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Gold Bug 3.5" Round Search Coil


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The 19 kHz Gold Bug was kind of the SD2000 of the day. Prior to it, the best thing going was the 15 kHz Garrett Groundhog circuit. Magazines of the time had many stories of people in Australia cleaning up with these old Gold Bugs. That was, as you note, more a function of being first on the ground, not any magical powers the machine had. It is what I call a "low gain" 19 kHz, not as hot on tiny gold as the new 19 kHz digital models, which are running higher gain circuitry. As I noted, however, this allowed the machine to handle really bad ground relatively well for a VLF detector.

The coil does look tiny. Here is my father using one back around 1990. The coil is described variously as a 3.5" coil or 3-3/4" coil, but it is 3.5" without scuff cover, closer to 3-3/4" with cover. As you can see it is also very thin, especially compared to other coils of the day or even today. Most similar size coils are over twice as thick. Yes, this is a concentric coil, as are all analog Gold Bug coils.

The old coil I am having serviced was used without a scuff cover and is slightly worn through to the epoxy along one edge. The older coil has minimal use and still has the scuff cover on it.

Another note on old Gold Bug models. The earliest are like in the photos below, with a white lower rod as part of the two piece shaft. The coil cables are gray or silver, and did not go to black until later. A three piece rod was offered as an option, and it was so popular it eventually became standard.

FREE BOOK - Advanced Nugget Hunting with the Fisher Gold Bug

bud-herschbach-fisher-gold-bug-1989.jpg
Bud Herschbach with original 19 kHz Fisher Gold Bug

bud-herschbach-fisher-gold-bug-chisana-1989.jpg
Bud Herschbach with original 19 kHz Fisher Gold Bug

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I assume Dave Johnson was still at Fisher (first time around) and had a major hand in the original Gold Bug's design.  How long after it came out before the Gold Bug 2 was released?

Is that gray cable on the coil in your photo actually shielded, double coax??  If so that sure seems weird.  And if not shielded, even weirder!

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Steve,i really do like reading these topics that you post,the images that you also add really complete the story so we can fully understand how these early classic detector and equipment was used.It all makes so much more sense when you can see the images as well.

Bravo,another classic article.

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22 hours ago, GB_Amateur said:

I assume Dave Johnson was still at Fisher (first time around) and had a major hand in the original Gold Bug's design.  How long after it came out before the Gold Bug 2 was released?

Is that gray cable on the coil in your photo actually shielded, double coax??  If so that sure seems weird.  And if not shielded, even weirder!

Dave started with Fisher in 1981 and the Gold Bug came out around 1990. Any detector is a group effort, but Dave is considered the key player on the Gold Bugs. The Gold Bug 2 came out in 1995, and Dave left at about the same time. See the forward in the book below for details.

FREE BOOK - Advanced Nugget Hunting with the Fisher Gold Bug by Pieter Heydelaar & Dave Johnson, Fisher Labs

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That's quite a recounting of history, through the eyes of an icon of metal detector engineering.  Ironically (maybe 'coincidentally' is the better word) I was thinking in literally the last couple days that it would be interesting to read about the milestones of metal detector development.  I think Dave nailed two of them -- ~1974 -- the invention of ground balancing VLF detectors, and ~1981 -- the development of motion all-metal and discrimination techniques.

There are other tidbits in that article, too, such as his statement "The lessons learned from the 1265-X made the later CZ's possible. The 1200 series is gone except for the 1280 Aquanaut which is a specialty nitch item: the CZ platform (originally the CZ-6) is still with us, circuitry almost unchanged 23 years later as the CZ-3d and the CZ-21."  (Steve, I think you've said this or similar here on at least one occasion.  Now we have it from "the horse's mouth.")

As I review my old treasure magazines from 1970 onward, it's an interesting contrast to today's development/innovation.  They went from no ground balancing, no discrimination detectors (BFO's and T/R's) to motion discrimination in about 8 years.  They didn't stop and rest on their laurels then, either.  And it wasn't just one company protecting (with armed guards) patents like they were Fort Knox gold.  It was many companies frantically creating products in competition -- great for the consumer. 

There has been speculation here that Minelab intentionally holds new detectors on the shelf until either competition starts to creap in or they need some extra capital.  Personally I question if they do that, but certainly back from the mid-70's all the way up into the 2000's I doubt anyone dare take such a risk.  "You snooze, you lose."

Thanks for the link, Steve.  (Got anymore?  😁)

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Steve .... Can you do a more detailed review of the Fisher Gold Bug detector with a 3.5 "concentric coil? ... and also a comparative comparison with some other gold detectors? ... on your more mineralized terrain?

I believe that this coil will bring increased sensitivity to very small gold ,,,

I think it would be an interesting topic ..

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Once I get the detector back I'll do something up. But I have used this detector and coil combo before and there are limits to what a small coil can do as far as enhancing small gold capability. The machine itself has inherent limits. However, nobody has compared the original Gold Bug to the modern digital version. Since I just happen to have a new 19 kHz model on hand, I will test them both on tiny nuggets to see just what the difference is. I believe it will be instructive as people tend to focus just on frequency, but there is more to it than that.

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On 9/23/2020 at 6:40 PM, GB_Amateur said:

Is that gray cable on the coil in your photo actually shielded, double coax??  If so that sure seems weird.  And if not shielded, even weirder!

The cable appears to be simple, cheap speaker wire. No markings on it. The connector is five pin but only four used. Two wires, clear and red, and the other two actually use the shielding from those two wires as connections.

fisher-old-coil-cable.jpg
Close up of coil cable

fisher-1990-gold-bug-coil-wires.jpg
And the connections

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