Oddball detector frequencies

[steve herschbach]

Hi,

This is off the top of my head but I was looking at some info on the old Fisher Gold Strike that got me wondering about it. The unit was very unique in that it operated at 30 kHz.

The Tesoro Lobo runs at 17.5 kHz and the new XP Deus has an 18 kHz mode. The Fisher Gold Bug runs at 19 kHz.. The XT 18000 and Eureka Gold can be set for 20 kHz. The White's V3i has a 22.5 kHz mode.

The aforementioned Fisher Gold Strike ran at 30 kHz. The Minelab XT 17000 and American Gold Striker both could run at 32 kHz.

Then we jump to the White's Goldmaster/GMT/GMZ at 48-50 kHz, Minelab Eureka Gold at 60 kHz and Fisher Gold Bug 2 at 71kHz.

I am sure people can add to this list.

I get the less than 20 and 50 or more thing. Lower versus higher. It is that rare 30-40 kHz range that is interesting due to the obvious lack of units that run there. A reason I have heard is power line harmonics in that range.

No real point to this post but it did get me wanting to get my hands on a Gold Strike just to mess around with it as it was a real odd duck. The owner manual explanation for the threshold control should go down in metal detector history:

"The THRESHOLD control can be adjusted with the arrow buttons between -99 (high threshold) and +4 (low threshold). Use the UP arrow button to

 

[PennyFinder]

The Fisher GoldStrike was another nugget machine ahead of it's time, maligned for it's computer program in it and the fact is was a silent search machine.
Most folks thought it was an odd duck like it's cousin the CoinStrike, so Fisher dropped it an later went bankrupt. It's a shame as they were really great machines.
In hot rocks and the silent seach allowed me to keep an ear open for bears, which is why I never sold mine.
Steve there is a new GoldStrike here if you want one,

http://www.ebay.com/itm/NEW-FISHER-GOLD-STRIKE-METAL-DETECTOR-GOLD-NUGGET-DETECTOR-/251179946258?pt=US_Metal_Detectors&hash=item3a7b7dd112

HH

PennyFinder

 

[steve herschbach]

I was and am still one who maligned the Gold Strike. I told Fisher when I tested a prototype it was a fail and fail it did. I am not saying it does not work. It simply did not deliver what people expected. Personally all I wanted was a Gold Bug 2 that could be flipped into a lower frequency. The Gold Strike was a rather spectacular failure at the retail level. As a Fisher dealer at the time I saw Fisher sales decline to almost nothing when the Coin Strike and Gold Strike came out.

I saw that unit on eBay and question how a unit not sold new for many years was supposedly just purchased new. And frankly, you almost have to give a Gold Strike away so the price is way too high. I might be tempted at half what they are asking. I know I would eventually sell it and would be lucky to get much if anything for it.

If the Gold Strike was half the size and had a control interface that made sense it might have had a chance. As it was it was doomed to failure.

Steve Herschbach

 

[PennyFinder]

True the GoldStrike had it's bad points, but it also had some good ones, like the chest harness or hip mounting, it was deeper than the GB2 on big stuff, and handled hot rocks better.
I like mine for micro jewelry hunting on mineralized dry sand beaches with hot rocks, there are only a handful of machines that will acheive this.
I like the silent threshold for that while beach hunting. Not many machines are the perfect machine, they all have their strengths as does the GoldStrike.
Now don't get me wrong I love my GB2 as well...Dave did a wonderful job on this masterpiece, as well as the clever little Diablo

 

[steve herschbach]

The Gold Strike may also have got a bum rap because, truth be told, Fisher could barely make a functional detector by that stage of the came. Quality control was non-existent and so many Gold Strike units may have problems that less aware user would take as being normal.

I broke one of my own rules with the Gold Strike. I usually try and figure out what a detector does best. In the case of the Gold Strike I focused so much on what it was not that I probably missed out on what it did well.

Steve Herschbach

 

[PennyFinder]

The folks on the CZ forum speak of the quality control issues of the non Los Banos made machines and they hold the Los Banos machines in high esteem.
It was the 1021-1121 series I believe. I was lucky to find a Los Banos CZ-70 Pro, it really is one of the great top 10 machines in my opinion.
I guess the writing was on the wall around the Fisher plant with the employees. The moral dropped off severely after that serial # run, combined with the finance department suffering with an extreme case of hypothermic blood supply deficiencies, which left Fisher doomed and frozen in the throws of bankruptcy and it's demise.
Compass pre-fire detectors suffered from the same employee demoralization, as their Made in America pride died there on the factory floor.
It really is a shame, both companies made some of the finest machines ever.
We all benefit with the greater competition between manufactures.
To this day the almost 18 year old design Fisher Gold Bug 2 is still one of the most popular VLF gold nugget detector made even today.
Wonder what Fisher and Compass would have offered us for nugget detector if they were still in the game?

