment. Can you tell the difference between a small target that is shallow, , , such as a lead .22 Short 29Gr rimfire projectile at 4" deep vs. a U.S. nickel at 12" depth. These are both non-ferrous targets. ....... And can you tell the difference between a 2-Penny nail at 7" vs. a Wheat penny at 12". This latter example... is the MOST common and MOST important test for the astute detectorist,,,, as it poses the greatest challenge with the most significant, rewarding resultant. Of note; Dinosaurs can be miles beneath the Earths surface. Egyptian sunken cities are dozens of feet deep........ thusly; the 100 year-old coins we wish to find are a foot or two deep.
NOW.......... that being said…. (((( If you are in a nail infested area, and you do NOTaudibly fatigue easily = = = )))) IF, IF, IF, you can handle a lot of noise.... and the detector can handle (not EMI plagued) a Disc setting of '0' and a Sens setting of '99'....then hunt in 2, 3, 4 tones (your choice),,, hunting for the "deepies". YES.....the detector will mask some targets in this audio selection config (ie 2, 3, 4 tones are selected) because any (heavily masked) target that VDI ID's as a '15' or below will present a 'iron' audio response (as so stated in example above),,,,, BUT, the trade-off is; the F-75 will go deeper just by virtue of the Disc setting being '4' or below (especially '0').
Soooooooo, I am saying (by this set-up config) = MORE MASKING, BUT GREATER DEPTH. Hmmmmmmmm... trade-off. Which one does better? Disc '6' & monotone
? or Disc '0' and multi-tone? The answer is: They BOTH do!!!!!!!!!
I am saying; HUNT the area in Disc '6' & monotone...... and perform all of the 'unmasking' that you can. THEN hunt in Disc '0' and a tone-option of your choice.... going for all the deepies.
NO...... you can not have both at the same time.
In theory,,,,,,, in an ideal world; Targets are spaced far enough apart so as to be single, solo targets....... not tilted, not near hot rocks, not near iron, no dirt mineralization etc....... This would allow the detector to ID targets with greatest accuracy. HOWEVER; This is not reality ..... not the real world. Fact of the matter is; Nearly all targets are somewhat/somehow handicapped. First; as a good target (say a coin) is moved closer to any other metallic object, a multiplicity of problems are introduced to the detector. Now add dirt mineralization, tilt the coin, add a hot rock or two, etc..... WELCOME TO THE REAL WORLD! This is genuinely what we contend with as detectorists and detector engineers. How do you correct and compensate for infinite unpredictable variables?! Secondly; What may be categorized and classified as "these two targets are too close to each other" to Brand 'A' detector & coil Assy…. may present different results to Brand 'B' detector & coil Assy. The extremely enhanced adjacent target separation characteristics afforded by a elliptical Double D coil presents just exactly such. A coin and a pull-tab... both at a 6" depth....... and adjacently separated by 6", poses a severe problem to a 10.5" concentric coil,,,,, but does not even approach "problem" status to a 11" elliptical DD coil.
When absolute maximum overdriven performance is desired:
1) Starting point = Factory Preset and Ground Balance.
2) Hold coil parallel to ground.... and at a height (approx) 8" above the ground. Do not tilt the coil upward. Increase Sens to '99' and verify detector is audibly stable. This is the FIRST step. (((Shut down your intents if you cannot ascertain stability with Sens on '99'))).
3) Next....... IF no EMI is encountered with '99' Sens........ THEN you may start to bring Disc down. Start with Disc '6'.
4) IF the detector is still EMI stable.... see what happens to EMI stability.... by lowering Disc BELOW '5'. '5' is not the magic number.... but '4' is. Going to a Disc setting of '4' is where sensitivity receives yet another boost. (((And USUALLY............... when you are at a Disc of '4' ... and ESPECIALLY lower... is where multitone option is virtually required))). Set Disc on '4' and verify detector remains audibly stable.
5) Now, Drop Disc to '3'... then '2'... then '1'... then ultimately '0'….. verifying audio stability is still retained.
6) Now select JE mode and verify detector remains audibly quiet.
((( IF .... during any of these steps, the detector becomes audibly 'chattery' .... you have electrical interference (EMI).... and must back-up in procedure,,,,, until you re-find electrical stability,,,,......,,,,,,, and these are the settings you should hunt with ))).
7) Start sweeping the coil..... with the coil remaining 8" above the ground,,,, and verify detector remains audibly stable.
8) Start lowering the coil closer to the ground while continuing to sweep....and verify detector remains audibly stable. If you manage to get the coil all the way down onto the ground while sweeping..... and the detector is audibly stable,,,,, you are home-free!!!!... and have the most powerful relic detector currently on the market. Remember, many relics are very low conductors (in the 'foil' range).
((( IF..... while lowering the coil to the ground as you are sweeping,,,,, and the detector THEN becomes audibly unstable..... you have ground interference ... most probably from high volumes of tiny flakes of rust/iron (a VERY common dirt occurence)..... which then, you must back out of the JE mode ))).
9) It is your choice for 'tone options'.
I have YET to be able to handle a nail infested site with the detector in monotone.... and a Disc setting of '0'. This means that you hear absolutely everything.
It is not so much that a DE would over-engineer a detector to be audibly unintelligible; it's more a 'sensitivity function' of a gold prospecting capable unit..... coupled with a extremely fast microprocessor/clockspeed and very tight electromagnetic footprint eminating from the coil. Little flecks of iron will cause this particular detector set (F-75 & T-2) to sound electromagnetically unstable. On a recent hunt, I (as usual) was overdriving the F-75...and, in one area, it became electrically unstable (((so I thought))). Coil in the air.... and unit was stable. Coil on the ground and not moving.... and unit was mostly stable. Sweeping coil.... and EMI interference ensued. Hmmmmm....... let's dig some of these so-called "chatters". Resultant: About every 2" or 3"..... I was finding #2 lead shot from a shotgun.... at a depth of approx 1.5". I quit recovering them once I had about a dozen in my hand. The small spot of land that I recovered/removed these small BB's.... suddenly had no 'electrical chatter' in this one localized location of coil-sweep. Exterior of this sans spot,,,,, the electrical chatter resumed. I knew I was 'overdriving' the F-75.... and decided to drop the Sens to a setting of '70'..... and the ‘perceived’ electrical chatter (the BB-shot).... as coil was being swept.... suddenly vanished. I had desensitized the detector enough to no longer detect these small targets,,,, and the unit became stable again. Masking was still taking place though. It hurts me to drop Sens to lower levels; however, I could ascertain a more stable/intelligible unit and could then somewhat "hunt". (Targets beneath these BB's are going to be partially or completely "masked").
