The interesting phenomenon of the breakup of continuous liquid jets into droplets has significant practical applications, including inkjet printing. Regardless of print mode (i.e., ondemand vs. continuous), as applications require increasingly precise droplet control, inherent noise in the breakup process is becoming an area of increasing interest. We examine jitter to infer the underlying velocity fluctuations in thermally stimulated continuous fluid jets. Based upon comparisons of jets having different diameters D, as well as jets stimulated at different frequencies (hence different wavelengths λ), we find that the jitter depends significantly upon the dimensionless wavelength λ/D, showing a minimum at the natural frequency of the jet (corresponding to λ/D = 5) and a marked enhancement over the range 6 < λ/D < 8. We present an analysis of the frequency dependence of the jitter in the context of a simple model for growth of radial perturbations on the jet.