HH

PennyFinder

 

[steve herschbach]

The divide was not Los Banos and El Paso. It was Lewellen and Cimino. There was Fisher of the 80s and 90s with Jim Lewellen at the helm and Dave Johnson on board. That is when we got the Gold Bugs and CZs and X series. The good old days.

Then Jim and Dave left and Roger Cimino took over. Basically it was all downhill after that. Fisher was still at Los Banos but plenty of junk got built there near the end. When First Texas took over they had a real mess to clean up when the move was made to El Paso.

First Texas hired Dave Johnson back, and Dave was very frank with me in admitting they had a tough year or two at first. I was not happy with El Paso myself early on but I can attest personally that although problems may still crop up they are addressed with impressive speed. The El Paso Fisher is doing a good job having worked through all the transition issues. More to the point, Dave is really one of the engineers who really get what detecting is all about. Since he was the guy behind the Gold Bugs and CZs and the newer Fisher models I think we are seeing exactly what the old Fisher would have done. The Jim Lewellen Fisher, not the Cimino Fisher.

Compass though, that is a real shame. Too bad they did not survive.

Steve Herschbach

 

[Dave J.]

Thanks, Steve. I think you just explained it better than I ever have. Besides, any explanation coming from me, someone can say I'm biased. Folks, Steve built a business on selling products he thinks are good because he uses them, and that includes products from most of our competitors. He likes some of our products but it's not like he's a Fisher shill.

Steve, I'll add a bit to your post.

* * * * * * * * * * * * *

First, the beginning of the end came when Jim hired a new engineering manager, Lido Scardigli. The guy was okay at first but after a while it became clear that he was going to destroy the entire company (not just engineering dept.) and Jim wasn't going to stop it from happening. (I've always been mystified why Jim let it go on until the bitter end, rather than dynamiting the guy to Kansas.) Most other people did their best to ride out the storm, but being the lead engineer I was in Scardigli's crosshairs and I had to get out of there under my own power before he stopped all my work and then used that to prove I was an unproductive employee and then can me. So, I solved Scardigli's problem by leaving Fisher to go work for Jack Gifford in Prescott.

I've often puzzled how it was that so many Fisher fans blamed the folks in El Paso for so much of what actually went wrong long before First Texas bought the carcass of Fisher. I suppose the key to understanding it is that the old Fisher consumer products we sell now are all virtually the same as what I'd designed before I left Los Banos. With almost nobody buying the Cimino-era stuff, almost nobody knew what a shambles the company had fallen into. Even COHU (the company that owned Fisher) was in denial for several years, but when it got to the point where Fisher was losing a million bucks a year on $7M revenue and Fisher's business plan was to "stay the course" (!!), COHU finally woke up.

Before we did the deal, I went to LB to take a look at what it was we were proposing to buy. I was shocked at what I saw. Same building and mostly the same people, but just at a glance it was a completely different company. When I looked at the books I was shocked again. I didn't know a business could be run this badly and still be in business, and the truth of the matter is that it can't be unless you've got a clueless benefactor, which they did in COHU. My recommendation was to bid no more than $0. As a matter of public record my advice was not taken, we actually paid something for the mess that had been costing COHU a million bucks a year.

Even the stuff we still sell, Los Banos had screwed it up. They forgot how to make GB2 searchcoils right, they forgot how to calibrate CZ's, they forgot how to seal CZ21's. It took us a while to discover what a mess we'd inherited and then to clean it up.

It wasn't possible to continue operations in Los Banos without continuing to lose money, so we hauled what we could to El Paso and made lemonade out of the lemon. It was no fun having to lay off a slew of people in Los Banos, many of whom I knew personally and held in high respect. We managed to entice several key people to move to El Paso. And I gotta put in the good word for the part of Fisher that's still in central California, engineers Marvin Jones and Ross Spain who work at home and telecommute to El Paso.