Another known engineering fact is that a single freq unit has the ability to handle Fe better than multi-freq units. Both types of units are still blinded (masked & silent masked) by iron,,,,, but the single freq units can ID iron with better accuracy, less falsing.... and a hair-splitting Disc setting is more ascertainable with a single freq unit.
Something worth mentioning; in reference to the CZ (and nearly all other units). When the coil is passed over a target (or multi-target co-locate scenario), the reporting circuitry will remain silent. When peak signal strength is ascertained, the detector reporting circuitry will STILL remain silent. When the electronics see the received signal strength 'start' to decay (decrease), then ....and only then, will the detector take a "best-guess" and report a target & ID. Keep in mind..... if multiple targets are under the coil at the same time, these types of detectors will wait until the largest COMPOSITE signal strength (only one) is achieved. And now...... the different animals; the T-2 & F-75. Their electronics and audio will 'fire' on ANY target,,,,, and take multiple "snap-shots" and report each one. Hence; the F-75 & T-2 will audibly sound very 'noisy'. Said differently: Let's say the dirt is Sans.... except for one single coin target at several inches deep. At a normal sweep-rate,,,,, the F-75 & T-2 will 'fire' many many many times (dictated by micro-processor clock speed) on the coin..... and report each 'firing' individually...... BUT; what do your human ears hear/register? It just simply sounds like one continuous "beep" to you. It's not! Now..... pass your coil over many extremely close (and very small) co-located targets with 75/2 and see if your brain can process at the same speed of the 75/2. You will also notice the VDI jumping radically. Do you think the VDI is incorrect!!! These steroiditic detectors (unfortunately) are mentally fatiguing......... not because of the detector,,,,, but due to our ears clock-speed. The CZ's are a MUCH smoother, MUCH better sounding unit..... and SO much easier to detect/hunt with. BUT, they can be quite blind (easily masked) and can close doors....... where the 75's/2's can re-open hunted-out sites with tremendous success…. especially with a slower coil sweep-speed in hi trash areas. ----Food for thought.
COMPILATION #2
Posted by: NASA-Tom (IP Logged)
Date: December 04, 2008 11:25AM
F-75 – BETTERING YOUR PERFORMANCE & UNDERSTANDING
On the F-75 (and T-2) .... by invoking the '4H' tone option..... the unit will sound very similar (audibly) to the 4-tones of a CZ-3D/CZ-70. And ONLY in this 4/4H mode ... it will then perform in a very similar fashion to the CZ-3D in respect to ..... specifically; "OLD COINS" with one small exception. Many folks are "old coins" hunters; and the 4/4H tone option is specifically targeted to aid them in the recovery of old coins that would otherwise audibly report as a trash tone (mid-tone). By invoking/selecting the 4-tone option (or 4H) some unique things happen. The following is a INCOMPLETE list of coins that will (now) ID audibly as the 3rd highest tone (a separate tone that is just below the highest tone the F-75/T-2 produces):
Many silver Half-Dimes
All silver 3-Cent Trimes
Many 'tilted' silver dimes & quarters and copper coins
Many 'partially masked' silver & copper coins
All Indian Head pennies
All Flying Eagle Cents
Many Half Cents
All U.S. $5.00 gold Half-Eagle pieces
Many coins 'on edge'
Many tokens
All of these items will audibly ID as a mid-tone (trash tone… just like aluminum trash) if 3 or 3H tone option is invoked. By invoking 4 or 4H…… all of these aforementioned targets will audibly report HIGHER than a mid-tone……. sounding almost as high as the high-tone…….yet MOST of the aluminum trash will still report as a mid-tone/trash-tone whilst in 4 or 4H tone option. As far as the ‘small exception’ in reference to the CZ-3D…… all of the aforementioned targets will ID as the highest tone on the 3D as long as the ‘Enhance’ mode is invoked, with most aluminum trash still reporting as a mid-tone/trash-tone. The conductivity of yesteryears coins are different as compared to modern coinage; hence the 4/4H tone option on the F-75/T-2 and the ‘Enhance’ mode on the CZ-3D. To date, all other manufacturers detectors do NOT have this option.
On the F-75 (and T-2), the VDI, audio tone-ID, and Disc are completely independent of each other. If anything, the audio ID vs. the Disc setting more closely parallel each other, yet still differ. This electronic design architect is deliberate..... and is a attribute that you will witness as you accrue some field experience.
Try this experiment, time permitting….. in a few different locations (different dirt scenario/resultants). Place Disc on a setting of '0' (zero). Find/detect a few different old-generation nails in their natural dirt setting. You will see them ID as say: '10' & '13' & '11'. Now..... place Disc on '7' and watch them completely disappear!!!..... both audibly and VDI.
__Another case-in-point --- recent experience/example;
I had been detecting a parcel of land in Sanford, FL for nearly 2 years with the F-75. For very specific testing reasons, I have always kept the Disc on a setting of '10' for this specific site ONLY. (Normally, I run Disc on ‘6’ or lower). This parcel of property was moderately heavy with iron trash. I removed ALL non-ferrous targets out of this area with F-75..... to the best of my (and F-75's) ability at a Disc setting of ‘10’. -----Now...... my testing would ensue. I now (finally) dropped Disc to a setting of '6' ((( been waiting to do this for a LONG time ))). MANY more non-ferrous targets came to light. The most noteworthy educational target was a fairly worn 1963 silver Roosevelt dime at a measured 6" depth. Out of the ground...... It ID'd as a continous '70'. In the ground, it ID'd as a 'bouncer'........ VDI jumping from 46 to 97 AND DEPTH WAS READING 11". In 'monotone', the audio was fairly clean and solid. Invoking 4H tones.... and the target audibly ID'd as a moderately solid/somewhat repeatable 3rd highest 'zinc' tone (what would be catagorized as CZ-70 'relic' tone). If I put the F-75 into 3 or 3H tone option..... the dime would ID as a mid-tone/aluminum soda-tab trash tone. This is somewhat unimportant....and not nearly as important as the following info.... prior to recovery:
When I first detected this target (1963 silver dime)..... First, I was surprised that I had missed this specific non-ferrous target (and many other non-ferrous targets). Second, BEFORE I even thought of digging this target...... I flipped the Discrim back to '10' and found my primary answer. The dime completely disappeared. NO audio response.....and no VDI. Dropping the Disc down to '6' again...... and the silver dime NOW was bouncing again on the VDI between 46 to 97. How and Why would this VDI 46-to-97 non-ferrous target be Disc'd out at a Disc setting of '10'? When I first attempted recovery of this target, I dug a 8" x 8" x 8" cube of soil/plug. I pulled the plug out of the ground and flipped it over. Because the target was reading 11" deep.... I had some certainty that the 8"-cube plug did not contain the target; subsequently resulting in my 'dunking' the coil down to the bottom of the hole....... only to find no target. Then I swept the coil over the up-side-down plug I just pulled from the ground...... and found the target only 2" deep from the bottom side of the plug (6” deep from the grass-side of the plug). I scraped away the dirt until I found a silver dime..... and could see the impression of the dime in the dirt at the 6" depth strata. The F-75 was completely wrong on the ID and also completely wrong on the 11" depth reading. Hmmmmmmm. Not happy and needing definitive resolution acquisition....."WHY" this happened. I proceeded to rapidly 'shave' the dirt plug from the bottom side... at approx 1/16" increments .... utilizing 20 lbs test monofilament fishing line until I found the answer; a blood spot in the soil (from a COMPLETELY decomposed small nail) at the 4" depth strata..... partially masking the dime. ........This validates the independence of VDI vs. audio ID vs. Disc setting. It also validates EM signal attenuation via the iron oxide blood spot..... and why the 6" deep dime registered as 11" deep. Good thing the dime was not an inch deeper (7" deep)...... or… the masking blood spot was not 1" shallower!
