Changing detector frequency?

Thread Starter

Eaglewings3229

Joined Aug 30, 2017
3
Hello, this is my first post.
I have been reading several of the projects and I am confident that I am at the right place.
Firstly, I know nothing about electronics. I have "bright ideas", but no idea how to implement them. Well here goes.....
All of the pinpoint metal detectors on the market are tuned to a broad range of frequencies.
The higher the frequencies, the more sensitive they are.
I own an Falcon MD20 detector probe. It operates at the 300 kHz range, which covers ALL metals. (Which does discriminate iron). The best and most sensitive detector for finding small gold is the Fisher Gold Bug 2, and it operates at the 71kHz.
So.... Is it possible to take an old coin detector that operates at 6 kHz, and somehow increase the operating frequency to the 71 kHz level? There are other differences, mainly that the coin detector is analog, where the Gold Bug is digital.

Idea #2... how to take a pinpointer and change the frequency. Or how to build a detector that operates at that range and add a ferrite rod with 3 coil wraps.

With all you super smart people I am hoping y'all can help me design and build this.
I look forward to the discussion.

Kerry
 

BR-549

Joined Sep 22, 2013
4,936
I never fooled with one but it looks like fun.

"So.... Is it possible to take an old coin detector that operates at 6 kHz, and somehow increase the operating frequency to the 71 kHz level?"

No.

"Idea #2"

No.

It's because of resonance and wavelength. But I'm sure some hobbyist has built a custom rig with interchangeable heads. Maybe some here...stick around.

You detector guys have a great future when this new terra hz stuff gets out. It should really change prospecting.
 

recklessrog

Joined May 23, 2013
988
Near where I live are the remains of a Roman fort, the roadway from it runs through a huge wooded area. Over the last few years a lot of the fort has been excavated with many artifacts found. To survey the wooded area, I saw that they were inserting rods into the ground and using very low frequency that swept from 0.1 to 7 Hz signals to produce a map of areas of about 60 sq.ft. on a print out. It showed all sorts of anomaly's some as small as coins.
So maybe that is also something to look into.
 

BR-549

Joined Sep 22, 2013
4,936
That's really something......that they can get that kind of resolution from those frequencies. What do they call that type of sensing? How would I search?

This rf stuff is really progressing. We're stamping out cheap, stable and reliable GHz units for everything now.

The increased speed and rate of communications will be nothing compared to the sensing of internal structure of materials and objects with THz. Or sensing thru them. Being able to remotely detect the structure, composition and density of elements and compounds, in a distant volume.......is a great smart phone application. I believe it was in the late 60s when it was first suggested.

Phased arrays should not be physically large, allowing a sweeping beam to be used. And because of the wavelength....sweeping large frequency bands should be possible. And I'm hoping that this tech comes on line quicker than microwave tech did. It should......just for the communication demand.

Not to hijack the thread....by any means.
 

recklessrog

Joined May 23, 2013
988
That's really something......that they can get that kind of resolution from those frequencies. What do they call that type of sensing? How would I search?

This rf stuff is really progressing. We're stamping out cheap, stable and reliable GHz units for everything now.

The increased speed and rate of communications will be nothing compared to the sensing of internal structure of materials and objects with THz. Or sensing thru them. Being able to remotely detect the structure, composition and density of elements and compounds, in a distant volume.......is a great smart phone application. I believe it was in the late 60s when it was first suggested.

Phased arrays should not be physically large, allowing a sweeping beam to be used. And because of the wavelength....sweeping large frequency bands should be possible. And I'm hoping that this tech comes on line quicker than microwave tech did. It should......just for the communication demand.

Not to hijack the thread....by any means.
The guy operating the equipment did not know details of the way it worked and I suspect the low frequency is used as a carrier with some h.f modulation of some sort. Like you, I could not figure out how such good resolution could be obtained at V.L.F.
 

Thread Starter

Eaglewings3229

Joined Aug 30, 2017
3
Ok, it's not possible ?? I was hoping that it would be as simple as changing a few parts out. Like I said, I'm not an engineer. I know what I need, but don't know how or if it's possible.

Well, if it's not possible to make changes and achieve it, is there someone here that knows the workings of a detector that can help me build one? With me paying for it of course !!
 

bertus

Joined Apr 5, 2008
20,053
Hello,

Here is a list of metal detector articles from the chemelec site:

A BFO Metal Detector"
Not the best, but Simple, and Now with a PCB.

A BETTER BFO Metal Detector"
Much Better and Simple, Parts and PCB Available.

Metal Detector Coils, for my PI Detectors

Small Detector Coils, with Ferrite Cores for my PI Detectors

Testing Metal Detector Coils,
for Free Air Resonance and Interwire Capacitance.


A Metal Detector, for Pin Pointing.
"Possibly More info to come later".

My "SUPER SENSITIVE", Pin Pointing Metal Detector.

"Metal-AV, A Pulse Induction Detector."
A PI Detector with "Audiable & Visual" Indications of Targets. Suitable for use on some Conveyor Belts.

Metal Detector, A Pulse Induction Detector. "Pulse-1"
Hundreds of this Detector have been built with Very favourable Feedback.
This is "the Most Most Popular Project on my site".

Pictures of My Pulse-1 & 2 Metal Detector Project.
These Detectors have been "Built by Various Persons",
And I included their Comments on it's performance.


Metal Detector, My "Pulse-2" Induction Type Detector
This is a Revised Version of the Pulse-1 above with Additional
Controls for Possibly More Flexibility.
This Detector is "Definately Not for the Beginner".

My Metal Detector Coil Jig
This is Not a Project, But this is how I make the Flat Radial Coils.
I have Shown this here because of Numerous Requests.

"Metal Detector", based on the CS209, Now Discontinued.
Especially Suited to find studs in Walls.
Note: this IC is discontinued and getting hard to obtain.

"Metal Detector", based on the TDA0161.
Preliminary Circuit Article...More Info to Come.

Bertus
 

Thread Starter

Eaglewings3229

Joined Aug 30, 2017
3
Thank you for the info. I'm a bit apprehensive, as I've never assembled anything electronic before.
Is there a chance I can buy the parts and pay you to assemble it for me?
I've had a stroke and those small parts would really make my head spin.
Plus I've read that you need other equipment to calibrate some of them. I don't know if these require that or not.
Anyway, thank you again Bertus, you are awesome !!!
 
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