While searching for that "gold coin" info on this forum...

...I found this quote from NASA-Tom (in a post where he had evaluated an E-Trac for Aaron...)

Quote

Coin hunting:

Here is where I have been struggling for several days. I have been trying to create a 'magic' program for inland 'old' coin hunting. The fact of the matter is: there is no magic programming secret. Reason: Using a $5.00 gold Half Eagle coin as my minimum conductivity platform/coin..........there have been TOO many real-world scenarios that have 'voided' any of my special 'coin' programs. With this coin slightly tilted.....................or....................... a few small flecks of rust in close proximity to the coin (this is representative of the real world) ............and the coin is 'nulled' (Disc'd). Ironically............with nothing Disc'd out..........the cross-hairs land in a white/clear region on the LCD screen where ........... flipping over to the special 'coin' program(s).....is NOT Disc'd out; yet, the detector 'nulls' over the coin. Sooooooo...............in a nutshell: detect primarily by audio responses. Secondarily, focus your efforts on the upper right quadrant of the screen. (( The factory 'coins' program is not bad, yet, has a few flaws..... due to real-world conditions )).

Focusing on the part where NASA-Tom had a gold coin "nulling" when running a disc. pattern, but which was giving a crosshair readout in a WHITE (non-discriminated) portion of the screen...

WHAT?

I don't get it. At all...I am thinking about this, and it does not make sense to me...I can see a "tone ID" algorithm giving a different "ID" than the "VDI" algorithm, but on the FBS units, the way I have understood it is if you DISC OUT, say, the 12-01 pixel, then the audio -- WHICH REPRESENTS the 12-01 pixel will present itself as a "null." But NASA-Tom verified a scenario where the audio response was a NULLED threshold, but the VDI/cursor ID value that this target was registering as, was NOT BEING DISCRIMINATED...

Explanation anyone???

Further, I do not understand NASA-Tom's conclusion to "detect primarily by audio responses." While I AGREE with this, I don't know how that is the conclusion arrived at BASED ON the scenario given. In other words, if a "threshold null" is resulting over a given target -- EVEN WHEN RUNNING A FULLY OPEN QUICKMASK SCREEN (i.e. NO discrimination), how is the audio helping you in this case? (Unless, the implication is, run an open pattern, and DIG the NULLS!!!)

Steve

I like my E-Trac...a lot. I have not had it long, and haven't experimented with a lot of the settings but I do know this. The stock coin program, even with the sensitivity turned up in the 22-25 range, is not good on lower conductive targets. It is a great clad and silver finder in trash, but for nickels and gold, not good.

When hunting for lower conductive targets in trashy areas, I pretty much run wide open ( quick mask with only the bottom 2-3 lines blackened out ) in conductive mode, with multi tones, and listen for any mid tone and higher sound that repeats and I dig it up. I don't rely on the screen numbers or cross hairs much at all. I only use this method with the Sunray X-5 coil (sometimes the Sunray X-8 but can't with the stock Pro Coil due to too much garbage). I dig lots of trash, but have found gold and lots of nickels this way.

When I did use my E-Trac in the wet, salt sand a few times with the Pro-coil, I was having trouble finding lower conductive targets even in the beach program. I knew they were there due to finding deep sinkers and a few nickels with another unit, so I ended up running the above setting and found a lot of deep med and small sinkers, nickels and a big 18k earring and figured that was the way to go for gold.

Steve...... in the coins program Disc pattern..... the coin 'nulled'. Running the unit without any discrimination (wide open screen)..... the coin did not null. Hence; the recommendation of utilizing the audio moreso over the VDI.

This (unfortunately) is a very common phenomenon with any detector.......... in the real world............. in real dirt....with infinite variables. 'How' each detector handles these different scenarios may be somewhat different; yet, the end-resultant may be the same.

OK...makes better sense regarding your advice to use audio that it nulled using disc, but DID NOT null using open screen. Given that, the advice makes complete sense...

Still don't understand a coin nulling the threshold, when it IDs as a value that is NOT a discriminated value...