The F-75 was incorrect about ID and depth. That's okay..... as the Explorer completely 'nulled' over this target..... the Coin$trike was silently masked with no audio at all..... and the CZ was iron-falsing with high-tone/low-tone bounces.... very indicative of what 90-Deg. bent nails do to a CZ. The only detector that prompted me to dig this target…… was the F-75. It reported the most…… and was confused the least……….and……… the detector is not to blame, as there were ‘interference producing’ culprits under the coil. The least amount of filters utilized in the detector…. and lower Disc settings most always provide the best raw data and unmasking capabilities.
Many times, I have witnessed a non-ferrous target or coin (IH pennies, Ag dimes) report nothing at all (Disc'd out) with a Disc setting of '8' on the F-75 due to partial masking. Subsequently, dropping the Disc to '6'..... and these coins now suddenly VDI'd as severe VDI spectrum bouncers....bouncing between say; 11 all the way up to the high 90's. Other detectors would just simply report ‘iron’…. or remain completeley silent (silent masking).
Another somewhat similar phenomenon/example:
Say; you have a silver dime and a non-oxidized nail in very close proximity (nearly touching) at a handful of inches deep. The two targets are close enough to each other.... and laying in such a fashion so as to give you a VDI ID of...say; '13' (a higher ID than what most nails will ID….. but still within the ‘iron’ ID range). Let's say your F-75 Discrimination is on a setting of '6'.
1. If you are in '1' tone (monotone).... the F-75 will give you a good audio response to the target….. regardless of what the VDI is indicating. Since you are in 1-tone (monotone) there is no “tone-ID” per-se. (((You will most probably recover the target))).
2. Now….. say the F-75 is in 2-tone (or 3, 3H, 4, 4H tone options etc.....). And NOW......... the F-75 will respond with a ‘tone’ audio response that most detectorists will NOT dig/recover. The F-75 will report a 'iron' tone (the lowest sounding audio tone). The non-ferrous silver target will most likely NOT be recovered....... even though most all nails will discriminate out at a Disc setting of '6'.
THIS IS BECAUSE; When 2-tone (or 3, 3H, 4, 4H etc.....) is selected = ANY target that results in a VDI ID reading of '15' or below....will report as a 'iron' LOW-tone. Most folks will NOT recover iron tones……. Especially in nail infested areas.
Conclusively:
In situations like this..... COMPLETELY ignore the VDI. Rotate your body around the target until you have the best/most clear audio report. ((( This is usually best performed in monotone ))). NOW...... and only NOW,,,,, you may look at the VDI,,,, but for a distant secondary data input. You should already know (at this point) that you will/will not recover this target.
..... Also at this point, you may want to play with a interesting geophysics iron hysteresis, permiability and magnetism phenomenon; At the point of 'Max Q' audio resolution (where you acquire the cleanest/best audio response) on a partially masked target...... start rotating your body AWAY from this ‘Max Q’ point whilst sweeping coil from side-to-side, directly over the suspected good target……with your body encircling the target. You will notice that when you start rotating deeper into the iron masking culprit .... you will witness the VDI numbers climb very high,,,,, until you rotate far enough out of detectability of the non-ferrous target…. and too deep into the iron target. Audibly, the signal will sound very ratty....,,,,, just prior to complete loss of the non-ferrous 'good' target. Iron masking does weird things! USUALLY….. oxides of iron in close proximity of a non-ferrous target will cause the VDI to “up-average” on the non-ferrous target of interest….. and solid iron objects that are NOT rusted…… will cause a VDI “down-averaging” effect when a co-located non-ferrous & ferrous (coin & nail combo) is detected. BUT, since iron objects nearly always rust/oxidize……… you may have the solid iron object with all of it’s associated rust oxide… in concert with the non-ferrous target you wish to detect…….. presenting a wide array of resultants. The SIZE of the solid (remaining) iron object vs. the AMOUNT of surrounding oxides dictates the resultant.
NOW…… all of the above being said; Invoking a Disc of ‘0’ and a (required) multi-tone option of your choice (I prefer 4-tones)……. and hunting iron infested areas…….. if you can put up with all of the incredible iron-tone reporting audio fatigue, , , , your unmasking resultant can be phenomenal. Rightfully so; most folks cannot handle this incredibly audio fatiguing set-up; hence, my lack of ‘focus’ on this style/type of hunting. This is a whole different chapter (at some later time)……. and is for you to discover! ((( Most folks can handle a Monotone & Disc ‘6’ setting which causes most nails to ‘snap, crackle, pop’….. and any audio report that has ‘audio length’ to it…. a elongated audio report……. is worth investigating ))).
SUMMATION/CONCLUSION: Severely Fe masked coins and other non-ferrous targets can do VERY weird things to the detector (especially ID circuitry)...... and USUALLY..... MOSTLY in the fashion of VDI "UP-AVERAGING" (but never a guarantee)! -Welcome to the world of infinate variables!!!
