Interview, David Johnson and John Gardiner

[ivconic]

ApBerg pointed me on this:

http://www.fisherlab.com/hobby/davej...rinterview.htm

I find this interview very interesting, informative and educative!

[ivconic]

I will quote out the parts i find as most interesting:

[ivconic]

DS: Would you mind giving us a list of detectors you’ve had a hand in developing?

Dave: "Old Fisher: 1260, 1220, 1210, 1225, 1235, 1265, 1266, 1280, Impulse, CZ6, CZ5, CZ20, Gold Bug, Gold Bug II, TW6/Gemini, FX-3, and several industrial products.

Tesoro: Diablo MicroMax, Lobo Supertraq.

White’s: DFX, Beachhunter ID, GMT, MXT

Troy: Shadow X5

Bounty Hunter & related products: nearly everything we manufacture. Many of these products are adapted from the original Teknetics which was designed by George Payne. The Teknetics T2 however was an entirely new design.

New Fisher: F75, F4, and everything else since then.

On most of the above I was the lead engineer. On the White’s DFX and Beachhunter ID I developed the multiple frequency circuitry, and other engineers designed products around that circuitry. In addition to the above there are many products on the market which are adaptations by other engineers of products I designed."

John: "Bounty Hunter : I have had a hand in most of our current line up from the bottom to the top, from Guardian to the Time Ranger.

Teknetics : T2 I was main programmer

The Fisher’s : The F4 and F75"

[ivconic]

And this i found as MOST EDUCATIVE:
(very important to read, especially those "depth chasers" who will not stop annoying with depth demands!)


Dave: "Getting extra depth out of a VLF, multifrequency, or PI machine is very difficult, because these machines follow an inverse 6th power law relationship between signal voltage and depth. If everything else is maintained equal, doubling the depth requires 64 times as much signal. If this is done by increasing transmitter power, doubling depth requires 4,096 times as much battery drain. That’s the basic reason why depth increases come so slowly in this industry.

The biggest impediment to getting usable depth in the ground, is interference from magnetic and electrically conductive minerals in the ground, which can produce signals hundreds of times as strong as that of the metal target you’re trying to detect and hopefully identify. There are several approaches to extracting the metal signal from the ground mineral signal, but they all have their limitations. That’s why you see several different technologies coexisting in the market."

[ivconic]

About "HALLO" effect:

DS: The “halo effect”… fact or fiction?

Dave: "Mostly fiction. A lot of what people attribute to “halo” actually has to do with what happens to the natural magnetic and conductive structure of the soil matrix when you disturb it.

The rust that remains from a rusting iron object is definitely a “halo” which can have a definite effect on detectability and on target ID.

Corrosion from nonferrous metals is essentially neutral to metal detectors and is present in too small an amount to affect detection. It is plausible that the electrochemical corrosion process of nonferrous metals influences the geochemistry of the iron minerals in the immediate vicinity of the target; however I doubt that such an effect would be sufficiently prominent as to influence detectability.

Nonetheless, there are a lot of beeperists whose actual field experience leads them to believe that the halo effect is real, independently of the question of whether the conventional explanation (“conductive corrosion products”) is right or wrong. I’ve been around the block enough times to have encountered things which seemed impossible and yet there they were. One of these days I may have to eat my words about “halo effect”."

I am afraid you will ...!

[ivconic]

Question 11:
DS: “Detectable depth of a target cannot exceed the diameter of the coil” ie: 8” coil goes 8” deep. Agree or disagree?

Dave: "Not true. Most metal detectors will detect a manhole cover at least 2 feet deep, and most won’t detect a 1-grain gold nugget 1 inch deep. Small coils usually detect deeper than people expect them to, and large coils usually buy you sweep width rather than additional depth."

John: "Disagree. We already have a unit that with a 4” coil can detect coin size objective at 6”."

[ivconic]

"The old Fisher site in California had a carefully designed and constructed test bed with several different sections where we imported different soil minerals so we could emulate almost any mineral condition besides alkali or salt water. It was an expensive undertaking which we haven’t replicated here in El Paso because we don’t own the premises...."