Steve

There are many detectors............ especially the newer digital ones, where the "VDI" vs the "audio" report are separate/independent systems.

I have never understood that, Tom. I know the F75/70 are independent systems but I have never had an occurance where I noticed a difference. In heavy iron when trying to unmask coins it seems to me they are in synch. Whenever I get a repeatable high tone they VDI has always briefly shown a corresponding flash into the 60-80 area depending on the denomination. I have, however, noticed that many time when using pinpoint the ID graph will show a much lower target than either the audio or VDI indicated. Many time bottle caps do that for me as well as other larger junk target. Are there other ways to benefit from the independant audio/VDI?

steveg Wrote:
-------------------------------------------------------
> Still don't understand a coin nulling the
> threshold, when it IDs as a value that is NOT a
> discriminated value...
>
> Steve

I believe in this case the iron flecks brought the VDI signal down into discriminated range of the coin program, thus causing a null. While running a wide open screen, the flecks brought the VDI signal down but did not null because of zero discrimination. I also believe that is why Tom said to hunt by the audio not the VDI.

lgc68............... start with the following test with the F70/F75. Dig up a rusty nail. Then........... lay it on top of the ground .... in a clean area. Place your Disc on 0 or 1. Get a VDI of the nail. It'll probably be a VDI of 11 or 12. Raise your Disc to '6' ..... and witness it being discriminated out.

Non-ferrous targets are a bit different; yet, follow the same principle. What they will ID vs 'where' they will be Disc'd out...... may not be the same...... especially in the ground........... with mineralization and masking further amplifying the err/phenomenon.

schultzie --

I hear you, and know what you are talking about. I guess my issue was, the coin was giving a "cursor position" -- a numerical ID value -- that was NOT disced out; NASA-Tom specifically said that the cursor (showing the target ID value) was in a "white" (i.e. non-discriminated) location in his coin pattern, on the smartfind screen.

The scenario you described, as I understand it, was for instance a dime, that would normally ID as a "70," was located while hunting, with a machine where you have all values below "60" discriminated. Now, I can fully see where rust flakes near this dime in the ground could cause the dime to ID at "50," and thus be disced out due to the lowered "mis-ID" of the dime (due to the rust flakes). I'm good with that. My issue is, though -- that WHATEVER value the rust was causing NASA-Tom's coin to "improperly" ID as, WHATEVER the cursor position was that was showing up as the "ID number" for that coin/rust combination target, THAT specific ID value was NOT a disced-out value. Yet, the threshold null revealed that the target WAS IN FACT being dicriminated! IF the rust caused the coin/rust cursor position to fall in a BLACK (disced-out) location on the screen, no problem. A threshold null would be the logical result. It's the fact that this rust-altered target ID was NOT an ID that was selected to be disced out -- but it still ended up being disced out anyway.

NASA-Tom -- what you described in the prior post, a nail that IDs as 12, but will be "disced out" if you raise the disc to "6" on an F70/F75...I will accept that and remember it. BUT -- I do NOT understand it.

Steve

Steve,

There's some 1) physics, 2) phenomenon, 3) engineering design platform architect.......... that causes this.............. and I WISH I had more time to give a better explanation!

In a nutshell.... I can say this much though........ as far as the engineering design; VDI (((the visual ID numbers (or cross-hairs) presented))) may be taken BEFORE or AFTER the audio discrimination circuits. This is partially what dictates dependency or independency of VDI vs Disc.

