F75 and it's expanded Iron ID Range.

[Sunny Jim]

Sure does open up a new world in detecting. The Iron range is 1 to 15 and there is much information in that range that small low conductive targets like lead and distant gold can indicate in. No, the targets are not iron but the REAL DEEP low conductors masked out by other machines in an iron discrimination setting are passed up by those who cannot detect the difference.

A Great Machine!

SJ

 

[damiano]

For me lead occur in range 35-50 (lead balls from shrapnell).
On what settings you work ??

 

[Sunny Jim]

hello D.,

If you are looking for lead, the values you have are good for a near-target VDI. Now take a small sinker and with the machine in Discrimination and ZERO discrimination do some tests. At the edge of detection you will likely get hits in the low iron range. In the ground you may get readings of VDI that are jumpy and trend upwards. By using little (4,5,6) or no discrimination these targets will show. If you just dig the sure-thing VDI's you will find lead but the deeper or smaller ones will be passed up. I found 6 to be the setting that small lead would begin to report in and would jump to 12 or more. Lead's VDI is not always the same and size and distance are variables. If your targets are similar then you can count on a near field VDI that falls within a small range of VDI numbers.

Good luck.
SJ

 

[SteveP(NH)]

No offense but the Tek T2, which is a brother machine with the F75 & F70 since all 3 are based on the same Dave Johnson design, has the big iron range of the 3 - it goes from 1 to 40, lead usually shows up in the mid 60's on it.

 

[Cal_Cobra]

Jim I guess the trick is to know (and if you do, please by all means do share) when to dig those fringe depth targets that beep in the iron range but you suspect are non-ferrous targets. Any insight as to using the discriminator between the ears to vet out iron from non-iron when it hits in the iron range ?? It seems like we go back to the "dig everything" theory if we don't want to miss the chance of finding good deep targets.

hh,
Brian

 

[Elton]

Example Nickles 58 on the T2..30 on the F-75 a lot of the basic character elements are the same. The two machines are very different in operation.

 

[Sunny Jim]

Brian,
You do not have to dig all the good targets. Please leave them for me.
As for the T2, though I am not familiar to this machine, it no doubt is akin to the F75 and awesome in it's own domain.


Facts:
VID goes up with the target size. It can go down in the presence of iron.


Fiction:
VID never varies for a given target.

Fact:
VID goes up:
Test some lead sinkers and in different sizes. A small 5 gram sinker gives a repeatable VID that is lower than a 10 oz weight of the same alloy. If lead is what you are looking for, then testing at home would give you an idea of what to look for in the field. The VID on lead can be jumpy and trending upward to it's near-field repeatable ID. So you may look for this quality while hunting.
{ a note on Discrimination vs. All Metal Mode:F75
Discrimination modes are to be swung fast Vs. a slower AMM swing. Full swings!
In Disc., Tone 1 listen for the quality of the signal; iron has a different quality to a coin
sound. Small good low conductors (gold, lead) and good high conductors have a
good quality of sound compared to say a rusty nail. Now listen in Delta pitch to see if there is
tone(s) above iron. Test from different sweep angles. AMM VIDs can range wide but not
as wide as DISC modes can, especially in JE. AMM jumpy, high VID is more true to the
near-field VID, same mode. Sometimes all you have is a tone and no VID. What does that tone tell you?}

A pop-can can have high VID like a quarter and the same metal in a smaller amount, the pull-tab has a lower VID. The smaller or farther the high conductor is, the lower it's numbers in VID. So, if the metal is one you are after, and it in mass is a high conductor, you will see lower VID numbers when the mass is small, or large and far away.

Take your test lead (acts like gold!) and see what kind of things you learn air testing. For practice on small lead, I found the discrimination at 6 to be the point at which the machine will begin to detect the weak signal. I'm not taking credit for that number because it is a fact. Now the same test piece will give higher VID numbers in a near-field test : a repeatable value that you see. Maybe say, 12 on the VID is repeatable ( in JE could jump a little higher). Gold has an irregular shape and a lead sinker is fairly round. Round Targets seem to give good repeatable VID's. So the true near-field VID and the iffy jumpy distant VID has size and shape and distance as variables (sensitivity settings too).

