Spectra V3

[Davor]

It is surely greatly conserved by tank capacitances and the Q factor for each frequency. In fact, there are very little losses in interaction with the soil, so it is mostly the coil resistance that spoils the Q.

Long ago I played with such digital waveforms to synthesize sine-like exciters, not to exaggerate harmonics but to suppress them. A nice and surprisingly clean signal is obtained using two shifted f/3 waveforms, but that one has a zero half the time and must be realised as a bridge. It could be used to improve tone for the most of the nowadays detectors.

This V3 thing has a non-return-to-zero output so it narrows the choice of usable waveforms. But surely it can do any combination of the (f1, f2, f3), and not necessarily all of them together. Maybe it is the way it achieves the depth that is advertised. Some extra 10dB juice using a single frequency ... not bad.

[ODM]

Would this help?http://forums.whiteselectronics.com/...0&d=1347182782

Oh, that clears a lot. Seems like a self repeating 9 bit stream that's inverted for the half cycles. Or is there some very fine pulse width trickery going on to equalize the levels?

[Davor]

A binary signal is by itself a NRZ one, so if symmetrical it will have all even harmonics cancelled. Some fine tweaking of the transitions timing may influence suppression of some higher harmonics, but in this particular case it is not needed. In a way this solution is squeezing the most juice out of 3 small lemons. Somewhat larger lemons could be squeezed in a bridge configuration that would allow for zeroes as well, but it is more straightforward this way.

[kt315]

interesting story http://phazitron.narod.ru/repair/wV3i.htm
for whom reading russian.