One of the issues with either plasma or with RF is the law of inverse squares. This basically states that as the distance from the source increases, the concentration decreases exponentially.
If there is a sufficient signal contained in 1 square foot of area at a distance of 1 foot, at a distance of 3 feet, that signal is diluted to spread over an area of 3 feet by 3 feet or 3 times 3 equals 9. This means that at a distance of 3 feet, the signal is 1 ninth of the strength that is was at 1 foot of distance. at 5 feet, it becomes 1 25th, at 10 feet, it becomes 1 - 100th or 1 percent of the strength that it was at 1 feet.
For this reason, neither plasma not RF can be very effective unless you are sitting or standing at a distance of only a foot or so from the source. This is also why the Plasma and RF type machines need so much power ( watts ).
If you were to make some crystal resonator, the results would be the same.