ITMD4

[Carl-NC]

I am beginning to think about what ITMD4 might look like. I would like to mostly expand on digital designs, multifrequency, and multiperiod PI. ITMD3 is already 634 pages so here's what I'm thinking: Make ITMD4 a 2-volume set, like this:

Volume 1: The same as ITMD3, except remove Digital Techniques (Ch1 and all of Advanced Methods (Ch24-26). Maybe add chapters that focus on the design trade-offs in VLF and PI. This means Volume 1 will cover mostly all-analog designs. It will end up with 500-600 pages.

Volume 2: Take Ch18, split it up, and significantly expand on all its topics, with coded example projects. Also do the same for Advanced Methods. I'd also like to add some chapters on other geophysical devices like mags, resistivity, and data loggers, all with example circuits. Probably another 400-500 pages.

What I would like to know from readers of ITMD3 are the following:

• What topics in ITMD3 were not done so well, not enough depth, or not clear?
• Were the circuit examples appropriate and easy enough to follow?
• Are the drawings and graphics sufficient?
• ITMD3 includes zero AI material. I'm thinking of using AI at least for creating better graphics. Any thoughts on that? Or other AI usage?
• Volume 2 will likely have a lot of software-driven designs; any ideas on how to document this in the book? (ITMD3 code was all posted to the forum)
• What additional topics would you like to see covered?

I am just starting to collect ideas; writing ITMD4 will take at least another 5 years (probably more, I always underestimate) so don't get annoyed if you only just bought ITMD3.

[GeoMax]

Hi Carl,

Regarding the topic of software-driven designs (Volume 2): I would break this down into a couple of categories. First, there’s the scenario where the software simply handles the timing; then, there’s the approach of using software to analyze the target signal. Why? For many simple DIY projects, it’s sufficient for the microcontroller to handle just the timing—most of them can keep up with that. Anyone looking for more can delve into signal digitization.
Another interesting topic would be hybrid PI systems.

[Altra]

Hi Carl,
You could also do a "Cookbook" approach. Go deep into a single topic and publish. For instance do a series of "Inside the Digital PI ", "Inside the Digital VLF", "Inside the Multi-frequency" etc. Five years is a long time in the tech world, much of the info would be stale in that time. Probably more satisfying for you to publish one topic and move on to the next. Down the road you could combine these into one large volume. My two cents...

Thanks for maintaining Geotech all these years!

[Taktyk]

Hi Carl,

Splitting the book into two volumes sounds like a perfect plan! Going deep into digital and multi-frequency PI is exactly what the community needs right now. Here are a few thoughts from my side regarding your questions:

1. Code & Software Documentation
Definitely go with GitHub. Printing pages of code in a book is tough to read, takes up space, and gets outdated the second a bug is found. My suggestion: only print the "meat" of the code in the book (core logic, DSP algorithms, or pseudocode), and drop a QR code or a short link (like bit.ly) right next to it, pointing straight to the GitHub repo.

2. AI Graphics & Data Visualization (Seaborn!)
You mentioned using AI for graphics. Just a quick heads-up: be very careful with AI image generators for technical stuff. AI doesn't understand physics or electronics, so it tends to "hallucinate" incorrect schematic connections or impossible waveforms.
However, AI is amazing at writing Python code for data visualization. You can use ChatGPT to write scripts using Matplotlib or Seaborn. Seaborn is absolutely brilliant for this - you can feed it your data and easily generate publication-quality vector graphics, heatmaps for magnetometer data, or beautiful multi-frequency phase plots. It takes the visual quality to a whole new level.

3. LTspice / Simulations
For the analog and mixed circuits, it would be a massive upgrade if you provided downloadable simulation files. Allowing the reader to load up the exact circuit from the book on their PC and hook up a "virtual oscilloscope" to see how it behaves is an absolute game-changer for learning.

