One of the problems I had with producing the RF BEAM was to actually be able to see what was happening as I tuned things and adjusted elements. After a lot of thought I came up with the idea of using a Fluorescent Tube mounted several feet away from the source elements. As you adjust the various components you can see the tube light up and display the RF intensity as the thing becomes more of a beam. The ionized gas follows the width of the beam so you do get an idea of what is going on as you set up the phase and amplitudes of the "E" and "H" fields. There has to be an RF Absorber placed behind the tube to stop reflections etc upsetting the result and to stop it going anywhere else. (see previous articles on making a cheap RF Absorber). We used to measure RF in Volts /Square metre however in the RF Beam you cannot but it is in Volts / Square inch in my first tests finally it will be Volts /Square mm but not that far advanced yet. Because the RF has been compacted down to say 1" then you automatically have a larger amount of electrons in a smaller area and this can be 1000/2000 times more even with a simple 1" beam (yet the power level is the same just concentrated). I mounted the tube in the "E" plane.