F - 70

[longsocks]

Well I did it I ordered a f - 70 today.... I flipped a coin a thousand times should I do it or not... Well after I ordered it, then I got this sinking feeling, maybe I shouldn't have...I always do that when I buy something, don't know why I get so bagged up... Guess I will now have a new learning curve to go thru if it ever warms up outside.. well guess I have a week or so to wait till it comes.. LOL hope it will pay for itself..

 

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[SaginawIan]

Congratulations on your new machine! You made a good choice! I own one and I love it. It's every bit as good as people are saying, and I think you will be happy with it. It is light, economical, deep seeking, accurate ID, and has cutting edge processing speed. I can't say anything bad about the machine and it just plain finds stuff.

Ian

 

[Sky Pilot]

Socks, Skypilot02 here! Ian and Jim are right on the mark! I happen to also own both, and LOVE my '70!! You will not regret it, just wait! Great hunting and good luck all!!!! Regards, Richard

 

[Michigan Badger]

Another word of encouragement to help calm your jittery nerves.

I just bought the F70 myself and have had it now for about a week. I got it mostly because the members here who really know their stuff highly recommended it. I think the thing that really convinced me was when a big promoter of the Nautilus company machines (Team Nautilus, etc.) told me he used the F75 (very similar) for his personal hunts I really thought that was humorous!

Anyway, it's still bad winter weather up here so all my testings have been indoors. Last night I got the F70 out and turned down the discrimination and set the sensitivity so the machine was picking up our house wiring (a little noisy). That doesn't bother me because I used the Tesoro Tejon for years and the only way to get super depth with it is to run it too high in sensitivity so it's noisy.

WOW! I air tested the F70 and even with a little noise the targets sound and read clearly! In air distance it beats the crap out of any brand I've ever owned. The distance it will sound on a dime is scary! I didn't have it in my jig to get an exact inches reading but I'd guess well over _________ well I'd better wait till I test it in the jig.

You done good pal! The F70 and the latest F75's will forever change the metal detector industry.

Fisher done did it again. Some of old farts recall how the Fisher 1260-X rocked the boat back in 82. That new fangled sci-fi rod design was laughed at for a few months and then copied by everybody. The same will happen with this new series.

Badger

 

[longsocks]

Ian, Jim, Richard, Badger

Thanks for the support and well wishes .... I guess my agonizing more or less had to do with, its just not a 200 dollar detector and I guess laying out the money for it in these troubled times might have caused me some pang's of guilt.. Hummm guess I just hope , it comes when the wife is at work Well any how I don't buy very often for my self, I got my Garrett in 1996 so its time.. and I'm sure I will enjoy it a lot... I think by the time it comes the temp should be up enough that I can go out and not freeze my fingers off. I would imagine it will be shipped monday so prolly maybe friday or the following monday it should be here ...
HH paul..

 

[Michigan Badger]

Ian, Jim, Richard, Badger

Hummm guess I just hope , it comes when the wife is at work HH paul..

I thought I was the only one here who did things this way

Hang in there my friend..."We're in this thing together."

 

[MajorBeep]

"No machine can go deeper in the ground than it's air test"

This is a Myth and has been disproved in a peer reviewed scientific study in various soil types against various targets. In the following publication:

http://serac.jrc.it/dmdocuments/Interim_Final_Moz-201205_02_web_optimized.pdf

Beginning at page 34 of the report, a series of graphs demonstrate that a Minelab F1A4 detector is capable of reaching targets deeper in ground than in air tests on a consistent basis. This is a non-biased independent scientific review that was rigorous in nature.

MajorBeep

 

[Sky Pilot]

No problem, Socks!! Regards, Richard

 

[Michigan Badger]

Re: "No machine can go deeper in the ground than it's air test"

This is a Myth and has been disproved in a peer reviewed scientific study in various soil types against various targets. In the following publication:

http://serac.jrc.it/dmdocuments/Interim_Final_Moz-201205_02_web_optimized.pdf

Beginning at page 34 of the report, a series of graphs demonstrate that a Minelab F1A4 detector is capable of reaching targets deeper in ground than in air tests on a consistent basis. This is a non-biased independent scientific review that was rigorous in nature.

