Hair brained scheme, need feedback

[Hayden]

You can now get a freq generator module off ebay for less than $10. What if you took one and build a magnetic loop around 3 feet in diameter and built a amp to feed it in the 10 watt range at say 1.8 mhz or the resonate freq of gold.

This is easily doable and you could mount it on a tripod and make it very portable.

Then what if you built a receiving antenna, enclosed it in a faraday cage with a 2 inch opening (maybe a 2 inch piece of copper pipe) to allow signal in, that could be hand held and very directional. Could you scan the ground for pieces of gold a distance around the loop for the reflections?

How far do you think it might detect small pieces of gold? How long before the FCC shows up

Just asking.

[WM6]

Such a GPR already exist, but not really useful for gold nuggets detecting (maybe for bigger gold ore deposits (vein) only).

[Carl-NC]

What do you think is the resonant frequency of gold?

[Hayden]

Well Carl, the magnetic resonate freq seems to be about 1.78 mhz. That is in the 160 meter band of course. I hear arguments that that can't be duplicated outside a lab, but any metal can be made to vibrate at it's resonate freq if hit wth enough energy. Else we wouldn't have music! A steel string can be made to resonate at say a 440 A by correct tension and force. You bring a tuning fork near it and it will vibrate in sympathatic vibration to the fork or visa versa. Harmonics of the fundamental will work also but at a degraded performance, else we wouldn't have sideband by mixing crystals and taking the sum or difference and amplifying them. But you have to know all this

A 1/4 wave of 1.7 mhz would be about 250 feet long so a dipole is out. The only way to get a portable antenna is a magnetic loop tuned with an air variable cap. 3 feet diameter is below optimum for a loop in this range but with enough capacitance you can tune it. A 10 to 25 watt linear ain't no step for a stepper and a small lawnmower battery would run it in short bursts and last for a while if you used pulsed CW. Which leaves 2 problems. Building a very directional receiver, hand held. And interference to others on that band. Also the effective range would be small, a few feet or yards. If it worked (and I don't know that it would) You could light up gold bearing rocks electronically and walk over, hit them with a detector to verify, and pick them up

I said this was a hair brained scheme I got old brain cells you know. To much RF in the past cooked it! I worked on television transmitters. Some were so leaky that the florescent lights in the building lit up, even with the switch off.

If gold does have an actual resonate freq of 1.7 mhz this should work on a somewhat limited basis of course. Alloys would make no difference as you would be vibrating the gold atoms only. Any 2 box detector does something similar. This would just be gold specific one would hope as other metals wouldn't be set in sympathetic vibration to the same degree. If we get that one working, we could start on Platinum next. As I said, hair brained

[Carl-NC]

Hayden, what is the resonant frequency of the steel used to make the 440Hz 'A' string? (Hint: the exact same steel can be used to make a 330Hz 'E' string.)

[kt315]

Ernest Rutherford stays out nervously smoking cigarette. he did not hear about the discovery.

[Hayden]

That is true Carl, but isn't it also true that a VLF that works at 40khz finds more gold than one that works at 20? If not then why are the gold machines designed higher in frequency? Why won't my 1260 find more gold than my Gold Strike? The 1260 is much easier to use.

How do you know that a machine operating at 1.7 mhz will not do any better job than one that works at 20 khz? We won't know till we build one will we? If what is available is to judge, you double your take from 20 to 40 khz. What is to say the rise will not be exponential as you aproach 1.7 mhz? How can you say that a 40khz isn't better because it is aproaching a harmonic of the resonate frequency of gold whereas a 20 isn't dead as a bag of hammers to what gold likes to viberate at?

If you reduce the tension on that guitar string a 440 tuning fork for will no longer make it viberate at all, while it will make the A string jump. Do engineers at the MD factories just pick freqs out of a hat or do they keep increasing freq with a signal generator at the breadboard till they get a better reaction with pieces of gold? If they do that, are they not searching for and finding a derivitive of the harmonic freq of gold? I see nothing strange about a gold atom having a resonate frequency. The entire universe is made from vibrations of pieces of energy. Why would gold or other metals be any different from hydrogen other than the freq itself.

My job for years was to take 1 megawatt of energy, devide it 459 mhz per second and send it into space to thousands of Televisions whose receivers would tune that specific freq in and watch the video we were broadcasting. That always seemed such a simple physical fact. I never questioned that the materials the transistors in the front ends of those receivers were not made to vibrate at that freq. if you wanted to watch our channel, you had to have a piece of electronics that would search out and find the source at our transmitter and frequency.

Tesla said he had found the harmonic freq of the earth itself in the late 1800s and said he could destroy it by linear amplification of that freq and sending it through the earth's crust.

[Gwil]

Hi Hayden

I'm not going to comment on whether or not your plan will work but I should point out that metal detectors respond to eddy currents in conductive targets, not to atoms vibrating.

Gwil

[Qiaozhi]

That is true Carl, but isn't it also true that a VLF that works at 40khz finds more gold than one that works at 20? If not then why are the gold machines designed higher in frequency? Why won't my 1260 find more gold than my Gold Strike? The 1260 is much easier to use.