Yes, all of the above applies to the F-70 also. Keep in mind..... the F-70 (overall) has nearly identical performance to the F-75... but MUST have the same coil as the F-75 (yes, can be interchanged). With the 9.75" elliptical coil on the F-70.... on average,,,, there is approx a 1.5" loss in depth capabilities on coin-sized targets. This can be circumvented by installing the elliptical DD 7 x 11 (F-75) coil on to the F-70. As far as F-70 threshold..... I have noticed minimal/negligible variation differential with performance operating characteristics...... having changed entire spectrum availability on the F-70..... with Florida dirt conditions. On the F-5, slight changes in threshold... presents dramatic performance changes. On the Coin $trike..... the Threshold function is akin to the F-5.... dramatic. There was to be (some form) of linearity with Thresh adjustments.....but varying dirt (and other variables) will alter this to some extent. Yes, I fully agree that a mid-depth coin-sized target should NEVER disappear..... no matter what Thresh value is dialed-in. The C$'s intended target was to tackle black magnetic dirt. It performed such..... (almost) regardless of coil-sweep speed,,,,,, and would trump a multifreq CZ. Dimitar performed such matters with the utilization of a single freq 7.1Khz platform. Commendable..... all things considered (details refrained). He was hired by FRL.... given a clean slate..... and deliberately NOT given ANY blueprints to currently-in-production designs...... so as to circumvent "preprogramming" of already-existing mindset. Considering the utilization of electromagnetics in electromagnetic dirt (yep, self-defeating)... he accomplished a mission of partial paradox.
Tone break following/tracking Disc setting is nothing new.... but can be a tremendous aid. I believe the Cobra II (and others) employed such function.
It is only now....... with the utilization of F-75/T-2....... are we BEGINNING to learn how critical (and how crippling) iron masking truly is. Pandora's box has been opened....... no one wanted to face (tackle) the music..... ((( many never even knew it even existed; hence, could not combat a 'unknown' problem ))) and MOST designers choose to NEVER open this box. Bruce Candy has performed masterfully with this problem..... but in a tangential expenditure by virtue of HIS type of (magnetic/iron) dirt.... with the inception of FBS incorporated into the Explorer. It's just that..... even with the recently released Explorer E-Track...... the unit will "null" TOO TOO much in nail-laiden soils. This portion.... I simply can not accept. . . . YET.... I highly praise the Explorer's 'bad dirt' handling capabilities.... (a product of Australia dirt). IN THE MEANTIME..... Dave & John made the maiden 1st tackle. Single freq (which handles iron better), correct selection of freq, extremely tight EM footprint elliptical DD coil, large-scale iron Disc adjust, extremely rapid processing clock-speed microprocessor (matching....or exceeding/beyond human brain processing speed,,,,...... sometimes frustrating the fallible 'human' element)..... and a host of other attributes. It certainly has revolutionized the way we think/hunt...... and "opens the mind" to future exploration & possibilities. How do you commend?
Tom
This is from Tom Dankowski's forum. [Thanks Gates21]
This works.
COMPILATION #1
Posted by: NASA-Tom (IP Logged)
Date: November 10, 2008 06:07PM
F-75 Peak Performance - Disc '6' & mandatory 'monotone' relic hunting justification
When the F-75 is placed on a Disc setting of '6' and 'monotone'; This set-up config allows (under MOST circumstances) the best iron see-thru ability..... in locating non-ferrous targets in areas that are loaded with ferrous (usually nails) environments. The older the site....... the more nails will be present; subsequently, the more good targets will be masked. Most detectors will 'shut-down' under these scenarios. The F-75 (& T-2) are the only detectors currently available on the market that begins to tackle this type of (extremely common) scenario.... with some 'unmasking' success.
.... With F-75 Disc on '6' and 'monotone',,,,,,.....,,,,,, the moment you invoke a different tone option; Say 2-tone, 3-tone, 4-tone, etc.... the ‘audio’ portion of the Disc, ....even though Disc is set on '6'...... will instantly become a Disc setting of '15'. What does this mean? = Any target that is between a Disc level of "6 thru 15" will now audibly report as a "Low Tone" (iron tone). BIG PROBLEM for a multiplicity of reasonings. Now, any target that is ABOVE a "15" (VDI reading)... MIGHT report a higher tone,,,, (tone freq depending on what tone option is invoked). -------Most folks do not dig iron. And most folks WILL miss masked non-ferrous targets when multitones are selected. Said differently via utilization of a "extremely common occurrence" example;
----- Recently, I recovered a badly masked Barber dime. When I (first) detected this severely handicapped dime, the F-75 was in 'monotone', Disc '6', 'PF' and Sens on '99'. In monotone, the dime AUDIBLY sounded good. (( I was going to dig this target )). The VDI was terrible - would/could NOT lock on to anything close to resembling a highly conductive piece of silver. I then invoked 2-tone..... leaving ALL other settings alone. Now.... the dime was constantly audibly reporting as low-tone (iron-tone).....even as I rotated my body around target. The VDI was jumping all over the board…. mostly in the iron ID range. I made the decision to NOT recover the target, primarily due to low iron-tone..... and walked away. Several hours later, I decided to go back and recover this target (and MANY other similar responding targets)..... with F-75 back in 'monotone'. Results = One 2" nail, two 1/2" long nails..... and one 1893 'O' Barber dime. Yep; MOSTLY iron, but certainly not ALL iron. The 2-tone mode did not lie. Justification = The composite of the 4 targets (3 nails & one dime) were higher in conductivity than any one of the nails individually...... but TOTAL conductive composite was HIGHER than any nail (or combination of nails) would have cumulatively registered. Because I (and the detector) knew that the detected target (suspected co-locate/composite of multiple targets under coil) were higher than the conductivity of most nails... yet STILL ID'd in the 'Fe/iron' range...... this target was needing recovery. Good thing! Selecting any other tone option..... and the detector would audibly report the composite as "low-tone/iron-tone". Yes, the F-75 will still unmask more non-ferrous targets than other detectors if 2-tone or multiple tones are selected; however, a substantially greater level of unmasking performance can be ascertained when unit is placed in 'monotone'. ((( The T-2 with a Disc setting of '21' is the exact same thing as all of the info above ))). Having the ability to adjust how MUCH iron you choose to discriminate….is a major attribute. Small iron items….. such as nails…… will Disc out at a fairly low iron Disc range.
This is Approx 10% of F-75's capabilities.
In addendum:
#1 On both the T-2 & F-75..... running a higher Sens gain in the trash (especially iron) presents a MUCH enhanced resolution on non-ferrous targets amongst iron. This is a paradoxical contradiction; what is....... but should NEVER be. Next time you find a non-ferrous target amongst high iron trash concentration (with high Sens settings)....... drop the Sens and see what happens. The non-ferrous target audio resolution will decrease.......possibly even disappear completely (depends how badly masked the non-Fe target is). The more masking... the HIGHER the Sens needs to be on the T-2/F-75. ((( This is not a typo )))!
