Gentlemen, you are all right - and WRONG. Follow me through this. An opera singer can break a glass because she reaches the exact frequency of the glass, which is already vibrating at its own frequency just like everything in the Universe does. Her voice increases the amplitude of that frequency and finally, the glass vibrates its self to pieces. It is definitely putting out its own frequency even before the opera singer hits its frequency, but it doesn't go very far. The singer's voice acts as an amplifier for the signal of the glass. If it is too much, the glass will break.
Now, gold vibrates at approximately 5000 cycles per secind. If you have a cash of gold buried in your general area, you could use a frequency generator set at 5000 cps, then run through an audio amp, like the ones of 50 or 100 watts for your car, and connect the output of the amp to a wire going to a copper clad rod driven in the ground about 2 feet deep.
This signal now proceeds through the ground in all directions. When it hits the gold, which is already vibrating at 5Kc, the gold vibrates much harder, but still at the same frequency. It, in effect, becomes a transmitter its self powered by the matching signal from our transmitter.
It sends out a signal of 5Kc and harmonic frequencies at 10Kc, 15Kc, 20Kc etc.
So, you are sending out your signal through the ground from your transmitter and the gold is sending out its signal through the ground. Now, take a loop antenna 18" to 24" in diameter and go to a spot well away from your transmitter. The loop (direction finding) antenna will be connected to a pre-amp module to boost the signal strength and will then send it on to a meter and/or sound module that you can hear through ear phones.
Turn the loop antenna until you tune in the best signal for your signal generator transmitter. You know the direction is right because you know where the transmitter is. Now, slowly turn the antenna away from the transmitter until you get another signal rise at the same frequency. If you mark a GPS location on a simple grid showing the transmitter and your first location where you receive the second signal, you can mark an azimuth, or a straight line on the paper grid in the exact direction of the gold. You don't know how far away it is, but you have a straight line to its location.
Now go to a spot well on the other side of your transmitter and repeat the process. When you draw your azimuth line this time, where the two lines cross - X marks the spot. You can figure the GPS location where the lines cross, go there and find the gold with a conventional metal detector.
By the way, the TR Discriminator metal detectors work by this exact principal. But it is a stupid design because they are still made to look like a metal detector. The signal is sent out through the coil - THEN THROUGH THE INSULATING AIR, and finally into the ground. That's why even though they work better than other detectors, they don't have near the reach they would if the antenna were contacting the ground.
You don't have to be a scientist to see this is correct. Remember, the glass breaks because it is saturated by it's own frequency from the opera singer. You can actually hear the glass singing before it breaks because it is TRANSMITTING A SIGNAL at its frequency. The same goes for gold or silver or iron or a Tuna Fish Sandwitch! This is just like tuning in a radio station. You can tune in a weak signal, even though a very strong signal is closer to you. You are not tuning the frequency of the strong signal.
As far as I know there are no units like this on the market. I have wanted to make one for a long time, but I have too many other areas of interest to stop and do it right now. Hope this helps in the discussion. You may email me for further comments.
mlammers1@midsouth.rr.com