I think Carl is trying to demonstrate to you that target response (as a function of frequency) has more to do with the target's size, shape and orientation than it has to do with its composition. There are many factors at play here, and simply increasing the frequency even further to 1.7Mhz will bring other factors into the equation, as there will also be an interaction with the ground matrix. Higher frequencies are used in gold detectors for the simple reason that gold targets tend to be smaller, and eddy currents die away more quickly due to the lower time-constant. Higher frequencies tend to produce a better eddy current response, up to the limit where skin effect becomes important. This idea of certain target types having an associated resonant frequency is completely false, and belongs to the fanciful world of LRLs. You might be better off discussing your thoughts over at www.longrangelocators.com where science tends to take a back seat.

[Hayden]

As I said I have absolutely no idea if a piece of gold can be lit up electronically. But I also would venture that if you took exactly the same size disc of gold, silver, copper, and iron and ran each one across my old Master Hunter 7, it would still tell the metalic identity of each one in turn. It has to be measuring more than just the decay of eddy currents because of size. When you charge that disc with a transmitted signal, the return contains the identity of that metal. If all were the same you couldn't get a discriminator to work.

LRLs are the realm of con-men and crooks. I am not advocating that at all. What I am advocating is that the professors and Phds at MIT and Stanford hardly qualify as enthusiasts of LRLs But they do say they can scientifically measure the resonate frequency of gold in their labs. I do not believe they are lying about it, as they wouldn't remain professors for very long. Apparently, this is repeatable and provable. I was just trying to come up with a concept to use that scientific fact to my benefit.

Apparently, a scientific LRL has already been made and is working very well. Else how do geology satellites penetrate the earth from space and tell you exactly where an ore body of gold, oil, coal, silver, platinum are located and the depth and quantity of the ore body? Rich man's metal detector? Maybe they are just dowsing it up I will bet you a puter button that it is frequency dependent! Although in the microwave spectrum. Ping each item with the right frequency and the return will tell the tale.

Our metal dectors may not be modified to accomplish that, but someone at government level has the keys to the kingdom!

Just think, if true we could build a detector that would only register on pull tabs! All my friends love to dig those up! I have a pretty extensive collection myself

[Carl-NC]

Hayden, what you are advocating is exactly the same as what the LRL con men advocate. And, like them, you are mixing and mingling NMR frequencies with mechanical resonant frequencies, and they are not at all related. The short of it is, NMR-based gold detection is unfeasible at more than a few inches, and no more reliable at discrimination than the average metal detector. Gold doesn't atomically vibrate in a way that you can just "light it up" with a resonant transmitter and then use a directional receiver to pinpoint. If it did, we'd already have those locators in the field.

- Carl

P.S. -- I can make gold, silver, copper, and aluminum discs that your MH7 cannot tell apart. Skin effect plays a huge role in target ID on a metal detector, more so than the alloy, which is why a silver dime and a silver dollar have very different IDs, despite having the exact same alloy.

[kt315]

just think, EMF in range 1...2...3 MHz does not penetrate the ground as you so hope. this is be cause had been choiced VLF VERY low freq diapazon of EMF as
the result of many experiments. if you will detaily search one pulse (delta pulse) of PI detector you will notice VERY wide spectre. in your theory yes there is a x Mhz constituent too that puts in the resonanse.
but seems you have not have a tiny representation about what is the SPECTRAL ANALYSIS. (this b-sht science that does me crazy dummer)

[Hayden]

Well, you boys are right and apparently I am wrong. I found this from an engineer out there on the net.

"Some people have proposed transmitting a signal that will cause buried gold to resonate or oscillate, and somehow detecting the direction/location of resonance. So is this feasible?

Gold has an NMR frequency of 1.754MHz relative to hydrogen @ 100MHz, which establishes the test magnetic field at about 2.35T. The Earth has an average field of about 50uT, so buried gold would have an NMR frequency of about 37Hz. Someone please correct me if I'm wrong.

So would this be a feasible method? I think not, if for no other reason than 37Hz is way too low to make any kind of realistic directional receiver. But even if you could figure out a solution to the electronics, would the basic physics work? I know in magnetometry and I think MRI as well, hydrogen is the element at work. Is this because the single-proton nucleus is easy to precess? Would a solid gold structure exhibit any measurable level of NMR precession when pinged with an impulse field? Also, would a 37Hz magnetic field cause a sustained resonance?

I'd like to hear any thoughts on this approach. I am an electronics engineer with the normal physics & chemistry coursework, and I've designed metal detectors & magnetometers.

Thanks."

Back to the hair brained scheme drawing board Thanks all!

[kt315]

yes, there was the schematic and article in belorusian magazine RADIOLIUBITEL with you wrote about. probably it was spreaded widely and was been translated in net.
nothing of true - it was only April 1 joke. the schematic is consisted from parts of another schematics. somebody believe it fool joke nowaday...

[golfnut]

A fast sweep generator with sychronised Rx may get a statistically bigger or near optimal return from a huge range of target volumes.

You could look at the result hit amplitudes versus freq and get an idea of the target vol