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Interview With The Tarsacci Inventor Dimitar Gargov


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I've been reading through Dimitar's patent today. It uses a square wave (voltage) transmitter which produces a triangle wave current. When the coil is non-ideal (due to resistance) the triangle wave becomes slightly exponential, especially at lower frequencies. The patent describes an analog correction process after the preamp that compensates for this. Then it describes a the possibility of multiple demod stages (I/Q pairs), each with a preceding notch filter. One demod pair has a notch filter for ground, the others have different notches for different target responses. That's as far as I got, these things are tough to read. I fell asleep twice.

Bottom line is, the Tarsacci is 100% continuous-wave VLF. It is NOT sinusoidal like most single-frequency VLFs, but the demods are continuous-time just like SF-VLFs so it does not use time-domain demodulation like BBS/FBS. However, the preprocessing before the demods is done in time-domain fashion, so overall I would call it mixed time/frequency domain. I have to admit, I've not seen things done quite like this.

My own developments have included square-wave drive designs and I've considered coil compensation methods but at this point I've pushed it into DSP. But I understand exactly what Dimitar is doing there. The ground/target notching is more interesting to me and I think I know what he's doing but I need to keep reading.

Congratulations to Dimitar on a different and clever solution. Too bad FTP didn't hang on to him.

 

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I for one hope you continue to study his patent and share your thoughts here. It is nice that you have settled the issue VLF or PI, at least to my satisfaction. Very nice compliment to Dimitar I think coming from you. I can tell you, he stands behind his detector and is never to busy to talk with anyone. Very down to earth guy. Look forward to more reports on the detector.

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