#2 The mandatory "monotone" instructions is primarily for iron nail pits. Long description:
--- If a non-ferrous target is co-located in very close proximity to iron/multi-iron scenario.......,,,,,,,, then......... as you rotate your body around the composite target; the audio will be bouncing between all of the different tones (same with VDI)...with each tone being exceptionally short in duration. You may even encounter a multi-tone audible reporting in ONE sweep of the coil !!! ..... Surely enough to confuse most detectorists into a NON-recovery decision..... as the target is audibly confusing,,, and is not a 'clean' or "solid" repeatable sounding target. ((( Most masked targets are not 'clean' audio targets ))). Each of the multi-tones reporting will be audibly shorter in duration. Kind of a "ratty" sounding/bouncing signal. NOW..... when monotone is selected/invoked,,,,,, this SAME composite target(s) will audibly report a LONGER duration SINGLE-tone audible presentation (instead of several ‘shorter-in-length’ different tones in one sweep of the coil)..... that will less-likely confuse the operator ..... and authorize the operator to make a much better profiling of the composite target audio signature ..... with the end resultant being a more intelligible target-recovery decision from less audible fatigue. Tech Terms; A better signal-to-hull emitter correlation. I'd rather hear ONE "longer" monotone vs. several shorter multi-tones in rapid succession….in a single coil sweep. NOW....... IMAGINE sweeping the coil in a iron nail pit with 2 or 3 or ---- especially 4 tones selected. A hill-billy jug band!!! Try and make non-fatigued intelligent audio decisions under this common scenario! The VDI is extremely "jumpy" in iron pits.... AND SO WOULD BE THE MULTI-TONES!!! ...... At least,,,, in monotone,,,,, as the VDI is presenting extreme variances .... the one monotone will be CONSTANT and STABLE......even as the conductivity of the multi-target scenario varies dramatically ........ even with only one sweep of the coil.
#3 On CZ-3D.... in the 'enhanced' mode; Nearly ALL old coins.... and new coins,,,,, will report as "hi-tone". On the F-75 & T-2, you MUST invoke 4-tone...... which will then cause the OLD coins to audibly report in the 3rd highest tone region (vs. mid-tone)...... and the new coins will remain in THE highest tone. If you select 3-tone on T-2/F-75.... only the NEW coins will report as high-tone.... and SOME of the older coins might report as high tone. Most of the older coins would then audibly report as mid-tone (just like the alum soda tabs).
#4 If you run Disc on 0-4 on the F-75..... all nails will report as good targets in monotone. With F-75 Disc on '6'..... MOST (not all) nails will report as a snap-crackle-pop....tick-click (not a solid audio); which, in turn..... can be ignored. Axe heads, hammers, gun barrels and other large iron targets will give a good audio with Disc on '6' on the F-75. .... But, MOST fields we hunt are not loaded with axe heads, gun barrels and hammers.
#5 The F-75/T-2 have a tendency to "up-average" non-ferrous target ID numbers when near disintegrated iron or bad minerals. VERY common occurence. It is partial 'silent masking' coupled with conductive target response. I have several documented experiences exactly relating to this.
+++ Let's say that you detect a slightly masked silver dime. Normally (without being masked) it would VDI at '71'. But now..... it's slightly masked. It may now VDI at '89'..... a somewhat "up-averaging" VDI common resultant. In both cases, the detector reports "hi-tone". No problems yet.
A slightly corroded buffalo nickel will VDI at '28' in open air...and audibly report as a 'hi-tone'. Now....... with this same nickel in the dirt ... in a natural setting and partially masked..... IT TOO will "up-average" (just like the silver dime) ,,,, to,,, say = VDI '47'. Hmmmmmm, now the nickel 'looks' like a soda tab to the detector...and the unit will now report the slightly masked nickel as a mid-tone. ((( All of this holds true for medium conductivity items...such as relics & gold jewelry ))).
....If you are recovering Mercury dimes at (say) the 11" depth strata...... You may want to ALSO recover the 11" depth strata mid-tones.... as many of these will be the corresponding era Buffalo nickels.
The T-2 & F-75 electronic design architect is notorious for "Up-Averaging" non-ferrous targets in the presence of iron & iron oxides. Not a problem, considering other single freq units would remain completely silent.
ALL detectors have a difficult time ID'ing nickels. CZ's do the best ID job, but are not immune to EASILY mis-ID'ing nickels.
#6 All-Metal mode is the deepest mode; HOWEVER, coin-sized objects will still ID to depths of only 12" or so. The depth at which a target will properly ID in the ID mode..... is the same depth it will properly ID in the AM mode (F-75 & T-2). Yes, targets will audibly report to greater depths in the AM mode...... but the VDI screen will remain blank on the deeper targets. Now,,,,,,, that being said...... IF you are a extremely seasoned hunter...you can take advantage of these greater (no VDI) deeper depths. If you can audibly 'profile' deep/weak targets, you are in for some serious enjoyment. Can you tell the difference between a small target that is shallow, , , such as a lead .22 Short 29Gr rimfire projectile at 4" deep vs. a U.S. nickel at 12" depth. These are both non-ferrous targets. ....... And can you tell the difference between a 2-Penny nail at 7" vs. a Wheat penny at 12". This latter example... is the MOST common and MOST important test for the astute detectorist,,,, as it poses the greatest challenge with the most significant, rewarding resultant. Of note; Dinosaurs can be miles beneath the Earths surface. Egyptian sunken cities are dozens of feet deep........ thusly; the 100 year-old coins we wish to find are a foot or two deep.
NOW.......... that being said…. (((( If you are in a nail infested area, and you do NOTaudibly fatigue easily = = = )))) IF, IF, IF, you can handle a lot of noise.... and the detector can handle (not EMI plagued) a Disc setting of '0' and a Sens setting of '99'....then hunt in 2, 3, 4 tones (your choice),,, hunting for the "deepies". YES.....the detector will mask some targets in this audio selection config (ie 2, 3, 4 tones are selected) because any (heavily masked) target that VDI ID's as a '15' or below will present a 'iron' audio response (as so stated in example above),,,,, BUT, the trade-off is; the F-75 will go deeper just by virtue of the Disc setting being '4' or below (especially '0').
Soooooooo, I am saying (by this set-up config) = MORE MASKING, BUT GREATER DEPTH. Hmmmmmmmm... trade-off. Which one does better? Disc '6' & monotone
? or Disc '0' and multi-tone? The answer is: They BOTH do!!!!!!!!!I am saying; HUNT the area in Disc '6' & monotone...... and perform all of the 'unmasking' that you can. THEN hunt in Disc '0' and a tone-option of your choice.... going for all the deepies.
NO...... you can not have both at the same time.