Regarding what might have come out of Los Banos had things not gone the way they did, nobody knows since thing did actually go the way they went. The Lobo ST is a clue, but it wouldn't have been done like that in Los Banos, the Lobo ST is what Jack Gifford asked for, not what Jim Lewellen asked for. Later I worked for Kenny White and Troy Galloway and since 2003 for Tom Walsh, but those companies' products were developed under the direction of those CEO's and are not what might have produced under the direction of Jim Lewellen.

--Dave J.

 

[PennyFinder]

Cheers and thanks to Dave J. for having his fingers on the pulse of detectorists needs and wants...I can't wait to see what he has up his sleeve next despite the conflict of the inverse 6th power law relationship between signal voltage and depth!

HH

PennyFinder

 

[Dave J.]

Inverse 6th power law expressed as voltage, but this is handheld stuff running on batteries, which supply power. The power law is inverse 12th power.

And that, folks, is why when it comes to basic hots, there's not a huge improvement nowadays over the hottest units that were being sold 25 years ago. Silicon works on a Moore's law of silicon manufacturing processes and metal detection works off an Inverse 12th Power Law law of sensitivity vs. power consumption where the latter is relatively fixed by battery capacity which hasn't improved a whole lot meanwhile. From a scientific-technical perspective, huge advances have been made in translating power to sensitivity: the problem is that it takes huge increases in sensitivity to get even small increases in "air hots".

And then you have ground minerals working against you just as they always have; and meanwhile a near-exponential increase in electrical interference from wireless communications networks. The amazing thing is that detectors work as well as they actually do.

Here's an example. In 1982, Fisher introduced the 1260-X, a second derivative motion discriminator with air hots of about 7 1/2 inches on coins. It ran on 8 AA cells and right there in the factory we frequently had problems with electrical interference from powerlines running down the alley.

30 years later we have a Fisher F75SE second derivative motion discriminator with air hots of about 13-17 inches on coins running almost forever on 4 AA cells. Granted that ground rejection and interference rejection haven't kept up with the basic air hots number, but looking at the air hots number it represents a power efficiency improvement on the order of 10,000:1. I didn't misplace a decimal point. That's ten thousand.

And we've got a GB/G2 second derivative motion discriminator running off a single 9 volt battery with air hots less than the F75 but performance in every respect far beyond the 1260-X, with superb electrical interference immunity too despite the EMI mess the 21st century is inflicting us with.

Other companies have made major advances too. To the average customer our advances may not look like much, but from a scientific-technical point of view, we are battling the inverse 12th power law at about the same rate that the semiconductor industry is increasing the efficiency of silicon active element fabrication (Moore's Law).

It's sort of like the automotive industry and gas mileage. In 1970 I test drove a production Honda automobile (the pregnant guppy hatchback 600cc twin) that got 55 mpg. It kept up with freeway traffic uphill and was stable in heavy crosswinds, absolute fun to drive. I could have bought it for $1,400 but wasn't yet ready to move from motorcycles to cars. And then Detroit had the Feds outlaw it, but that didn't stop the war against gasoline. Nowadays even Detroit (or wherever) is sucked into that same game and is not far from doing what was already done in 1970 as a commercial success. The basic problem is not political or even engineering stupidity, it's the principle of Carnot Efficiency and the physical limitations of the materials available to build internal combustion engines. Meanwhile emissions regulations and the desire of the public for big cars that cruise at 75 have worked against the dream of 55 mpg. All that stuff you've heard about some inventor came up with a carburetor that turned a gas guzzler into a 150 mpg miracle that Detroit paid the guy a million bucks to go away, it's all malarkey. What the world has in abundance is con men and also people who literally don't know how to measure gas mileage, and what we haven't got now or any time in the future is that miracle carburetor.

I don't even like cars, I own one because I live in a society which has made them necessary and regard them as one of civilization's greatest mistakes. But automotive engineers, them I hold in respect and admire what they've managed to achieve given the obstacles they have to work against. I feel that same way about metal detector industry engineers in general. Some of them have accomplished things that we haven't, and there's stuff we've done better than anyone else. There's room in the world for all of us, and what we have in common is that we've accomplished a lot more than what the detecting public realizes, because of that terrible cloud that hangs over us all forcing to do battle for every inch-- the 12th Power Law of induction balance (and even mono PI).

