AFAIK no specific frequency has been found. I think it depends on the transformer setup.
Tony says he generated hot water using his alternating dc circuit, and I believe him.
However, I think he is doing something more exotic with the transformer or the cell, as those are
the only two variables, beside the two signal inputs, that could affect it.
I believe the frequency will depend on the cell, transformer, and the water, but you would think
it would be more forgiving than the resonant cavity, as it is simply alternating HV on and off...
Another curious fact is meyer's steam resonator coil has much thicker wire than the dunebuggy
coils - does this tell us it was a lower voltage than on the resonant cavity coils?