steveg Wrote:
-------------------------------------------------------
> schultzie --
>
> I hear you, and know what you are talking about.
> I guess my issue was, the coin was giving a
> "cursor position" -- a numerical ID value -- that
> was NOT disced out; NASA-Tom specifically said
> that the cursor (showing the target ID value) was
> in a "white" (i.e. non-discriminated) location in
> his coin pattern, on the smartfind screen.
>
> The scenario you described, as I understand it,
> was for instance a dime, that would normally ID as
> a "70," was located while hunting, with a machine
> where you have all values below "60"
> discriminated. Now, I can fully see where rust
> flakes near this dime in the ground could cause
> the dime to ID at "50," and thus be disced out due
> to the lowered "mis-ID" of the dime (due to the
> rust flakes). I'm good with that. My issue is,
> though -- that WHATEVER value the rust was causing
> NASA-Tom's coin to "improperly" ID as, WHATEVER
> the cursor position was that was showing up as the
> "ID number" for that coin/rust combination target,
> THAT specific ID value was NOT a disced-out value.
> Yet, the threshold null revealed that the target
> WAS IN FACT being dicriminated! IF the rust
> caused the coin/rust cursor position to fall in a
> BLACK (disced-out) location on the screen, no
> problem. A threshold null would be the logical
> result. It's the fact that this rust-altered
> target ID was NOT an ID that was selected to be
> disced out -- but it still ended up being disced
> out anyway.
>
> NASA-Tom -- what you described in the prior post,
> a nail that IDs as 12, but will be "disced out" if
> you raise the disc to "6" on an F70/F75...I will
> accept that and remember it. BUT -- I do NOT
> understand it.
>
> Steve

This is interesting to say the least. I am no scientist, but I would speculate that since the audio & visual circuits are separate, the visual circuit "saw" the larger surface area of the coin and reported it as a good target. The flecks of iron, I would assume, were spread out somewhat covering more physical area than the coin and the audio circuit "read" this as a larger target and reported it as such. Also, in Tom's scenario, he was using a $5.00 gold Half Eagle coin, which, ID's considerably lower in the VDI scale than a dime. It will be interesting to see how Tom explains this. I was always told (and read) to trust the audio and not the visual on deep targets. In this scenario, trusting the audio would fail to report a good target and it would be missed. I guess nothing is fool proof.

NASA-Tom --

I followed you perfectly on your explanation of the WHEN being important, in terms of VDI "circuit" (if "circuit" is the right term) and the disc. "circuit," and in what order these things occur in the machine (and thus "dependency" or "independence" of the VDI vs. disc.)

I would ask a few more questions about that -- as I can fathom many implications arising from this (the dependency, or "independence" of the VDI "circuit", the audio ID "circuit," the discrimination "circuit...", and of course that doesn't touch on the PHYSICS or the PHENOMENON part of it; but -- I fully respect your limited time, which is why I didn't ask in the first place. )

I thank you for the info you did provide, it really helps alot. Every tidbit you offer is like a little goldmine...it answers/appeases one puzzle in my brain, but inevitably, in the next moment, two or three or four FOLLOW-UP questions start running in my mind...reading this site, and in particular your answers, are like "mental gymnastics!"

schultzie --

Your speculation is interesting...wonder if you are on to something? I, like you, have always been told to "trust the audio" as well. And yes, trusting the audio here would have failed you, IF -- IF -- you were running a discrimination pattern. HOWEVER, NASA-Tom did say that when he ran NO discrimination pattern at all, that the coin DID report...

Quote

Steve...... in the coins program Disc pattern..... the coin 'nulled'. Running the unit without any discrimination (wide open screen)..... the coin did not null. Hence; the recommendation of utilizing the audio moreso over the VDI.

SO -- I guess "trust the audio" is still a good piece of advice, schultzie, but with this caveat -- trust the audio....BUT -- trust it most when you DON'T run any discrimination!

Trying to figure this out is tying my brain in knots. A gold coin IDs as, say, 50. Rust flakes near the coin, in the ground, cause it to IDs as, say, 40. If you run NO disc, you get an audio report, and a VDI of 40. BUT, IF you run DISC, discriminating all values below 30 (and say 30 and below is an "iron" ID), we now know that there is a scenario (i.e. like the scenario that NASA-Tom is describing here), where you get a VDI of 40...but you get NO audio report (your threshold "nulls" ), implying the target is a 30-or-below ID'd IRON target! VDI says "40," but if you run DISC, the "ID" of the target is apparently SUB 30.

Apparently, based on NASA-Tom's follow-up, the unit ran the return signal through two separate "circuits" -- one to give VDI of a target, and one to discriminate targets. AND THE TWO CAME UP WITH A DIFFERENT ANSWER on what the target ID was!

