Kevin has made a good point:
The pulses must be very sharp (duration measured in nanoseconds) in order to generate harmonics that extend well into the hundreds if megahertz.
It isn't a case of trying to find the resonant frequency of the electrode cylinder, or the resonant frequency of the water molecule; but rather to find the pulsing frequency that stimulates the disassociation of the water into Atomic Hydrogen and Oxygen.
When that frequency of pulsing is found, by trial and error, you should see bubbles of the gases forming between the electrodes in addition to a smaller number of bubbles appearing on the surfaces of the electrodes.
That is why the cell must be biased with just enough steadily applied D.C. current to produce only a trickle of gas bubbles. Then when you apply the pulses on top of that, and adjust the frequency of the pulses, you will clearly see when the rate of gas production increases markedly.
Then you will need to determine that frequency, the optimum pulse height, and optimum pulse width in order to tune the cell for maximum output of hydroxy.
It will take some time, patience, and perseverence to finally get it right. And to track the change in frequency as conditions in the cell change.
He who runs the race with determination will finally reach the finish line.
Stan revealed just enough detail in his interviews and patents, in a strange sort of terminology, to possibly replicate a barely functional device. He was protecting the "trade secret" details in order to make it very difficult for others to make the cell work well.
This is very common, obfuscation is used to preserve the real knowlege. To effectively lead the "casual reader" astray.
You must "read between the lines" in order to arrive at the truth. You must be able to discern the electrical/electronic principles at work in order to find the "true" answers.