*Posted with permission of Metal Detector Engineer Dave Johnson*
First Texas Head Engineer Dave Johnson has always done an awesome job “educating” the metal detecting masses. Thanks again for sharing your knowledge Mr. J.!
Time of day influences the amount and type of electrical interference, not just local sources but also longwave radio communications (mostly military) from thousands of miles away.
Fisher and Teknetics Chief Designer Dave Johnson has written an AWESOME book on gold prospecting with a VLF metal detector! Tons of great information for prospectors and potential prospectors…as well as folks who just want to “learn more” about metal detectors! Special thanks to Dave Johnson and Mike Scott for allowing me to reprint the book in it’s entirety here on www.detectorstuff.com !
VISIT the brand new Teknetics website HERE! http://www.tekneticst2.com/
*reprinted with permission of First Texas Products*
VLF Metal Detector
Dave Johnson, Chief Designer
First Texas Products & Fisher Research Labs
This book explains how to use a VLF induction balance metal detector for gold prospecting. The author has nearly 30 years’ metal detector design engineering experience and has designed machines in every major metal detection technology category.
Because of the high sensitivity of modern metal detectors coupled with the proliferation of sources of electromagnetic interference, you are likely to encounter electrical interference at times during the use of your metal detector. It is important that you recognize electrical interference when present, and take appropriate measures to deal with it. This will prevent you from giving up on a worthwhile site unnecessarily, or from sending in for a repair a machine which is working properly.
Symptoms of electrical interference
Electrical interference can cause a metal detector to “chatter” spontaneously, to lose sensitivity for no apparent reason, or to cause periodic audio “wobble” or slow waves of spontaneous sound. What you’ll hear will depend on what model of metal detector you’re using, what operating mode you’re using it in, how you have the adjustments set, and what the source of the electrical interference is. The most common manifestation is spontaneous chatter.
All metal detectors are susceptible to electrical interference, but they vary in what kinds of electrical interference affect them. In a given environment some metal detectors may be affected by electrical interference whereas others may not.
Two metal detectors of the same model in the same environment may be affected differently, because of minor differences in operating frequency or because the controls have been adjusted differently.
Common sources of electrical interference
Common sources of electrical interference include: overhead electric power lines, underground power lines, other metal detectors, telephone lines carrying electronic data, computer systems, electric fences, old CRT-based televisions, cell phones, thunderstorms, fluorescent lights, metal vapor lamps, military aircraft with electronic warfare countermeasures turned on, electric motors, VLF military communications systems, and automobile ignition systems. It will sometimes be the case at home, in the showroom, or in an urban environment that there are several different sources of electrical interference present simultaneously.
*reprinted by permission of First Texas and Dave Johnson
File: El Paso Chapter GPAA talk 12 Feb 08 Dave Johnson minor update 25 march 09
Good evening! My name is Dave Johnson, and I’m the Chief Design Engineer for the world’s largest manufacturer of hobby type metal detectors located right here in El Paso. The brand names we manufacture include Fisher Research Lab, Bounty Hunter, Teknetics, and a number of private labels. I’ve been designing metal detectors for 27 years for several different companies, so there’s half a chance that if you swing a metal detector, I had something to do with it.
My presentation this evening is on the history of metal detectors, with an emphasis on gold machines. I’m not here to sell my company’s products, but it’d be downright discourteous of me to show up and not bring some literature and a Gold Bug 2 to demo. So after the meeting if anyone is interested I’ll be happy to talk with you.
* * * * *
*Reprinted by permission of First Texas*
Posted originally on American Relic Hunters Official Teknetics Forum
Hello! and, Omega
Posted By: dave johnson
Date: Friday, 13 February 2009, at 1:10 p.m.
Hello, this is my first forum post on this website. Some of y’all I recognize from other venues.
Since the Teknetics Omega is in the process of being released to production, there will be a lot of curiosity about it. Most of the questions will relate to features and performance in the field. There’s no need for me to go into those matters, since other people will quickly fill in the details. What follows here is a bit of information which is probably better coming direct from engineering department.
Once the Omega gets into people’s hands, it’ll become obvious that there is some sort of relationship between the Tek Omega, and several earlier Fisher and Bounty Hunter products. Here’s what that relationship is.
First of all, I want to thank Tom Walsh, Mike Scott, Tricia Richardson, Dave Johnson and John Gardiner for their help in arranging this interview. I think it’s a fair statement that First Texas – Fisher is one of the most exciting metal detector companies on the planet right now, and as such, has piqued the interest of the hobby detecting world in a way that hasn’t been seen for quite a while.
I had the idea for this interview months ago, before I had started this web site. There was quite a buzz in the forums when rumors started of a new Dave Johnson design coming from First Texas under the Teknetics moniker. After the subsequent release and success of the T-2, the hobby community was set on fire with excitement over the prospects of “things to come”. Another wave of excitement hit when it was learned First Texas had acquired Fisher, and that wave turned into a tsunami with the release of the F-75. Mr. Johnson was quick to point out that the T-2 and F-75 were team efforts, not solo projects, and that Engineer John Gardiner was key to the success of both machines.
The purpose of this interview is to give the fans of metal detecting a “behind the scenes” glimpse of the engineers who designed the T-2, F-75 and F-4. There is an unusual “connection” people in this hobby have with their metal detectors. Over time, they seem to take on a personality of their own, becoming an extension of the owner/user. Because of this “personal” connection, most view the responsible engineers with a sense of awe and mystery. I feel that “getting to know” the Engineers will help people appreciate and applaud the outstanding efforts of these geniuses behind the scenes.
All questions below are for both Mr. Johnson and Mr. Gardiner, unless otherwise designated.
DS: What got you interested in engineering metal detectors?
So, my current mission to test all the metal detectors in my stable against a deep silver dime in my test garden continues. Now…remember…variables is a key word here. Meaning, time constraints won’t let me test all of the machines on the same day…and I have witnessed numerous times that the exact same metal detector can NOT get the dime one day and then (with identical settings) can get it the next. The variables I’m talking about are ground moisture, “invisible” RF interference, etc….heck, it could even be moon phases, gov’t conspiracies and UFO’s for all I know.
So, this take this test for what it is…different detectors on the same targets but on different days. Up to bat today is the venerable Fisher CZ3D. The original CZ design is dual frequency and originally the brain child of Dave Johnson. It has had many iterations since with the last being the 3D. This is a design that goes back to the late 80’s/early 90’s! Amazing that it still holds it own against the modern crop of metal detectors.
Teknetics Eurotek Pro Review
You know, the Eurotek Pro kind of frustrates me! No, no…not because it has any problems . …but, instead , because it performs so blasted well while being so inexpensive ! I mean, I have quite a few much higher priced detectors that can’t do what this little fella does. Sure, it doesn’t have a lot of the features found on high-enders like backlight, notches, etc. But what it does bring to the table is the best performance I’ve found in ferreting out non-ferrous targets that are surrounded by iron.
2014 is here and the start of a new year can be a time to reminisce. As I’m building up some new content, I thought it may be good to also remind folks of some of the great stuff we’ve had here over the years. I’ve been fascinated with the people behind the scenes that make our hobby fun by creating new and amazing metal detecting equipment! Below are links to some of our past interviews with industry leaders….
Teknetics G2 review
“In the Spring a young man’s fancy lightly turns to thoughts of love”. For the not-so-young man (me), in the Fall my fancy turns to thoughts of metal detecting. The Teknetics G2 arrived just in time to tickle my fancy! (read more…)