In theory,,,,,,, in an ideal world; Targets are spaced far enough apart so as to be single, solo targets....... not tilted, not near hot rocks, not near iron, no dirt mineralization etc....... This would allow the detector to ID targets with greatest accuracy. HOWEVER; This is not reality ..... not the real world. Fact of the matter is; Nearly all targets are somewhat/somehow handicapped. First; as a good target (say a coin) is moved closer to any other metallic object, a multiplicity of problems are introduced to the detector. Now add dirt mineralization, tilt the coin, add a hot rock or two, etc..... WELCOME TO THE REAL WORLD! This is genuinely what we contend with as detectorists and detector engineers. How do you correct and compensate for infinite unpredictable variables?! Secondly; What may be categorized and classified as "these two targets are too close to each other" to Brand 'A' detector & coil Assy…. may present different results to Brand 'B' detector & coil Assy. The extremely enhanced adjacent target separation characteristics afforded by a elliptical Double D coil presents just exactly such. A coin and a pull-tab... both at a 6" depth....... and adjacently separated by 6", poses a severe problem to a 10.5" concentric coil,,,,, but does not even approach "problem" status to a 11" elliptical DD coil.
When absolute maximum overdriven performance is desired:
1) Starting point = Factory Preset and Ground Balance.
2) Hold coil parallel to ground.... and at a height (approx) 8" above the ground. Do not tilt the coil upward. Increase Sens to '99' and verify detector is audibly stable. This is the FIRST step. (((Shut down your intents if you cannot ascertain stability with Sens on '99'))).
3) Next....... IF no EMI is encountered with '99' Sens........ THEN you may start to bring Disc down. Start with Disc '6'.
4) IF the detector is still EMI stable.... see what happens to EMI stability.... by lowering Disc BELOW '5'. '5' is not the magic number.... but '4' is. Going to a Disc setting of '4' is where sensitivity receives yet another boost. (((And USUALLY............... when you are at a Disc of '4' ... and ESPECIALLY lower... is where multitone option is virtually required))). Set Disc on '4' and verify detector remains audibly stable.
5) Now, Drop Disc to '3'... then '2'... then '1'... then ultimately '0'….. verifying audio stability is still retained.
6) Now select JE mode and verify detector remains audibly quiet.
((( IF .... during any of these steps, the detector becomes audibly 'chattery' .... you have electrical interference (EMI).... and must back-up in procedure,,,,, until you re-find electrical stability,,,,......,,,,,,, and these are the settings you should hunt with ))).
7) Start sweeping the coil..... with the coil remaining 8" above the ground,,,, and verify detector remains audibly stable.
8) Start lowering the coil closer to the ground while continuing to sweep....and verify detector remains audibly stable. If you manage to get the coil all the way down onto the ground while sweeping..... and the detector is audibly stable,,,,, you are home-free!!!!... and have the most powerful relic detector currently on the market. Remember, many relics are very low conductors (in the 'foil' range).
((( IF..... while lowering the coil to the ground as you are sweeping,,,,, and the detector THEN becomes audibly unstable..... you have ground interference ... most probably from high volumes of tiny flakes of rust/iron (a VERY common dirt occurence)..... which then, you must back out of the JE mode ))).
9) It is your choice for 'tone options'.
I have YET to be able to handle a nail infested site with the detector in monotone.... and a Disc setting of '0'. This means that you hear absolutely everything.
It is not so much that a DE would over-engineer a detector to be audibly unintelligible; it's more a 'sensitivity function' of a gold prospecting capable unit..... coupled with a extremely fast microprocessor/clockspeed and very tight electromagnetic footprint eminating from the coil. Little flecks of iron will cause this particular detector set (F-75 & T-2) to sound electromagnetically unstable. On a recent hunt, I (as usual) was overdriving the F-75...and, in one area, it became electrically unstable (((so I thought))). Coil in the air.... and unit was stable. Coil on the ground and not moving.... and unit was mostly stable. Sweeping coil.... and EMI interference ensued. Hmmmmm....... let's dig some of these so-called "chatters". Resultant: About every 2" or 3"..... I was finding #2 lead shot from a shotgun.... at a depth of approx 1.5". I quit recovering them once I had about a dozen in my hand. The small spot of land that I recovered/removed these small BB's.... suddenly had no 'electrical chatter' in this one localized location of coil-sweep. Exterior of this sans spot,,,,, the electrical chatter resumed. I knew I was 'overdriving' the F-75.... and decided to drop the Sens to a setting of '70'..... and the ‘perceived’ electrical chatter (the BB-shot).... as coil was being swept.... suddenly vanished. I had desensitized the detector enough to no longer detect these small targets,,,, and the unit became stable again. Masking was still taking place though. It hurts me to drop Sens to lower levels; however, I could ascertain a more stable/intelligible unit and could then somewhat "hunt". (Targets beneath these BB's are going to be partially or completely "masked").
Another known engineering fact is that a single freq unit has the ability to handle Fe better than multi-freq units. Both types of units are still blinded (masked & silent masked) by iron,,,,, but the single freq units can ID iron with better accuracy, less falsing.... and a hair-splitting Disc setting is more ascertainable with a single freq unit.
Something worth mentioning; in reference to the CZ (and nearly all other units). When the coil is passed over a target (or multi-target co-locate scenario), the reporting circuitry will remain silent. When peak signal strength is ascertained, the detector reporting circuitry will STILL remain silent. When the electronics see the received signal strength 'start' to decay (decrease), then ....and only then, will the detector take a "best-guess" and report a target & ID. Keep in mind..... if multiple targets are under the coil at the same time, these types of detectors will wait until the largest COMPOSITE signal strength (only one) is achieved. And now...... the different animals; the T-2 & F-75. Their electronics and audio will 'fire' on ANY target,,,,, and take multiple "snap-shots" and report each one. Hence; the F-75 & T-2 will audibly sound very 'noisy'. Said differently: Let's say the dirt is Sans.... except for one single coin target at several inches deep. At a normal sweep-rate,,,,, the F-75 & T-2 will 'fire' many many many times (dictated by micro-processor clock speed) on the coin..... and report each 'firing' individually...... BUT; what do your human ears hear/register? It just simply sounds like one continuous "beep" to you. It's not! Now..... pass your coil over many extremely close (and very small) co-located targets with 75/2 and see if your brain can process at the same speed of the 75/2. You will also notice the VDI jumping radically. Do you think the VDI is incorrect!!!