MajorBeep

I've passed this info on to others and am now waiting for their replies.

I sincerely hope their findings are correct but I must say I rather doubt it.

Ground minerals hinder depth, they don't increase it. At least that has been my thinking.

Any other comments from other readers?

Badger

 

[Michigan Badger]

longsocks, congrats on the new F-70. I own the 75, but understand the 70 performs very similar to it. By all accounts an excellent choice, so cheer up. I have also agonized over these decisions, and had the same feelings when I bought my 75. It's the best unit I've ever owned, it still astonished me wrt depth especially, and I would not be without it. Hope you'll see it the same way. Take care and HH,

Jim.

Jim, what do you think of the Minelab depth report posted by MajorBeep?

Badger

 

[Sky Pilot]

Michigan Badger, I've studied the results listed in the document MajorBeep posted, and will say, at first look, it would appear that some detectors, not just Minelab, are capable of achieving SLIGHTLY more detection depth in certain scientifically categorized soil. However, after close examination, not just 1 of 100 some pages, of course, ALL the machines in use are military grade mine detectors, specifically for finding land mines, and in nearly all instances, there is a margin of error close to the amount of difference in air vs. soil comparisons. Also, these units were pulse induction units, not the type of discriminator units we detectors generally use on land! However, the most telling part of this analysis, is near the end of the document, which states:
In general, (in-air maximum detection heights, measured with the detectors set-up to a
particular ground, are not equal to the in-soil maximum detection depth in the same
ground). There did not seem to be any simple and direct way to predict in-soil performance
from the in-air measurements.
At the time of writing, it appears that it is necessary to carry out in-soil measurements to
obtain reliable in-soil data. Accordingly, this should be considered during the next CWA
review along with the ground reference height technique described before (section 6.2) pp.103. The parentheses are my own, but take careful note: The units were ground balanced for a specific soil BEFORE the air test was done! So, in closing, not only do I metal detect in North American soil, instead of Mozambique, I use a regular discriminating unit to hunt with, and my air tests are done without ground balancing first, which of course, will effect the depth a given unit will respond to a target in the air! No, other than occasionally salt water beaches, my detectors, (of which I am blessed to own several), have never reached a depth in soil, beyond a specific "air test", nor do I believe this is probable, as if that were the case, then one would logically take this as proof that minerals actually HELP a detector reach greater depths, and, if so, units with ground balance capabilities would actually HINDER detection depth! Great hunting and good luck, all!! Regards, Richard

 

[Michigan Badger]

Michigan Badger, I've studied the results listed by the document MajorBeep posted, and will say, at first look, it would appear that some detectors, not just Minelab, are capable of achieving SLIGHTLY more detection depth in certain scientifically categorized soil. However, after close examination, not just 1 of 100 some pages, of course, ALL the machines in use are military grade mine detectors, specifically for finding land mines, and in nearly all instances, there is a margin of error close to the amount of difference in air vs. soil comparisons. Also, these units were pulse induction units, not the type of discriminator units we detectors generally use on land! However, the most telling part of this analysis, is near the end of the document, which states:
In general, (in-air maximum detection heights, measured with the detectors set-up to a
particular ground, are not equal to the in-soil maximum detection depth in the same
ground). There did not seem to be any simple and direct way to predict in-soil performance
from the in-air measurements.
At the time of writing, it appears that it is necessary to carry out in-soil measurements to
obtain reliable in-soil data. Accordingly, this should be considered during the next CWA
review along with the ground reference height technique described before (section 6.2) pp.103. The parentheses are my own, but take careful note: The units were ground balanced for a specific soil BEFORE the air test was done! So, in closing, not only do I metal detect in North American soil, instead of Mozambique, I use a regular discriminating unit to hunt with, and my air tests are done without ground balancing first, which of course, will effect the depth a given unit will respond to a target in the air! No, other than occasionally salt water beaches, my detectors, (of which I am blessed to own several), have never reached a depth in soil, beyond a specific "air test", nor do I believe this is probable, as if that were the case, then one would logically take this as proof that minerals actually HELP a detector reach greater depths, and, if so, units with ground balance capabilities would actually HINDER detection depth! Great hunting and good luck, all!! Regards, Richard

Great job Richard, thanks!

