Hi Geo,
thanks for the explaination. Seems really easy to use.
Now we have to discover how it works to define what's the operating principle behind this.
lets guess...
HERE ARE JUST MY GUESSES :
I'm sure there are problems with noise due to power lines etc like other lrl suffer from. I guess could be extremely unstable in presence of E fields.
Think that tx stage sends sharp step function bursts at 800KHz carrier frequency by a tuned antenna to minimize losses due to impedence asymm between osc section and radiating element(s) and think it need a gnd plane too.
I guess that it has a broadband amplifier in rx stage and then some kind of filtering system to get just only wanted variations on received signal. I guess too that device could be made by a kind of off-resonance detector where target signal unbalance normal cancellation thus resulting in audio signal.
Resonance point would be located, for me, at normal signal feedback response from clean "ground" - this is done in preliminary setup (putting sens at middle...).
Then after a short 800khz burst, signal is detected and then filtered. Must be some correlation between metal object and rx freq. variation (just few Hz or decade of Hz).
At the end, if guesses are right, I would consider it as an enhanced kind of TR/off-resonance metal detector, based on same idea of original off-resonance detectors with coils, but in the hi part of long waves spectrum, without search coils and with antenna(s).
Probably some ELF generation is due to burst function (generates infinite set of harmonics at various freq.) and what's detected is an interference due to sum or sub of main rx freq (due to soil matrix) and signal from object skin effects due to eddy currents flowing in surface of target.
To find out if this is true a simple test could be made using a 2x2'' piece of foil, buried say at 10'' underground from say 2 meters away.
AS I SAID BEFORE, JUST MY GUESSES
don't take for rock-solid-solution...
IS USEFUL ? CAN DETECT STUFF UNDERGROUND ? WHAT KIND OF STUFF ? AT HOW DEEP? THERE ARE FALSE SIGNALS ? CAN DISC ?
I don't know can just guess - I'm not going to spend thousands of dollars to test myself one of these (and not even less).
Best regards,
Max