I seriously doubt that you have least chance to see and check on these damn hotrocks and minerals which are so frequent and common here on our soils!
Come here and "taste" the real deal!

P.S.
F75 is real piece, hats down to it! But even F75 is performing pretty erratic here!
When you cut down adjustments - than you don't see some performances on it...
In that matters; CZ3D and 1266 turned to be more advanced ...at least here on these soils..

[ivconic]

"There are several detecting forums that I take a look at almost every day. They’re good for the hobby, and they’re also a valuable source of information for us. I don’t post on the forums, because I don’t have time to get into nonsense arguments with people. Once in a while when we feel it would be beneficial for information to be posted on a forum, for instance to get a stupid rumor straightened out, we leak the information semi-officially to people who are already active on the forums and give them permission to post it if they feel like it."

[ivconic]

"In general, higher frequencies are better for smaller and lower conductivity stuff, and lower frequencies are better for larger and higher conductivity stuff. Relic hunters are generally looking for stuff that is smaller or lower conductivity than US clad, copper, and silver coinage. However, frequency is not critical, and a 7 kHz machine can be good on relics and a 13 kHz machine can be good on coins.

Metal detector manufacturers generally avoid the 20-30kHz range because of electrical interference from military communications."

[ivconic]

"We’re building on a legacy that was created by many people. The progress we make is the work of many people. Of these many people, most never get any credit other than a paycheck and maybe a thank-you.

I would like to name two of those unsung heroes. Javier, who assembles prototype boards faster than anyone else on the planet and somehow does that while making no assembly errors. Aurora, who worked hard to make sure every T2 went out right, even while she was losing her fight with cancer.

First Texas Products is still benefiting from the genius of George Payne, whose basic target ID system has gone into more metal detectors sold, than all other target ID systems put together. Thanks, George.

Finally, I would like to thank my former employers for the privilege of having worked for them."

[ivconic]

Ok, those were interview parts i wanted to emphasize here.
I think this is very educational and good to read several times.

[bernte_one]

thanks ivconic for posting this

read more than the half by flying over and it was all interesting

[ivconic]

Those are simple facts, usually we all do know about, but seems we need to refresh our memories about those from time to time.
Now, reading same facts, pronounced by somebody else, those, kind a carrying more weight.
It is always like that, good to hear it from somebody else.
Especially from somebody such experienced and conversant.
That's why i reposted those here; just as excellent reminder.
Between the lines there are few crucial facts we all must learn and remember...

[Monolith]

And this i found as MOST EDUCATIVE:
(very important to read, especially those "depth chasers" who will not stop annoying with depth demands!)


Dave: "Getting extra depth out of a VLF, multifrequency, or PI machine is very difficult, because these machines follow an inverse 6th power law relationship between signal voltage and depth. If everything else is maintained equal, doubling the depth requires 64 times as much signal. If this is done by increasing transmitter power, doubling depth requires 4,096 times as much battery drain. That’s the basic reason why depth increases come so slowly in this industry.

The biggest impediment to getting usable depth in the ground, is interference from magnetic and electrically conductive minerals in the ground, which can produce signals hundreds of times as strong as that of the metal target you’re trying to detect and hopefully identify. There are several approaches to extracting the metal signal from the ground mineral signal, but they all have their limitations. That’s why you see several different technologies coexisting in the market."

The old brick wall of extra depth.

Can we break through this wall? YES WE CAN! YES WE DID!

How? Can you blame me for keeping it secret?

I give you a hint though.

Interestingly, Dave Johnson did the first step with the IMPULSE. Sadly, corporate decisions had him abandon the path. 20 years later many things have changed. Many things are possible now, that were not then.

But, still it is the market that drives the industry.

Is there really a market for an extra deep detector?

Monolith

[WM6]

Is there really a market for an extra deep detector?

No, because no-one are willing to dig ten 3.5m deep hole per day for rusty washers only.
Depth have to be accompanied with accurate target identification.
Depth alone mean nothing.
At the end we have devices that can go very deep, only hole diggers are missing.