--Dave J. (and please forgive the weekend reminiscing mode of an old man)

 

[PennyFinder]

I stand corrected said the man with new orthopedic shoes! Thanks Dave.
With all the ever-shrinking micro-circuitry being engineered now a days, I wonder how small you could build a simple ultralight pack packing nugget shooter running on a lipo cell or two worn around your wrist, with a bluetooth head-set?
Show no fear and dare to dream I always say!

It is interesting you say Detroit and their bed fellows outlawed that little Honda, I think they did the same to the VW diesel at one point and all the Toyota, Nissan and Mitsubishi diesel vehicles. Most vehicles are diesel powered in the rest of the world except in the US and Canada. Once I owned a VW Rabbit diesel, the first ones imported in the late 70's...that little stinker got 60 miles to the imperial gallon with 4 passengers and a tail wind! They should be able to do better now 35 years later!

I wonder what Nikola Tesla was building in that big bee hive tower to provide electricty to the grid before JP Morgan found out it would be free to all people and then he pulled the financial plug on that project.
Perhaps we have been running the Tesla coil backwards and should be pulling the electricity out of the air and harvesting the electricity?

https://www.google.ca/search?q=nikola+tesla&hl=en&client=firefox-a&hs=TlK&rls=org.mozilla:en-USfficial&prmd=imvnsob&tbm=isch&tbo=u&source=univ&sa=X&ei=UIaoUNXyJ6KeiALOo4GQAg&ved=0CCsQsAQ&biw=1280&bih=497

HH

PennyFinder

 

[PennyFinder]

Tesla Wardenclyffe Project.

"Electric power is everywhere present in unlimited quantities and can drive the world's machinery without the need of coal, oil, gas, or any other of the common fuels."
- Nikola Tesla




HH

PennyFinder

 

[Dave J.]

Back in the 1980's I built a PI metal detector smaller than a pack of cigarettes. Ran off a 9 volt battery and had fairly decent performance by the standards of that day. It was just an engineering experiment to see what was possible, not a prototype of an actual product.

Regarding Nicola Tesla, nobody disputes that the man was a genius. He was also wrong about a lot of stuff. His wireless power distribution scheme was a really bad idea and that's why investors pulled out of his scheme. The fact that he was a genius and also wrong about a lot of stuff is the reason why it's almost impossible to find a practicing productive radio engineer who's a Tesla cultist, the Tesla cult (as I've observed it) is made up of people who dabble in a mixture of science and pseudoscience and who don't know low frequency radio engineering. Tesla's name crops up on a regular basis on LRL forums where science is not even wanted, but crops up essentially never on real low frequency radio engineering forums where the people posting are interested in things that really work. Despite Tesla's technical achievements which were impressive in their time, Tesla contributed essentially nothing to the commons of radio theory, so radio science evolved without him. It's hard for radio engineers to love the guy considering what he could have contributed had he cared to do so. As it was, he was......... Tesla, technical showman chasing rich benefactors with mixed success.

--Dave J.

 

[Reno Chris]

Although he was wrong about a lot of things, Tesla and Westinghouse did win the war of AC vs. DC and I think we are better off at least for that.

Getting back to Steve's original post on detector frequencies, in the last couple years we've gotten a whole host of mid-frequency, multi-purpose automated digital detectors with lots of features and digital displays - from almost everyone who makes detectors. Some are lower end price-wise and some with more features are higher end price wise. Still all of them are low to mid frequency and while capable of finding gold, they still dont compete with the old high frequency detectors for finding the small stuff. There is no question that the greatest market demand is for these "do everything" detectors, but every maker now has entries into this niche.

It just seems like there is a wide open slot that no one seems interested in making a detector to fill - a feature rich automated digital high frequency prospecting detector with a digital display. The GMT (another one of Dave's detectors) comes closest to this, but even the GMT is now more than 10 years old. With the price of gold at $1700 per ounce and interest in prospecting at an all time high, it just seems like there would be a good market for such a machine - and no one has one. I know that a number of prospectors when we first heard of the Goldstrike were kind of hoping it would be that type of machine, but it wasnt. In spite of the fact that its nearly 20 year old all analog technology, I bought myself a GB2 last fall because there is just nothing on the market that which is significantly better at finding small gold.

 

[argyle]

I get the less than 20 and 50 or more thing. Lower versus higher. It is that rare 30-40 kHz range that is interesting due to the obvious lack of units that run there. A reason I have heard is power line harmonics in that range.

