What indicates the correct value of terminating resistance for a Beverage antenna?

A Beverage antenna is a type of traveling wave antenna. When it is properly terminated with a resistor that matches its characteristic impedance, RF energy traveling toward the far end is absorbed rather than reflected back toward the feed point. Because there are no significant reflections from the terminated end, standing waves do not form on the antenna wire. Consequently, the antenna acts as a non-resonant system, which results in a relatively flat SWR curve across a wide range of frequencies. If the terminating resistance is incorrect, reflections will occur, standing waves will form, and the SWR will fluctuate significantly as the frequency changes. Therefore, finding the minimum variation in SWR across your desired frequency range is the practical way to confirm you have chosen the correct terminating resistance.