Badger

 

[Sky Pilot]

No problem, Badger! Glad to get that sorted out! Heck, if ANY unit produced better results in soil than air, everything being equal, (g.b., sens, disc, ect...), then I would own one machine, and have lots more space around the house!! Badger, thank you for the kind words! Great hunting and good luck! Regards, Richard

 

[Charlie P. (NY)]

I can add this twist to the air vs. soil test. My F75 is unstable if I hold it horizintal at chest level in most sites or situations but calms down with the coil to soil. In that case it does MUCH better in the soil than as air testing. I can crank the sensitivity up - which increases the potentrial maximum depth. A deep signal (or long air test) is no good if you can't pull it out of the background clutter noise.

I put very little faith in air tests, anyway. If I am doing comparisons I set the coins on the ground, but a buried test garden is best of all (next to blind testing side-by-side on buried unknown targets).

 

[Sky Pilot]

Jim, Great to hear from you! Of course, I hope you know me better than to think I was trying to "put my two cents worth in", without regard to your opinion, which I value very highly indeed! I was offering my evaluation of the above noted results based on what I, myself, have experienced. The detectors used were being evaluated to find and remove unrecovered landmines, and the article described these units, (I believe I read correctly, please correct me if not), as pulse induction military ordnance detectors, as I believe the report stated, defined by Jane's Military Definitions, a standard of British Military evaluation. I am sure glad you wrote in response, as I was doing my best to explain what I understood the results of said evaluation to conclude, and felt it only fair to include closing observations of this evaluation, instead of only page 32. In other words, I, as I believe you were conveying, do not think it is responsible to conclude a "myth", as stated by MajorBeep, has been busted by taking one page out of context. And you also pointed out the less than ideal situation which these units were tested in, which I purposely left out, as I (obviously) wrongfully assumed would be irrelevant, as the closing comments (which I, once again, wrongfully assumed), in my mind, summed up the inadequate test conditions. Many thanks, Jim! Again, I defer to your expertise, and hold your opinion in the highest regard! Respectfully, Richard.

 

[Michigan Badger]

Badger, sorry about the delay in responding. I've been waiting on some further technical input, but that can be provided later.

I see Majorbeep’s position on this issue as being suspect at least where single frequency units are concerned. We all know that as non-conductive iron mineralization increases, depth of detection decreases. This consideration does not exist in air testing. Air testing is done with the object, but questionable value, of determining it's unhindered depth performance capability. We often see quite a discrepancy when the coil is over the ground.

None of my VLF single frequency units will detect deeper in undisturbed ground here than in an air test. Even less depth can be had in my disturbed ground test plot.

I qualify these remarks by reminding you that (a) The soil here is high mineral with a goodly amount of magnetite filings (0.1% by volume). Test results will improve in less mineralized ground. (b) Soil depths achieved by some units such as the F-75, can come very close to matching air test depths, even in disturbed ground test plots. The jury is reserving opinion about undisturbed ground until such time as a suitably deep coin is retrieved. (c) I have no first hand experience with (ground balancing) PI units, and cannot give an opinion on that subject.

I see that Richard has commented on the report. I have perused most of the report but read what I considered to be the salient information on how the test was performed. I generally agree with his comments although I’m uncertain about the terminology used to describe detector types. Certainly there were a number of pulse units tested.

There are further considerations as to how the test was conducted: (a) as Richard noted prior to air testing, units were ground balanced according to the soil test plot. For those units without suitable GB capability, the sensitivity was reduced according to soil mineral levels. More still, those units that could not be adjusted fully to soil conditions, were held at an appropriate distance above the ground whereby a signal could be measured. Such “above ground” distance was then subtracted from the air test depth measurement in an attempt to set an equal playing field between the air vs soil depth testing results. I do not agree with this arbitrary data manipulation. A units performance wrt ground minerals is part and parcel of the test, and should be kept independent of air test results.(b) the test plots were prepared on a daily basis, and the soil was not compacted to simulate undisturbed ground as far as such test conditions would permit. How valid are these test results?