WHY DOES VID DIFFER WITH THE SIZE OF A TARGET:
ANSWER: EDDIE CURRENTS

Eddie currents love to run around and through metal. The more, the merrier.
If we did not have laminated cores in our wall-wart transformers, they would likely melt off the wall.
Here the Eddie currents are not allowed to gang-up and make heat. Eddies love mass and symmetry. Sharp corners and pointy things can have quite a collection and collision of Eddie currents and can produce a range of VIDs. The more metal the Eddies have to run around in, the happier they are and those happy Eddies give us a report. Different metals have different qualities for Eddie currents to run free. Shape has an effect on how well they play together along with size and the strength of the electromagnetic field inducing the Eddy current( distance and angle of sweep). You may want to evaluate a target at a lower sensitivity or distance. To excite the small and distant targets, you have to be able to hear the weak Eddies sing (use little or no discrimination). They may sing low like they are swimming in iron, but a closer induced field makes them sing truer. They need a little more energy a bit closer to start dancing and they sing,... I like to move it, move, it,....she likes to move it, move it,.. we like to move it, move it! Move it!


Coins can generally give good repeatable signals.

Try the test for yourself and start with no discrimination to see what the lowest VID is for a small target of what you are hunting, near and far to the coil. What is the lowest VID? What is the highest? What is the most repeatable VID?


Fact:
VID can go down in the presence of ironsmall iron nails etc.)
Iron sucks VID down. Read around and see for yourselves about iron masking and unmasking a good target that is near an iron target. You will have to have low discrimination settings and no notch.
( I want to work with low notch settings and compare them to low discrimination). So if you are looking for lead or gold or some mid to high conductor, you need to know what VIDs you might see on the machine from the low VID to true VID. These targets are not easily detected and if their low VID values are in the iron range, any discrimination in iron may make the targets transparent.

So we sweep fast in the discrimination mode and listen to the sounds. Monotone, (tone 1) can help you listen and concentrate on the quality of the signal (Raspy/smooth). Delta pitch can give a bit more information about the presence of higher conductors (high tones). All Metal mode can narrow down the actual true VID. FeO meter can detect the black rust on old buried iron in a wet/
water environment (pump the coil).

A target that is jumpy and trending upward in VID away from iron can be a crap-shoot, but any VID numbers that come in repeatable that look good may need a closer look. A .2gram nugget, the size of a paper match head has a true repeatable VID of 18. If I was in the right country looking for such metal, I would consider a 12 or 13 or 16 VID as an indicator in a Jumpy VID that could go to 20 in JE. This happens more exaggerated with bigger deep targets and the numbers go up. I hear a high tone and I see a VID leaving the iron range and that is a good sign. The 20's is the gold range when alarms should be going off. The sound of a dinner bell; winner, winner, Chicken Dinner!

Now then, others may discriminate these signals out and pass them by. If coins are laying all over the deck, I would not waste my time investigating the faint iffy targets. Go DE, no notch and turn down the gain to like 20 and clean-up! Make you discrimination at 20! Lick that plate clean and go back for some extreme hunting another day. There is lots more silver out there to be found than people are willing to admit.

Hopes this helps and you discover the world beneath your feet normally passed by.

SJ

 

[Cal_Cobra]

Hey Jim,

Thanks for posting your thoughts on this topic, I hear what your saying, and it makes sense.

I'm to the point where if a target sounds "good" I'll dig it no matter what the F70 says it is, and more often then not it turns out to be something at least interesting. I recently hunted an area that originally had an 1850's adobe (no sign of it now that I can tell), and targets were few and far between. I'll probably be back up there in a couple of weeks, and I think I'll try (shudder) AM mode this time, as there was almost zero modern trash, most of the targets I found were all pre-1900 aside from a 1916D Mercury dime and a couple of doo-dads.

A place I want to hunt that will really take some serious effort is loaded with square nails, so many so that they litter the top of the ground in some areas. The little DD might do well here.

hh,
Brian