4. Dedicated Book Software (A wild idea...)
Thinking about the software-driven projects in Vol 2... If I were doing something like this, I’d actually want to develop a dedicated companion app. Something like a universal "Metal Detector Studio" tailored specifically to the projects, algorithms, and data loggers in your book.
In fact, I'm really interested in this area and I would be totally open to collaborating with you on developing this kind of software if you're up for it!

Five years gives us plenty of time to build something awesome. Let me know what you think!

Cheers,

[Carl-NC]

Regarding the topic of software-driven designs (Volume 2): I would break this down into a couple of categories. First, there’s the scenario where the software simply handles the timing; then, there’s the approach of using software to analyze the target signal. Why? For many simple DIY projects, it’s sufficient for the microcontroller to handle just the timing—most of them can keep up with that. Anyone looking for more can delve into signal digitization.

Some of the PI projects in ITMD3 already use a PIC micro for timing. The intent is to add projects that include DSP, for that I will switch to STM32.

Another interesting topic would be hybrid PI systems.

Can you elaborate? ITMD3 cover some hybrid approaches, but I'm not sure what you mean by "hybrid PI."

You could also do a "Cookbook" approach. Go deep into a single topic and publish. For instance do a series of "Inside the Digital PI ", "Inside the Digital VLF", "Inside the Multi-frequency" etc.

I thought about that: ITMD: Multifrequency; ITMD: Coils; etc. But I did a lot of cross-referencing in ITMD3 and it's nice to have everything together. 5 years is a long time, but the metal detector world doesn't really change quickly.

[Carl-NC]

Hi Carl,
1. Code & Software Documentation
Definitely go with GitHub. Printing pages of code in a book is tough to read, takes up space, and gets outdated the second a bug is found. My suggestion: only print the "meat" of the code in the book (core logic, DSP algorithms, or pseudocode), and drop a QR code or a short link (like bit.ly) right next to it, pointing straight to the GitHub repo.

You are correct, I should post the code to GitHub. The QR code is a good idea.

2. AI Graphics & Data Visualization (Seaborn!)
You mentioned using AI for graphics. Just a quick heads-up: be very careful with AI image generators for technical stuff. AI doesn't understand physics or electronics, so it tends to "hallucinate" incorrect schematic connections or impossible waveforms.

I'll continue to make the schematics (Visio) and data plots (Excel) myself, but the more "artistic" illustrations are better handled by AI. I wanted to show a typical sweep range for a coil so I asked AI to make an overhead view of a guy swinging a coil and this is what it created:


It is exactly what I envisioned buy could not draw myself. Stuff like this.

However, AI is amazing at writing Python code for data visualization. You can use ChatGPT to write scripts using Matplotlib or Seaborn. Seaborn is absolutely brilliant for this - you can feed it your data and easily generate publication-quality vector graphics, heatmaps for magnetometer data, or beautiful multi-frequency phase plots. It takes the visual quality to a whole new level.

I will look into this.

3. LTspice / Simulations
For the analog and mixed circuits, it would be a massive upgrade if you provided downloadable simulation files. Allowing the reader to load up the exact circuit from the book on their PC and hook up a "virtual oscilloscope" to see how it behaves is an absolute game-changer for learning.

Another good idea, I had not considered this. I currently use EasySpice so I need to switch over to LTSpice.

4. Dedicated Book Software (A wild idea...)
Thinking about the software-driven projects in Vol 2... If I were doing something like this, I’d actually want to develop a dedicated companion app. Something like a universal "Metal Detector Studio" tailored specifically to the projects, algorithms, and data loggers in your book.
In fact, I'm really interested in this area and I would be totally open to collaborating with you on developing this kind of software if you're up for it!

Not sure what you mean, tell me more. PM if you don't want it public.

Good suggestions, thanks.

[ivconic]

I am beginning to think about what ITMD4 might look like. I would like to mostly expand on digital designs, multifrequency, and multiperiod PI. ITMD3 is already 634 pages so here's what I'm thinking: Make ITMD4 a 2-volume set, like this:

Volume 1: The same as ITMD3, except remove Digital Techniques (Ch1 and all of Advanced Methods (Ch24-26). Maybe add chapters that focus on the design trade-offs in VLF and PI. This means Volume 1 will cover mostly all-analog designs. It will end up with 500-600 pages.