Along these lines, I am not sure, but it almost sounds like the raw data comes in, and is "split," such that "raw data" goes simultaneously into two different "circuits" -- a "VDI" circuit AND a "discrimination" circuit -- such that at times, the two circuits ID a target differently -- at least on some machines. This is apparently the "dependent" vs. "independent" thing NASA-Tom is talking about, and this "split" of the raw data into different circuits would be an "independent" type of situation. On the other hand, if the raw data came in, and instead of being split, it runs through different "circuits" sequentially...i.e. raw data comes in, and runs through a VDI circuit, and then the "processed" data comes out of there and then goes into a "discrimination" circuit, I guess this would be called "dependent."

Steve



Edited 1 time(s). Last edit at 03/13/2012 01:18AM by steveg.

steveg Wrote:
-------------------------------------------------------
> Apparently, based on NASA-Tom's follow-up, the
> unit ran the return signal through two separate
> "circuits" -- one to give VDI of a target, and one
> to discriminate targets. AND THE TWO CAME UP WITH
> A DIFFERENT ANSWER on what the target ID was!

Maybe it works similar to the Correlate Mode on the V3, where it takes two frequencies (raw data) and compares their signals and if they do not "pair up" (for lack of better words) it rejects the data and give you no signal. Meaning in Tom's case, if the audio circuit and the visual circuit do not "jive" it drops out and/or nulls.... thinking it is an iron target which has been discriminated out. Correlate Mode is helpful in heavily iron infested ground, as Iron tends to ID in a broad area of the VDI scale.

Interesting stuff on the "correlate," schultzie. I do see how there is some similarity here, in terms of what is going on with "raw" data in different machines...

I would like to understand all of this better...but we are obviously delving into complex (and possibly, proprietary) aspects of how machines work, such that specific, detailed answers may not be as readily available as I'd like...

Steve

YES.... and YES!

Just to set your mind at ease, get yourself a F75 LTD (5'coil, BP, disc #1, sens 99, all met.) to use in the areas where you believe a gold goin to be...you wont miss it then.



Edited 1 time(s). Last edit at 03/13/2012 02:07AM by Aaron.

Aaron --

While I'd love for it to be that easy, I also like to hunt deep silver in trashy parks, and in my soil, on those sites, the F75 is not the right tool for the job. I'd need BOTH the F75 (for the "relic sites" where those gold coins would be more likely), and the Explorer or E-Trac for silver hunting in public places. Given the sparsity of "relic sites" in my "young" state, $1200 is too much to spend, for a machine that would only be used on occasion, in certain scenarios. Thus, the better option, for me, is to learn to find them with an Explorer... (while realizing it's not the "best" tool for that job...)

Steve

Awesome posts

Understandable, however you can always get a used one for $700.
I can't emphasize enough how well the LTD works in the iron sniffing out the small good stuff, along w the Etrac.

Aaron --

I hear you...good point.

Perhaps mistakenly, I spent that money for a "second" detector on a Gold Bug Pro, hoping to get SOME of the benefits of the F75 (its skill in iron) -- plus give me some gold prospecting ability for the rare times I head to the gold fields. When I relic hunt, I do/will use the Gold Bug Pro. It's not the F75, but it is FAST, and supposed to be real good in iron. However, NASA-Tom has challenged me to run some depth testing on the Bug's 5" coil, which I haven't used as much yet (my machine came stock with the 11" DD, and I added the 5" later). I plan to do so soon, and HOPEFULLY, I get decent results, depth-wise, with the Bug's 5". If so -- it may do what I need it to in the iron, and I KNOW it is sensitive to lower conductors, so it may fit the bill...but, NASA-Tom implies I'm not going to be pleased with the depth I get from that 5" coil (especially compared to the F75 w/5" coil).

Anyway, that was my "other" detector purchase -- though I must admit there are times I really wish I had "boost process" (plowed fields and high-grass sites).

I really would like to have an F75 LTD...

And yet...there's a new machine coming from FT, too...

What to do...what to do...

Steve