No real point to this post but it did get me wanting to get my hands on a Gold Strike just to mess around with it as it was a real odd duck. The owner manual explanation for the threshold control should go down in metal detector history:

"The THRESHOLD control can be adjusted with the arrow buttons between -99 (high threshold) and +4 (low threshold). Use the UP arrow button to

 

[PennyFinder]

Tesla's work involved frequencies which is one reason I brought him up. Interestingly he had professed that if he generated a certain frequency and vibrated a bridge with it he could destroy it.
The frequency spectrum encompasses not only the radio spectrum but continues higher to light to infinity in both directions.
The earth vibrates a 7.8 hz and we have adapted vibrate the same.
Minerals have various frequencies and different metal detector frequencies have an affinity to various metals as we all know, as described by George Payne:
"
The higher the conductivity of the target the higher will be the targets -3db frequency. Conversely, the lower the conductivity the lower the -3db frequency. The -3db frequency of the high conductivity target will also make the r signal peak at a high frequency, normally well above the operating frequency of the VLF detector. This will make the high conductivity target have lower sensitivity on the VLF detector because the r signal amplitude drops if we are significantly below the -3db frequency. Simply put, maximum sensitivity on a VLF detector would be if we position the operating frequency directly at the target

 

[PennyFinder]

So in conclusion if you will, back to metal detector frequencies, if you look at gold's resonant frequency of 274 Mhz , we divide it by 10 we have 27.4 Mhz.
The closest metal detector frequency to this would be the Fisher GoldStrike.
Now if you divide 27.4 Mhz by 2, you have a resonant frequency of 13.7 Mhz which the Frequency of the Compass Gold Scanner. The MXT runs at 13.889Mhz.
John Earle was the designer of this machine. He also designed the AU-52 and the AU-2000 which ran at 52 Mhz which is a close resonate frequency of 27.4 x 2 which equals 54.8 Mhz.
John Earle later moved from Compass over to Whites to develop the Whites Goldmaster Vsat, GM3 and the GM4, which ran at 50 Mhz.
The GMT, of course is Dave's baby.
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Monte covers it here:

" Monte
August 23, 2012 02:14AM avatar Admin
Registered: 2 years ago
Posts: 474
many readers of these, or any, forums are newer to this great outdoor sport and the topic of operating frequency of the popular Transmit/Receive models has long been a point of discussion. For a brief overview for newcomers, let me offer this:

 

[Dave J.]

Tesla's work involved frequencies which is one reason I brought him up. Interestingly he had professed that if he generated a certain frequency and vibrated a bridge with it he could destroy it.

The earth vibrates a 7.8 hz and we have adapted vibrate the same.

Minerals have various frequencies and different metal detector frequencies have an affinity to various metals as we all know, as described by George Payne:
Mineral Frequencies:
http://wiki.afterworld.ru/wiki/Frequency
(Notice gold's frequency is 274mhz.)


PennyFinder

The bridge to which Tesla referred was the Tacoma Narrows Bridge, but Tesla himself didn't know that. No magic.

The earth doesn't vibrate at 7.8 Hz but the fundamental Schumann resonance is at about that frequency. My sheath fault locator design filters it out. No magic.

The selection of frequency at which to operate a metal detector has nothing to do with molecular or atomic resonances. No other magic, either. However on LRL forums when guys are desperate for magic frequencies I tell them that "the gold frequencies" are 19 and 71 kHz, which at Fisher is a provable statement.

--Dave J.

 

[PennyFinder]

Dave, what is your take on HAARP?

http://liestheytellus.com/2011/05/mechanical-resonance-and-haarp/

In you statement here: " I tell them that "the gold frequencies" are 19 and 71 kHz, which at Fisher is a provable statement."

I wonder why Fisher chose 30Mhz for the frequency for the GoldStrike?

HH

PennyFinder

 

[Dave J.]

Dave, what is your take on HAARP?

http://liestheytellus.com/2011/05/mechanical-resonance-and-haarp/

In you statement here: " I tell them that "the gold frequencies" are 19 and 71 kHz, which at Fisher is a provable statement."

I wonder why Fisher chose 30Mhz for the frequency for the GoldStrike?

HH

PennyFinder

Whoever wrote the essay you linked didn't understand the science involved, he was just telling a Tesla cult story and making stuff up to impress the true believers. Meanwhile HAARP is what it is, and ain't what it's not.

Regarding the GoldStrike debacle, I wasn't involved in that. Obviously no magic frequencies though.

--Dave J.