Volume 2: Take Ch18, split it up, and significantly expand on all its topics, with coded example projects. Also do the same for Advanced Methods. I'd also like to add some chapters on other geophysical devices like mags, resistivity, and data loggers, all with example circuits. Probably another 400-500 pages.

What I would like to know from readers of ITMD3 are the following:

• What topics in ITMD3 were not done so well, not enough depth, or not clear?
• Were the circuit examples appropriate and easy enough to follow?
• Are the drawings and graphics sufficient?
• ITMD3 includes zero AI material. I'm thinking of using AI at least for creating better graphics. Any thoughts on that? Or other AI usage?
• Volume 2 will likely have a lot of software-driven designs; any ideas on how to document this in the book? (ITMD3 code was all posted to the forum)
• What additional topics would you like to see covered?

I am just starting to collect ideas; writing ITMD4 will take at least another 5 years (probably more, I always underestimate) so don't get annoyed if you only just bought ITMD3.

I stole a few minutes from the construction work to check out what's new on the forum.
Carl... in principle there is nothing to complain about the previous book.
ITMD4 should be completely dedicated to DSP and the theoretical development of the most suitable algorithms (or set) for use in metal detectors.
I wouldn't advise too many beginner projects... ITMD4 should be aimed at experienced readers and experts first.
I would divide the book into 3 main chapters:
1) DSP in general, list of algorithms and their pros&cons (tradeoffs, compromises, etc.),
2) Baseband sampling,
3) Direct sampling.
Along with the last 2 chapters, I would give a couple of advanced projects.
When I say "advanced"; I mean something more advanced than what we already have on the forum.
I wouldn't "blur" too widely and I wouldn't go back to the topics covered in ITMD3.
My 2 cents.
Cheers!
See you ... sometime ... when I finally finish the damn construction work!

[ivconic]

[ivconic]

I think it's better to publish my posts in the form of pictures instead of text, further on...

[Carl-NC]

I'll go ahead and share my current thoughts on contents:


* Material mostly verbatim from ITMD3. Might have some minor additional contents.
+ Material from ITMD3, but greatly expanded.
N New material.

This is very preliminary as I've only just begun thinking about it. What have I missed?

[ivconic]

Volume 2 looks quite reasonable and interesting.

[ivconic]

This probably isn’t material for an ITMD book. ITMD1 through ITMD3 have
already established their own direction. But as an enthusiast, I have
always been fascinated not only by technology itself, but also by the
people behind it.

If you ask anyone what they remember most fondly in life, the answer is
usually the same: the beginning.

About twenty-six years ago I finally got my first dial-up Internet
connection. Like many newcomers, I immediately started searching for
anything related to metal detectors. Today that sounds trivial. Back
then, it was anything but.

Finding a useful schematic was extremely difficult. Finding a
professionally designed PCB was even harder. Information was scattered
across obscure websites, old magazine scans, and fragments of articles.
Then one day I discovered the U.S. patent database. To me, it felt like
discovering a hidden library.

I spent countless sleepless nights waiting for a single patent PDF to
finish downloading over a painfully slow modem. Every patent introduced
another unfamiliar name. Those names eventually became legendary to me.
Even today, when I read them, I feel the same excitement I did back
then.

Ironically, I never cared about the rivalries between companies, the
business competition, or the personalities behind corporate conflicts.
Living in a small country that had just emerged from one of the darkest
periods of its history, all of that seemed very distant. To me, these
people were simply pioneers. They were the creators of the machines I
had dreamed about as a child.

Over the following twenty-six years, I became increasingly interested
not only in their inventions but in their stories. Who were they? How
did they begin? Which famous detector was really their idea? How much of
the work was individual inspiration, and how much was teamwork? What
happened behind the scenes of the companies whose products later became
legendary?

