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In addition to nugget hunting I am also a history buff and I would like to learn more about metal detector technology, its history and sequence of development.   I understand that the BFO (Beat Frequency Oscillator) technology was used in the very early metal detectors.  Right now I would like to learn what is the difference between TR (transmitter receiver), induction balance, and VLF technologies and when was each one introduced to the market.   Is there anywhere where I can find a list of manufacturers, the models (technology) they offered and date range they were offered?  I have searched the forum without success.  Is there a link to a thread or article that I have missed?  Thanks in advance for your help.

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https://www.icmj.com/magazine/article/detectors-past-present-and-future-3466/

https://www.detectorprospector.com/magazine/steves-reviews/metal-detector-technical-specification-notes/

https://www.detectorprospector.com/forums/topic/1424-vlf-detectors-and-depth/

https://www.detectorprospector.com/forums/topic/3193-selectable-frequency-and-multiple-frequency/

https://www.treasurelinx.com/home1.html

https://www.detectorprospector.com/magazine/steves-guides/steves-guides/

 

More here: https://www.detectorprospector.com/magazine/steves-guides/metal-detecting-and-prospecting-library/

Especially these two:

How Metal Detectors Work by Mark Rowan & William Lahr - Originally published by White's Electronics as a booklet P/N 621-0395. Basic but rather technical information on how induction balance and pulse induction metal detectors work.

Metal Detector Basics and Theory by Bruce Candy - Bruce is a co-founder of Minelab and the man behind their most advanced designs. This information delves into much greater detail than the above link and has many more illustrations and diagrams.

Before Carl Moreland was Engineering Manager at White's Electronics (and now First Texas), he created a website that has more technical information on metal detectors than any I know of. The Geotech website has lots of interesting stuff and in particular it has a lot of "build your own" metal detector projects for the electronically minded. I have never done this myself but if you were ever curious about what makes detectors tick a lot can be learned here.

Projects http://www.geotech1.com/cgi-bin/pages/common/index.pl?page=metdet&file=projects.dat

Info http://www.geotech1.com/cgi-bin/pages/common/index.pl?page=metdet&file=info.dat

George Overton & Carl Moreland, co-admins for the Geotech web site, also wrote the new book, Inside the Metal Detector. This is not another "how to use a metal detector" but rather a look inside to the operating principles and electronics that make a detector work.

Inside the Metal Detector explains theory and offers numerous experiments and projects that demonstrate the theory. You can build an off-resonance pinpointer, a GEB-discriminator, and a microprocessor-controlled PI detector. Even if you're not inclined to build a detector, the concepts learned from ITMD will help you better understand how your own detector works and what all those controls are really doing. The book can be purchased in paperback or Kindle versions on Amazon

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    • By WhiteRabbit
      Hello, now here’s an opener that might just get me banned on my first post!
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      I always have my ears perked up for something new in metal detectors and metal detecting technology. I’m not educated enough to really get deep into the technical side of it, but I have a general layman's knowledge of the subject.

      A couple years ago Carl Moreland, the Engineering Manager for White's Electronics, was interviewed on a radio show. I tripped over a reference to the interview on another forum and checked it out. It is very long, and near the end Carl dropped a bombshell. At least I thought so, but it went unnoticed and uncommented on in the metal detecting online world. I thought about posting it on a forum back then but decided to wait and see what developed. Here is the applicable portion of the interview:

      Relic Roundup Radio Show, January 17, 2012, Interview with Carl Moreland, Engineering Manager, White’s Electronics
      http://en.1000mikes.com/app/archiveEntry.xhtml?archiveEntryId=260469

      Transcript beginning at 50:57 mark:

      Carl Moreland - “I can mention one technology that we’re working on because the patent has already been published… or the application, not the patent hasn't gone through yet. We’re working on something called half sine technology, which has actually been around since the 1960’s in geophysical prospecting applications. This is where instead of transmitting a sinusoidal signal you actually just transmit half of the sine and you can do that at extremely high voltages and high ? rates and so on. It’s technically not pulse induction but it’s not VLF either and it is a time domain method. And with that we can get really good depth and we can even get target id information and do discrimination and so forth.”

      Can you see why I perked up at that? I am still amazed it did not get any notice at the time. Nothing happened for a long time. Then I got this PM from Rick Kempf recently:

      Sent 29 January 2014 - 09:04 AM

      Was looking for info on my new SD 2100 this AM when I sort of fell down a rabbit hole of old forum posts and emerged reading Whites new patent. About the first thing I noticed was that you were cited in "prior art".

      Here's what they cited: http://www.voy.com/76600/7/475.html

      The patent is here: http://www.google.com/patents/US20110316541

      Is this something you knew about? Just wondering.

      Rick Kempf

      I told Rick, yeah, heard about that. It was the patent finally being granted from the application Carl mentions in the interview. It was fun getting a mention in a patent though I think it was just the examiner studying up on the subject and finding my old post helpful in simplifying the subject.

      For a long time the Holy Grail in metal detecting has been something that combines the target identification of an Induction Balance (IB or more commonly known as VLF) detector with depth of a Pulse Induction (PI) detector. There have been many promises and false starts over the years, and that was one reason I kept the radio interview mention quiet the last couple years. Frankly, I had half forgot about it until Rick brought the patent being granted to my attention. Notice the title:

      Hybrid Induction Balance/Pulse Induction Metal Detector

      A new hybrid metal detector combines induction balance and pulse induction technologies. Target signals are generated from a transmitted wave that has both induction balance and pulse current inducing characteristics and uses pertinent sampling of the receive data. Combining the two data sources provides eddy current target identification while excluding ground permeability and remanence obscuration.

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