Air tests should be run with sens as high as possible, and GB set to “ferrite” or in other words…to what the metal detector manufacturers refer to as “preset GB” on many of their units. This ensures peak performance for air depth testing. The following from DJ @ Fisher Labs….regarding air testing:

“How much depth should I get? There is no single answer to that question. In a few places, you may get in-ground depth almost as good as in an air test. There are also a few places with so much iron or salt mineralization that most detectors are not even usable.”

“Air test sensitivity” refers to the maximum repeatable detection distance achievable in air using a standard metal test piece (typically a US nickel coin), with the searchcoil that’s standard with that model, in a location without electrical interference, the machine adjusted to just barely eliminate background chatter. If ground balancing is available on the machine, it must be done using ferrite. A properly done “air test” provides an indication of a machine’s potential to “go deep” on buried coins. Because of interference from magnetic iron minerals in the ground, actual detection depth will usually be much less than what’s achieved in “air test.”
As per the quoted statement above re: using ferrite to GB the unit, one can safely go to the F-75’s preset GB setting of “90” and that will suffice to give an indication of the units ultimate/optimal potential. The “90” GB setting is pretty much in line/slightly above GB comp point of solid magnetite samples (natural ferrite).

Some hobbyists realize that reducing ground balance will reduce depth/sensitivity especially to lower conductive targets…especially at low mineral or conductive salt settings. For example, in an air test on a small gold nugget, reducing GB from “85” (my high mineral soil) down to “5” (wet salt setting) will reduce depth by 70%. Yes, 70%, three inches down to one inch detection depth. While the impact is much less on coin size targets, this example emphasizes the importance of following DJ’s advice when setting up air depth tests to determine the units potential capability. That mean using the ferrite GB setting to obtain max air test depth performance

As an aside to this topic, reducing GB will also help stabilize the unit, something to note if you have a modest/lower ground balance soil offering a larger “window” of tolerance (flexibility) to optimal GB compensation.

In any event Badger, I would have to conduct this test myself, and see it to believe it. In this part of the country, I have never enjoyed this alleged performance capability with any single frequency VLF units.

Meanwhile, I have put this question to others far more knowledgeable wrt metal detector technologies/capabilities. I will provide a brief response soonest. You could try Carl, Engineer over on the White’s forum (not the White’s forum we see here on Tnet) if you are in the mood. It's available from White's Electronics web site. There is a sub-forum where you can speak directly to him. Many do. Later,

Jim.

Hi Jim, I'm on my way out and will be away from T-Net for maybe a month or so. But I wanted to quickly reply so you (and the others commenting here) would know I appreciate your replies.

I think if we take all this and put it together we can understand why the struggle between air testings and ground testings. The bottom line is, if a machine can't detect an object through a nonrestrictive medium (such as air) at a distance of 12 inches it certainly will not be able to detect an object 12 inches deep in a restricted medium (such as dirt permeated with metallic particles).

Like you fellows have stated in different ways; a detector is basically a transmitter/receiver. It doesn’t matter if it’s BFO or PI; it’s still a transmitted/received signal.

I recall from my days of studying for a 1st class FCC license; radio waves travel a greater distance through air than through rock. Any radio technician will tell you that a FM radio tower must be as high and free of obstacles as possible--because trees, etc., can greatly reduce signal coverage.

All metal detectors (no matter the frequency) are basically mini radio stations with little receivers to hear their own broadcasts.

The BIGGEST things that make for a deeper machine are a higher quality receiver and coil (size/type is also important). The signal processing from the coil to the receive section is the depth.

The FFC limits the output power.

What we’re seeing today are much-improved receivers and better coil designs. The better these are the greater will be the air distance testings.

Got to go.

HH,

Badger

 

[Sky Pilot]

Thanks, Jim! I knew you would understand my intent! I agree, we DO have a dandy little sub-forum here, and I have learned so much, and am continuing to learn, from educated, experienced users such as yourself! Regards, Richard

 

[Sky Pilot]

Jim, Thank you for the kind words! No, as a matter of fact, I haven't really, I guess, taken the time to examine the new Whites offerings. I will now, though! I agree, we are definitely in a very exciting place in detector evolution! I can't hardly wait to see if Tesoro jumps up front with a new T.I.D. unit! I will check out the new offerings very soon! Great hunting and good luck, Jim! Regards, Richard