I've been looking at a patent for a simplistic high frequency pulse generator (US3798461A). It's basically two disks spaced apart with a spark gap in the middle. There's brass tubes in alignment, running out from the disks, with coax threaded through the tubes. Each disk is connected to its own external capacitor, and when these caps discharge through the spark gap, the apparatus produces one pulse for each two sets of brass tubes, with the frequency determined by the length of the coax. The number of desired pulses determines the number of tubes.
The patent says there is advantage to not stripping the coax, which indicates to me that the shield can be used for the central capacitive conductor, rather than the coax's inner wire. This would provide a larger diameter, higher capacitance inner conductor than just running a normal wire through snug fitting tubes.
The patent also says an asymmetric output can be produced by replacing the lower tubes and coax with resistors joining the central conductors coming down from the top. So the pulse output could be strictly positive or negative. Then the length of the coax would be half of the output wavelength. (It seems to me.)
With a lower supply voltage, the spark gap can be replaced with a diactor, or TVS diode.
For microwave frequencies, the device would be fairly small. But water's specific dielectric resonant frequency can be produced.
And there will be a slight pause between the pulse strings, as the supply caps recharge. This pause will be shorter with smaller, faster charging caps.