That is why I believe there is room for a completely different kind of
book.

Not another technical manual, but a historical record of the people who
built this hobby. A collection of biographies, personal stories,
interviews, photographs, patents, company history, and the fascinating
background behind the detectors that became icons.

For many people this might sound overly sentimental. Perhaps it is.

But context matters.

Twenty-six years ago, our region was emerging from a decade of wars,
sanctions, economic collapse, and international isolation. We
desperately needed something positive to focus on—something that
belonged to a better world. For me, metal detectors became that escape.
They were therapy as much as they were a hobby.

Owning a Fisher 1265 seemed like the ultimate dream. The same was true
for White’s, Garrett, C.Scope, Tesoro, and, of course, Minelab. They
weren’t just products. They represented a world that felt impossibly far
away.

People in Western countries probably never attached this kind of emotion
to these machines because they were simply available. Here, they
symbolized opportunity, freedom, and the possibility that life could
become normal again.

The timing was unique. The Eastern Bloc had collapsed, the Berlin Wall
was gone, and the world was changing rapidly. Information slowly began
crossing borders. We collected every brochure, every flyer, every
catalog we could find.

One catalog remains unforgettable: the enormous Conrad Electronics
catalog from Austria. Among hundreds of pages filled with electronic
components and tools, only two or three pages were devoted to metal
detectors. Those few pages became my first real “book” about the hobby.
I literally removed them from the catalog and kept them like scripture.

The industry itself was also very different. Companies guarded their
technology closely. Finding the schematic of a metal detector often felt
more difficult than finding military documentation. Looking back today,
it’s almost funny.

Many of the pioneers whose names appeared on those patents are sadly no
longer with us. Yet their work continues to influence every detector
built today. Their contributions deserve to be remembered—not only
through patents and product names, but through their personal stories.

This forum contains many remarkable pieces of that history, but they are
scattered across thousands of posts, and much of it is difficult to
find. A few magazine interviews are not enough to preserve the legacy of
the people who shaped this industry.

I won’t even attempt to list the names because I would certainly forget
someone important. There were many brilliant engineers, inventors, and
scientists whose work advanced the field. Yet a relatively small group
truly changed the history of metal detecting.

A book dedicated entirely to those people—their biographies, careers,
inventions, collaborations, successes, failures, and the stories behind
the detectors that became legends—would be something truly unique.

I believe such a book would find readers. More importantly, it would
preserve a part of our history that deserves to be remembered.

To me, it would become the closest thing our hobby has to a Bible—a
collection of the stories of the pioneers whose ideas shaped the world
of metal detecting for generations.

[ivconic]

It's a real shame that I'm not filthy rich—but probably not for the reason you're thinking! Ha, ha, ha!
If I had that kind of money, I wouldn't be buying yachts or sports cars.
I would build a large museum dedicated entirely to the history of the metal detecting industry.
From time to time I come across genuine treasures in online auctions and estate sales.
Every now and then, another piece of history from a company that no longer exists quietly disappears into someone's private collection... or end up in recycling centers and landfills.
It's unfortunate to watch these artifacts being scattered around the world, sold one by one with no preservation plan, when many of them really belong together as part of a permanent historical collection.
I believe this industry deserves a museum worthy of its legacy.
It wouldn't only display detectors. It would tell the complete story—from the earliest prototypes to the latest digital designs.
Every major brand would be represented in chronological order, showing how the technology evolved over the decades.
Original prototypes, production models, patents, engineering drawings, advertising material, catalogs, photographs, company documents, and personal memorabilia from the engineers and designers who created these machines would all have a place there.
The idea itself isn't impossible. The difficult part is the cost.
If I lived in the United States, collecting such a museum would already be a challenge.
Living on the other side of the Atlantic makes it dramatically more expensive.
Shipping costs alone would be enormous, and acquiring many of these rare pieces would require a substantial budget.
Still, it's a dream I often think about.
Because every year, another small piece of this industry's history quietly disappears forever.