These steroiditic detectors (unfortunately) are mentally fatiguing......... not because of the detector,,,,, but due to our ears clock-speed. The CZ's are a MUCH smoother, MUCH better sounding unit..... and SO much easier to detect/hunt with. BUT, they can be quite blind (easily masked) and can close doors....... where the 75's/2's can re-open hunted-out sites with tremendous success…. especially with a slower coil sweep-speed in hi trash areas. ----Food for thought.COMPILATION #2
Posted by: NASA-Tom (IP Logged)
Date: December 04, 2008 11:25AM
F-75 – BETTERING YOUR PERFORMANCE & UNDERSTANDING
On the F-75 (and T-2) .... by invoking the '4H' tone option..... the unit will sound very similar (audibly) to the 4-tones of a CZ-3D/CZ-70. And ONLY in this 4/4H mode ... it will then perform in a very similar fashion to the CZ-3D in respect to ..... specifically; "OLD COINS" with one small exception. Many folks are "old coins" hunters; and the 4/4H tone option is specifically targeted to aid them in the recovery of old coins that would otherwise audibly report as a trash tone (mid-tone). By invoking/selecting the 4-tone option (or 4H) some unique things happen. The following is a INCOMPLETE list of coins that will (now) ID audibly as the 3rd highest tone (a separate tone that is just below the highest tone the F-75/T-2 produces):
Many silver Half-Dimes
All silver 3-Cent Trimes
Many 'tilted' silver dimes & quarters and copper coins
Many 'partially masked' silver & copper coins
All Indian Head pennies
All Flying Eagle Cents
Many Half Cents
All U.S. $5.00 gold Half-Eagle pieces
Many coins 'on edge'
Many tokens
All of these items will audibly ID as a mid-tone (trash tone… just like aluminum trash) if 3 or 3H tone option is invoked. By invoking 4 or 4H…… all of these aforementioned targets will audibly report HIGHER than a mid-tone……. sounding almost as high as the high-tone…….yet MOST of the aluminum trash will still report as a mid-tone/trash-tone whilst in 4 or 4H tone option. As far as the ‘small exception’ in reference to the CZ-3D…… all of the aforementioned targets will ID as the highest tone on the 3D as long as the ‘Enhance’ mode is invoked, with most aluminum trash still reporting as a mid-tone/trash-tone. The conductivity of yesteryears coins are different as compared to modern coinage; hence the 4/4H tone option on the F-75/T-2 and the ‘Enhance’ mode on the CZ-3D. To date, all other manufacturers detectors do NOT have this option.
On the F-75 (and T-2), the VDI, audio tone-ID, and Disc are completely independent of each other. If anything, the audio ID vs. the Disc setting more closely parallel each other, yet still differ. This electronic design architect is deliberate..... and is a attribute that you will witness as you accrue some field experience.
Try this experiment, time permitting….. in a few different locations (different dirt scenario/resultants). Place Disc on a setting of '0' (zero). Find/detect a few different old-generation nails in their natural dirt setting. You will see them ID as say: '10' & '13' & '11'. Now..... place Disc on '7' and watch them completely disappear!!!..... both audibly and VDI.
__Another case-in-point --- recent experience/example;
I had been detecting a parcel of land in Sanford, FL for nearly 2 years with the F-75. For very specific testing reasons, I have always kept the Disc on a setting of '10' for this specific site ONLY. (Normally, I run Disc on ‘6’ or lower). This parcel of property was moderately heavy with iron trash. I removed ALL non-ferrous targets out of this area with F-75..... to the best of my (and F-75's) ability at a Disc setting of ‘10’. -----Now...... my testing would ensue. I now (finally) dropped Disc to a setting of '6' ((( been waiting to do this for a LONG time ))). MANY more non-ferrous targets came to light. The most noteworthy educational target was a fairly worn 1963 silver Roosevelt dime at a measured 6" depth. Out of the ground...... It ID'd as a continous '70'. In the ground, it ID'd as a 'bouncer'........ VDI jumping from 46 to 97 AND DEPTH WAS READING 11". In 'monotone', the audio was fairly clean and solid. Invoking 4H tones.... and the target audibly ID'd as a moderately solid/somewhat repeatable 3rd highest 'zinc' tone (what would be catagorized as CZ-70 'relic' tone). If I put the F-75 into 3 or 3H tone option..... the dime would ID as a mid-tone/aluminum soda-tab trash tone. This is somewhat unimportant....and not nearly as important as the following info.... prior to recovery:
When I first detected this target (1963 silver dime)..... First, I was surprised that I had missed this specific non-ferrous target (and many other non-ferrous targets). Second, BEFORE I even thought of digging this target...... I flipped the Discrim back to '10' and found my primary answer. The dime completely disappeared. NO audio response.....and no VDI. Dropping the Disc down to '6' again...... and the silver dime NOW was bouncing again on the VDI between 46 to 97. How and Why would this VDI 46-to-97 non-ferrous target be Disc'd out at a Disc setting of '10'
? When I first attempted recovery of this target, I dug a 8" x 8" x 8" cube of soil/plug. I pulled the plug out of the ground and flipped it over. Because the target was reading 11" deep.... I had some certainty that the 8"-cube plug did not contain the target; subsequently resulting in my 'dunking' the coil down to the bottom of the hole....... only to find no target. Then I swept the coil over the up-side-down plug I just pulled from the ground...... and found the target only 2" deep from the bottom side of the plug (6” deep from the grass-side of the plug). I scraped away the dirt until I found a silver dime..... and could see the impression of the dime in the dirt at the 6" depth strata. The F-75 was completely wrong on the ID and also completely wrong on the 11" depth reading. Hmmmmmmm. Not happy and needing definitive resolution acquisition....."WHY" this happened. I proceeded to rapidly 'shave' the dirt plug from the bottom side... at approx 1/16" increments .... utilizing 20 lbs test monofilament fishing line until I found the answer; a blood spot in the soil (from a COMPLETELY decomposed small nail) at the 4" depth strata..... partially masking the dime. ........This validates the independence of VDI vs. audio ID vs. Disc setting. It also validates EM signal attenuation via the iron oxide blood spot..... and why the 6" deep dime registered as 11" deep. Good thing the dime was not an inch deeper (7" deep)...... or… the masking blood spot was not 1" shallower!The F-75 was incorrect about ID and depth. That's okay..... as the Explorer completely 'nulled' over this target..... the Coin$trike was silently masked with no audio at all..... and the CZ was iron-falsing with high-tone/low-tone bounces.... very indicative of what 90-Deg. bent nails do to a CZ. The only detector that prompted me to dig this target…… was the F-75. It reported the most…… and was confused the least……….and……… the detector is not to blame, as there were ‘interference producing’ culprits under the coil. The least amount of filters utilized in the detector…. and lower Disc settings most always provide the best raw data and unmasking capabilities.
Many times, I have witnessed a non-ferrous target or coin (IH pennies, Ag dimes) report nothing at all (Disc'd out) with a Disc setting of '8' on the F-75 due to partial masking. Subsequently, dropping the Disc to '6'..... and these coins now suddenly VDI'd as severe VDI spectrum bouncers....bouncing between say; 11 all the way up to the high 90's. Other detectors would just simply report ‘iron’…. or remain completeley silent (silent masking).
Another somewhat similar phenomenon/example:
Say; you have a silver dime and a non-oxidized nail in very close proximity (nearly touching) at a handful of inches deep. The two targets are close enough to each other.... and laying in such a fashion so as to give you a VDI ID of...say; '13' (a higher ID than what most nails will ID….. but still within the ‘iron’ ID range). Let's say your F-75 Discrimination is on a setting of '6'.
1. If you are in '1' tone (monotone).... the F-75 will give you a good audio response to the target….. regardless of what the VDI is indicating. Since you are in 1-tone (monotone) there is no “tone-ID” per-se. (((You will most probably recover the target))).
2. Now….. say the F-75 is in 2-tone (or 3, 3H, 4, 4H tone options etc.....). And NOW......... the F-75 will respond with a ‘tone’ audio response that most detectorists will NOT dig/recover. The F-75 will report a 'iron' tone (the lowest sounding audio tone). The non-ferrous silver target will most likely NOT be recovered....... even though most all nails will discriminate out at a Disc setting of '6'.
THIS IS BECAUSE; When 2-tone (or 3, 3H, 4, 4H etc.....) is selected = ANY target that results in a VDI ID reading of '15' or below....will report as a 'iron' LOW-tone. Most folks will NOT recover iron tones……. Especially in nail infested areas.
Conclusively:
In situations like this..... COMPLETELY ignore the VDI. Rotate your body around the target until you have the best/most clear audio report. ((( This is usually best performed in monotone ))). NOW...... and only NOW,,,,, you may look at the VDI,,,, but for a distant secondary data input. You should already know (at this point) that you will/will not recover this target.
..... Also at this point, you may want to play with a interesting geophysics iron hysteresis, permiability and magnetism phenomenon; At the point of 'Max Q' audio resolution (where you acquire the cleanest/best audio response) on a partially masked target...... start rotating your body AWAY from this ‘Max Q’ point whilst sweeping coil from side-to-side, directly over the suspected good target……with your body encircling the target. You will notice that when you start rotating deeper into the iron masking culprit .... you will witness the VDI numbers climb very high,,,,, until you rotate far enough out of detectability of the non-ferrous target…. and too deep into the iron target. Audibly, the signal will sound very ratty....,,,,, just prior to complete loss of the non-ferrous 'good' target. Iron masking does weird things! USUALLY….. oxides of iron in close proximity of a non-ferrous target will cause the VDI to “up-average” on the non-ferrous target of interest….. and solid iron objects that are NOT rusted…… will cause a VDI “down-averaging” effect when a co-located non-ferrous & ferrous (coin & nail combo) is detected. BUT, since iron objects nearly always rust/oxidize……… you may have the solid iron object with all of it’s associated rust oxide… in concert with the non-ferrous target you wish to detect…….. presenting a wide array of resultants. The SIZE of the solid (remaining) iron object vs. the AMOUNT of surrounding oxides dictates the resultant.
NOW…… all of the above being said; Invoking a Disc of ‘0’ and a (required) multi-tone option of your choice (I prefer 4-tones)……. and hunting iron infested areas…….. if you can put up with all of the incredible iron-tone reporting audio fatigue, , , , your unmasking resultant can be phenomenal. Rightfully so; most folks cannot handle this incredibly audio fatiguing set-up; hence, my lack of ‘focus’ on this style/type of hunting. This is a whole different chapter (at some later time)……. and is for you to discover! ((( Most folks can handle a Monotone & Disc ‘6’ setting which causes most nails to ‘snap, crackle, pop’….. and any audio report that has ‘audio length’ to it…. a elongated audio report……. is worth investigating ))).
SUMMATION/CONCLUSION: Severely Fe masked coins and other non-ferrous targets can do VERY weird things to the detector (especially ID circuitry)...... and USUALLY..... MOSTLY in the fashion of VDI "UP-AVERAGING" (but never a guarantee)! -Welcome to the world of infinate variables!!!
Yes, all of the above applies to the F-70 also. Keep in mind..... the F-70 (overall) has nearly identical performance to the F-75... but MUST have the same coil as the F-75 (yes, can be interchanged). With the 9.75" elliptical coil on the F-70.... on average,,,, there is approx a 1.5" loss in depth capabilities on coin-sized targets. This can be circumvented by installing the elliptical DD 7 x 11 (F-75) coil on to the F-70. As far as F-70 threshold..... I have noticed minimal/negligible variation differential with performance operating characteristics...... having changed entire spectrum availability on the F-70..... with Florida dirt conditions. On the F-5, slight changes in threshold... presents dramatic performance changes. On the Coin $trike..... the Threshold function is akin to the F-5.... dramatic. There was to be (some form) of linearity with Thresh adjustments.....but varying dirt (and other variables) will alter this to some extent. Yes, I fully agree that a mid-depth coin-sized target should NEVER disappear..... no matter what Thresh value is dialed-in. The C$'s intended target was to tackle black magnetic dirt. It performed such..... (almost) regardless of coil-sweep speed,,,,,, and would trump a multifreq CZ. Dimitar performed such matters with the utilization of a single freq 7.1Khz platform. Commendable..... all things considered (details refrained). He was hired by FRL.... given a clean slate..... and deliberately NOT given ANY blueprints to currently-in-production designs...... so as to circumvent "preprogramming" of already-existing mindset. Considering the utilization of electromagnetics in electromagnetic dirt (yep, self-defeating)... he accomplished a mission of partial paradox.
Tone break following/tracking Disc setting is nothing new.... but can be a tremendous aid. I believe the Cobra II (and others) employed such function.
It is only now....... with the utilization of F-75/T-2....... are we BEGINNING to learn how critical (and how crippling) iron masking truly is. Pandora's box has been opened....... no one wanted to face (tackle) the music..... ((( many never even knew it even existed; hence, could not combat a 'unknown' problem ))) and MOST designers choose to NEVER open this box. Bruce Candy has performed masterfully with this problem..... but in a tangential expenditure by virtue of HIS type of (magnetic/iron) dirt.... with the inception of FBS incorporated into the Explorer. It's just that..... even with the recently released Explorer E-Track...... the unit will "null" TOO TOO much in nail-laiden soils. This portion.... I simply can not accept. . . . YET.... I highly praise the Explorer's 'bad dirt' handling capabilities.... (a product of Australia dirt). IN THE MEANTIME..... Dave & John made the maiden 1st tackle. Single freq (which handles iron better), correct selection of freq, extremely tight EM footprint elliptical DD coil, large-scale iron Disc adjust, extremely rapid processing clock-speed microprocessor (matching....or exceeding/beyond human brain processing speed,,,,...... sometimes frustrating the fallible 'human' element)..... and a host of other attributes. It certainly has revolutionized the way we think/hunt...... and "opens the mind" to future exploration & possibilities. How do you commend?
Tom
